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The response to diets of different nutrient densities was evaluated in male turkeys. In 2-week experiments with 1-week-old and 14-week-old turkeys the growth response to nutrient density appeared to be biphasic with an accelerated response at the lower and a much smaller response at the upper range of nutrient density. Results suggest that the uppe...
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... birds from the extreme treatments were taken for carcass fat evaluation. The results, given in Table 5, show no significant differences in either abdominal fat or skin dry matter. ...Citations
... 67, September 2011weight gain in birds. Many studies have demonstrated that growth rates and feed intakes decreased when environmental temperature increased (Hurwitz et al., 1983; Hai et al., 2000; Ciftci et al., 2005). Niu et al. (2009) suggested that for every 10°C increase in ambient temperature above 20°C, there is a 17% reduction in feed intake. ...
... Hai et al. (2000) also reported that the amount of chyme in the whole digestive tract was decreased by the cold environment (5°C ) and increased by hot temperatures (32°C). Environmental temperature is the most important variable affecting feed intake and (Hurwitz et al., 1983;Hai et al., 2000;Ciftci et al., 2005). Niu et al. (2009) suggested that for every 10°C increase in ambient temperature above 20°C, there is a 17% reduction in feed intake. ...
Heat stress is associated with compromised performance and productivity in poultry due to declines in feed intake, nutrient utilisation, growth rate, egg production and quality, feed efficiency and immunity. Additionally, heat stress is characterised by reduced antioxidant status in birds, resulting in increased oxidative stress. Heat stress is also linked with increased economic losses due to mortality of birds. Vitamin E is a major chain-breaking antioxidant in biological systems. An optimum response with supplementation of vitamin E in feed has been found to improve feed intake, body weight gain, feed efficiency, egg production and quality, nutrient digestibility, immune response and antioxidant status in poultry birds. This work compiles past and present information about the role of vitamin E in heat-stressed poultry.
... Fat supplementation reduced— whereas carbohydrate supplementation stimulated— liver lipogenesis. In the turkey, specific effects of fat on growth and carcass fat were dependent on age (Hurwitz et al., 1983), and environmental temperature (Hurwitz et al., 1987). Supplementary fat may also change the physical quality of the diet. ...
... In agreement with previous studies such as those of Hurwitz et al. (1983 Hurwitz et al. ( , 1987 ), the present study demonstrated growth promotion by increasing dietary energy density, in addition to the expected increase in feed efficiency, in all experiments. It may be recalled that in each experiment, the protein (amino acid) ratios to energy were kept constant in the list of dietary restrictions. ...
... Pesti et al. (1983), Jackson et al. (1982a) observed linear responses of growth to energy up to a dietary level of 3,300, 3,400 and 3,600 kcal/kg, respectively. On the other hand, some studies (Waldroup et al., 1976; Jackson et al., 1982b; Deaton and Lott, 1985; Hurwitz et al., 1983) suggested an upper limit for the response of growth to energy (nutrient) density, within the practical range of dietary energies. Deaton and Lott (1985) observed an upper limit for the response at 3,250 kcal/kg. ...
The efficacy of fat and carbohydrates as energy sources was compared in 1- to 4- and 4- to 7-wk-old broiler chickens and in
16- to 19-wk-old turkeys. An increase in dietary energy by carbohydrate was made by a graded replacement of wheat bran by
wheat. Energy was increased by fat through a graded replacement of soybean hulls with refined soybean oil. In the experiments
with broiler chickens, the feed efficiency responses to added energy were observed within the entire range of dietary energy
tested, with no significant differences between the responses to carbohydrate and fat as energy supplements. The growth response
to energy from either source appeared to be characterized by diminishing returns in the chicken. In the 16- to 19-wk-old turkeys,
the growth and feed efficiency responses were linear within the range from 2,650 to 3,250 kcal/kg. In chickens and in turkeys,
the growth and feed efficiency responses to energy supplied by fat were indistinguishable from those of carbohydrates. In
chickens, the fractions of abdominal fat and pectoral muscle were not affected significantly by the energy density and source.
... In support of this postulation, Sell and Owings (1981) found an effect of fat on body weight and feed efficiency irrespective of dietary metabolizable energy. However, several studies of turkeys as well as chickens (Waldroupefa/., 1976;Coon etal., 1981;Owen et al., 1981;Hurwitz et al., 1983a;Summers et al., 1985) show general growth and feed efficiency responses to increased energy or nutrient density in the diet. Earlier work of Jensen et al. (1970) and Jensen and Fallen (1973) 'Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, Number 1622-E, 1985 Series. ...
Growth, feed efficiency, and carcass fat were evaluated in turkeys fed diets in which added fat varied, holding energy or the calories:protein ratio constant. In the 1 to 3-wk-old turkey, growth and feed efficiency increased with dietary energy, but did not change significantly when fat was added isocalorically. The 12 to 14-wk-old turkey responded with improved growth and feed efficiency when dietary fat was added either isocalorically or with increasing energy density. However, the response to the isocaloric fat addition was smaller in magnitude than the response when fat was added without calorie adjustment. No difference could be detected in 12 to 15-wk-old turkeys in the performance response to tallow and soybean oil. Carcass fat deposition generally increased with dietary fat supplementation, regardless of the caloric change. The results suggest that in the midterm of development of the growing turkey, dietary fat per se affects growth, feed efficiency, and carcass fat. Growth and feed efficiency responses to nutrient density occur in both young and older birds.
