Gonadal and Extra – Gonadal Sperm Characteristics of Rabbit Bucks Fed Cottonseed Cake – Based Diets Supplemented With Vitamin E

The aim of this study was to investigate the effect on sperm characteristics of rabbit bucks fed cottonseed cake based diets supplemented with vitamin E. Sixty–four (64) weanling rabbit bucks, aged 5 – 6 weeks, with an average weight of 511.28g, were randomly allocated to eight treatment combinations comprising four levels (0, 5, 10 and 15%) of cottonseed cake (CSC) and two levels (0, and 30 mg / kg diet) of vitamin E supplementation, with eight replicates in a 2 x 4 factorial arrangement within a completely randomized design experiment. Animals were first fed the CSC-based diets for eight weeks in a pre-pubertal trial, after which the diets were slightly adjusted to suit their growing phase. They were then fed the test diets for another 12 weeks. At the end of this trial, 3 rabbits per treatment were slaughtered and their reproductive organs dissected out for gonadal and extra-gonadal sperm assessment. Gonadal sperm reserve (GSR), daily sperm production (DSP) and daily sperm production per gram testis (DSP/g) for the bucks fed 5, 10 and 15% CSC without vitamin E supplementation were significantly (P < 0.05) lower compared to the control group, but were similar to one another. Supplementing the CSC diets with vitamin E increased the GSR, and DSP significantly (P < 0.05) at corresponding levels of CSC. Rabbits fed the CSC-based diets supplemented with vitamin E had significantly (P < 0.05) lower GSR and DSP than those fed the control diet supplemented with vitamin E. The DSP/g for the supplemented groups increased (P < 0.05) with increasing CSC level. Extra-gonadal sperm concentration (EGSC), sperm motility (EGSM) and percentage normal sperm cells (NSC) were significantly depressed with increasing CSC level without vitamin E supplementation. Supplementing the diets with vitamin E tended to improve the EGSC, EGSM and NSC at all levels of CSC. It was concluded that prolonged feeding of CSC to rabbit bucks adversely affected both gonadal and extra-gonadal sperm characteristics. Supplementing CSC-based diets with vitamin E tended to ameliorate the adverse effects. Thus rabbit bucks intended for breeding should not be fed CSC-based diets unless adequately supplemented with vitamin E.