Evaluation of sexed semen deposition site on the in vivo embryo production of Nelore breed

This study’s aim was to verify if the site of sexed semen deposition influences the quantity and quality of embryos from superovulated Nelore cows. Twelve cycling females were used and went through a superovulation protocol (SOV), FTAI and embryo collection. The females received an intravaginal progesterone-releasing insert (1.9g P4, CIDR®, New York, USA) and 2 mg (I.M.) of estradiol benzoate (Estrogin®, Sao Paulo, Brazil) at a random day of the estrous cycle, day 0 (07h). Superstimulation was induced with 133 mg of FSH-p (Folltropin-V®, Ontario, Canada) in 8 decreasing doses at every 12h, I.M., beginning at D4. At D6, two 25 mg treatments of PGF2α were administered (07 and 19h, I.M., Lutalyse®, New York, USA). The progesterone devices were removed 36h after the first PGF2α, and a treatment of 0.25 mg of gonadorelin (I.M., Fertagyl®, Millsboro, USA) was given 48h after the first PGF2α. FTAI was performed at 18 and 30h after the gonadorelin treatment, with two straws, each containing 2.1x106 sperm cells, and the embryo collection was done 7 days after the gonadorelin treatment. Two replicates were performed, in a crossover design, according to semen deposition site, body or uterine horns, reaching a total of two collections per treatment. Images of the ovaries were taken and transferred to a computer, for measurement and analysis of the follicles, using the IMAGEJ® software (National Institute of Mental Health, Bethesda, USA). For statistical analysis, the PROC MIXED OF SAS® 9.0 (Statistical Analysis System, Cary, EUA) was used. There were no effect of treatement in any response variables analysed. At the beginning of the superstimulatory treatment, 5.2 ± 2.4 and 5.5 ± 1.9 follicles were identified, with mean diameter of 5.4 ± 1.7 and 5.1 ± 1.9mm, for the groups inseminated in the uterine body and horns, respectively. At the end of the treatment, 12.0 ± 3.0 and 12.3 ± 4.4 follicles were identified, with mean diameter of 8.6 ± 2.5 and 8.7 ± 2.4mm, for the groups inseminated in the uterine body and horns, respectively. It was noticed that 66.7% (8/12) of the animals had CL at the day of FTAI, been four animals in each group, and ultrasonography indicated possible failure to respond to the PGF2α. The group inseminated in the uterine body had embryo recovery rate of 41.1% (23/56) and the group inseminated in the uterine horns had 35.7% (15/42). It was observed a decrease in the embryo recovery rate across repetitions, where the first repetition achieved 44.3% (27/61) while the second showed embryo recovery rate of 29.7% (11/37). Yield was 52.2% (12/23) of morulas code 1 and 2 and early blastocyst (viable embryos) for the group inseminated in the uterine body and 60.0% (9/15) for the group inseminated in the uterine horns. In conclusion, based on the mean and standard deviations obtained, semen deposition site in the uterus following timed AI of superovulated cows did not affect quantity or quality of embryos recovered.