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

Abstract

The effect of dry season supplementation with crop residue based rations on body weight, scrotal circumference and serum testosterone concentrations in Red Sokoto weaner bucks at 5, 6 and 7 months of age was investigated in this study. There were 7 treatment groups which comprised of a positive control ration (conventional concentrate) fed at 1 and 2% of the bucks' body weights (rations 1A and 2A), two crop residue based test rations each fed at 1 and 2% of body weight (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 basal diet. Body weight and scrotal circumference of the bucks significantly increased (P<0.05) with age from 5.9 Kg at 5 months to 10.2 Kg at 7 months of age and 4.40 cm to 6.95 cm, respectively. Bucks on ration D (unsupplemented group) had the lowest body weight 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 body weights (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 regards 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 pre-pubertal Red Sokoto bucks has a significant influence on their body weight, 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.