Effect of dry season nutritional supplementation on fertility in bulls in Sanyati smallholder farming area, Zimbabwe

Twelve indigenous bulls, allocated to two groups comprising six bulls each, were used in the study to determine the effect of dry season nutritional supplementation on scrotal circumference and semen characteristics. One group was supplemented with silage while the other acted as the control. Soundness evaluations were conducted in October, December and February. Breeding efficiency of bulls was measured by pregnancy rates. Month and nutrition significantly affected body condition and body weights in both groups (P 0.05) for the supplemented bulls than the control group in October (36.3 ± 1.5 versus 32.0 ± 2.6 cm). Nutrition and month of collection did not affect scrotal circumference and semen characteristics in both groups (P > 0.05). There were no significant differences in sperm motility between the two groups. Sperm concentration was higher in the control group in all months of collection (P < 0.05). Body condition scores and body weights of cows increased initially but declined to a minimum in December (2.9 ± 0.34; 298 ± 15 kg, respectively). Highest mean pregnancy rate (42%) was recorded in Jese village in October while the lowest (13%) was recorded in Makomo village during the same month. It was concluded that supplementary feed did not influence semen characteristics and reproductive capacity of the bulls.   Key words: Bull, nutrition, scrotal circumference, semen, breeding soundness evaluation, pregnancy rate, ovarian activity.