EFFECTS OF ARTIFICIAL PHOTOPERIODS ON SEXUAL-BEHAVIOR AND SPERM OUTPUT IN THE RABBIT

Male rabbits aged from 4 to 4.5 months were subjected to a 8L:16D phot operiod for 4 weeks and were then split into two groups. One group of 13 males was maintained at 8L:16D (group 8). The other included 16 mal es and was submitted to 16L:8D (group 16). Two successive ejaculates w ere collected and analysed once a week for 6 months. Animals from grou p 8 were sexually more active and ejaculated significantly larger volu mes of semen than those from group 16. Performance of males from group 16 was better for all other measurements, whether these were qualitat ive (motility, percentage of live spermatozoa) or quantitative. Averag es for the total number of spermatozoa and number of live spermatozoa per ejaculate were significantly greater in males submitted to 16L:8D (509 and 408 v. 452 and 344 X 10(6) spermatozoa, respectively). Howeve r the testes of rabbits in group 8 had a significantly greater volume than those in group 16 (22.3 v. 17.4 cm(3), P < 0.001). After the anim als were slaughtered when 11 months of age, the volume and weight of t he testes and the testis and epidydimis reserves did not differ signif icantly between groups. Under our experimental conditions, the sperm o utput of bucks exposed to 16 h of daylength was greater than that of b ucks exposed to 8 h of daylength but in vivo and post-mortem measureme nts did not reflect this difference.