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

SIMPLE SUMMARY: This study mainly aimed to evaluate the seasonal and breed effects on spermatozoa (SPZ) traits of ten Portuguese sheep breeds, cryopreserved and stored in the Portuguese National Germplasm Bank. The mean volume and SPZ concentration of the ejaculate was 0.77 mL and 5039 ± 51 × 10(6)/mL, respectively, and were affected by breed but not by season. The viability (alive SPZ), individual motility, and abnormal morphology of fresh semen were 63.2 ± 0.2%, 61.41 ± 0.2%, and 10.1 ± 0.1%, respectively. A significant decrease of 28.5% of the viability and 35.5% of individual motility, as well as an increase of 54.5% in the SPZ abnormal morphology was observed in thawed semen. An effect of breed, but not of season, was observed on these SPZ traits. Nonetheless, breed × season interactions influenced individual motility and abnormal morphology, except for tail defects. Overall, the effect of season on ejaculate and SPZ traits was not significant and local rams are able to be SPZ donors for cryopreservation during the whole year in our latitudes. 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.