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The effects of ambient temperature and humidity on pregnancy rate in Beefmaster cows in a subtropical environment of Mexico
Abstract and Figures
Pregnancy rates of a Beefmaster herd with improved management in the east coast of Mexico under intense heat load during most part of the year (THI range = 56-102) were evaluated, using the GENMOD procedure of SAS, with respect to temperature-humidity index (THI) prior or after artificial inseminations (AI; n = 2039 inseminations). There was a departure from linearity (P<0.05) between THI and conception rates, as maximum THI exceeded 92 units pregnancy rate decreased more rapidly, although conception rate changed only five percent points over the THI range found in this study. When heat stress was as it maximum the day of AI (THI = 88-96) lower or higher THI one or three days prior or after AI did not affect conception rates (47-56%). With lower heat load at AI (THI = 80-88) higher THI before or after neither modify conception rates (48-58%). Pregnancy rates of cows differed among seasons (P<0.01), peaking in the fall (62%) and decreasing in spring (44%). Inseminations per pregnancy were lower in summer and fall (1.5) than in other seasons (1.9-2.0; P<0.01). There was a weak association between days open (average 242 days for 14,910 calvings) and monthly average THI during the study period, with longer intervals between parturition and pregnancy in cows calving in the fall. The main conclusions of this study were that pregnancy rate was mildly compromised by extreme heat load in Beefmaster cows in this subtropical environment, and that cooler or warmer temperatures prior or after AI bear no consequences for pregnancy rate during the warmest seasons for this breed of cattle.
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... Even though trees and shrubs may contribute to cattle survival during dry periods, digestive disturbances may occur because of their high fiber content and low digestibility (Saville 1981); thus, secondary production would be compromised. Also, in arid regions drought pushes livestock outside their comfort zone quicker (Avendaño-Reyes et al. 2012), leading to problems for maintaining homeothermy and a decrease in pregnancy rates (Mellado et al. 2010) or to even eventual death (Spain and Spiers 1996;Vitali et al. 2015). ...
Extreme weather events represent a large risk to food production systems. In this study, we evaluated the impacts of the 2011–2012 drought in Mexico, the worst in the last 70 years, on free-ranged livestock populations to link extreme weather events and production. We also considered the potential prevalence of recurring droughts under two contrasting future climate scenarios to examine what could happen over this century. Our results showed that cattle and goat stocks decreased about 3% in response to the drought countrywide. Regionally, the changes in cattle and goat populations generally mimicked the precipitation anomaly, with the strongest reductions across the driest areas in central and northern Mexico. Our work showed that the biophysical and management components of livestock production interact depending on the regions and the type of livestock, leading to a mosaic of spatial responses. It seems that the management of large herds limits the economic viability of drought crisis management options such as the importation of fodder and water, or by moving the animals to other pastures. Sheep herds were much less affected since more than 50% of the total sheep stock is raised in wetter states, which showed a relatively small (~ − 10%) precipitation anomaly during the drought. Under the severe climate change scenario, a greater frequency of extremely dry years (once every 3 years) would have negative impacts on livestock production regionally. Climate change together with already existing trends in overgrazing and soil erosion could further increase the sensitivity of livestock production across the country.
Graphical abstract
... Heat stress has a deleterious effect on the reproductive performance of cattle have been documented in the literature (Amundson et al., 2006;Mellado et al., 2010;Biffani et al., 2016). Climate changes and global warming have strongly contributed to further research in this field (Scholtz et al., 2013). ...
The objective of the present study was to identify genetic variation in heifer pregnancy due to heat stress in Nelore cattle during the breeding season. The Nelore heifers were born between 2003 and 2013 on six farms located in three Brazilian States. Heifer pregnancy (HP) was analyzed as a binary trait, with a value of 1 (success) assigned to females that were diagnosed pregnant and a value of 0 (failure) assigned to those that were not pregnant after breeding season. A threshold-reaction norm model was adopted to estimate (co)variance components and genetic parameters over temperature-humidity index (THI) values for HP. On the phenotypic scale, HP of Nelore cattle was slightly reduced by the increase in THI values (-0.85%/THI). The posterior means of the heritability estimates ranged from 0.17 at THI 82.5 to 0.01 at THI 88. The mean genetic correlations for HP between different THI values were below the unity. The genetic correlation between extreme THI values (82.5 and 88) was -0.47 (0.10). Genetic variation in the response to heat stress and heterogeneity in the (co)variance components and genetic parameters were observed across the THI scale. The breeding values of animals for HP were sensitive to changes in THI, thus demonstrating an important effect of the genotype-by-environment interaction due to heat stress.
