Effects of cooling rate and storage temperature on equine spermatozoal motility parameters

• Published in: Theriogenology Vol. 29; no. 5; pp. 1043 - 1054
• Main Authors: Varner, D.D., Blanchard, T.L., Love, C.L., Garcia, M.C., Kenney, R.M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 1988
• Subjects: cooling rate; motility; semen storage; spermatozoa; stallion; cooling rate; motility; spermatozoa; stallion; semen storage
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/S0093-691X(88)80028-1

Two experiments were conducted to examine the effects of cooling rate and storage temperature on motility parameters of stallion spermatozoa. In Experiment 1, specific cooling rates to be used in Experiment 2 were established. In Experiment 2, three ejaculates from each of two stallions were diluted to 25 × 10 6 sperm/ml with 37°C nonfat dry skim milk-glucose-penicillin-streptomycin seminal extender, then assigned to one of five treatments: 1) storage at 37°C, 2) storage at 25°C, 3) slow cooling rate to and storage at 4°C, 4) moderate cooling rate to and storage at 4°C, and 5) fast cooling rate to and storage at 4°C. Total spermatozoal motility (TSM), progressive spermatozoal motility (PSM), and spermatozoal velocity (SV) were estimated at 6, 12, 24, 48, 72, 96 and 120 h postejaculation. The longevity of spermatozoal motility was greatly reduced when spermatozoa were stored at 37°C as compared to lower spermatozoal storage temperatures. At 6 h postejaculation, TSM values (mean % ± SEM) of semen stored at 37°C, slowly cooled to and stored at 25°C or slowly cooled to and stored at 4°C were 5.4 ± 1.1, 79.8 ± 1.6, and 82.1 ± 1.6, respectively. Mean TSM for semen that was cooled to 4°C at a slow rate was greater (P<0.05) than mean TSM of semen cooled to 4°C at a moderate rate for four of seven time periods (6, 24, 72 and 120 h), and it was greater (P<0.05) than mean TSM of semen cooled to 4°C at a fast rate for five of seven time periods (6, 12, 24, 72 and 120 h). Mean TSM of semen cooled to 4°C at a slow rate was greater (P<0.05) than mean TSM of semen cooled to 25°C for five of seven time periods (24 to 120 h). A similar pattern was found for PSM. Mean SV of semen cooled to 4°C at a slow rate was greater (P<0.05) than mean SV of semen cooled to 25°C for all time periods. A slow cooling rate (initial cooling rate of −0.3°/min) and a storage temperature of 4°C appear to optimize liquid preservation of equine spermatozoal motility in vitro.