The effect of testosterone propionate on growth of broiler chickens

The effects of testosterone propionate (TP) on body weight, tissue percentages of body weight, serum IgM, and rectal temperature (2 h postinjection) of male and female broiler chickens were investigated at 28 and 48 days posthatching. Testosterone propionate was dissolved in sesame oil and was injected at 2 mg/kg of body weight every other day, and controls were treated with sesame oil at similar volume, starting Day 7 posthatching. Administration of TP reduced (P < .05) body weight and percentages of liver, testes, and bursa of Fabricius at 28 and 48 days of age. At 28 and 48 days of age, muscle percentage and comb growth of TP-treated birds increased (P < .05) but ovarian weight was unaffected. Concentrations of IgM in serum of TP-injected birds was unchanged at Day 28, but increased (P < .05) at Day 48. Testosterone propionate did not affect percentages of bone or abdominal fat in either sex. Rectal temperature was depressed (P < .05) by TP treatment in both sexes at both ages.