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A review on the use of indigestible dietary markers to determine total tract apparent digestibility of nutrients in horses
Abstract
This review was written to summarise knowledge available on the use of markers to determine total tract apparent digestibility in horses, and to quantify differences in estimates obtained between marker techniques and total collection of faeces. Differences were quantified with a unitless standardised effect size (Hedges's g) and effect sizes within marker, diet (all-forage, forage and concentrate) and nutrients were combined with random effects models to account for unexplained heterogeneity among experiments. Digestibility of all-forage diets estimated by total faecal collection was not different to measurements obtained with acid detergent insoluble ash, 2 N HCl acid insoluble ash, or the n-alkanes C27, C29 and C31. With diets containing forage and concentrate, acid detergent insoluble ash, chromic oxide, indigestible acid detergent fibre, indigestible cellulose or n-alkanes presented similar nutrient digestibility coefficients, and 2 N HCl acid insoluble ash higher dry matter digestibility, compared to total faecal collection. Acid detergent lignin resulted in lower apparent digestibility coefficients with both types of diets. However, combined effect sizes for acid detergent insoluble ash and n-alkanes were based on 2–3 experiments conducted in few (1–2) studies, and should be interpreted accordingly. It is concluded that acid insoluble ash currently presents the most reliable marker that, with certain precautions, could be applied to determine apparent total tract apparent digestibility in horses.
... mordants, artificially labelled feeds or markers applied by boluses). They provide specific information on intake, diet composition, digestibility or passage kinetics but must fulfil some general criteria: (1) non-toxic (Sales, 2012), (2) non-impact on physiological processes (Sales, 2012) or the digestion of nutrients (e.g., formation of complexes), (3) non-resorbability, (4) a close association to the phase of digesta that is target to label (Faichney, 1975), without risks of marker separation, sedimentation or adhesions in the digestive tract, and (5) consistency and predictability of faecal recovery (Sales, 2012). However, the importance of such criteria may depend on the objective and the method of marker application. ...
... mordants, artificially labelled feeds or markers applied by boluses). They provide specific information on intake, diet composition, digestibility or passage kinetics but must fulfil some general criteria: (1) non-toxic (Sales, 2012), (2) non-impact on physiological processes (Sales, 2012) or the digestion of nutrients (e.g., formation of complexes), (3) non-resorbability, (4) a close association to the phase of digesta that is target to label (Faichney, 1975), without risks of marker separation, sedimentation or adhesions in the digestive tract, and (5) consistency and predictability of faecal recovery (Sales, 2012). However, the importance of such criteria may depend on the objective and the method of marker application. ...
... mordants, artificially labelled feeds or markers applied by boluses). They provide specific information on intake, diet composition, digestibility or passage kinetics but must fulfil some general criteria: (1) non-toxic (Sales, 2012), (2) non-impact on physiological processes (Sales, 2012) or the digestion of nutrients (e.g., formation of complexes), (3) non-resorbability, (4) a close association to the phase of digesta that is target to label (Faichney, 1975), without risks of marker separation, sedimentation or adhesions in the digestive tract, and (5) consistency and predictability of faecal recovery (Sales, 2012). However, the importance of such criteria may depend on the objective and the method of marker application. ...
The basis of a successful assessment of the nutritive value of feeds and an animal's supply with dietary energy and nutrients is having sufficient knowledge on key indicators such as feed intake, diet composition, digestibility and the kinetics of gut passage. In horses and other equids, the determination of such indicators is impractical outside controlled conditions, particularly in pasture-based husbandry. Natural wax components such as n-alkanes, alkenes, primary alcohols and fatty acids might be beneficial estimators, but their application is limited in practice. This review provides a concise view into the application of plant wax components, especially alkanes and their external counterparts, in equine nutrition studies. Recent methodological developments and the current state of knowledge are summarized as an interim conclusion. Methodological limitations still hamper an easy application of the method, and some perspectives for future methodological research are discussed. Conclusively, little information is available on feed plant concentrations and variations of primary alcohols, fatty acids and alkenes, and their natural carbon isotope (¹³C/¹²C) ratios. Moreover, the magnitude and the (in)consistency of faecal recovery of these markers is barely described. Methodological research should continue focusing on an effective application of plant markers. In horses, especially plant marker-based methods for the estimation of diet composition and passage kinetics will require much more consideration.
... In horses, these methods are not applied due to ethical approaches or other limitations (e.g. sport horses); therefore, the importance of marker-based techniques is growing, although not much data is published in the available literature (Sales 2012). ...
... The application of this harness reduces the time-consuming nature of experiments and allows grazing or even moderate use of horses. Nevertheless, the use of harnesses and bags for faeces collection will always restrict, to a certain extent, the horse's movements, which influences its behaviour and, consequently, affects the harmonious course of digestive processes (Sales 2012). ...
... So far, chromium oxide appears to be the most popular marker among those employed as a feed supplement in digestibility experiments on horses (Sales 2012). In a comparative experiment with the most commonly applied natural markers (as well as ytterbium (Yb), a chemical element derived from rare earths and applied as an additive to feeds), this compound turned out to be the most effective (Martin et al. 1989). ...
The aim of the review is to present mechanisms of digestion in horses through a functional description of the digestive system’s structure with emphasis on nutrient digestibility. In the era of an increasingly intensive and specialised sport usage of horses, also the significance of balancing their dietary nutrient value in accordance with individual requirements of these animals is gaining in importance. At the same time, it is not possible to meet nutritional requirements of a sport horse without knowledge about feed utilisation. In many farm animal species, digestibility is measured post mortem or via complicated and expensive cannulation of the digestive system. In horses, these methods are not applied due to ethical approaches or other limitations (e.g. sport horses); therefore, the importance of marker-based techniques is growing, although not much data is published in the available literature (Sales 2012). Moreover, in contrast to other non-ruminants, horses are naturally adapted to a constant intake of large quantities of roughages. However, during intensive sport training, they are primarily fed concentrated diets with high amounts of easily digestible, non-structural carbohydrates and reduced amounts of dietary fibre fractions. Therefore, the risk of metabolic diseases and behavioural disorders in the horse increases.
... Indigestible markers have found a widespread use in animal nutrition studies due to less timeconsuming and laborious experiments compared to conventional direct digestibility methods (Sales 2012). Digestibility coefficients obtained by ADL method (Table 3) were lower in comparison with those found by TFC. ...
... Many authors reported the failure of this method because of low recovery rates of lignin in faeces and consequent great underestimation of digestibility coefficients (Chachulowa et al. 1994;Miraglia et al. 1999;Araujo et al. 2000;Oliveira et al. 2003;Goachet et al. 2009;Siqueira et al. 2009;Arbabi et al. 2016). Digestion of a fraction of lignin by microbial activity, source of plant lignin and content of lignin in the diet might be the factors responsible for incomplete faecal recoveries (Sales 2012). Assuming the possibility of partial digestibility of lignin, Oliveira et al. (2012) suggested using only the indigestible fraction of lignin as a marker in digestibility studies. ...
Twelve adult Slovak warmblood sport horses were used to study the effect of dried grape pomace (DGP) on health through blood serum biochemical indicators, and on apparent total tract digestibility of dry matter (DM), organic matter (OM), crude protein (CP), acid detergent fibre (ADF) and neutral detergent fibre (NDF). The digestibility analysis was carried out by two in vivo methods, total faeces collection (TFC) and using lignin as a marker (ADL). Animals were divided into 3 groups: control group (C, without supplementation), experimental group 1 (E1, feed rations + 200 g of DGP) and experimental group 2 (E2, feed rations + 400 g of DGP). In animals, no health problems were detected during the trial. Of the blood serum indicators, only the concentrations of potassium (increase in E2 group compared to C group) and alanine aminotransferase (decrease in E2 group in comparison with E1 and C group) were affected (P < 0.05). The ADL method resulted in underestimated digestibility coefficients due to low recovery rates of lignin (less than 90%) in C group and E1 group. According to TFC, in E1 group higher digestibility coefficients were detected for DM, OM and CP (P > 0.05) compared to C group. However, in E2 group lower digestibility of all the studied nutrients was found (P > 0.05) in comparison with C group and E1 group. These results suggest that DGP could be used in horse diets up to 200 g without negative effect on their health and for a possible digestibility improvement of some nutrients.
... Direct measurement of voluntary DMI of hay is difficult when using large numbers of group-housed animals and warrants use of indigestible markers as an alternative strategy (Sales, 2012). Dual-marker systems, consisting of an internal and an external marker, can be used to estimate DMI in pasture-housed animals by measuring DM digestibility and fecal output, respectively (Cochran et al., 1986(Cochran et al., , 1987Owens and Hanson, 1992). ...
... Direct measurement of voluntary DMI of hay cannot be used in group-housed animals and warrants use of indigestible markers as an alternative strategy (Sales, 2012). Thus, alternative methods must be used to estimate intake indirectly by dividing total fecal excretion by indigestible nutrients from the diet (Dove and Mayes, 1991). ...
