The effects of sperm dose, semen quality, and retrograde sperm blockage on accessory sperm number and embryo quality in the artificially inseminated bovine

Abstract

This study was designed to: 1. Determine the effects of sperm dose and retrograde sperm blockage on mean number accessory sperm/ova. 2. Evaluate the relationship between mean number accessory sperm/ova and fertilization status/embryo quality. 3. Determine if mean number accessory sperm/ova or embryo quality are affected by semen quality. 4. Compare the percentage of morphologically normal accessory sperm with the percentage of normal cells in the inseminate. Using excised reproductive tracts, a French insemination rod housed in a 24-gauge Foley catheter was determined to be effective in blocking retrograde flow of semen following insemination. In a preliminary study, blocked vs conventional inseminations (control) were made using average quality frozen semen at 20 x 10⁶ sperm/dose. Although not different (P > .1), the mean number accessory sperm/ovum was 20 ± 40 (n= 24) and 13 ± 28 (n= 26) for the blocked and control methods, respectively. In Expt. 1, the conventional (control) and blocked system were again compared in a 2x2 factorial using low quality semen at 20 and 40 x 10⁶ sperm/dose. Mean number accessory sperm/ova was not affected by dose, blocking, nor the interaction. Embryo quality was negatively affected by blocking (P < .1), and unaffected by sperm dose. In Expt. 2, embryo quality and accessory sperm numbers were unaffected by a 40 x 10⁶ sperm dose of either average or below average quality semen. However, embryo quality tended to be improved by the average quality semen. Accessory sperm were significantly enriched with morphologically normal cells when compared with those in the inseminate (P < .01). Viable quality embryos (poor thru excellent) had the highest mean number accessory sperm/ovum (16.2 ± 28.9), most unfertilized ova (UFO) contained zero accessory sperm (.27 ± .83) and degenerates embryos were intermediate in number (5.4 ± 8.7). The relationship between embryo quality and accessory sperm number appears to vary in response to semen quality.