1. Broiler breeder hens were used in an experiment lasting 10 weeks (29 to 38 weeks of age) to measure the responses to dietary lysine and methionine, the main objective being to determine whether the coefficients of response to these amino acids were the same for broiler breeders and for laying pullets. 2. The hens were offered 150 g/d of one of 20 dietary treatments, 10 being lysine-limiting and 10 being methionine-limiting. The diets were mixed by diluting one of two concentrate (summit) mixes with a protein-free dilution mixture. The lysine-limiting summit diet was designed to supply approximately 1300 mg lysine/bird d, while the other supplied 520 mg methionine/bird d, when fed at 150 g/bird d. 3. Birds on the 5 lowest concentrations of both lysine and methionine did not consume the allotted amount of food, the amount decreasing, in a curvilinear fashion, to approximately 105 g/bird d. 4. The minimum egg weight recorded was 0.8 of the maximum, whereas the rate of lay of birds fed on the diets with the lowest amino acid concentrations was 0.2 of the maximum. 5. Using the Reading Model, the coefficients of response were calculated to be (for lysine) 16.88 E and 11.2 W, and for methionine, 7.03 E and 1.52 W, where E = egg output, g/bird d, and W = body mass, kg/bird. An average, individual, broiler breeder of 3 kg, producing 45 g of egg output per day, would need 793 mg of lysine and 321 mg of methionine daily. This intake of methionine is similar to that estimated by means of coefficients used for laying pullets, but the lysine requirement would be underestimated by 0.18 if the coefficients for laying pullets were used. 6. The coefficients for maintenance for both lysine and methionine, determined in this experiment, are considerably lower than values published previously, whilst the coefficients for egg output are, in both cases, higher. The resultant flock response curves therefore differed significantly from those in which the coefficients of response for for laying pullets were used.(ABSTRACT TRUNCATED AT 400 WORDS)
1. Three experiments were designed to determine the response of broiler chickens to dietary isoleucine, and to quantify the antagonistic effects of excess leucine and valine on this response. 2. A dilution technique was used to measure the responses in growth rate and food intake to a range of diets differing in their isoleucine concentrations. A summit diet was formulated to contain isoleucine at 1.14 times the requirement and with leucine (1.76 times the requirement) and valine (1.87 times the requirement) at the minimum possible concentrations, given the ingredients available. A dilution mixture, devoid of protein, was formulated to correspond in all respects, other than in amino acid content, to the summit diet. These two basal diets were blended in different proportions to give a range of diets of decreasing isoleucine and protein content. 3. In experiment 1 the response was measured to isoleucine with leucine and valine remaining in the same proportion to isoleucine throughout the range of diets fed. In experiments 2 and 3, however, L-leucine and L-valine were added to the diets either singly or in combination to give 6 isoleucine concentrations and 3 ratios of each of leucine and valine to isoleucine. 4. Weight gain decreased as the isoleucine content of the diet was reduced, whereas food intake of broilers fed on the marginally deficient diets increased to a maximum and then decreased. FCE decreased curvilinearly as the isoleucine concentration in the food decreased, reflecting a concomitant change in the fat content of the broilers. 5. It is possible that the amount of dietary isoleucine assumed to be available to the broilers in these experiments was overestimated by hydrolysing the food samples for 72 h, and the doubt thus created makes an estimate of the efficiency of retention of isoleucine suspect. 6. Excess valine had no effect on the response to isoleucine, whereas an increase in the leucine to isoleucine ratio depressed food intake and hence weight gain, but only at the lowest concentrations of isoleucine. 7. If the food content of isoleucine is sufficient to meet the requirements of the broiler, relatively large excesses of leucine, of valine, or of both will not depress growth.
Data for individual feed intake, liveweight, and egg production were recorded for five genetically different groups of 40 pullets each during 10 test periods of 28-days each. Average ambient temperature at cage level varied from 6.7 C during January to 21.1 C during June. A 2890 kcal/kg metabolizable energy (ME) diet with 16% crude protein (CP) was fed ad lib. Average egg production for the Small Leghorns (SL) was about 60%, for white-egg hybrids (WL) about 75%, for brown-egg hybrids (BL) about 72%, for female line broiler breeders (BB) about 48%, and for broiler-cross pullets (B) about 51%. Average grams liveweight and grams feed intake per hen day were: SL, 1426 and 83.7; WL, 1809 and 104.9; BL, 2610 and 122.9: BB, 4197 and 156.2; and B, 4158 and 167.7.Partition equations which describe the data for SL, WL, BL, and BB, assuming 70% efficiency of use of feed ME for maintenance, tissue formation, and egg formation were: F = (.534 -.004T)W .653 + 2.76AW + .80EM and F = (.259 -.00259T)W-75 + 2.76AW + .80EM. Similar equations for B, assuming 65% efficiency use of ME, are: F = (.589 -.0044T)W°5 3 + 2.9AW + .85EM and F = (.275 -.00275T)W-75 + 2.9AW + .85EM. The terms are: F = grams feed/hen day; T = ambient temperature in °C; W = grams liveweight; AW = grams daily change in liveweight; EM = grams egg mass per hen day.Equations which assume 70% efficiency of use of ME are shown to predict feed intake of a diet containing 2890 kcal of apparent ME per kilogram for white and brown-egg layers and broilerbreeder pullets varying in individual body weights from about 1 to 5 kg. Equations, assuming 65% energetic efficiency, describe feed intake for a group of broiler-cross pullets. (
The current market and economic challenges faced by pork producers are unprecedented and therefore there is a constant need to determine the economically optimal nutrition and management solutions. Simulation models can be used to fulfill this need provided they have the capacity to integrate animal responses, management practices and economics into an optimization process that produces reasonably accurate predictions under a wide range of commercial practices. Some of the key components required to successfully implement an optimization model in commercial practice include: (i) the ability to predict feed intake; (ii) integration of an animal biology model that predicts animal responses to nutrient, management and environmental changes and the financial consequences thereof, with a feed formulation system; (iii) knowing the variation in responses between individual animals and understanding the source of animal variation; (iv) the effect of shipping management on mean performance; and (v) model validation. Such integrated optimization models (e.g. Watson® 2.0 used by Nutreco) can be used strategically to drive significant nutritional or production changes with large economic consequences. For example, based on the findings of a model, a commercial feed company may change the nutrient profile of all their standard nursery diets in response to increasing ingredient prices. Or a model may help a producer to understand the risks, costs and benefits of changing genetics, or provide producers with a reference guide to help decide what is the optimum shipping weight bearing in mind rapidly changing pig and/or feed prices. Just as helpful but on a much smaller scale is using a model to help a producer improve feed efficiency or reduce costs or increase revenue by optimizing the nutrient density of the diet or optimizing when diets should be changed during the grower-finishing period. Fundamental to the successful application of optimization models in commercial practice is the need for an accurate biological model as well as a well-defined commercialization process.
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