Thirty pregnant mares (538 to 695 kg BW; 4 to 19 yr of age) were used to evaluate the effects of plane of nutrition on DMI of hay and mare performance (BW, BCS, and rump fat) during the last third of pregnancy. Mares were divided into 4 blocks by their expected foaling date and randomly assigned within block to either a hay or concentrate + hay diet (concentrate fed at 0.75% BW, as-fed) with 15 mares per treatment. Treatments began 110 d prior to expected foaling date (230 d of gestation) and terminated at parturition. Mares were housed by block and allowed ad libitum access to coastal bermudagrass (C. dactylon) hay, and concentrate supplemented mares fed twice daily in individual stalls. Performance variables were recorded every 14 d, with the last measurements obtained prior to foaling being considered a pre-partum measurement. To evaluate DMI of hay, a dual marker system was used at 9, 10, and 11 mo of gestation. Titanium dioxide was dosed at 10 g for 14 d. Fecal grab samples were obtained on the last 4 d twice daily via rectal palpation at 12 h intervals with times advancing 3 h each day to account for diurnal variation and to ultimately represent a 24-h period. Fecal samples were analyzed for TiO2 using a colorimetric procedure. Fecal, concentrate, and hay samples were also analyzed for acid detergent insoluble ash. Treatment tended to influence pre-partum BW (P = 0.09) and affected pre-partum BCS (P < 0.01) and rump fat (P = 0.01), with hay-fed mares decreased BW and BCS from d 0 (beginning of feeding trial or d 230 of gestation) until parturition, while mares fed concentrate gained BW and BCS (P < 0.01). Mares fed only hay consumed 2.3% BW of forage compared with 1.8% BW for concentrate-fed mares (P < 0.01). Regardless of treatment, month of gestation influenced forage intake (P < 0.06), with mares consuming less during the 10th month of gestation and more in the 11th month (1.9 and 2.2% BW, respectively). These data indicate that altered plane of nutrition of mares in late gestation influenced mare performance. Furthermore, DMI of hay was influenced by both diet and month of gestation. Continued research investigating manipulation of maternal nutrition and its effects on DMI would be beneficial to completely understand the relationships of these observations.
... Administration of markers is problematic as attaining a steady-state concentration in the rumen and, hence, faeces is influenced by dosing frequency or variable release rates from in-rumen capsules. While inert markers present in the diet have been studied, such as acid-insoluble ash or lignin, the question of how inert they really are remains (Sales 2012). The alternative approach of measuring the disappearance of DM from a grazed sward can also be used . ...
The measurement and prediction of pasture intake in extensive grazing systems, typical of northern Australia, remain elusive after 50 years of research. The aim of this paper is to review research conducted over the past 50 years, highlight advances in understanding, discuss remaining challenges and consider future developments with digital technologies. While the fundamental components of voluntary intake are well understood, their measurement is difficult, particularly in extensive grazing systems, which has limited the development of predictive models that adequately address the interplay of factors influencing intake from the bite to the landscape scale. Ongoing research by the authors is used as an example to highlight the potential application of digital technologies to overcome limitations in measurement and prediction. Digital technologies offer the opportunity for monitoring factors that control voluntary pasture intake at scale and under commercial conditions. However, our ability to ground-truth novel indices of intake remains limited without ongoing development of physical methods. This will limit the accuracy and precision of predictive models incorporating digital technologies that can be applied to the extensive grazing conditions of northern Australia. The advent of precision livestock management for extensive cattle production is essential if the industry is to remain viable in the future where production is transparent, ethically sound and environmentally defensible as well as profitable.
... Their passage rate should be identical to that of the solid phase of ingesta. The markers should accurately be detectable in faeces and should have a predictable recovery rate preferably close to 100% [18,19]. As internal markers, substances can be used that are naturally occurring in feed, enrichment or bedding materials (e.g. ...
Background
Domestic pigs have an evolutionary conserved exploratory behaviour. To comply with this requirement, the European Union aims at setting standards for appropriate enrichment materials for pigs (Council Directive 2008/120/EC). As recommended characteristics include ‘chewable’ and ‘edible’, pigs might also consume these materials (Commission Recommendation (EU) 2016/336), which are often additionally advertised to enhance lying comfort and hygienic conditions in stables. To date, a wide range of bedding, enrichment and disinfectant materials is available on the market to ensure environmental enrichment, a dry, hygienic environment or lying comfort. Previous studies revealed considerable amounts of undesirable substances in some of these materials possibly being a risk for food safety considering oral uptake by the animal. To determine interest and indicators for consumption of different types of materials by pigs during exploratory behaviour, a camera-assisted observational study with 12 female pigs (German Landrace) was conducted. We tested their preference for a disinfectant powder, peat, biochar and straw as reference material in a 4 × 6 factorial arrangement.
Results
Pigs manipulated and consumed all offered materials. However, longest manipulation time per pig was observed for biochar (63 min/day) and peat (50 min/day) (p < 0.05). Analyses of the bulk molecular-chemical composition and n-alkanes and acid insoluble ash as markers in the materials and in faeces clearly revealed the consumption of these materials by pigs.
Conclusions
Whether the consumption of considerable amounts together with certain levels of undesirable substances represents a risk for pig and consumer health could yet not be established. Future studies will address the quantitative contribution of undesirable substances by oral ingestion of bedding and enrichment materials and disinfectant powders to the daily feed ration.
... Several dietary markers have been used in equine studies, but variation in the recovery of markers has been a distinct disadvantage when using this technique (Sales, 2012). In the current study, mean cumulative faecal recoveries of AIA ranged from 113.8% to 134.7% over the four dietary treatments, with the greatest recoveries for the treatments 50H50C and 25H75C. ...
Methodological aspects of digestibility measurements were studied in four Welsh pony geldings consuming haylage-based diets with increasing proportions of a pelleted concentrate according to a 4×4 Latin square design experiment. Ponies were fed four experimental, iso-energetic (net energy (NE) basis) diets (i.e. 22 MJ NE/day) with increasing proportions of a pelleted concentrate (C) in relation to haylage (H). The absolute amounts of diet dry matter fed per day were 4.48 kg of H (100H), 3.36 and 0.73 kg of H and C (75H25C), 2.24 and 1.45 kg of H and C (50H50C) and 1.12 and 2.17 kg of H and C (25H75C). Diets were supplemented with minerals, vitamins and TiO 2 (3.7 g Ti/day). Voluntary voided faeces were quantitatively collected daily during 10 consecutive days and analysed for moisture, ash, ADL, acid-insoluble ash (AIA) and Ti. A minimum faeces collection period of 6 consecutive days, along with a 14-day period to adapt the animals to the diets and become accustomed to the collection procedure, is recommended to obtain accurate estimations on dry matter digestibility and organic matter digestibility (OMD) in equids fed haylage-based diets supplemented with concentrate. In addition, the recovery of AIA, ADL and Ti was determined and evaluated. Mean faecal recovery over 10 consecutive days across diets for AIA, ADL and Ti was 124.9% (SEM 2.9), 108.7% (SEM 2.0) and 97.5% (SEM 0.9), respectively. Cumulative faecal recovery of AIA significantly differed between treatments, indicating that AIA is inadequate to estimate the OMD in equines. In addition, evaluation of the CV of mean cumulative faecal recoveries obtained by AIA, ADL and Ti showed greater variations in faecal excretion of AIA (9.1) and ADL (7.4) than Ti (3.7). The accuracy of prediction of OMD was higher with the use of Ti than ADL. The use of Ti is preferred as a marker in digestibility trials in equines fed haylage-based diets supplemented with increasing amounts of pelleted concentrate.
... Although our digestibility coefficients of DM and OM determined in weanlings and in yearlings were slightly lower than those previously reported by Earing et al. (2010 and using the total faecal collection method, our digestibility values of NDF were higher (+10% and +6% points, respectively). This high value of NDF digestibility coefficient appeared inconsistent with previous results because using ADL as internal marker normally leads to underestimation of the digestibility values compared with total faecal collection (Goachet et al., 2009;Sales, 2012). The hay we used in this study contained 34.8% to 36.4% ADF, whereas ADF content of forage used in comparable studies ranged from 43.9% (Earing et al., 2013) to 38.0% (Earing et al., 2010). ...
Total tract apparent digestibility of dietary fibrous components and parameters of the faecal digestive ecosystem were compared at immediate and late post-weaning periods using five foals. The foals were abruptly weaned (day 0) from their mares at 6 months of age. Immediately (day 0 to day 14) and later (day 131 to day 194) after weaning, foals received the same basal diet consisting of hay and pellets. Pellets were fed at 0.36% BW. Hay was offered ad libitum and corresponded to 120% of the average voluntary hay intake measured individually during the immediate (days 1 to 4) and late (days 180 to 183) post-weaning periods. Total feed intake was measured during the two post-weaning periods (from days 7 to 10 and from days 187 to 190). Total tract apparent digestibility of DM, organic matter (OM), NDF and ADF was assessed using a 4-day partial collection of faeces (from days 8 to 11 and from days 188 to 191). Major bacterial groups in faeces, Fibrobacter succinogenes, DM, pH and volatile fatty acids were quantified at days -1, 1, 3, 7, 14 and 180. During the post-weaning period, minor changes were observed in the composition and activity of the faecal microbiota. The amylolytic count in faeces decreased immediately after weaning (between days 1 and 7) (P<0.05). Later (from days 14 to 180), the molar proportion of propionate decreased (P=0.03). The limited alteration seen in the hindgut ecosystem was probably due to the fact that the foals had undergone a gradual dietary transition from milk to solid feed before weaning. Such conclusions have also been reported in other animal species. Between the immediate and late post-weaning periods, the average daily feed intake and the digestibility coefficients of DM, OM, NDF and ADF increased (P<0.05). These results could suggest an increase in the fibre-degrading capacity of foals after weaning.
