Scrotal circumference, bodyweight and serum testosterone concentration of Red Sokoto weaner bucks as influenced by dry season crop-residue supplementation

The effect of dry season supplementation with crop-residue-based rations on bodyweight, scrotal circumference and serum testosterone concentrations in Red Sokoto weaner bucks at 5, 6 and 7 months of age was investigated in the present study. There were 7 treatment groups which were fed a positive control ration (conventional concentrate) fed at 1 and 2% of the bucks' bodyweights (Rations 1A and 2A), two crop-residue-based test rations each fed at 1 and 2% of bodyweight (1B, 2B, 1C and 2C), and a negative control that was unsupplemented (Ration D). All treatment groups had ad libitum access to natural pastures and Digitaria smutsii hay as a basal diet. Bodyweight and scrotal circumference of the bucks significantly increased (P < 0.05) with age from 5.9 kg to 10.2 kg, and 4.40 cm to 6.95 cm, at 5 and 7 months of age, respectively. Bucks on Ration D (unsupplemented group) had the lowest bodyweight and scrotal circumference. Bucks on Ration 2A showed a significant increase in basal testosterone concentration from 0.32 ng/mL at 5 months of age to 0.65 ng/mL at 7 months of age. Peak testosterone concentration also increased from 1.0 ng/mL at 5 months to 2.8 ng/mL at 7 months of age. Bucks on test Ration 2C had higher bodyweights (6.75, 8.00 and 10.00 kg at 5, 6 and 7 months of age, respectively) than bucks on the other test Ration B (6.20, 7.20 and 8.50 kg, respectively). There were no significant differences between the two test rations with regard to scrotal circumferences of the bucks at all ages. However, at 7 months of age, bucks on test Ration 2C had significantly higher peak testosterone concentration (1.80 ng/mL) than their counterparts on test Ration 2B (1.30 ng/mL). The secretory patterns of testosterone were episodic and pulsatile in nature. It was concluded that crop-residue supplementation in prepubertal Red Sokoto bucks has a significant influence on their bodyweight, scrotal circumference and testosterone production. Test Ration C was a cheap, affordable and better crop-residue-based ration for optimal reproductive performance than test Ration B.