Pregnancy percentage following deposition of sex-sorted sperm at different sites within the uterus in estrus-synchronized heifers

Our objective was to assess the effect on heifer pregnancy rate of deposition at three sites within the uterus of frozen-thawed sex-sorted sperm at a fixed time after estrus synchronization. Estrus was synchronized in 209 heifers by administration of PGF2a 14 days apart. At 80–82 h after the second PGF2a injection, X-chromosomes bearing fractions of semen with 2.2 × 106 sperm in insemination dose were used for single insemination into the uterine body (UB-AI, n = 91) or for intracornual deposition in the middle of the uterine horn (MH-AI, n = 57) or close to the utero-tubal junction (UTJ-AI, n = 61). The overall pregnancy rate was 43.1%. Pregnancy rates did not differ (P > 0.05) among sites of sperm sperm deposition, between the two farms at which the heifers were kept or between the two bulls producing the semen. Within UB-AI, MH-AI and UTJ-AI treatments, pregnancy rates were 41.8%, 49.1% and 39.3%, respectively (P > 0.05). Pooled across classes for deposition site, pregnancy rate was 25.1% higher (P < 0.01) for heifers showing strong signs of estrus than for heifers showing weak signs of estrus (45.9 versus 20.8%, respectively). Embryonic and fetal loss from diagnosis of pregnancy to term and at calving equalled 5.6%. Of 88 calves of identified sex, 93.2% were female. In conclusion, pregnancy rates of heifers did not differ significantly following deposition of 2.2 × 106 sex-sorted sperm 80–82 h after the second PGF2a injection near the utero-tubal junction, in the middle of the horn or into the uterine body.