Comparison of three diluents for the storage of fresh bovine semen

Abstract

In New Zealand, 95% of the semen used for artificial insemination in cattle is processed as liquid semen. Storage of liquid semen for up to 3 days in Caprogen ® diluent enables a 10-fold reduction of the insemination dose, compared to frozen-thawed semen, without a reduction in fertility. In this Caprogen ® diluent spermatozoa are stored under N 2 gas in the presence of catalase. However, a new diluent (CEP-2), which was originally based on the biochemical composition of bovine cauda epididymal plasma, could become an appropriate alternative to Caprogen ®. In this study, the effect of addition of catalase to bovine spermatozoa stored for 6 days in CEP-2 diluent under aerobic and anaerobic conditions was evaluated and compared with a Tris diluent. Additionally, the quality and in vitro fertilizing capacity of fresh bovine semen stored for 6 days at 5 °C in the Triladyl ®, CEP-2 (without catalase and N 2 gas) and Caprogen ® diluent were compared. Addition of 4.5 mg/mL catalase to CEP-2 diluent under aerobic and anaerobic conditions had no effect on sperm quality. Spermatozoa stored in CEP-2 diluent moved faster and straighter than spermatozoa stored in Triladyl ® or Caprogen ® diluent. The in vitro fertilization and polyspermy rates did not differ significantly between spermatozoa stored for 6 days at 5 °C in CEP-2 and Caprogen ® diluent, but were significantly lower for spermatozoa stored in Triladyl ® diluent. We can conclude that based on the in vitro results, the CEP-2 diluent is a better diluent than Triladyl ® and a good alternative to the Caprogen ® diluent for long term storage of fresh bovine semen at 5 °C. To confirm these promising in vitro results further in vivo experiments are required.