Seasonal variation in semen quality of Black Bengal bucks under subtropical conditions in Bangladesh

Seasonal variation in semen quality can influence the planning and efficiency of goat artificial insemination programmes. This study evaluated fresh semen characteristics of Black Bengal bucks maintained at the Artificial Insemination Center, Bangladesh Agricultural University, Mymensingh, Bangladesh, from July 2013 to June 2014. Ten bucks aged 17-23 months were included, and semen was collected weekly using an artificial vagina. The study compared ejaculate volume, sperm concentration, sperm motility, the percentage of live spermatozoa, and the percentage of morphologically normal spermatozoa across winter (November-February), summer (March–June), and the rainy season (July-October). According to the source thesis, seasonal differences were not statistically significant (P > 0.05) for any of the measured characteristics. Ejaculate volume and sperm concentration were numerically highest in winter (0.9 ± 0.1 mL and 3,978 ± 0.6 million/mL, respectively). Motility and the percentage of live spermatozoa were numerically highest in the rainy season (78.4 ± 1.0% and 90.2 ± 0.7%), whereas the percentage of normal spermatozoa was highest in summer (92.0 ± 1.3%). These results suggest that semen characteristics were broadly similar across seasons under the management conditions studied; however, the findings require cautious interpretation because the study involved only ten bucks, the original seasonal sample counts are inconsistently reported, and the standard errors for sperm concentration require verification. Reanalysis of the original repeated-measures data is recommended before drawing firm conclusions for artificial insemination programmes.