Seasonal changes in testosterone and thyroxine concentrations in Mediterranean rams and bucks and their relationship with sperm cryoresistance

This study examines the relationship between seasonal changes in plasma testosterone and thyroxine concentrations these sperm resistance to freezing-thawing process Merino x Precoz crossbreed rams Florida breed bucks. Plasma concentration, head area, variables their cryoresistance ratios were analyzed throughout a year. Both species showed rise preceding fall. higher during autumn than spring summer (P<0.05), whereas not influenced by season. Conversely, bucks differences levels, with winter In bucks, negative correlation was detected ratio for membrane integrity (R=-0.88; P<0.05) from April September total motility (R=-0.66; P<0.05), curvilinear velocity (R=-0.61; amplitude of lateral displacement (R=-0.77; beat-cross frequency (R=-0.74; The results suggest that annual variation may be related endocrine changes, at least goat. Winter are most appropriate seasons collect freeze