... The present AFR were in the range given by Sales (2012) for plant alkanes. According to Sales (2012), AFR of alkanes was gener- ally high but not consistently complete. Incomplete AFR may be explained by the partial absorption of alkane molecules in the small intestine (Kolattukudy & Hankin 1966;Mayes et al. 1988) and probably not by microbial fermentation ( Keli et al. 2008), as di- gestion does not occur over the time of passage. ...
SUMMARY In horses, the quantity of faeces and the faecal concentrations of plant and synthetic alkanes are inconsistent throughout the day. The estimation of feed intake and digestibility can additionally be limited by irregular and incomplete faecal recovery of alkanes that are used as dietary markers. The correction of alkane concentrations minimizes the bias of estimates, but requires the determination of faeces quantity by total collection. However, in consideration of the dynamics of alkane concentrations in faeces, sampling at selected timeframes throughout a day may be useful in avoiding such correction. Five adult horses were fed a hay-based diet offered three times a day in equal amounts. Horses received a bolus with similar quantities of n -octacosane (C28), n -dotriacontane (C32) and n -hexatriacontane (C36) synthetic alkanes twice a day. Total faeces were quantified over 3 consecutive days. Dry matter intake (DMI), output (DMO) and digestibility (DMD) were determined from the total collection trial and additionally estimated for each of 12 equal timeframes throughout the day. The diurnal patterns of the single faeces quantity (SFQ) and faecal alkane concentrations were similar between horses and were repeated from day to day. The intra-day dynamic of SFQ was pronounced. The dynamic of the faecal concentration was much more pronounced when the alkane was administered twice instead of three times a day. The faecal recovery of alkanes that has been calculated from the total collection trial ranged from 82 ± 4·1% for C36 to 108 ± 11·1% for C28. Measured DMI was 12·0 kg/day, measured DMO was 5·9 kg/day and measured DMD was 0·51. Reliable estimates were obtained for DMI with 12·3 ± 0·79 kg/day for the combination of n -nonacosane (C29) and C28 and 12·1 ± 1·01 kg/day for the combination of n -tritriacontane (C33) and C28 at 2 h after administration, and 12·1 ± 0·96 kg/day for the combination of n -hentriacontane (C31) and C32 at 2 h prior to the morning meal, which included the first bolus administration. When calculated from DMO and DMD, DMI was 12·2 ± 0·89 kg/day for C29 and 12 ± 1·0 kg/day for C33 between 5 and 6 h after the morning meal. Estimates of DMD were unbiased between the 3rd and 4th hour after the morning meal with 0·52 ± 0·014 for C29 and 0·51 ± 0·021 for C33, respectively. The DMO was 5·7 ± 0·34 kg/day and 6·1 ± 0·43 kg/day when estimated 3–4 h after the 2nd meal, or prior to the 2nd bolus administration, using the product of SFQ and the daily defecation frequency or the synthetic alkanes, respectively. Knowledge of defecation dynamics might be helpful for simplifying experimental trials. They specifically followed intake dynamics, which can prospectively be used to select sampling timeframes. Based upon current results, a selection of two to three spot samples of faeces that are evenly distributed between 2 h before and 6 h after the morning meal, which was the time of bolus administration, allows for the greatest reliability. Defecation dynamics are probably less influenced by ration/bolus type, rate of exercise, or gut peristalsis, which nevertheless can result in individual shifts of optimal timeframes.
... In the current experiment, the recovery rate of lignin in feces was %. On the other hand, fecal recovery is reported to be more reliable when Acid Insoluble Ash (AIA) was used as an internal marker (Sales, 2012;De Marco et al., 2012). However, digestibility coefficients determined in competitively trained Arab horses, employing naturally occurring markers such as lignin and AIA, turned out to be overestimated in comparison with the total fecal collection when diets consisted of forage and concentrates (Goachet et al., 2009). ...
In this experiment, sixteen Turkmen horses with average weights of 430±46 kg and age 7±3 years were used. Four feeding frequencies of 2, 4, 6, and 8 meals per day were used for a period of 28 days. Data were statistically analyzed based on a completely randomized design, and the results showed that increased feeding frequency led to more stable serum glucose levels throughout the day and an increase in the digestibility of nutrients (P< 0.05). However, ether extract digestibility was not influenced by feeding frequency. Means of chewing and swallowing (per kg DM) of alfalfa were not influenced by feeding frequency. Also, the chewing and swallowing rates of concentrate for the treatment of 2 meals per day increased (P< 0.05). By increasing the feeding frequency, alfalfa intake decreased, but duration of forage intake increased in the treatment of 8 meals per day (P< 0.05). In contrast, by increasing the feeding frequency, concentrate intake was increased, but duration of concentrate intake was decreased in the treatment of 8 meals per day (P< 0.05). In conclusion, feeding 2 times per day more often resulted in lower digestibility of different nutrients and less steady-state level of serum glucose than other feeding frequencies.
... Digestibility markers may be considered an attractive alternative for TFC (Kotb and Luckey, 1972). Commonly used digestibility markers in equines are Cr 2 O 3 , AIA, and ADL (Sales, 2012), although the use of Cr 2 O 3 is decreasing due to health concerns (Myers et al., 2006). Fecal recovery (% of intake) of (Miraglia et al., 1999;Bergero et al., 2005), with recovery of AIA frequently reported to be greater than 100% (Goachet et al., 2009;Agazzi et al., 2011). ...
Methodological aspects of digestibility measurements of feedstuffs for equines were studied in four Welsh pony geldings consuming four grass-hay diets in a 4 × 4 Latin square design. Diets contained either a low (L), medium (M), high (H), or very high (VH) ADF content (264, 314, 375, or 396 g·kg DM, respectively). Diets were supplemented with minerals, vitamins, and TiO (3.9 g Ti·d). Daily feces excreted were collected quantitatively over 10 consecutive days and analyzed for moisture, ash, ADL, AIA, and titanium (Ti). Minimum duration of total fecal collection (TFC) required for an accurate estimation of apparent organic matter digestibility (OMD) of grass hay was assessed. Based on literature and the calculated cumulative OMD assessed over 10 consecutive days of TFC, a minimum duration of at least 5 consecutive days of fecal collection is recommended for accurate estimation of dry matter digestibility (DMD) and OMD in ponies. The 5-d collection should be preceded by a 14-d adaptation period to allow the animals to adapt to the diets and become accustomed to the collection procedures. Mean fecal recovery over 10 d across diets for ADL, AIA, and Ti was 93.1% (SE 1.9), 98.9% (SE 5.5), and 97.1% (SE 1.8), respectively. Evaluation of CV of mean fecal recoveries obtained by ADL, AIA, and Ti showed that variation in fecal Ti (6.8) and ADL excretion (7.0) was relatively low compared to AIA (12.3). In conclusion, the use of internal ADL and externally supplemented Ti are preferred as markers to be used in digestibility trials in equine fed grass-hay diets.
... Lignin was rejected as a reliable marker to calculate digestibility because the actual value was greatly underestimated, probably because of the lack of recovery in feces (Miraglia et al., 1999). This is also consistent with recent findings by Sales (2012). In that study, a meta-analysis of independent experiments showed that digestibility coefficients of forage-only diets were similarly estimated by AIA and total collection whereas acid detergent lignin resulted in lower apparent digestibility coefficients with both forage-only and forage and concentrate diets. ...
This study examined the P balance and fecal P losses in growing Standardbred horses in training fed a forage-only diet with or without P supplementation, and assessed the magnitude and proportion of the soluble, inorganic P (Pi) fraction in feces. Fourteen Standardbred horses (age, 20.0 ± 0.3 mo) adapted to ad libitum intake of grass forage containing 0.25% P were used in a cross-over experiment investigating 2 dietary treatments with (high-P) and without (low-P) mineral supplementation for 6 d. Daily feed intake and refusals were weighed. Spot samples of feces were collected twice daily on d 4 to 6 and analyzed for total P and Pi. Acid-insoluble ash (AIA) was used as a marker for total fecal output. Spot samples of urine were collected once on d 4 to 6 and analyzed for P and creatinine. Daily P intake was greater (P < 0.001) for the high-P diet (32.0 ± 0.6 g) than the low-P diet (17.5 ± 0.6 g), and the individual intake ranged from 13.3 to 38.4 g/d. Total fecal excretion of P was also greater (P < 0.001) for the high-P diet (30.3 ± 0.8 g/d) than the low-P diet (17.0 ± 0.8 g/d), while excretion in urine was less than 0.2 g/d on both diets. Using simple regression analysis, fecal endogenous P losses were estimated to be less than 10 mg/kg BW. Phosphorus retention was 1.6 ± 0.6 and 0.3 ± 0.6 g/d on the high- and low-P diets, respectively, but only that for the high-P diet was greater (P < 0.05) than 0 g/d. The proportion of Pi of total fecal P excretion was 100 ± 3% for the high-P diet and 87 ± 3% for the low-P diet (P = 0.005) and Pi increased linearly with P intake (Y = 1.10x - 4.44; r2 = 0.91; CV = 9.9%; P < 0.001). In conclusion, on this forage-only diet significant retention of P occurred at a daily P intake of 7.1 g/100 kg BW. Phosphorus was mainly excreted in feces and both total fecal P and Pi excretion had a strong relationship to P intake. More than 80% of total P appeared to be soluble. Fecal endogenous P losses were similar to those described previously in growing horses.
