Effect of Dietary Amino Acid Level on Change from Starter to Grower Diets for Broiler Chickens

Abstract

Two experiments were conducted to determine effects of time of changing from starter to grower feed for broilers as influenced by amino acid density of the diet. Diets were formulated to provide a minimum of 100, 110, and 120% of suggested amino acid levels for male broilers. Starter diets were fed to 0, 7, 14, and 21 days of age with grower diets fed to 40 days, and finisher diets from 40 to 45 days of age. Broilers were processed to examine treatment effects on carcass composition and parts yield.Although amino acid content of the diet significantly affected a number of live performance parameters, there was no interaction of time of diet change and amino acid composition of diets. Mean weight of broilers at 40 days was significantly reduced when birds were placed on grower diets at 0 days, but mean weight at 45 days did not differ significantly among treatments. Mean 45-day weight of females placed on grower feed at 0 days was significantly less than that of females placed on grower feed at 7 or 14 days, but did not differ significantly from that of females placed on grower feed at 21 days of age. Time of change from starter to grower diets had no significant effect on feed utilization, calorie utilization, mortality, dressing percentage, abdominal fat content, or parts yield of male or female broilers. When diets were changed from starter to grower at 0, 7, or 14 days of age, there was a linear increase in breast meat yield of males as the amino acid content increased; however, when diets were changed from starter to grower at 21 days of age, there were no differences in breast meat yield among males fed the different amino acid levels.Based upon prevailing feed prices and performance data from the present experiments, changing from starter to grower diets at 7 or 14 days of age would result in the lowest feed cost to produce a pound of chicken, with no loss in live performance.