Efficiency of different extenders on cooled semen collected during long and short day length seasons in Martina Franca donkey

Artificial insemination with cooled semen is routine in equids because of its good fertility rates and relatively low costs. In several donkey breeds, especially in restricted populations, the use of cooled semen could be seen as the best way of improving reproductive performance and avoiding excessive inbreeding. Furthermore, most jennies have ovulatory estrous throughout the year, and thus, cooled semen could also be used during short day length season. The aims of this study were to evaluate the effects of different extenders on sperm quality during cooling in the Martina Franca breed, and to verify the preservation of cooled semen collected during long day length (May-June) and short day length (November-December) seasons. Three ejaculates were collected at 10-day intervals from each of six jackasses during both May-June and again in November-December time periods. Each ejaculate was cooled in INRA96 or E-Z Mixin at a low cooling rate and evaluated daily over a 120-h preservation time. The results showed a significant extender influence on preservation time in both periods. Semen diluted with INRA96 maintained a progressive motility of 36% and a straightness of 89% at 120h, whereas semen extended with E-Z Mixin had a mean progressive motility of 32% and a straightness of 81% at 48h during the May-June period. Despite having the same initial characteristics, semen collected during the short day length season had a higher rate of decline in semen quality during storage at 5 degrees C with E-Z Mixin.[...]