Seasonal Changes in Semen Quality and Cooling Ability in the Caspian Pony.

Abstract

Because only poor and conflicting information is available about annual changes in semen characteristics especially sperm morphology and semen cooling ability the aim of this study was to investigate seasonal changes in Caspian pony semen quality and to determine the best time for semen cooling. Experiments were performed using 10 Caspian pony from animal breeding center of Iran. Ejaculates were collected and cooled once every other week during 1 year in each of the four seasons. Volume, concentration, motility, and the number of morphologically normal sperm and sperm with major defects (abnormal heads, proximal droplets and abnormal midpieces) were evaluated. For all cooled semen samples motility as well as progressive motility was analyzed with CASA, and the hypo osmotic swelling test (HOS) was performed. To analyze seasonal differences 4 periods of 3 months each were defined: autumn, winter, spring and summer. During the 1 year experiment all semen quality parameters showed a clear seasonal pattern. The volume, total sperm count and motility in fresh semen were significantly higher (P < 0.05) in spring than in autumn, while sperm concentration was significantly lower in autumn compared with the other seasons. Regarding morphology, normal sperm was significantly lower (P < 0.05) in summer than at any other time of the year and higher values (P < 0.05) were found for major defects in autumn compared with spring and summer. The HOS test revealed that significantly (P < 0.05) more membrane damaged spermatozoa in autumn than in winter, spring, and summer. In conclusion, in our climatic conditions clear seasonal differences occur in semen quality of fresh and cooled semen, and that cooling of stallion semen should preferably be performed in spring. (platform)