... Mellado et al., (2000) also observed uninterrupted copulations of bucks all day round, a scenario that suggest that bucks exhibit a desire to mate at any time of the day while were able to locate and mate does irrespectively of both an increased THI and even during the dark hours. The uninterrupted copulation activity of bucks besides to the self-imposed decreased feed intake during the mating period generated a drastic loss of body mass in bucks during the breeding season, a trend in line with previous reports (Mellado et al., 2010). These findings emphasize the importance to keep good body energy reserves for bucks under extensive systems, particularly during the dry season. ...
aUniversidad Autónoma Agraria Antonio Narro, Periférico Raúl López Sánchez y Carretera a Santa Fe, CP 27054 Torreón, Coahuila, MexicobUniversidad Autónoma Chapingo, Unidad Regional Universitaria de Zonas Áridas, Bermejillo, Durango, MexicocInstituto Tecnológico de Torreón, Torreón, Coahuila, MexicodUniversidad Autónoma Agraria Antonio Narro, Departamento de Nutrición Animal, Saltillo, Coahuila, Mexicoa
... Mellado et al., (2000) also observed uninterrupted copulations of bucks all day round, a scenario that suggest that bucks exhibit a desire to mate at any time of the day while were able to locate and mate does irrespectively of both an increased THI and even during the dark hours. The uninterrupted copulation activity of bucks besides to the self-imposed decreased feed intake during the mating period generated a drastic loss of body mass in bucks during the breeding season, a trend in line with previous reports (Mellado et al., 2010). These findings emphasize the importance to keep good body energy reserves for bucks under extensive systems, particularly during the dry season. ...
... When the heat loss is overrun by heat gain, the homeostatic mechanism triggers the thermoregulatory response of animal to maintain the body temperature within normal range. During heat stress, increase in the core body temperature due to failure of homeostatic mechanism reduces productivity of the animals below their original genetic potential in growth [1], milk production [2][3][4], milk constituents, [5,6] and reproduction [7][8][9][10]. ...
Aim:
One of the major biochemical aspects of thermoregulation is equilibrium of ion gradient across biological membranes. Na(+)/K(+)-ATPase, a member of P type-ATPase family, is a major contributor to the mechanism that actively controls cross-membrane ion gradient. Thus, we examined ATP1A1 gene that encodes alpha-1 chain of Na(+)/K(+)-ATPase, for genetic polymorphisms.
Materials and methods:
A total of 100 Vrindavani (composite cross strain of Hariana x Holstein-Friesian/Brown Swiss/Jersey) and 64 Tharparkar (indigenous) cattle were screened for genetic polymorphism in ATP1A1 gene, using polymerase chain reaction single-strand conformation polymorphism and DNA sequencing. For association studies, rectal temperature (RT) and respiration rate (RR) of all animals were recorded twice daily for 3 seasons.
Results:
A SNP (C2789A) was identified in exon 17 of ATP1A1 gene. Three genotypes namely CC, CA, and AA were observed in both, Vrindavani and Tharparkar cattle. The gene frequencies in Tharparkar and Vrindavani for allele A were 0.51 and 0.48, and for allele C were 0.49 and 0.52, respectively, which remained at intermediate range. Association study of genotypes with RT and RR in both cattle population revealed that the animals with genotype CC exhibited significantly lower RT and higher heat tolerance coefficient than CA and AA genotypes.
Conclusion:
Differential thermoregulation between different genotypes of ATP1A1 gene indicate that the ATP1A1 gene could be potentially contributing to thermotolerance in both, Tharparkar, an indigenous breed and Vrindavani, a composite crossbred cattle.
... The lowest average pregnancy rate of Murrah buffaloes was obtained under CHSZ as compared to the HSZ and NHSZ along with the decrease in number of buffaloes from NHSZ to the CHSZ. Mellado et al. (2010) indicated the variation in the pregnancy rate of Beefmaster cows in different seasons in a year. The lowest pregnancy rate was observed as o.44±0.02 in April-June (spring) while October-December (fall) months showed peak pregnancy rate 0.62±0.02 in Beefmaster cows. ...