Knowledge of endogenous nutrient losses is important when estimating the nutrient requirements of animals. It has been suggested that faecal endogenous phosphorus (P) losses differ between growing and adult horses, but studies on foals are scarce. In addition, studies on foals on forage‐only diets with different P contents are lacking. Thus this study: (1) assessed faecal endogenous P losses in foals fed a grass haylage‐only diet close to or below estimated P requirements; (2) evaluated use of serum cross‐linked carboxyterminal telopeptides of type‐I collagen (CTx) as a marker of bone resorption secondary to low‐P intake; and (3) examined whether analysis of faecal P concentration on a dry matter (DM) basis could be used as an indicator of P intake. Six foals were fed three grass haylages (fertilised to contain different amounts of P: 1.9, 2.1, 3.0 g/kg DM) for 17‐day periods in a Latin square design. Total collection of feaces was performed by the end of each period. Faecal endogenous P losses were estimated using linear regression analysis. There was no difference in the concentration of CTx in plasma between diets in samples collected on the last day of each period. A correlation was found (y = 0.64x − 1.51; r2 = 0.75, p < 0.0001) between P intake and faecal P content, but regression analysis indicated that underestimation as well as overestimation of intake is likely if faecal P content is used to assess intake. It was concluded that faecal endogenous P losses in foals are low, probably no higher than in adult horses. It was also concluded that plasma CTx cannot be used to assess short‐term low‐P intake in foals and that faecal P content cannot be used to assess differences in P intake, at least not when P intake is close to or below estimated P requirements.
The objectives of this study were to determine the effects of dietary prebiotic fructooligosaccharides (FOS) from inulin and Enterococcus faecium on nutrient digestibility, fecal pH, and some blood parameters. In this experiment, twelve adult Kurdish horses with average bogy weight of 416 ± 43.3 kg and age averaging 6 ± 1.8 yr were used in a replicated 4 × 4 Latin Square experiment with a 2 × 2 factorial design during 4 periods of 28 days, including 21 days for dietary adaptation and 7 days for sampling. Horses were offered 1 of 4 treatments: (1) no FOS or 2.5 × 10¹¹ colony forming units (CFU) of Enterococcus faecium supplementation (Con), (2) 10 g of FOS without Enterococcus faecium supplementation (Pre), (3) 10 g of Enterococcus faecium without FOS supplementation (Pro), and (4) 10 g of FOS plus 10 g of Enterococcus faecium supplementation (Mix). Results showed that fecal pH decreased in horses fed Pre or Pro treatments compared with those not supplemented (P < 0.05). Also, triglyceride and cholesterol decreased when Pre was added to the diets (P < 0.05). The concentration of triglyceride and cholesterol decreased in horses fed the Mix and Pro diets. Pre × Pro supplementation interactions were significant for high-density lipoprotein (HDL) concentration and tended to be significant for low-density lipoprotein (LDL) concentration, and horses fed the Mix treatment had the greatest and the lowest concentration of HDL and LDL, respectively (P < 0.01). The IgM concentration was greater in horses fed Pre or Pro compared with those not supplemented (P < 0.05). The treatments had no effect on IgA, IgG or liver enzymes concentration. Moreover, results indicated that FOS and Enterococcus faecium adding may interact to affect blood parameters, but did not affect nutrient digestibility under our experimental conditions, therefore further researches with higher supplementary doses are warranted.
This study was conducted to determine the fecal recovery rate of n-alkanes and compare the precision and accuracy of the n-alkane technique and the conventional total fecal collection method in estimating the apparent nutrient digestibility of mixed hay diets fed to horses. Six castrated male adult horses (361 ± 12 kg body weight) were fed diets composed of different proportions of Tifton 85 bermudagrass (Cynodon dactylon) hay and alfalfa (Medicago sativa) hay in a 6 × 6 Latin square design. Treatments were as follows: T100, 100% Tifton hay; T80, 80% Tifton hay and 20% alfalfa hay; T60, 60% Tifton hay and 40% alfalfa hay; T40, 40% Tifton hay and 60% alfalfa hay; T20, 20% Tifton hay and 80% alfalfa hay; and T0, 100% alfalfa hay. The n-alkane detected at the greatest (P < 0.05) mean concentration in feed was n-hexatriacontane (C36H74), followed by n-hexacosane (C26H54), n-heptacosane (C27H56), n-nonacosane (C29H60), n-hentriacontane (C31H64), n-tritriacontane (C33H68), and n-pentatriacontane (C35H72). A strong correlation (r = 0.91, P < 0.001) was found between carbon chain length and fecal recovery. The n-Hentriacontane, n-tritriacontane, n-pentatriacontane, and n-hexatriacontane had the greatest fecal recovery (mean = 0.91, P < 0.05) and were therefore used to estimate nutrient digestibility. None of the n-alkanes provided consistent results. Fecal recovery was incomplete, and fecal recovery rates above 100% were obtained regardless of the proportion of Tifton and alfalfa hay in diets. Dry matter, crude protein, neutral detergent fiber, acid detergent fiber, and mineral matter digestibility estimated using n-alkanes differed (P < 0.05) from digestibility values obtained by the reference method (total fecal collection). The simplest explanation for these results would be that horses preferred one type of hay over the other and had an uneven intake of each diet. Because Tifton and alfalfa hay differ greatly in composition, their uneven intake makes estimation of nutrient digestibility by fecal recovery of n-alkanes unreliable. Even after correction for fecal recovery, n-alkanes were inaccurate markers of nutrient digestibility.
Twelve Turkmen horses with an average weight of 425 ± 4 kg and age of 6 ±1.8 years were used in the experiment. In all rations, the ratio of concentrate to forage was 65:35. Corn and oats, barley and wheat and barley with oats were used as a source of starch in 1, 2 and 3 ration respectively. Lignin and acid insoluble ash (AIA) were used as internal markers to determine the nutrient digestibility. Using lignin or AIA methods, the digestibility of dry matter, organic matter, ether extract and digestible energy were significantly increased in treatment 1 (P <0.05). Digestion coefficients of ash-free neutral detergent fibre, ash-free acid detergent fibre, cellulose and hemicellulose were increased for treatments 1 and 3 (P <0.05). The digestion coefficients obtained by using both markers there was not significantly different (P >0.05) except in the case of ADFom and cellulose in diet 1 and ADFom, hemicellulose and cellulose in diet 2. However, the recovery rate of AIA and lignin were 106% and 91% respectively, the recovery rates of these markers are highly correlated with the total faecal collection method. In general, the inclusion of corn and oats in the ration has led to improve the nutrients digestibility compared to those without corn and oats.
The use of markers to determine digestibility of feeds overcomes the need to make exact measurements of feed intake and total faecal output in the traditional total collection method. Although several external and internal markers have been evaluated through the years, a marker that satisfies all the criteria of an ideal marker is yet to be found. This review describes the use of acid-insoluble ash (AIA) as a marker in digestibility studies. Three variations of the original gravimetrically method, based on burning of organic matter in the sample by ashing, boiling in hydrochloric acid, and re-ashing, are commonly used to determine AIA contents. A summary of the recovery rate of AIA determined in several species with different diets presented a mean around 100 %. Of 45 studies where the AIA method was compared to the total collection method to determine digestibility of feeds in different species, 26 showed similar results, nine an underestimation by the AIA method, and 10 an overestimation. No significant diurnal or daily variation in faecal AIA has been found in poultry, sheep, pigs, or cattle. Analytical error could be described as the most common reason for failure when using AIA as marker, especially in feeds with low natural AIA content. It is concluded that AIA presents a reliable marker with several advantages that could be successfully utilize to determine faecal digestibility in animal species under certain circumstances, and with the application of some precautions.
The accuracy, precision, and robustness of the cutin, acid detergent lignin (ADL), chromic oxide, and total feces collection to estimate the apparent digestibility of the organic matter of diets for equines were evaluated. For such, four male horses were used. They averaged 10 month-old and 197kg (170 to 216kg). The experiment was carried out in four periods with duration of eleven days each, being the first eight for adaptation to the diets and the three subsequent to obtain the results. The experimental design was a 4x4 latin square. The balance of the coefficients of digestibility of the organic matter for the markers was made by means of the bias. The accuracy and the precision were determined by the comparison of the predicted data with the observed ones, and the robustness by the comparison of the bias with other studied factors. The cutin did not show efficient as an internal marker, therefore it overestimated the apparent digestibility of the organic matter and showed to be less accurate and precise. The chromic oxide presented low fecal recovery and underestimated the apparent digestibility of the organic matter, even though it was more precise. The acid detergent lignin was the marker that got the best fecal recovery and was the most accurate, therefore, the most efficient marker.
