Motility and fertilizing ability of frozen-thawed ram sperm from two sheep breeds

Abstract

The aim of the study was to evaluate motility parameters of Lacaune (Lc) and East-Friesian (EF) ram frozen-thawed spermatozoa by CASA (Computer-Automated Sperm Analysis) technique in relation to their in vivo fertilizing ability. Fresh ejaculates were diluted in a Triladyl extender containing 20 % egg yolk, 6 % glycerol and 0.1 % trehalose and frozen in a liquid nitrogen vapour. The evaluation of frozen-thawed semen showed significant differences in sperm motility between the two sheep breeds by 30 (P<0.001) to 120 (P<0.05) min post thawing. Whole motility of spermatozoa was significantly reduced during incubation and by 120 min it was dropped to 7.68 (Lc) and 13.36 (EF) %. Similarly, the percentage of progressive motile spermatozoa was significantly reduced (P<0.001) during incubation, and only 6.31 % of Lc and 11.81 % of EF ram spermatozoa were progressive motile by 120 min of incubation. Significant decline of the velocity characteristics, such as a path velocity (VAP), curveilance velocity (VCL) and progressive velocity (VSL) was observed by 30 min (P<0.001) and 120 min (P<0.05) post thawing in Lc compared to the EF ram semen. Ram frozen-thawed semen was used for insemination of 99 hormonally synchronized ewes. The differences detected in the motility parameters of frozen-thawed spermatozoa from two sheep breeds were reflected in the pregnancy (12.24 and 28.00 %) and lambing rate (0.0 and 56.00 %) for EF and Lc, respectively. In conclusion, cryopreservation significantly affects the quality of frozen-thawed sperm by lowering sperm motion characteristics. This study revealed differences in basal motility parameters between ram sperm of two sheep breeds.