EFFECT OF INSEMINATION VOLUME AND CONCENTRATION OF SPERMATOZOA ON EMBRYO RECOVERY IN MARES

Two experiments were conducted to determine 1) if an insemination volume of 50 ml yielded a lower embryo recovery rate than an insemination volume of 10 ml, when both volumes contained a total of 250 million progressively motile spermatozoa , and 2) if an insemination volume of 50 ml yielded a lower embryo recovery rate than an insemination volume of 10 ml, when both volumes contained 25 million motile spermatozoa/ml of extended semen. Mares exhibiting estrus for 2 or more days and having a follicle > 35 mm were inseminated every other day throughout estrus with extended semen. For the first experiment, insemination volumes (10 or 50 ml) of extended semen contained 250 million progressively motile spermatozoa. There was a significant (P<0.05) reduction in embryo recovery from mares inseminated with the 50-ml volume. The second experiment utilized 10-ml insemination volumes of extended semen containing 25 million motile spermatozoa/ml. Also utilized were insemination volumes of 50 ml containing either 5 or 25 million motile spermatozoa/ml. There was a tendency (P=0.17) for reduced embryo recovery from mares inseminated with the 50-ml volume containing 5 million motile spermatozoa/ml compared with mares inseminated with the 10-ml volume containing 25 million motile spermatozoa/ml. However, there was no difference in the embryo recovery rate between mares inseminated with the 50-ml volume containing 25 million motile spermatozoa/ml when compared to the 10-ml volume containing 25 million motile spermatozoa/ml. These results suggest that a large insemination volume containing a low concentration of motile spermatozoa may yield a lower embryo recovery rate than the same volume containing a higher concentration of motile spermatozoa.