Semen characteristics, gonadal and extra-gonadal traits of dutch-belted rabbits fed supplemental doses of zinc
The effect of zinc on the semen characteristics, gonadal and extra-gonadal traits of male rabbits was assessed. Thirty-two rabbit bucks aged approximately two months were used for the experiment. The rabbits were randomly assigned to four experimental diets each supplemented with zinc at 0 ppm/kg (control), 50 ppm/kg, 100 ppm/kg and 150 ppm/kg of feed and designated as Treatments 1, 2, 3 and 4. The feeding trial lasted for eighty-four days in a completely randomized design. Semen sample was collected from individual rabbit bucks using artificial vagina and semen characteristics were measured. Four rabbit buck from each treatment were sacrificed and eviscerated for measurement of testicular and other reproductive organs including testes weight, length and circumference, epididymis weight and length, vas deferens length. The results showed that there were significant differences (p<0.05) in all the parameters measured for semen characteristics. Semen volume was highest in T3 (0.778 ml) but was similar (p>0.05) to the values obtained for T2 and T4. It was lower (p<0.05) in T1 (0.61 ml) than in T3 but similar (p>0.05) to the values for T2 and T4. Sperm concentration was similar (p>0.05) among T2, T3 and T4 and their values were significantly (p<0.05) higher than that for T1. Total sperm was highest in T3 which was similar to T4. T4 was similar to T2 but significantly higher than T1 (64.8 x 106/ml). Sperm motility was highest in T3 (89%) which was significantly (p<0.05) higher than the other treatments. Average testis weight was similar (p>0.05) between T2, T3 and T4 but was lowest (p<0.05) in T1. Average epididymis weight was similar (p>0.05) between T2, T3 and T4. It was also similar between T1, T2 and T4. From the results, it can be concluded that zinc supplementation improved semen traits as well as the gonadal and extra-gonadal parameters of Dutch-belted rabbit bucks. Since supplementation beyond 50ppm/kg of feed made only marginal improvements in reproductive parameters measured, it is recommended that level of zinc supplementation be used for Dutch-belted rabbit bucks to improve their reproductive potentials.
Keywords: Dutch-belted rabbits, supplementary zinc, semen characteristics, gonadal/extragonadal traits