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Poultry nutritionists should constantly evaluate their feeds and feeding programs in view of the changes that continue to be made to the potential growth rate of broilers and egg production in laying hens with the objective of providing the birds with the optimum economic level of nutrients at all times. In this review, the models generated at Universidade Estadual Paulista (UNESP) Jaboticabal, to estimate the optimum intake of amino acids (AA) for broilers and laying hens are presented. These models were used to estimate the variation in AA intake within a broiler population making use of coefficients of variation that represent the real situation in a commercial broiler operation. The range of AA intakes obtained was compared to some commonly applied feeding programs and recommendations. Based on results of our developed models and other feeding programs, feeds were formulated and growth was predicted using a growth simulation model (Avinesp). The prediction of growth showed that these models are reliable and useful tools to assist the nutritionists in decision making. In a study with laying hens, the Reading model (RM) was used to establish optimum economic AA intakes in a flock of hens. The input variables were the means and standard deviations of egg output and BW, and the relationship between the marginal cost of the AA and the marginal revenue for eggs. Based on this model, the optimum intake of each AA can vary with each of the variables considered. The models proposed in our study enable important decisions to be made regarding AA intakes to be used to obtain optimum economic performance from a population of broilers and laying hens.

SUMMARY Amino acid content of the defeathered broiler carcass at different ages may provide needed information for meeting nutritional requirements. Both sexes of 2 strain-crosses were reared on corn- and soybean meal-based diets exceeding the minimum nutrient recommendations. Defeathered carcasses from the heaviest and lightest birds per pen were individually ground and amino acid (AA) content was determined. Broiler age played a greater role than either sex or strain for influencing individual, total essential, and total nonessential AA contents. Certain of the essential and nonessential AA were influenced differentially by broiler age and sex. Total nonessential AA, as a percentage of total essential AA, were influenced by broiler age and sex in a similar manner. The influence of age on carcass AA content is considered to reflect compositional changes occurring in response to growth. Despite selection differences in body fat content between the 2 broiler strain-crosses, carcass AA content, expressed as a percentage of carcass protein, was not affected by this, suggesting genetic selection does not have a major influence on carcass AA contents. If this is true, then future improvements in broiler production parameters would require only that carcass protein content be analyzed to determine carcass AA content. Analyzing the carcass for protein would be quicker and less expensive than analyzing for AA.

SUMMARY A study was conducted to evaluate the efficacy of a multi-carbohydrase enzyme, Roxazyme G2, when administered in water or in feed to broiler chickens. The enzyme generally improved (P < 0.01) weight gain and feed conversion efficiency (FCE). Supplying the enzyme in water resulted in a slight reduction in feed intake as well as an increase in weight gain and FCE compared with values obtained when the enzyme was supplied in feed. Between 7 and 14 d of age, the feedsupplemented treatment improved (P < 0.05) weight gain and FCE more than did supplementation in water. The results showed that microbial enzymes whose activities are adversely affected by high temperature feed extrusion can be supplied to poultry via water.

A description of the feather amino acid content from two distinct broiler strain crosses may provide needed information for nutritional purposes. Both sexes of the Ross x Arbor Acre and Steggle x Arbor Acre strain crosses were reared on corn-soybean meal-based diets exceeding the minimum NRC (1984) nutrient recommendations, with pooled feather samples taken from selected birds for amino acid analyses at different ages. Broiler age played a greater role than strain cross or sex in influencing individual and total essential amino acid contents. Total non-essential amino acids as a percentage of total essential amino acids increased as the bird aged, indicating feather compositional changes occurring during this time.

A study was conducted to compare the performance of two distinct broiler strain-crosses and to provide genetic descriptions of them for modelling. Ross x Arbor Acres (RxAA) and Steggle x Arbor Acres (SxAA) broiler strain-crosses were reared on corn-soybean meal diets exceeding the minimum NRC nutrient recommendations. Diets were fed from 0 to 4 (starter), 4 to 8 (grower), and 8 to 16 (finisher) wk of age. Birds and feed were weighed at 2, 4, 6, 8, 12, and 16 wk of age. Carcass and feather compositions were determined on sample birds at 0, 2, 4, 6, 8, 12, and 16 wk of age. Lower body weights, better feed efficiency, and less feed intake per period, with the exception of the last period, were exhibited by the SxAA broilers vs. the RxAA broilers. Lower weights, feed consumption, poorer feed efficiency, and more carcass fat were evident for the female broilers vs. male counterparts. Strain-cross and sex initially influenced breast meat yield, but after day 14, the primary influence was strain-cross or sex. The RxAA broilers contained more carcass fat on a dry matter basis than the SxAA broilers, reflective of the selection for lean mass in the Steggle breed. Generally, feather yield was greater for male broilers than for females. Protein, fat, and ash content of feathers varied. Overall information attests that broiler strains and their sexes differ in their demands for growth.