Effects of aromatase inhibition by Letrozole on Ross 308 broiler chicken’ sex phenotype and performance

This study was conducted to evaluate the effects of an aromatase inhibitors on chick’s sex phenotype in order to produce more male birds which are economically beneficial to the broiler industry. In ovo injection of an aromatase inhibitor was carried out with 360 eggs of Ross 308 that randomly divided into six groups with 5 replicates. Experimental groups included: 50 (L50) and 100 (L100) µg of Letrozole, multivitamin + antibiotic (MA), antibiotic (A), male and female mixed control group (C1), and also male and female separated control group (C2). Hatched chicks were reared with the same diet and condition up to 42 days of age. Percentage of hatchability, hematological parameters, level of steroid hormones, bone strength, and biochemical composition in the progeny broiler chickens were evaluated. In ovo injection of Letrozole did not cause any significant effect on percentage of hatchability and the chicks’ hematological and serum biochemical parameters whereas notably resulted in increased percentage of male phenotype and their serum testosterone level, feed intake, and improved feed covvertion ratio in the broiler chicks (P<0.05). This study reveals that in ovo Letrozole administration results in a higher male phenotype of hatched broiler chicks and markedly improved feed conversion rate of the progenies without negative effects on their survival and hatchability.