Effect of storage temperature, cooling rates and two different semen extenders on canine spermatozoal motility

Abstract

Ejaculates were collected form three mixed-breed male dogs daily for 3 d. The semen was diluted in either a nonfat dried milk solid-glucose (NFDMS-G) or egg yolk citrate (EYC) extender at a concentration of 25 × 10 6 sperm/ml. The diluted samples were exposed to three different storage temperatures (35, 22 and 4°C). Three cooling rates (−1.0, −0.3 and −0.1°C/min) were also investigated at the lowest storage temperature (4°C). The semen was evaluated for total motility, progressive motility and velocity at 0, 6, 12, 24, 48, 72, 96 and 120 h after collection by two independent observers. Interactions between extenders, temperatures and time after collection were found for each of the variables. Nonfat dried milk solid-glucose diluent was superior to EYC (P<0.05) in preservating sperm motility parameters that were evaluated for most of the observations. The evaluated sperm motility parameters were also significantly superior (P<0.05) in semen stored at 4°C than at 35 or 22°C for most of the observations. The progressive motility and velocity of sperm in semen cooled at 4°C in NFDMS-G were higher (P<0.05) at the fast and medium cooling rates (−1.0 and −0.3°C) than at the slow cooling rate (−0.1°C/min) at 24 and 72 h, and at 48 h, respectively. In conclusion, the present study suggests that canine spermatozoal motility is well preserved when a NFDMS-glucose extender is added to the semen and the semen is cooled at a medium or fast rate to a storage temperature of 4°C. Additional studies are needed to evaluate the fertility of semen stored in this manner.