Pregnancy Loss Associated with Timed-Artificial Insemination Using Gender-Selected Semen in Cows.

Pregnancy rates are lower for gender selected (GS) than non-selected, industry standard semen (STD) when used in timed-artificial insemination (TAI) protocols; however, lower pregnancy rates could be due to lower fertilization rates or early pregnancy loss post-TAI. The objective of this study was to determine pregnancy rates for GS compared to STD semen when used in combination with TAI between d 30 through 45 of gestation. Multiparous Angus (AN) and AN-cross cows (n = 80) were stratified by BCS, BW, and days post-partum; and assigned to be inseminated with GS (enriched for Y chromosome containing sperm), or STD semen. Cows were synchronized using the 7-day CO-Synch + CIDR procedure and TAI performed between 60 and 66 h post-CIDR removal. Cows were exposed to natural service beginning 14 d post-TAI. Pregnancy status was evaluated by ELISA for pregnancy specific protein B concentration (PSPB; BioPRYN, BioTracking, Moscow, ID) in maternal serum at d 30 and 45 of gestation (TAI = d 0) and by transrectal ultrasound on d 30, 35, 40 and 45 of gestation. Differences in pregnancy rates due to semen source within day of gestation were determined using Chi Square analysis. Pregnancy rates were lower when using GS semen on d 35 (P = 0.04; 35 and 57.5% for GS and STD, respectively) and d 40 (P = 0.04; 35 and 57.5%, for GS and STD, respectively) of gestation as determined by ultrasound. No difference in pregnancy rates due to semen source was observed at d 30 or 45 of gestation. Pregnancy rates as determined by PSPB levels did not differ at d 30 of gestation due to semen source (12.5 vs 15% for GS and STD, respectively); however, pregnancy rates at day 45 of gestation were lower for the GS group compared to STD at day 45 of gestation (P = 0.04; 40 versus 62.5 %, respectively). Of the animals identified as pregnant at d 30 by PSPB concentration, 55% were determined to be open by transrectal ultrasonography at d 45 and 73% did not calve to the TAI date. Increases in pregnancy rates at d 45 observed via ultrasound, compared to earlier dates were due to natural service. Pregnancy evaluation using ultrasonography indicated that GS pregnancies were lost by d 35 post-TAI which was not observed using PSPB ELISA and pregnancy rates at d 30 and 45 were not consistent between the two methods for determination of pregnancy.