Effect of Breed and Season in Buck Semen Cryopreservation: The Portuguese Animal Germplasm Bank

Abstract

The aims of this study were to characterize the semen as well as the influence of breed, season, and semen processing on spermatozoa (SPZ) traits of four native Portuguese goat breeds used for the bank of Portuguese animal germplasm (BPAG). A total of 1017 ejaculates from Serrana (n = 30), Bravia (n = 15), Charnequeira (n = 11), and Preta de Montezinho (n = 3) bucks were collected between 2004 and 2020 at (EZN-INIAV; 39° N) during the whole year under natural conditions. All the fresh and cryopreserved (−196 °C) semen was evaluated and stored in the BPAG. Bravia bucks (the smallest breed) produced less (p < 0.05) volume of ejaculate than all the other breeds, which was higher during the full breeding season (September–January; p < 0.05), regarding all the other breeds. Contrarily, in general, SPZ concentration was lower during September–January, but total SPZ per ejaculate remained similar (p > 0.05) during May–August and September–January in Serrana bucks. The SPZ viability and SPZ midpiece defects were slightly influenced by breed and SPZ head defects by season (lowest % in February–April; p < 0.05). On the contrary, the freezing–thawing cycle strongly influenced (p < 0.01) all SPZ traits. The correlation coefficients of these traits between fresh and thawed SPZ were low (up to 0.33; p < 0.01), highlighting the importance of semen processing in semen cryopreservation. We conclude that breed and season had a relevant effect on ejaculate traits, but it was much less evident for the studied SPZ traits. These native goats can serve as semen donors throughout the year, under natural conditions.