RESPONSES OF NIGERIAN LOCAL COCKERELS TO DIETARY VITAMIN A SUPPLEMENTATION

Abstract

A five-week experiment was conducted to investigate the effect of dietary vitamin A (VA) supplementation on blood testosterone and semen quality characteristics of Nigerian local cockerels. Sixty-four, pubertal local cockerels were divided into 4 groups of 16 birds, and each group replicated four times. Each group was assigned to one experimental diet in a completely randomized design designated Q (0 mg VA per 300 g dry matter (DM feed)), Q (0.75 mg VA per 300 g dry matter (DM feed)), Q2 (1.50 mg VA per 300 g dry matter (DM feed)) and Q, (2.25 mg VA per 300 g dry matter (DM feed)). Semen and blood samples for analysis were randomly obtained from 2 birds in each replicate and analysed statistically. A quadratic equation was used to determine the VA levels for optimum serum testosterone and semen values. Daily VA supplementation at 0.75 mg/ 300g DM feed increased (P<0.05) ejaculate volume and sperm concentration value. In addition, daily VA supplementation at 1.15 mg/300 g DM feed increased normal sperm and active motile cells by 1.78% and 24.51%, respectively while, daily VA administration at 2.25 mg/300 g DM feed reduced (P<0.05) sluggish motile cells by 57.32% and increased (P<0.05) serum testosterone by 49.00%. Results of quadratic function revealed that VA levels of 2.03, 3.27, 2.24, 1.22, 2.57 and 2.08 mg/300 g DM feed supported optimum ejaculate volume, pH, sperm concentration, active motile sperm and normal sperm production while the highest ratio of 4.16 supported optimum testosterone level. There are significant (P<0.01) regression effect on sluggish motile sperm and serum testosterone value of local cockerels on daily VA. It is concluded that daily vitamin A supplementation at 0.75 -2.25 mg /300 g DM feed positively influenced blood testosterone and some semen traits of local cockerels.