Four crosbred mares averaging six years and 400 kg BW were allotted to latin square design. The objective was to evaluate the nutritive values and kinetics of digestive tract of dry grains or high-moisture grains silage of sorghum with low and high tannin in the feeding of equines. The treatments consisted of diets containing two hybrids of sorghum grains (low and high tannin) and to methods of conservation (dry an ensiled). Diets were formulated to be isoprotein (12.4% CP) with daily DM intake established in 1.5% BW (hay to concentrate ratio of 50:50). The parameters of gastrointestinal transit were: k1 (passage rate in the large intestine); k2 (passage rate in the stomach); TT (transit time); MRT (mean retention time) and TMRT (mean total retention time). No effect treatment was observed for aCD of DM and starch, whose means values were 54.04 and 98.91%, respectively. A benefic effect of the ensiling of high tannin and high-moisture sorghum grains on digestibility of CP and NDF. The aCD of CP and NDF for diets containing high tannin and dry grains of sorghum was of 49.76% and 32.20% and for diets containing of low tannin sorghum grains (dry and ensiled) and high tannin and high-moisture sorghum grains was of 65.63 and 43.32%, respectively. There was effect only of the conservation method of the sorghum grains (dry versus ensiled) on the TMR, where the value for the diets with silages of high-moisture grains and dry grains was, respectively, of 40.08 and 37.9h. In conclusion, high tannin sorghum dry grains should not be used as the main grain in energetic concentrates for horses, because they reduced the digestion of protein and fiber.
Cinco éguas mestiças (idade e peso corporal médios de seis anos e 480 kg PV) foram distribuídas em delineamento experimental em quadrado latino para se e avaliar a utilização de dietas contendo grãos de triticale (secos ou ensilados) em substituição ao milho na alimentação de eqüinos, por meio do ensaio de avaliação do trânsito gastrintestinal e da digestibilidade. Os tratamentos consistiram de três níveis de grãos de triticale em substituição aos grãos de milho (0, 50 e 100%) e duas formas de conservação dos grãos de triticale (secos ou ensilados). As dietas foram isoprotéicas (12,5% PB), com ingestão diária de MS pelos animais de 2,0% PV (relação volumoso : concentrado de 50:50). Os coeficientes de digestibilidade aparente (CDa) da MS, MO, PB e FDN foram determinados indiretamente. Os parâmetros de trânsito gastrintestinal avaliados foram: k1 (taxa de passagem pelo intestino grosso), k2 (taxa de passagem pelo estômago), TT (tempo de trânsito), TMR (tempo médio de retenção) e TMRT (tempo médio de retenção total). Não houve diferença para os CDa da MS, MO, PB e FDN entre as dietas experimentais, observando-se valores médios de 64,31; 65,14; 74,13 e 57,25%, respectivamente. Considerando-se a cinética das fases sólida e líquida, notou-se efeito somente para k2 na fase sólida da digesta, cujo valor nas rações contendo 100% de triticale (seco ou ensilado) foi de 19,63%/h e na dieta controle (0% de triticale), de 23,72%/h. Observou-se efeito linear crescente para o TT na fase sólida da digesta, com a elevação dos níveis de substituição dos grãos de milho pelos grãos de triticale ensilados. Concluiu-se que os concentrados para eqüinos podem ser formulados com grãos de triticale secos ou ensilados em substituição total ao milho. A inclusão de grãos de triticale na alimentação desta espécie animal promoveu trânsito lento da fase sólida da digesta.
The accuracy, precision, and robustness of the cutin, acid detergent lignin (ADL), chromic oxide, and total feces collection to estimate the apparent digestibility of the organic matter of diets for equines were evaluated. For such, four male horses were used. They averaged 10 month-old and 197kg (170 to 216kg). The experiment was carried out in four periods with duration of eleven days each, being the first eight for adaptation to the diets and the three subsequent to obtain the results. The experimental design was a 4x4 latin square. The balance of the coefficients of digestibility of the organic matter for the markers was made by means of the bias. The accuracy and the precision were determined by the comparison of the predicted data with the observed ones, and the robustness by the comparison of the bias with other studied factors. The cutin did not show efficient as an internal marker, therefore it overestimated the apparent digestibility of the organic matter and showed to be less accurate and precise. The chromic oxide presented low fecal recovery and underestimated the apparent digestibility of the organic matter, even though it was more precise. The acid detergent lignin was the marker that got the best fecal recovery and was the most accurate, therefore, the most efficient marker.
Avaliou-se a eficiência da lignina purificada e enriquecida (Lipe®) como indicador externo para estimar a digestibilidade dos nutrientes de dietas em eqüinos em comparação aos métodos de coleta total de fezes e do indicador óxido crômico. Foram utilizadas seis potras Mangalarga Marchador, com média de 2 anos de idade e 345 kg de peso vivo, alimentadas com feno de alfafa e concentrado comercial na proporção de 50:50, para ingestão de matéria seca de 3,1%PV, e sal mineral. O experimento teve duração de 29 dias, de modo que os 24 dias iniciais foram destinados à adaptação dos animais à dieta e às instalações e os cinco finais para coleta total das fezes. Utilizou-se delineamento em blocos casualizados, no qual cada animal constituiu um bloco e cada método de determinação da digestibilidade, um tratamento. Os cálculos de produção fecal e digestibilidade de cada nutriente foram feitos utilizando-se os indicadores e a taxa de recuperação fecal de cada nutriente. Os coeficientes de digestibilidade dos nutrientes obtidos utilizando-se o óxido crômico foram superiores aos da coleta total e Lipe®. Os resultados obtidos com Lipe® foram similares aos determinados por coleta total. O método do óxido crômico é inadequado, enquanto o Lipe® é eficiente para estimar a digestibilidade de nutrientes da dieta em eqüinos.
Five crossbred mares (averaging six years and 480 kg BW) were allotted to latin square experimental design. The objective was to evaluate the utilization of diets containing triticale grains (dry or ensiled) in substitution of corn in the feeding of equine feeding, using assay of gastrointestinal transit and digestibility. The treatments consisted of three levels of triticale grains in substitution of corn grains (0, 50 and 100%), and two conservation forms of triticale grains (dry or ensiled). The diets were isoproteic (12.5% CP), with aDM intake by the animals of 2,0% BW (forage to concentrate 50:50). The apparent coefficients of digestibility (aCD) of the DM, OM, CP and NDF were determined by indirect method. The parameters of the gastrointestinal transit were: k1 (passage rate in the large intestine); k2 (passage rate in the stomach); TT (transit time); TMR (mean time retention) and TMRT (mean total retention time). No difference was observed for aCD of DM, OM, CP and NDF among the experimental diets, with means values of 64.31, 65.14, 74.13 and 57.25%, respectively. Considering the kinetics of the solid and liquid phases, it was found effect only to the k2 for the solid phase of digesta, whose values in the diets containing 100% triticale (dry or ensiled) was of 19.63%/h and the control diet of 23.72%/h. An increasing linear effect was observed for TT in the solid phase of digesta, as the levels of substitution of corn grain by ensiled triticale grain increased. In conclusion, the concentrates for equines may be formulated with dry or ensiled triticale grains in total substitution of corn grains. The inclusion of the triticale grains in the equine feeding promoted slow transit of the digesta.
Quatro éguas sem raça definida (idade e peso corporal médios de seis anos e 400 kg) foram distribuídas em delineamento experimental em quadrado latino para se avaliar o valor nutritivo e o estudo cinético do trato digestivo de grãos secos ou ensilados de sorgo de baixo e alto conteúdos de tanino na alimentação de eqüinos. Os tratamentos consistiram de dietas contendo dois híbridos de grãos de sorgo (baixo e alto níveis de tanino) e dois métodos de conservação (secos e ensilados). As dietas foram isoprotéicas (12,4% PB), com ingestão diária de MS estabelecida em 1,5% PV (relação feno:concentrado de 50: 50). Os parâmetros de trânsito gastrintestinal avaliados foram: k1 (taxa de passagem pelo intestino grosso), k2 (taxa de passagem pelo estômago), TT (tempo de trânsito), TMR (tempo médio de retenção) e TMRT (tempo médio de retenção total). Os tratamentos não afetaram os coeficientes de digestibilidade aparente (CDa) da MS e do amido, cujos valores médios foram 54,04 e 98,91%, respectivamente. Verificou-se efeito benéfico da ensilagem dos grãos de sorgo de alto conteúdo de tanino sobre a digestibilidade da PB e FDN. A CDa da PB e FDN para a dieta contendo grãos secos de sorgo de alto teor de tanino foi de 49,76 e 32,20% e para as dietas com grãos de sorgo de baixo conteúdo de tanino (seco ou ensilado) e grãos ensilados de sorgo de alto teor de tanino foi de 65,63 e 43,32%, respectivamente. Obteve-se somente efeito do método de conservação dos grãos de sorgo (secos vs ensilados) sobre o TMR, em que o valor para as dietas com silagens de grãos ensilados e secos foi, respectivamente, de 40,08 e 37,9h. Concluiu-se que os grãos de sorgo secos de alto teor de tanino não devem ser usados como principal grão energético nos concentrados para eqüinos, por diminuírem a digestibilidade da proteína e fibra.
