Effect of insemination-related factors on pregnancy rate using sexed semen in Holstein heifers

The objectives were to determine the effects of insemination with sexed semen at spontaneous and induced estrus, fixed-time insemination at synchronized estrus, the deposition site, estrous intensity, housing, age, body weight, and bull on the pregnancy rate in Holstein heifers, and to compare the quality traits of sexed sperm with those of unsexed semen. The study was conducted on 3206 heifers, housed in three free-stall barns and in four tie-stall facilities. After synchronization by two prostaglandin F2α (PGF2α) treatments 14 days apart, 281 heifers were inseminated conventionally and 118 intracornually with sexed semen, and 532 and 148 heifers, respectively, with unsexed semen 80–82 h after the second treatment. At spontaneous estrus, 1129 heifers were inseminated with sexed and 529 with unsexed semen, and at estrus induced by a single PGF2α treatment 185 heifers were inseminated with sexed and 284 with unsexed semen. Heifers were inseminated conventionally with sexed semen 12 h after detection of estrus, and with unsexed semen according to the a.m.– p.m rule. Sexed and unsexed semen doses from five bulls were evaluated for motility, morphology, membrane integrity, and chromatin stability. Overall pregnancy rate with sexed semen (41.7%) was 80.8% of that with unsexed semen (51.6%) and was lower than with unsexed semen irrespective of the type and intensity of estrus, and deposition site. Insemination at spontaneous estrus resulted in a higher pregnancy rate (53.4%) than at induced (41.9%) or synchronized (44.7%) estrus. Pregnancy rates did not differ after intracornual (44.9%) or conventional insemination (48.4%). Strong estrus resulted in higher pregnancy rate (by 14.4% points) compared to weak estrus. The type of housing, age, and weight of heifers had no effect irrespective of the type of semen. The total, progressive and linear motility, and membrane integrity were lower and proportions of immotile sperm greater, for sexed than for unsexed semen.