... An increase in nutrient density led to improved growth and feed efficiency in turkeys and chicks (Waldroup et al., 1976;Coon et al., 1981;Owen et al., 1981;Sell et al., 1985;Summers et al., 1985). The magnitude of growth response of turkeys to dietary energy was estimated to be approximately 1.7% per 100 kcal (Hurwitz et al., 1983a). Some responses to increases in dietary energy density have been attributed to specific "extracaloric" effects of fat rather than to energy (Jensen et al., 1970;Jensen and Fallen, 1973). ...
... First is the question whether protein (amino acids) should be kept constant or raised at the same proportion as energy in the experimental diets in order to ensure protein intake to offset the expected decrease in feed intake. As feed intake decreased in turkeys when dietary energy increased (Hurwitz et al., 1983a), the ration of protein and amino acids was kept constant in the minima used for diet formulation, although it is recognized that this practice may also result in deviations in the balance between the amino acids. The value of expressing amino acid requirements as energy ratios was discussed previously (Hurwitz et al., 1983b). ...
... This conclusion is based on information reviewed by Hurwitz etal. (1983b,c) concerning protein requirements of turkeys and by Hurwitz et al. (1983aHurwitz et al. ( , 1987 concerning response to dietary energy. However, on a strict basis, the effect of protein cannot be absolutely ruled out. ...
Interactions between environmental temperature and dietary energy sources were evaluated in 6 to 9-wk and 9 to 12-wk-old turkeys using weight gain, feed efficiency, and carcass fat as response criteria. The dietary variables (soybean oil or glucose) were added in five or six increments at the expense of each other or of the fiber supplements, keeping the minima for protein and amino acid/energy constant. The resulting diets were fed to birds kept at 10 and 27 C. Duplicate experiments were conducted for each mode of dietary variable addition.
Parallel increases in body weight gain and feed efficiency were obtained at the two temperatures when fat replaced carbohydrates or fiber, thereby raising dietary energy density. Some responses of weight gain and feed efficiency at the two temperatures were obtained also with a graded isocaloric addition of fat but the response was significant only at 27 C and not at 10 C. A greater response of gain and feed efficiency to energy supplied by dietary glucose was obtained at 10 C as compared with 27 C. Dietary fat supplementation resulted in increased deposition of carcass fat when given together with energy or isocalorically regardless of environmental temperature. Carcass fat was increased by glucose-energy at the low temperature only.
Maximization of profit in a turkey or broiler operation involves decisions about marketing age, dietary nutrient density, and ambient temperature as determined by fuel input. These interacting factors are dependent nonlinearly on the rate of growth as determined by the sex, breed, and husbandry conditions used; current prices of important production components such as feed; and cost of the day-old bird. Based on experiments with turkeys and chicks, production functions have been formulated in a simulation model capable of predicting performance under different environmental and dietary conditions. With the aid of simulation, expenses as well as income can be computed. These are discounted and the average daily net return is calculated. The most economical set of production conditions can then be selected. In addition, the program calculates the feeding schedule appropriate for the environmental temperature during the growing period and the bird density to be used at a given marketing age, including cumulative mortality. Using the program, the effects of environment, dietary energy density and the price of the day-old bird were evaluated. Model predictions were validated by comparison of the predicted values with the results of a Minnesota feeding trial (Waibel et al, 1976). The predicted body weights at 27.2 C were about 4% lower than the observed values. Energy intake was underestimated by about 12%, probably due to the additional needs in Minnesota resulting from activity, routine wastage, and high dietary protein concentration. The usefulness of the present model is discussed.
Heat stress has been associated with depressed growth in meat-type birds and a decline in egg production and quality in laying hens. During heat stress, feed intake tends to decrease, thus the availability of certain important minerals is reduced. Chromium (Cr) is one such mineral, which is required for maintaining growth performance in poultry due to its role in growth, metabolism and alleviation of lipid peroxidation. The available scientific literature on Cr has documented the beneficial effects of this essential mineral in improving poultry performance under conditions of environmental heat stress. In the present review, past and present information about the specific role of Cr in heat-stressed poultry is presented.
The effect of altering the proportion of dietary protein supplied as essential amino acids (EAA) on the performance and carcass characteristics of young turkeys (to 3 wk of age) was investigated at three dietary protein levels (22, 26 and 30%) using semipurified diets. Four ratios of EAA to nonessential amino acids (NEAA) were employed (70:30, 60:40, 50:50 and 40:60) at each dietary protein level. Maxima in weight gain, percent and total carcass protein and feed intake were observed when EAA supplied 60% of total protein (i.e., the 60:40 ratio) at each protein level. The differences in weight gain and total carcass protein were largely attributed to differences in feed intake, since feed conversion efficiency was relatively unaffected by altering the EAA: NEAA ratio. More specifically, weight gain was shown to be limited by total protein intake. Since weight gain was maximized at the 60:40 ratio diets (in which all EAA are supplied at 128% of requirement) at least one of the EAA requirement values is inco...
A dynamic linear programming model was developed to obtain a sequence of optimal least-cost rations over time for broiler chicks. At a user's choice of time interval, the model calculates daily requirements of total protein, amino acids and energy, and computes the appropriate diets.Gompertz growth curves govern body-weight trajectory over time and the proportion of carcass, feathers and fat relative to the weight of the birds. The computed optimal diets were considerably lower in protein and cost compared with those based on the National Research Council recommendations. The model identifes the limiting amino acid(s) for the diet at any time during growth.
