Precocious sexual maturity and enhanced egg production in chickens given goitrogen at an early age

Abstract

1. The effect of feeding methimazole to chicks from about 2 to 13 or 15 weeks of age on their sexual maturation and productivity was studied.

2. Methimazole caused a three‐fold increase in the relative weight of gonads in 9‐week‐old chickens, and there was histological evidence of precocious gonadal development.

3. Pullets aged 15 weeks and pre‐treated with goitrogen, matured earlier and produced more eggs if the treatment was discontinued at that age. Their growth rate was lower than that of normal birds.

4. Pullets fed on a diet containing 10 mg methimazole/kg from 10 to 92 d of age matured earlier and laid more eggs (P<0.01) than normal birds. They also grew more rapidly (P<0.01).