Endocrine manipulation of growth and tissue development of broiler chickens

Abstract

This study evaluated the potential use of in ovo administration of exogenous endocrine compounds to enhance growth and reduce fat content of posthatch broiler chickens. Effects of in ovo administration of growth hormone (GH) plus triiodothyronine (T3)on growth and adiposity of broiler chickens were investigated in experiment 1. Vehicle or vehicle containing .1 ng T3 plus .25 mg GH, . 1 ng T, plus 2.5 mg GH or .1 ng T3 plus 25 mg GH were injected into the albumen of fertile eggs on day 11 of incubation. Female broilers from eggs injected with .1 ng T3 plus 25 mg GH had significantly greater body weights as compared to controls from 5 weeks to 7 weeks of age. Administration of .1 ng T3 plus 2.5 mg G H resulted in a significant (P <. 05) 20.5 % reduction in fat pad weight in males. The effect of manipulating estrogen status in ovo on posthatch growth rate and skeletal development was examined by two trials in experiment 2. Effects of in ovo administration of tamoxifen citrate (T) or 17f3-estradiol (E) on growth and fattening of broiler chickens were assessed in trial 1. At day one of incubation, either vehicle, vehicle containing 20 Mg of E or 200 Mg of T was injected into the albumen of fertile eggs. Neither sex ratios, body weight, fat pad weight nor adipose cellularity parameters were altered by the concentrations of T or E administered in trial 1. In trial 2, eggs from a commercially selected broiler line and from a population of Athens-Canadian Randombreds (AC) were injected with either vehicle or vehicle containing 500 mg of T. At three weeks of age, chicks were sampled for fat pad weight and gonadal sex. The higher concentrations of T administered in trial 2 resulted in significant modifications in phenotypic sex ratios at hatch in both genotypes. However, these phenotypic changes in sex ratios did not yield significant alterations in body weight, fat pad weight or skeletal development. In conclusion, in ovo endocrine administration resulted in modifications of growth and tissue development in broilers. However, the alterations were dependent on the type and concentration of hormone.