Serum sexual steroid hormones and lipids in commercial broilers (Gallus domesticus) in Costa Rica

Abstract

The poultry-breeding industry worldwide has focused on the development of hybrids for meat or egg production. In Costa Rica, there is a popular belief that commercial broilers have a high growth rate because they are raised with steroid hormones. This study was conducted to assess BW, nutritional state, and serum concentrations of some steroid hormones in a representative sample of 600 male and female Cobb 500 broilers from commercial farms and to compare them with a control group of 38 Cobb 500 broilers of both sexes reared in an experimental station. Control birds were weighed weekly during the 40-d experiment. Feed for the control group was prepared by personnel at the Investigation Center in Animal Nutrition of the University of Costa Rica and was supplied ad libitum. Commercial birds were blood sampled, weighed, and slaughtered at 40 d of age. All biochemical analyses were performed at the Faculty of Microbiology or the Hematological Investigation Center and Related Sicknesses of the University of Costa Rica. Compared with commercial birds, control birds had lower mean BW (2,004 ± 168 vs. 2,127 ± 260 g; P = 0.004) and higher serum concentrations of total cholesterol (3.72 ± 1.01 vs. 3.12 ± 0.49 mmol/L; P < 0.001). No significant differences were observed in mean serum concentrations of triglycerides and steroid hormones between the control and experimental groups. We conclude that the high BW and growth rate reached by these broilers in approximately 6 wk was not due to circulating steroid hormone levels.