This research aimed to compare dry matter digestibility coefficient (DMDC) of horse diets by total feces collection (TC) and internal markers, indigestible cellulose (iCEL), indigestible acid detergent fiber (iADF) and acid insoluble ash (AIA). Sixteen adult mares of Mangalarga Marchador breed averaging from 3.5 to 18.4 years and 394.80 ± 46.22 kg were assigned to a randomized block design with four replicates. Diets were formulated to be isoprotein and isoenergetic and composed of coastcross hay (Cynodon dactylon cv. Coast cross) and 60:40 concentrate. Evaluation of DMDC estimated by the markers was performed by a model considering the bias, i.e., the difference between DMDC estimated by marker and by TC. No effect of animal age on DMDC. Among the evaluated markers, iADF was more accurate. Regarding precision, no differences were observed among markers. Concerning robustness, dry matter intake and DMDC affected iADF and iCEL estimates, whereas only DMDC affected AIA estimate. Markers recoveries were 98.49, 94.49 and 144.5% for iADF, iCEL e AIA, respectively and, only iADF recovery did not differ from 100%. Markers ranking concerning accuracy, precision and robustness were as follows: iADF, AIA and iCEL.
The digestibility of nutrients and nutritive values of cereals (barley, corn, naked oat, oat and quinor), oil meals (cotton seed meal, linseed meal and soybean meal), brans (defatted rice bran, wheat bran and wheat bran with flour) and hays (Italian ryegrass and orchardgrass) were determined by the chromic oxide index method in adult male Thoroughbreds. Because the nutritive values of feedstuffs are affected by the processing and producing countries, the effect of processing of feedstuffs, flaking corn, expanding quinor, extruding soybean meal, and chopping hays and countries producing oats were examined. The digestibility of CP in oats was higher, but that of gross energy was lower than that of other cereals. Among oil meals and brans, the digestibility of all nutrients in soybean meal and wheat bran with flour was higher. When long hays were supplied, the digestibility of all nutrients in Italian ryegrass was lower, but when chopped hays were supplied, that in Italian ryegrass hay was similar to that in orchardgrass hay. By flaking corn and expanding quinor, the digestibility of all nutrients except ether extract in corn and CP in quinor was improved. By extruding soybean meal, the digestibility of nitrogen free extract was improved, but the digestibility of CP was not improved. By chopping hays, the digestibility of all nutrients in Italian ryegrass hay was improved, but the digestibility in orchardgrass hay was not affected. Australian oat contained the highest ether extracts and gross energy. Compared to Australian oat, Canadian oat contained the same amount of CP and lower crude fiber, and Hokkaido oat contained lower CP.
In order to confirm the usefulness of chromic oxide as an indicator in the determination of digestibility of nutrients in feeds, two experiments were conducted on 4 male thoroughbreds 5 to 9 years old. In Experiment 1, in order to determine the timing of sampling, the time course of fecal chromic oxide after changing feeds and daily variation of the fecal concentration of chromic oxide were observed. Horses were given Feeds 1 and 2 containing 0.2% chromic oxide for 7 days. Feces were collected infeces bags. In Experiment 2, horses were supplied Feeds 1 and 2 for 10 days and feces were collected in the same way as in Experiment 1 for the total feces collection method and about 200 g of feces at 7:00 and 19:00 for the chromic oxide index method for the last 4 days. Fecal contents of chromic oxide reached a plateau at 48 hr after feeding Feeds 1 and 2 containing chromic oxide and remained constant after that. The digestibility of crude protein, ether extract, nitrogen free extract and crude fiber determined by the chromic oxide index method agreed well with that by the total feces collection method in both feeds. Because the timing of excretion of feces was relatively constant in the morning and evening feeding, it was easy to collect feces directly from the anus with a bucket.
Effect of exercise on apparent energy digestibility of timothy and alfalfa hay were estimated in two-year-old horses. Intensity of the exercise was equal to 80% heart rate max (180 beats/ min) for 5 min between warm-up and cool-down. Timothy and alfalfa hay intakes in the exercise and rest periods did not differ significantly. The apparent energy digestibility and digestibility energy (DE) of timothy hay in exercised horses were significantly lower than in rested horses but there were no significant differences between exercised and rested horses in the apparent energy digestibility or DE of alfalfa hay. These results suggested that exercise in this study decreased energy digestibility of timothy hay and it seemed that the effect of exercise on the energy digestibility of hay was altered by the composition of hay.
Six mature Quaner Horse-type geldings were used in a replicated 3 x 3 Latin square experiment to determine the effects of adding 5 or 10% feed-grade rendered animal fat to the concentrate diet fed to performance horses. The experiment was conducted over a 14-day pre-trial period to acquaint horses to the experimental apparatus, a 28-day conditioning period and 3 diet treatment periods of 21 days, each conducted in a Latin square amingement The horses were exercised on a dirt track and diet effects were evaluated during and following a submaximal exercise test (S'ET) on an equine treadmill. Physiological responses to the SET were determined following each experimental period. Relative to the control, the horses required 21 % and 25% less of the concentrate feed (P<.05), containing 5% and 10% added fat, respectively. There was an increase (P<.05) in muscle glycogen concentration as fat was added to the diet. There were no differences due to feeding fat in nutrient digestibility or in oxygen consumption, ventilatory capacity, respiracory quotient, heart rate,
blood lactate, or blood pH during the SET. However, there was an overall decrease (P<.05) in blood glucose and total ljpid
concentration, when 10% fat was added to the concentrate diet.
Apart from elimination of errors in obtaining exact measurements of feed intake and total faeces output in the traditional total collection method, the use of markers to determine nutrient digestibility of feeds in animal species would fit into animal welfare considerations. The external marker chromic oxide has been the prominent marker in the 1960s to evaluate metabolizable energy content of feeds for poultry. A preliminary feeding period of 5 days and collection of a sample representing day and night excreta over a 24 hour period have been suggested as protocol to get reliable results with the use of chromic oxide as marker. However, difficulty in obtaining repeatability between laboratories because of the analytical assay for chromic oxide, variability in results, incomplete and inconsistent recovery in excreta, and hazardous possibilities, resulted in replacement of the chromic oxide marker technique with the method of total excreta collection. Although titanium dioxide, which can be analysed by an accurate and simple colourimetrical assay, has been used in several studies in poultry, only one study has evaluated this marker for recovery (98%) in excreta. The internal marker, acid-insoluble ash, which also could present an external marker when the internal content is aided with the use of siliceous substances, is gaining popularity in recent times, although most studies presented higher digestibility values with this marker in avian species than those derived through the total excreta collection method. Lack of standardisation of analytical assays could partly explain the latter phenomenon. Although crude fibre has presented recovery rates of near 100% in excreta of laying hens and turkeys, fear of possible digestion of this substance by cecal microflora has prevented the further utilisation of this substance as marker. Lignin, determined by digestion in 72% sulphuric acid, presented recovery rates of 99 and 98% in chickens and ostriches, respectively, and similar (P>0.05) results than the total collection method in partridges. The elimination of the use of markers to determine energy metabolizability and nutrient digestibility with avian species have been based on a small number of studies conducted mainly before 1965, and extrapolation of results obtained with other animal species.
SUMMARY Whole corn plant pellets (WCPP) containing 6.2% crude protein (CP) were fed to five mature horses (500 kg) and to mature rabbits as a completely pelleted total ration (with and without protein supplementation). Apparent digestibility coefficients (%) were calculated by utilizing conventional total fecal collection or the acid insoluble ash (AIA) method. Apparent digestibility coefficients utilizing the total col- lection vs AIA techniques were not different (P>.05) for dry matter (DM), crude protein (CP), acid detergent fiber (ADF), cell wall constituents (CWC), digestible energy (DE), or ash for either horses or rabbits; however, ether extract (EE) was different (P
The objectives of this research were to determine the partial and total apparent digestibilities of dry matter (DM), organic matter (OM), crude protein (CP), and neutral detergent fiber (NDF) and to evaluate the effects of periods of ileal digesta collections upon the partial digestibility of DM, OM, CP, and NDF. Two ileal-fistulated, non-castrated male equines were used. The indigestible acid detergent fiber (IADF) was used as the ileal DM flow indicator. Two methodologies for collection of ileal digesta samples were adopted. The experiment was a randomized blocks design, where blocks were the combination of each animal with each method of collection. Average total apparent digestibilities of DM, OM, CP and NDF for diet 2 (hay and concentrate) were 26.0, 18.7, 29.6 and 13.2%, superior to diet 1 which contained hay exclusively. Times of collection of ileal digesta did not influence the partial digestibility of DM, OM and NDF of diet 1. The partial digestibility of CP was influenced by the times of the collection of ileal digesta when animals were fed hay exclusively.
