The influence of season on sexual behaviour and semen quality of crossbred (Saanen x Nubian) bucks in the Sudan

Elsir A. Babiker, Sharaf Eldin A. Makawi


This study was conducted to investigate the effect of season on some reproductive traits in crossbred (Saanen x Nubian) bucks. Sixty four semen samples were collected with an artificial vagina from four crossbred bucks. Sexual behaviour of the bucks was assessed by the reaction time to mating. Body measurements including scrotal circumference, heart girth and body condition scores were recorded throughout the study. The relationship between season and sperm characteristics (volume of ejaculate, concentration, mass activity, sperm motility percent, dead sperm percent and abnormal sperm percent) were studied. The influence of season on sexual behaviour was significant. The shortest reaction time was during autumn (35.75 sec.) and winter (40.20 sec.) while the longest was during summer (53.43 sec.). The effect of season on scrotal circumference was significant. It was highest (27.75 cm) during summer and least (25.05 cm) during winter. The influence of season on semen characteristics was significant. Highest ejaculate volumes were during summer (1.07 ml) and autumn (0.90 ml) and least during winter (0.87 ml). Highest sperm concentrations were during autumn (2.54 ± 0.40 x 109) and least during summer. Influence of season on mass activity of the semen was significant. Mean values were higher during autumn (3.32 ± 0.47) and progressively decreased during summer. Higher sperm motility (67.50 ± 6.45%) was during autumn and was least during summer. Less dead spermatozoa were during autumn (10.25 ± 4.23%) and were high during summer (16.87 ± 3.30%). All sperm abnormalities showed significant seasonal variations. Mean morphologic defects followed the same trend of dead spermatozoa. They were least in autumn (7.67 ± 3.42%) and highest in summer. Correlations calculated between scrotal circumference and ambient temperature, scrotal circumference and daylight, semen volume and ambient temperature, and semen volume and daylight were positive and significant (0.73, 0.68, 0.64 and 0.68, respectively), whereas dead and abnormal spermatozoa were negatively correlated with humidity (- 0.70 and - 0.67, respectively). The best semen was produced during autumn and winter compared to summer.

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