ACCESSORY SPERM - THEIR IMPORTANCE TO FERTILITY AND EMBRYO QUALITY, AND ATTEMPTS TO ALTER THEIR NUMBERS IN ARTIFICIALLY INSEMINATED CATTLE

Accessory sperm number and its relationship to fertilization and embryo quality was evaluated in cattle after nonsurgical recovery of ova or embryos 6 d after insemination. Efforts to alter accessory sperm number per ovum included 1) blockage of retrograde sperm loss at insemination using a modified insemination device, 2) elevated sperm number per inseminate (40 x 10(6) vs 20 x 10(5)), and 3) alteration in semen quality (percentage of viable and morphologically normal sperm in the inseminate). None of these efforts affected accessory sperm number per ovum or embryo. However, blockage of retrograde semen flow for 3 h or use of semen of below-average quality (decreased percentage of viable and morphologically normal sperm) resulted in significant decreases in number of viable embryos and increases in number of degenerate embryos and unfertilized ova compared with conventional insemination (P < .03) and use of semen with an average percentage of viable and morphologically normal sperm (P < .06). Number of accessory sperm per embryo or ovum was positively related to fertilization and embryo quality (P < .05). Mean accessory sperm +/- SD and the median value (in parentheses) for unfertilized ova, degenerate embryos, and embryos classified fair to poor and excellent to good were, respectively, .3 +/- .8 (0), 5.4 +/- 8.9 (1.0), 15.8 +/- 28.6 (3.5), and 16.9 +/- 29.5 (5.0). We conclude that efforts to improve accessory sperm numbers per embryo or ovum failed and that high variation and skewness of accessory sperm toward 0 may make median values more meaningful than means. The positive relationship between accessory sperm number and fertilization status/embryo quality encourages further efforts to improve this trait in artificially inseminated cattle.