Ram Semen Cryopreservation for Portuguese Native Breeds: Season and Breed Effects on Semen Quality Variation

Abstract

The semen quality is one of the determinant factors of ram semen cryopreservation. The present retrospective study aimed to characterize the seasonal ram pattern during the year for ten Portuguese local sheep breeds, hypothesizing that the breed and season had low effects on the main spermatozoa traits. A total of 1471 ejaculates were used and evaluated (fresh semen) from 85 rams between 2004 and 2020 and re-evaluated after thawing (thawed semen). The effect of breed, season, and sperm cryopreservation on nine semen traits were evaluated. The volume per ejaculate, spermatozoa (SPZ) concentration, and total number of SPZ per ejaculate, were affected by breed (p < 0.001) but not by season (p > 0.05). As expected, the semen processing was the most significant (p < 0.001) factor of variation on seminal parameters. Moreover, breed and interactions between breed × semen processing, modulated the response of alive SPZ, abnormal morphology, head, and intermediate piece defects. In fresh semen, season only affected the intermediate piece defects due to the highest percentage observed between February and April period in some breeds. Overall, and despite the mentioned particularities, there were similarities among the ten local breeds. We also concluded that the seasonal effect on ejaculate and SPZ traits is not significant in our region. These local ram breeds have low seasonality and can be employed in natural mating as well as semen donors for cryopreservation and assisted reproductive biotechnologies during the whole year at our latitude.