Effect of unilateral cornual insemination upon fertilization rate in superovulating and single-ovulating cattle.

In Exp. 1, 21 first-service cattle and seven repeat-breeder cattle, averaging 4.7 infertile services, were brought into estrus and superovulated by treatment with follicle-stimulating hormone and prostaglandin F2 alpha. At insemination, semen was deposited in the greater curvature of one uterine horn, about midway between the utero-cervical junction and the utero-tubal junction. Cattle were necropsied 2 to 7 d after estrus and ova were recovered and examined. The fertilization rate for first-service cows was 74% of 362 intact ova and for repeat-breeders, 43% of 128 intact ova (P less than .001). Fertilization rate in first-service cows was 81% on the side of semen deposition and 68% on the opposite side (P less than .01); the rates in repeat-breeders were 54% and 32% (P less than .025). Differences between sides were due mostly to four cows that averaged 93% fertilization on the side of semen deposition and 19% on the opposite side. The proportion of fertilized ova with accessory sperm (17%) did not differ between sides of the reproductive tract. In Exp. 2, 60 first-service and 32 repeat-breeder cows in natural estrus had semen deposited in the uterine body or in the greater curvature of one uterine horn, either on the side of impending ovulation or on the opposite side. At necropsy, 55 ova were recovered from first-service cows, of which 42 (76%) were intact and 13 (24%) were ruptured or fragmented. Of the 42 intact ova, 41 (98%) were cleaved. From the 32 repeat-breeders, 30 ova were recovered, of which 26 (87%) were intact and 4 (13%) were ruptured; 23 of the 26 intact ova (88%) were cleaved. Site of semen deposition had no significant effect on either fertilization rate or number of accessory sperm in either type of cow. First-service cows averaged more accessory sperm (40) than did repeat-breeders (19, P less than .01). Overall results indicated that sperm deposited deep in one uterine horn fertilized ova nearly as frequently in the opposite oviduct as in the adjacent oviduct except in 14% of superovulating cattle.