Combined effect of DHA and α-tocopherol supplementation during bull semen cryopreservation on sperm characteristics and fatty acid composition

Abstract

The aim of this study was to investigate the effect of adding n-3 fatty acids (FA) and α-tocopherol (VE) to semen extender on freezing ability and FA composition of bull sperm. Semen was collected from 10 Iranian Holstein bulls and was pooled. In the first experiment, semen was divided into 12 groups including 4 levels of n-3 FA (0, 0.1, 1, 10 ng ml(-1) ) and 3 levels of VE (0, 0.1, 0.2 mmol). The treatment of 0.2 mmol VE and 10 ng ml(-1) n-3 FA had the best post-thawed sperm characteristics (P < 0.01). In the second experiment, lipid composition of the latest treatment and control (without FA and VE) was determined. Adding n-3 FA increased docosahexaenoic acid (DHA) percentage before freezing and after thawing. The ratio of n-3 to n-6 before freezing was higher (P < 0.05) in treated group than in control, and this ratio in the fresh sperm was greater than in the post-thawed sperm (P = 0.1). Results suggested that adding DHA accompanied with an antioxidant to an extender could improve cryosurvival of bull sperm via altering membrane lipid composition.