Organic matter (OM) digestibility of 53 feeds was estimated in horses, sheep and in vitro using rumen fluid. Feeds tested were: roughages (grass hay, fresh grass, wilted grass silage, forage maize and artificially dried roughage), compound feeds and compound feed ingredients including cereals. Technical merits of the chosen procedure for digestibility trials with horses are discussed. Horse digestibility data for forages were consistently lower than sheep data, with a variable fibre level effect. For compound feeds and compound feed ingredients horse digestibility was about comparable to sheep digestibility allowing for considerable differences between feeds. In vitro digestibility gave a reliable estimation of OM digestibility in horses for the different group of feeds. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Two assays were carried out to evaluate the precision of internal markers in relation to the total feces collection method to estimate the apparent digestibility of nutrients in diets for equines. Six adult crossbreed horses, averaging seven years old, were used. In the first assay, the values of digestibility of the nutrients of coast-cross hay using HCl-insoluble ash (AIA), acid detergent insoluble ash (ADIA) and lignin by the total feces collection method were compared. In the second assay, the digestibility of the nutrients of the combination of elephant grass and coast cross hay was compared by the two methods. A completely randomized block design was used, where each horse made up a block and the methods of digestibility determination, the treatments. In both assays, the results showed that both AIA and ADIA were efficient as internal markers to estimate the apparent digestibility of the nutrients of coast-cross hay and of the combination of elephant grass and coast-cross hay. For the horses fed coast-cross hay, the average recovery in the feces of AIA and ADIA was of 100.12 and 99.66%, respectively. For the horses fed with hay and elephant grass the recovery were 101.32 and 96.33%, respectively. The lignin was unsuitable to estimate the apparent digestibility of nutrients in the tested diets.
In a crossover experiment, eight mature Quarter Horses were exercised by simulated cutting-horse training and fed either a control concentrate (C) or a 10% fat-supplemented concentrate (F) with Bermuda grass hay in a 60:40 ratio. The experiment consisted of two 28-day experimental periods with a 28-day standardization period between treatments. Digestion trials and standardized exercise tests (SET) were conducted every 7 days during experimental periods. Dietary fat had no detrimental effect on digestion of diet constituents, and all digestion coefficients were within expected ranges. Likewise, there was no significant difference in heart rates between treatments or SET days. Plasma lactic acid concentrations did not differ (P > .05) between treatments, however, there was a decline (P < .05) with advancing SET day. When horses were fed fat, there was an increase (P < .05) in muscle glycogen storage from days 0 to 28, but there was no increase (P > .05) in muscle glycogen over time when horses were fed C. On days 7, 14, and 28, muscle glycogen utilization increased (P < .05) from day 0 when horses were fed fat but not C. Pre-exercise data were normalized such that day 0 values equaled zero, due to higher (P < .05) glycogen concentrations for C than F on day 0. Subsequently, muscle glycogen concentrations on day 28 before exercise were higher (P < .05) when horses were fed F than C. The results of this study indicate that Quarter Horses in simulated cutting-horse training can adapt to digestion of a fat-supplemented diet by day 14. However, it may take up to 28 days of adaptation to a fat-supplemented diet to observe increases in glycogen storage and use.
The aim of this article was to study the conservation quality, chemical composition, gross energy, voluntary intake, and apparent digestibility of permanent meadow haylage and hay, fed to ponies at maintenance. The forages were from the same swath and harvested at early flowering stage. The apparent digestibility of the hay and haylage, which contained about 61% neutral detergent fiber and 38% acid detergent fiber, as fed, was determined by means of two in vivo digestibility trials, each performed on six ponies, weighing, on average, about 335 ± 80 kg and 334 ± 41 kg, respectively, over a 6-day feces collection period after a previous 14-day adaptation period. The voluntary intake was measured and the digestibility coefficients were calculated for dry matter, organic matter, gross energy, crude protein, neutral detergent fiber, and acid detergent fiber, using acid-insoluble ash as the internal marker. The haylages were evaluated for dry matter, pH, alcohols, lactic acid, and monocarboxylic acid. The conservation quality of the haylage was good and its chemical composition was similar to that of hay, except for the crude protein and gross energy contents, which were higher (P < .05) as compared with those of the hay. No differences were found between the hay and haylage with regard to the voluntary intake and digestibility coefficients.
The objective of this study was to evaluate the effects of live yeast (LY) in a high-fiber diet on nutrients digestibility in mature horses. Six Italian Standardbred mares (weight: 544 ± 14 kg; age: 15.30 ± 3.9 years) in a two-period crossover design were fed a basal diet (2.5% body weight [BW]) in a 70:30 forage:concentrate ratio with (LY) or without (CTR) the administration of 4.6 × 1010 colony forming unit (CFU)/d of Saccharomyces cerevisiae (MUCL 39885). An adaptation to the diet of 14 days, and an 18-day administration phase, with fecal collection in the last 3 days were performed for each period. Yeast was top-dressed twice a day during the concentrate meal (12:30 am and 09:00 pm). Change in BW was measured at the beginning of each experimental phase and the diet adjusted accordingly, and individual feed intake was recorded daily. Concentrate samples were collected at the beginning of each confinement period and individual hay samples were obtained for each confinement day 38 hours before fecal collection. No influence of LY was observed on BW change (P = .64), feed intake (P = .48), hay intake (P = .48), or concentrate intake (P = .47). S cerevisiae supplementation improved apparent digestibility of dry matter (64.5% vs. 60.1%, P = .03), organic matter (66.1% vs. 61.6%, P = .04), neutral detergent fiber (42.5% vs. 35.9%, P = .04), and acid detergent fiber (36.5% vs. 28.0%, P = .03) with a positive trend on crude protein (P = .08). In the present study, the administration of LY to horses significantly improved the digestion of the fiber fractions of the diet.
Inconsistent results of the effects of dietary betaine supplementation on important economic carcass characteristics of finishing pigs have been reported. This has motivated a quantitative meta-analysis that accounted for variability among experiments. Through an extensive literature search data have been identified to evaluate the effects of dietary betaine supplementation on average daily feed intake (ADFI; 11 experiments, 18 comparisons), average daily gain (ADG; 13 experiments, 21 comparisons), backfat thickness (BFT; 10 experiments, 13 comparisons), dressing proportion (DP; 7 experiments, 10 comparisons), feed conversion ratio (FCR; 12 experiments, 18 comparisons), longissimus dorsi muscle area (LMA; 9 experiments, 13 comparisons), proportion carcass lean (PCL; 7 experiments, 10 comparisons) and tenth rib fat thickness (TRFT; 7 experiments, 10 comparisons). Statistical analyses included: (1) fixed and random effects models to calculate summary statistics for standardised effect sizes (Hedges's g) of the difference between control and betaine-fed pigs; (2) meta-regression to evaluate the sources of heterogeneity of responses; (3) the assessment of possible publication bias. Dietary betaine supplementation had no influence (P>0.05) on ADG. However, feed per unit of weight gain significantly decreased (mean effect size of −0.361) in betaine-fed pigs. Whereas dressing proportion was increased (mean effect size of 0.358; P
Three series of digestibility experiments with mature geldings indicated no significant differences between the 4N-HCl insoluble ash indicator and the total collection methods for determination of apparent digestible nitrogen and digestible energy. There were significant differences (P < 0.05) between animals for the insoluble ash method in two of the three trials. No significant differences were found when the number of sampling days involved was reduced from 7 to 4 days and random grab samples of feces were used for insoluble ash determinations. Random grab samples taken for 1, 2, 3 or 4 days did not give significantly different digestion coefficients using the insoluble ash indicator method. Period differences in the insoluble ash method were observed when 3-day collections during five successive periods were taken from four individual geldings by the grab method. A study with four geldings during two test periods using cotton strips as indicators showed mean rate of passage of digesta to be 70.2 h. The overall results suggest that random grab fecal samples using the 4N-HCl insoluble ash method has potential for use in the determination of digestibility coefficients for horses.
