Effects of Cooling Rates, Plunge Temperatures and Warming Rates On Survival and Fertility of Cryopreserved Swamp Buffalo Spermatozoa

Abstract

Experiments were conducted to determine the effects of cooling rate, plunge temperature and warming rate on the motility and the acrosome integrity of swamp buffalo spermatozoa obtained from three bulls. There were three cooling rates: at 10°, 20°, and 30°C/min and each of them had -40°, -80°, and -120°C as the temperature before being plunged into liquid nitrogen. The spermatozoa frozen under nine cooling conditions mentioned before were then thawed both at 1000° and 200°C/min. The result of this experiment was shown that cooling rate, plunge temperature and warming rate significantly affected the survival of spermatozoa (p<0.05). Optimal cooling conditions were found to be cooling spermatozoa from 4° to -120°C either at 20° or 30°C/min. Rapid warming (1000°C/min) was superior to slow warming (200°C/min). In an additional study, comparing the fertility of spermatozoa frozen under optimal conditions and those frozen by a routine protocol used for semen processing were assessed. A total of 178 swamp buffalo cows were inseminated with cryopreserved spermatozoa, and their pregnancy status was assessed 60 days later by rectal palpation. There were no significant differences (p>0.05) in pregnancy rates between 43% (26/62), 40% (23/58) of cows inseminated with sperm cooled at 20°C/min and 30°C/min, respectively and 28% (17/60) of cows inseminated with sperm frozen by a routine protocol.