Heat stress has adverse effects on fertility of dairy animals. Decline in fertility is linearly associated with an increase in combination of both temperature and humidity. The purpose of this study was to investigate the relationship between temperature humidity index (THI) and the pregnancy rate of Murrah buffaloes in a subtropical climate. The effects of genetic and non-genetic factors viz., sire, parity, period of calving and age group at first calving were found non-significant on pregnancy rate. The effect of THI was found significant (p<0.001) on pregnancy rate of Murrah buffaloes calved for first time and overall pregnancy rate. The threshold THI affecting the pregnancy rate was identified as THI 75. The months from October to March showed THI<75 and considered as non heat stress zone (NHSZ), while months from April to September were determined as heat stress zone (HSZ) with THI≥75. The lowest overall pregnancy rate (0.25) was obtained in July with THI 80.9, while the highest overall pregnancy rate (0.59) was found in November with THI 66.1. May and June were identified as critical heat stress zone (CHSZ) within the HSZ with maximum decline (-7%) in pregnancy rate with per unit increase in THI. The highest overall pregnancy rate was estimated as 0.45 in NHSZ with THI value 56.7 to 73.2. The pregnancy rate was found to have declined to 0.28 in HSZ with THI 73.5 to 83.7. However, the lowest pregnancy rate was estimated as 0.27 in CHSZ with THI value 80.3 to 81.6.
Research carried out at the Sucupira Farm of Embrapa Recursos Genéticos e Biotecnologia, in Brasilia-DF, aimed to evaluate heat tolerance in five naturalized and two exotic breeds of cattle, at different temperatures and humidity, based upon physiological and blood parameters. The data collected included heart rate (HR), rectal temperature (RT), respiratory rate (RR), and sweating rate (SR). Blood was also collected for hemogram analysis and cortisol level. The measurements were taken at 7 am and at 2 pm after the animals were exposed to the sun, with water ad libitum. This procedure was repeated for six days, three in the middle of the dry season when temperatures and humidity were lower and three at the start of the rainy season when temperatures and humidity were higher. Significant statistical differences were observed in RR and HR for day, breed and animal within breed. The analysis indicated that the Junqueira and Nellore breeds are most adapted to climatic conditions in Brasilia; while Mocho Nacional and Holstein breeds were the least adapted. Although sample size is limited, these results are important to identify which breeds are most resistant towards climatic variations observed in the Brasilia region, as well as which physiological parameters are the most indicated for use in animal breeding programs intended to select animals and breeds adapted to thermal stress conditions.
The decision of when to calve beef females is critical to production efficiency and profitability in a cow and calf enterprise. Calf production and associated costs are affected by calving season because environmental conditions, stage of production, and season of the year interact to affect nutritional status and reproductive performance. Cow and calf producers typically choose to commence calving and breeding at times of the year when weather is least stressful and forage conditions are optimal. Choosing to do so can reduce the amount of supplemental feed needed to ensure acceptable pregnancy rates, resulting in reduced annual feed costs. However, the time of year when forage conditions are optimal varies across the United States because of not only environmental (ambient temperature, rainfall, day length) differences among latitudes and longitudes but also differences in soil types and topographies.
Consequently, forage species and their growth characteristics differ among regions. Given such differences, feeding strategies and feed costs vary among regions. Additionally, summer heat stress, particularly in southern states, has negative consequences on reproductive performance in both the female and male and will reduce calf performance. Such a wide array of production environments, productivity levels, and associated costs will cause profitability to vary among regions of the United States, making it impossible to identify a universally acceptable date to commence calving and breeding. Consequently, the decision of when to calve beef females should be based on site-specific conditions.
Future financial performance was pre-dicted for cow herds in dual, spring, and fall calving season regimens using a sys-tem dynamic model parameterized with historic production and financial data from King Ranch and future cattle prices estimated by CattleFax. Results are reported on a 1,000 cows/herd basis for predicted average annual pretax accrual adjusted net income, predicted average annual cost-based investment in breeding livestock, and predicted average an-nual return on investment on cost-based breeding livestock. The predicted results of the simulations indicated that over the next 10 yr, the fall calving season would generate more net income than either the dual or spring calving season on the King Ranch. However, a dual calving season would have less invested in breeding livestock and a greater return on breeding livestock than either the spring or fall calving seasons. Based on market risk, variation in precipitation, investment in breeding livestock, and return on breeding livestock, having a dual calving season is predicted to be a superior management strategy compared with spring-or fall-only calving seasons for the King Ranch from 2007 to 2016.
