Seasonal changes in semen characteristics, hormonal profiles and testicular activity in Zaraibi goats

Ten Zaraibi buck goats were used to study the effect of season on semen quality. Bucks were housed and fed according to standard recognized practices. Semen was collected twice a week for 7 consecutive weeks (starting from the 3rd to the 9th week) in the mid of the each season. During these periods scrotal circumference was measured fortnightly. The number of mounts terminating in ejaculation and the time interval between the first mount and ejaculation were also recorded. The physical parameters of semen and semen index (semen volume×spermatozoa concentration/ml×live spermatozoa%×progressive motility%) were measured for the first and the second ejaculates of each semen collection during the week. At the end of each season, testicular biopsies were obtained surgically from three bucks for histological evaluation. Plasma testosterone, FSH and LH concentrations were also determined twice weekly. Bucks demonstrated the highest libido in summer, using the least (P < 0.01) number of mounts and a shorter (P < 0.01) reaction time. This coincided with a higher (P < 0.01) level of plasma testosterone (10 ng/ml) and the best semen quality (semen index: 3354×106). During autumn, bucks recorded the highest (P < 0.01) ejaculate volume (0.98 ml) and the maximum output of sperm (4565×106), as well as a lower (P < 0.01) percentage of sperm abnormalities (8.8%). This was accompanied by high concentrations of plasma LH (average 2.9 mIU/ml). The histological structure of the testis indicated that during autumn (natural breeding season) seminiferous tubules (Sta) occupied the majority of the testicular tissues (76.6%) and the spermatic layers were highest. It can be said that Zaraibi bucks have distinct seasonal activity, with poor semen characteristics during winter and spring—which may be a critical obstacle for implementing intensive systems of three kidding in 2 years when natural mating is applied. © 2005 Elsevier B.V. All rights reserved.