Tryptophan requirements of different broiler genotypes
2001
Rosa, A.P. | Pesti, G.M. | Edwards, H.M. Jr | Bakalli, R.
Two experiments were conducted with broiler chicks in battery brooders from 1 to 18 d of age to determine Trp requirements and to evaluate the performance of different genotypes (classic vs. high yield and male vs. female). Experiment 1 was a 6 x 2 factorial experiment, with six levels of Trp (0.09, 0.12, 0.15, 0.18, 0.21, and 0.24% of the diet) and two broiler chicken strains (male Arbor Acres Classic and Arbor Acres High Yield). Experiment 2 was a 6 x 2 factorial design with the same levels of Trp as in Experiment 1 and two sexes (males and females); Ross x Ross 308 birds were used. Both experiments had four replicate pens of eight birds each per treatment. The basal diet was based on corn (70.79%), corn gluten meal (17.44%), and gelatin by-product and poultry fat (23% of CP and 3.34 kcal/g of ME). At 18 d of age, three birds per replicate were killed, and livers and fat pads were removed. The broken-line linear model was used to estimate the chicks Trp requirement. Liver or liver fat and fat pad weights (as a percentage of body weight) were affected by dietary Trp level. In Experiment 1, the Trp requirements differed little; for gain they were 0.18 +/- 0.002% and 0.17 +/- 0.002%, and for feed conversion they were 0.16 +/- 0.004% and 0.16 +/- 0.002%, for the Classic and High Yield broilers, respectively. In Experiment 2, the Trp requirement of males was 0.17 +/- 0.003% for BW and 0.17 +/- 0.003% for feed conversion, and that of females was 0.17 +/- 0.003% for body weight and 0.16 +/- 0.001% for feed conversion. There was no apparent difference in the Trp requirement of young broilers due to genetic stock or gender (P > 0.05).
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