A transversal study was carried out with the objective to know the reproductive status of dual-purpose cattle and to determine the effect of some environmental and breed group factors on the proportion of cows found pregnant (PCP) and calving to conception interval (CCI) in Yucatan, Mexico. The climate of the region is tropical sub-humid with monthly temperature and annual rainfall averages of 26 C and 1100 mm respectively. Main characteristics of the dual-purpose herds in south-eastern Mexico are: milking of cows once a day with calf at foot; the use of crossed Brown Swiss x Zebu or Holstein x Zebu cows, fed mainly on pastures and the use of rustic infrastructure. A team of veterinarians conducted the diagnosis from November 1996 to December 1999. A total of 5133 rectal palpations from 162 herds of a total of 340 herds were obtained. PCP data were analysed using Chi-square test and CCI data by time-event procedures. Fifty one percent of the cows palpated were pregnant. Of the non-pregnant cows, 35.3% were cycling. Statistical differences in PCP were found among zones, seasons of calving and breed groups. The east zone had the highest PCP (52.5%) followed by the south zone (49.8%). The dry season had the highest PCP (58.5%) and the worst corresponded to the rainy season (31.9%). Crossed Brown Swiss x Zebu and Holstein x Zebu cows had a higher PCP than the pure Brown Swiss or Holstein cows, although they were similar to the Zebu cows. CCI mean was 183+5.6 days. The probabilities that a cow gets pregnant at 4 or 6 months postpartum were 18.4 and 31.8%, respectively. The probability of an CCI of 180 days or less was lower for the crossed cows (Bos taurus x Bos indicus) compared to the Brown Swiss and Holstein cows.
During their separate evolution from Bos taurus, zebu cattle (Bos indicus) have acquired genes that confer thermotolerance at the physiological and cellular levels. Cattle from zebu breeds are better able to regulate body temperature in response to heat stress than are cattle from a variety of B. taurus breeds of European origin. Moreover, exposure to elevated temperature has less deleterious effects on cells from zebu cattle than on cells from European breeds. Superior ability for regulation of body temperature during heat stress is the result of lower metabolic rates as well as increased capacity for heat loss. As compared to European breeds, tissue resistance to heat flow from the body core to the skin is lower for zebu cattle while sweat glands are larger. Properties of the hair coat in zebu cattle enhance conductive and convective heat loss and reduce absorption of solar radiation. At the cellular level, genetic adaptations to resist deleterious effects of elevated temperature result in preimplantation embryos from zebu being less likely to be inhibited in development by elevated temperature than are embryos from European breeds. The zebu genotype has been utilized in crossbreeding systems to develop cattle for beef and dairy production systems in hot climates but success has been limited by other unfavorable genetic characteristics of these cattle. An alternative scheme is to incorporate specific thermotolerance genes from zebu cattle into European breeds while avoiding undesirable genes. Once specific genes responsible for thermotolerance in zebu have been identified or mapped, breeding strategies such as marker-assisted selection and transgenics can be applied to further the exploitation of the zebu genotype for cattle production systems.
In this study we examined, in two experiments, patterns of follicular development and dominance under conditions of heat stress. Estrous cycles were programmed to include two follicular waves (wave 1 and 2). On Day 1 of the estrous cycle (Day 0 = estrus), cows were assigned randomly to cooled (C; n = 6) or heat-stressed (H; n = 6) groups. In experiment 1, on Day 12 prostaglandin (PG) F2α, was injected and a controlled intravaginal drug release device (1.9 g progesterone) was inserted (this was removed on Day 17). In experiment 2, PGF2α, 0 was injected on Day 14. Ovarian structures were examined daily by ultrasonography, and blood samples were collected at each scanning. Cycle lengths were 20 and 17 days in experiments 1 and 2, respectively. Mean maximal body temperatures were higher (p < 0.01) in H (40.3°C) than in C (38.8°C) cows.
In experiment 1, the rate of increase in number of large follicles (≥ 10 mm) was greater in H than in C cows (p < 0.01), resulting in 53% more large follicles in H cows during wave 1; this was associated with a lower (p < 0.05) number of mediumsized (6−9 mm) follicles between Days 7 and 10 of the cycle. Heat stress hastened (p < 0.02) the decrease in size of the firstwave dominant follicle and hastened (p < 0.01) the emergence of the second dominant (preovulatory) follicle by 2 days. In H cows, lack of decline (p < 0.02) was noted in the number of medium-sized follicles during wave 2. In experiment 2, as in experiment 1, the rate of increase in the number of large follicles was greater in H than in C cows (p < 0.05), resulting in 50% more large follicles in H cows during wave 1. The preovulatory follicle emerged earlier (p < 0.05) in H cows, and greater variance (p < 0.05) indicated that in half of H cows the emergence of dominance occurred 4 days earlier. Heat stress suppressed (p < 0.01) plasma concentrations of estradiol during the second half of wave 1 and tended to reduce (p < 0.09) plasma concentration of inhibin.
