INSEMINATION RESULTS WITH SLOW-COOLED STALLION SEMEN STORED FOR 70 OR80 HOURS

An insemination trial was conducted to evaluate the fertility of exten ded slow-cooled stallion spermatozoa stored for 70 h or 80 h at 5 to 7 degrees C before insemination. Then, 1 or 2 of the first sperm-rich f ractions were collected with an open-ended vagina from 4 stallions. Se men from each stallion was diluted within 2 to 3 min after collection with a modified Kenney skim milk extender (6). The proportion of raw s emen in the insemination doses was 24 +/- 6%. One insemination dose (2 5 to 50 ml) consisted of approximately 2 billion total spermatozoa. In the trial, palpation per rectum and ultrasonography of 34 mares (40 c ycles) were performed every 12 h. The pregnancy rate per cycle (30-d) with semen stored for 70 h before insemination was 77% (17 cycles) and , with semen stored for 80 h, 57% (23 cycles). The difference was not statistically significant. The combined pregnancy rate per cycle was 6 5%. These results indicate that stallion semen can retain its fertiliz ing capacity for up to 80 h when collected and diluted using this proc edure and when the inseminations are done less than 12 h after ovulati on.