Fiber digestion was characterized in 8 yearling geldings (mean initial body weight, 341 kg) fed 4 typical diets differing in ingredient composition, with and without a commercial product that contained microbial xylanase and cellulase. The experimental design was a 4 x 4 Latin square with repeated measures in which horses were fed Coastal Bermudagrass hay at a rate of 1.5% of body weight daily (as-fed basis) plus sufficient textured sweet feed, pelleted concentrate, whole oats, or alfalfa cubes to meet National Research Council requirements for digestible energy and crude protein; enzyme status represented a within-unit repeated measures factor. Each experimental period consisted of a 10-day acclimation to dietary treatments, a 2-day fecal collection, a 7-day acclimation to exogenous enzyme administration, and another 2-day fecal collection during which enzyme was administered. Horses were introduced to successive diet treatments for 7 days between experimental periods, and feed allowance was increased as needed to ensure that horses maintained a body condition score of approximately 5. Diets were fed twice daily at 12-hour intervals, and water and plain salt were available for ad libitum consumption. Enzyme product was administered orally as a molasses slurry via syringe at time of feeding. Fecal samples were collected with rectal grab at 8-hour intervals advanced by 4 hours on the second day of collection, and apparent digestibility coefficients for plant cell wall constituents were calculated with reference to acid-insoluble ash concentrations in feed and fecal dry matter (DM). Digestibility of DM was lower (P < .05) for the alfalfa-based diet than for other diets (62.0% versus 69.4%), and a diet x enzyme interaction was observed such that digestibility of DM in the alfalfa-based diet was decreased (P < .10) and in the sweet feed-based diet was increased (P < .10) when enzyme was administered. Digestibility of neutral detergent fiber tended to be lower (P < .12) for the alfalfa-based diet than for other diets (53.9% versus 60.0%), and a diet x enzyme interaction was observed such that digestibility of neutral detergent fiber in the alfalfa-based diet was decreased (P < .10) and in the oats-based and sweet feed-based diets was increased (P < .10) when enzyme was administered. Digestibility coefficients for acid detergent fiber (ADF) and hemicellulose were not different among diets, but diet x enzyme interactions were observed such that digestibility of ADF in the alfalfa-based diet was decreased (P < .10) and digestibility of both ADF and hemicellulose in the oats-based and sweet feed-based diets were increased (P < .10) when enzyme was administered. Results suggest that exogenous fibrolytic enzymes have the potential to improve digestibility of plant cell wall constituents in typical graminaceous feeds fed to horses, thereby reducing the amount of feed that would be needed to meet digestible energy requirements. Further research is needed to elucidate why exogenous fibrolytic enzymes were ineffective when administered with the alfalfa-based diet and actually resulted in decreased digestibility of DM and plant cell wall constituents.
Four mature pony geldings weighing an average of 134 kg and fitted with ileal cannulas were used in a 4×4 Latin square experiment to determine the digestibility of soybean meal (SBM) protein in different segments of the equine digestive tract at various levels of protein intake. A complete basal corn-based diet was supplemented with SBM to formulate four diets with increasing crude protein. The diets, labeled A (basal), B, C and D, contained 4.9%, 9.5%, 14% and 16.5% crude protein (as fed), and provided nitrogen, per feeding, at approximately 44.8, 84.3, 123.9 and 146.3 mg/kg of body weight, respectively. Chromic oxide was fed to measure ileal flow and fecal excretion. Digestion and absorption of nitrogen was determined from changes in nitrogen: chromium ratios, and true digestion of nitrogen was computed by regression analysis. True total tract digestion of nitrogen was 95.7%. True digestibility of nitrogen in the small intestine over the range of linearity was 72.2%, while true digestibility of nitrogen reaching the large intestine was 89.8%. These data indicate that the protein in SBM was almost completely digested in the equine digestive tract. Furthermore, approximately 75% of the digestible protein was digested prececally when nitrogen intake was less than approximately 125 mg/kg of body weight per feeding.
Eighteen mares were used in a 92-day feeding trial to evaluate a complete, extruded feed for free choice feeding horses. The mares were assigned at random to one of three treatments as follows: Group A—Control—bahiagrass pasture+complete mineral free choice; Group B—Dry lot —Extruded feed + salt free choice; Group C—Stalled—Extruded feed + salt free choice. The pastured mares were on pasture 24 hours per day and had access to a complete mineral in a fiberglass mineral feeder. The mares fed in dry lot were fed only the extruded feed and salt, both of which were available to them 24 hours per day. The stalled mares were provided access to the extruded feed and salt for 22 hours per day. The other two hours they were turned out into a dry lot paddock for exercise. Fecal samples were collected from each of the mares on the extruded feed for estimation of feed digestibility. The pastured mares gained weight on pasture but lost girth, croup fat and condition score. Feed consumption by the dry lot fed mares peaked at three weeks at about 15.9 kg/animal/d and remained constant for the remainder of the trial. Feed consumption by the stalled mares peaked at 19.1 kg/animal/d but decreased to about 15.9 kg/animal/d during the second month and remained constant for the duration of the trial. Most of the stalled mares experienced some edema of the lower extremities which decreased during the last month of the experiment, probably due to increased activity when they were turned out. One of the stalled mares experienced multiple episodes of colic and was removed from the experiment. At the time of removal, the animal was consuming 22.7 kg of the extruded feed daily. The mares consuming the extruded diet gained more weight, heart girth, croup fat and condition score (P<0.05) than the pastured horses. The mares kept in stalls gained more weight and condition score than the mares fed in dry lot (P <0.05). Average daily mineral intake by groups A, B, and C were 80.2.4.7, and 11.4 g/d, respectively. Digestibilities by the two groups receiving the extruded feed were not different.
Mature ponies fitted with permanent ileal cannulas were used in two 3×3 Latin square experiments to quantify prececal, postileal and total tract digestion of N. In trial 1, corn, oats and sorghum were each fed with coastal Bermuda grass hay in 75:25 ratios. Apparent prececal digestibilities were similar (P>.05) and averaged 46.6%. By-difference procedures were employed to calculate digestibility of the cereal grain N only and apparent prececal N digestibility averaged 57.1%. In trial 2, a basal corn and hay diet was supplemented with cottonseed meal and soybean meal. Apparent total tract N digestibilities were similar (P>.05) across treatments, and prececal digestibility averaged 45.6%. By-difference calculations were used to determine digestibility of SBM and CSM N alone. Apparent prececal digestibility of SBM was 52.5% and was lower (P
Feed palatability and in vivo apparent digestibility of nutrients were compared in horses fed concentrates in which barley was, or not, partially substituted by 8% linseed oil. According to a cross-over design, three geldings and one stallion were fed at near maintenance level hay plus low or high fat diet (50/50). The last days of each 3-months sub-periods, partial faeces collections were performed and concentrate intake rate was measured to estimate the digestibility and the palatability of the diet. The inclusion of linseed oil did not affect the palatability of the diet and increased significantly (P
Passage rate through the equine gastrointestinal tract is best described by mean retention time (MRT). Transit times of digesta differ greatly between the different parts of the gastrointestinal tract. Passage through the stomach and small intestine is rapid (5 h on average), whereas a longer retention time is recorded in the cecum and colon (35 h on average).Important considerations in estimating MRT have been the use of a solute phase and a fluid phase marker and calculations applied, especially when sampling frequency is reduced.A number of animal and feed related factors influence MRT: body weight, pregnancy and lactation may increase passage rate, whereas the impact of exercise, the most important animal related factor, will depend on the exercise type and the fluid/particle ratio.Information on the effect of the main feed related factors is lacking. Smaller particles and feed with a higher water-holding capacity move slower through the gut, but reduced fibre length, increased feeding level and increased forage/concentrate ratio will accelerate passage rate. Feeding frequency seems not to affect passage rate.Sometimes, conclusions are contradictory as effect of animals, feeds and methods are confusing.
The characteristics of the Mediterranean forages used in Italy could determine some differences between their energy values and the data of other similar forages listed in the table values of INRA; an accurate determination of at least organic matter digestibility must be performed. For the determination of apparent digestibility coefficients, the total collection method, that is the reference method in the French system, could be replaced by the more easy internal markers method using acid insoluble ash (AIA). In this study we determined the apparent digestibility rates of some Mediterranean forages using both total collection of faeces and acid-insoluble ash (AIA) as internal marker. The digestibility coefficients, obtained by the AIA method and the total collection method are in the same range as those listed in the INRA tables: for the organic matter, the values obtained by the AIA method range from 42.4 to 62.2%, while those obtained by total collection range from 44.8 to 58.0%. The values obtained by the two methods are comparable, as shown also by regression equations, except for the coefficients obtained for crude protein, which are the most variable. For digestibility coefficients fast assessments, the AIA method can be considered suitable, but for the introduction of Mediterranean forages in the French nutritive value tables of feeds for horses the total collection method must be considered the correct choice.
Different lots of perennial ryegrass haylages were controlled for dry matter, buffering capacity, pH, soluble and ammonia nitrogen, lactic and monocarboxylic acids, alcohols, crude protein, crude fiber, gross energy, and ash. Net energy (UFC), and organic matter, were calculated. These forages were then fed to seven ponies, weighing on average 330 kg, during two different digestibility trials at maintenance or submitted to different workloads. Voluntary intake was measured, and digestibility coefficients were calculated for dry matter, organic matter, gross energy, crude fiber, and crude protein, using acid-insoluble ash as internal marker. Differences were found for the chemical composition of the three studied haylages; these differences can be ascribed to the different vegetative stage of the perennial ryegrass at harvesting. The conservation quality of these haylages was good or very good. Intakes were similar to those observed with hays. The OM digestibility of the haylages have been found to be lower than those measured for silages, and similar to those measured for good hays in literature. Increasing workloads decreases the dry matter and organic matter digestibilities; the same trend was found for gross energy, and crude fiber.
SUMMARY Comparisons were made of the total fecal collection method and Acid-Insoluble Ash (AIA) natural marker method for determina- tion of dry matter digestibility coefficients of rations by sheep. Three laboratory analytical procedures (Concentrated (Cone.) He1, 4N HCI and 2N HCI) which differed in ashing sequence, ashing temperature and acid strength, were used to determine the AIA content of feed and fecal samples. The dry matter digestibility coefficients esti- mated by the AIA marker method, by all three analytical procedures, were not significantly different from the coefficients determined by the traditional total fecal collection method. However, the digestibility coefficients esti- mated using the 4N HCI marker were higher (P