Results indicate that heat stress appears to impair follicular development and to alter the dominance of the first-wave dominant follicle and the preovulatory follicle in cattle.
Over the last few years there has been an ever-increasing interest in America in the Savory Grazing Method. During the recent annual meeting of the Society for Range Management in Albuquerque, N. Mex., nearly 500 people visited the nearby SGM scheme operating on tribal Indian land. As a consequence of such interest I have been invited to write this article for Ran gelands. I do so in the hopes of expanding understanding and of clearing some of the many myths and misconceptions about SGM abounding in the profession and amongst ranchers. For all conservationists, as well as livestock owners, an answer to the desertification problem has long been sought. It is needed to stop our dams silting, our water tables dropping ever-lower, our wildlife being increasingly threatened and to aid the millions of people living in abject poverty on drying lands in the Third World. Even America will soon realize that water is her Achilles heel and that her wealth and prosperity are dependent upon sta-ble catchments. In Holistic Resource Management (SGM), we undoubtedly have an economically sound, self-sustain ing answer to the desertification problem for America as well as the poorest nations bedevilled with it. The fate of many countries depends on how SGM is developed and extended from America. Unfortunately, for some reason America is a nation of extremes where people en masse rush into new things often with enthusiasm unmatched by knowl-edge, then after a few tragedies react en masse the other way. Generally the American attitude to SGM has been no dif-ferent. Many have rushed into SGM too fast and with too little knowledge. Most of the knowledge available to the average rancher or university is misinformation and myth spread by the universities themselves, i.e., "SGM is a wagon wheel system; SGM is a cell grazing system; SGM is short duration grazing; SGM is rapid rotation grazing," and so on. All of these descriptions are totally wrong. Yet how many ranchers, government agencies and universities do you know who have rushed into it in the belief that it is one or livestock on the land. It is riparian and fish management technique. It is also a method of managing livestock on the land whereby the livestock can be used to reverse the deser-tification process very economically with or without fencing. It is also a method of managing livestock on ranges or on planted pastures whereby greater production can be achieved both from the land and the animals and with greater profitability than conventionally. It is a method of making conventional range management techniques economically sound where they were economically unsound. It is not just another grazing system, of which there have been so many. Throughout the world there are vast areas of what are known as the "brittle environments". These are areas where there are prolonged periods of the year in which conditions for plant growth are adverse. In the most brittle of these areas periods adverse for plant growth occur in the growing sea-son as well as during the long non-growing season. Most of these areas are associated with arid and semi-arid climates but some can extend into remarkably high rainfall zones. Throughout America and the rest of the world these brittle environments are mainly used for livestock production. Throughout, they are deteriorating, become drier, carrying fewer and fewer animals and in fact becoming deserts to varying degrees and at varying rates.
Calving data recorded over a 28-year period were analysed for the effects of breed, filial generation,
lactational status, cow liveweight at mating and year of mating. The herd comprised six distinct
breeding lines ('breeds') and analysis was performed both within and across breeds. The least fertile
breeds were the high grade (314-718) Africander (A) and high grade (718-purebred) Brahman (B) cows
which had average calving rates of 56% and 55%, respectively. Crossing these with a Hereford-
Shorthorn line, which had an average calving rate of 6O%, resulted in 19% heterosis (in absolute calving
percentage units) in the F1 Africander-cross (AX) and 16% heterosis in the F1 Brahman-cross (BX). In
subsequent generations, 13% residual heterosis remained in the AX, while in the BX only 1%
remained. Reciprocal crossing of the AX and BX lines generated 6% heterosis in the Fl AXBX, and all
of this was maintained in subsequent generations. In the F2 et seq. generations of the AXBX, the line of
animals carrying the Bos indicus Y chromosome was similarly fertile (P> 0.05) to the line carrying the
Bos taurus Y chromosome.
Lactating mature (3 5-year-old) cows were on average 15% less fertile than non-lactating cows.
This lactation effect was larger in younger cows. There was a curvilinear response in fertility to
increasing liveweight at mating which was most pronounced in 2-year-old heifers. Breed appeared to
react differently to the effects of environmental stress where the AX and HS cows were limited more by
liveweight, and the BX and AXBX were more limited by lactation effects per se.
Lactating cows that also lactated in the previous year were 6% more fertile than lactating cows that
were dry the previous year, suggesting that calving records are moderately repeatable and therefore
that permanent differences in fertility could be established by phenotypic selection.