IN OVO TREATMENT WITH AN AROMATASE INHIBITOR MASCULINIZES POSTNATAL HORMONE LEVELS, ABDOMINAL FAT PAD CONTENT, AND GH PULSATILITY IN BROILER-CHICKENS

Vorozole, a selective aromatase inhibitor, was administered in ovo to test the specific embryonic role of estrogen in conferring the sex dis tinction in GH release and body phenotype in broilers. On Day 6 of inc ubation, eggs were injected with saline or with different concentratio ns of vorozole. Postnatal blood samples were analyzed for T-3, T-4, GH , estradiol (E-2), and testosterone (T). At the age of 4 wk, control a nd vorozole-treated birds were cannulated, and serial blood samples we re withdrawn every 10 min for 5 hr, wherein GH pulsatility characteris tics were determined using deconvolution analysis. The proportional ab dominal fat pad weight was reduced significantly in the treated groups , especially in female birds. The vorozole treatment increased plasma T-3, E-2, T, and GH concentrations, and decreased T-4. The frequency o f the GH pulses was lower and the interval between the bursts (min) wa s higher in the vorozole-treated group, as were the mass secreted per burst (ng/ml), the amplitude (ng/ml/min) and the production rate (ng/m l/5 hr). In conclusion, early in ovo treatment with a potent aromatase inhibitor is able to increase the mean serum T-3 and GH concentration and masculinize the GH pulse pattern, resulting in an economically fa vorable decrease in abdominal fat pad content in male and female broil ers at slaughter age. (C) Elsevier Science Inc. 1998.