Seasonal changes in sperm chromatin condensation in ram (Ovis aries), Iberian red deer (Cervus elaphus hispanicus), and brown bear (Ursus arctos)

The effect of seasonality (temperate environment, Spain) on the chromatin status of ovine (Churra breed), Iberian red deer, and brown bear spermatozoa was studied. This work aims to improve genetic resource banks (GRBs) by enhancing existing knowledge of the effect of season on sperm quality. Samples were obtained by electroejaculation in Iberian red deer and brown bear and by artificial vagina in ram. We used the sperm chromatin structure assay (SCSA) to study the level of chromatin condensation of the spermatozoa in each studied period. These periods were: ram, breeding season (from September to January), nonbreeding season (from February to June), and summer (July and August); red deer, breeding season (September and October), postbreeding (November and December), and nonbreeding (the rest of the year); brown bear, prebreeding (March and April), breeding (May and June), postbreeding (July and August), and nonbreeding (September to February). Chromatin in ram was more decondensated in summer, and no differences were observed between the breeding and nonbreeding season. However, in red deer, spermatozoa obtained during the nonbreeding season showed more condensed chromatin than those obtained in the rut and postrut periods. Similarly, brown bear rendered sperm with loose chromatin in the prebreeding and breeding seasons. Less condensed chromatin in the breeding season may be related to faster epididymal transit due to enhanced spermatogenesis.