Pregnancy risk in beef and dairy cows after supplementing semen with transforming growth factor beta-1 at the time of artificial insemination.

Our objective was to determine if the addition of a concentrated human recombinant transforming growth factor beta-1 (TGF) to bovine semen at the time of AI would result in increased risk of pregnancy in beef and dairy cows. Suckled beef cows (n = 1,132) in 11 herds across 2 states and lactating dairy cows (n = 2,208) in one organic-certified herd were enrolled. Beef cows received fixed-time AI (FTAI) following a 7 d CO-Synch + controlled internal drug release estrous synchronization protocol. Dairy cows were inseminated following observation of natural estrus expression. Cows received either no treatment as a control (CON) or 10 ng of TGF in 10 µL added through the cut-end of a thawed straw of semen immediately prior to AI. At the time of FTAI of beef cows, the mean ±â€…SD age was 5.0 ±â€…2.4 yr, BCS was 5.3 ±â€…0.7, and days postpartum was 78.2 ±â€…15.5 d. The overall pregnancy risk (PR) in beef cows was 55.2% to AI and 90.5% season-long. PR in beef cows was not affected (P = 0.27) by the addition of TGF (53.1% vs. 58.1%). Furthermore, there was no difference (P = 0.88) for season-long PR in beef cows that received TGF (91.2% vs. 91.5%). At the time of insemination of dairy cows, the mean ±â€…SD lactation was 3.0 ±â€…1.3 lactations, BCS was 2.9 ±â€…0.3, days in milk was 115.6 ±â€…56.6 d, and cows had received 2.4 ±â€…1.5 inseminations/cow. The overall pregnancy risk to AI in dairy cows was 23.1%. PR to AI for dairy cows was not affected (P = 0.32) by addition of TGF (22.0% vs. 23.8%). In conclusion, PR to AI was not affected by addition of TGF to thawed semen immediately prior to AI in beef or dairy cows.

Seminal plasma is the fluid portion of the ejaculate that is routinely removed or significantly diluted when preparing semen for artificial insemination. Seminal plasma has been shown to elicit changes to the tissues of the uterus at the time of insemination that improves pregnancy outcomes in rodents and swine. Here, we supplemented the molecule of seminal plasma, transforming growth factor beta-1, to semen at the time of artificial insemination in an attempt to improve pregnancy rates in beef and dairy cattle. In total, 3,340 cows were inseminated; half received no treatment, and the other half received a supplementation of transforming growth factor beta-1. We found that supplementing transforming growth factor beta-1 did not improve the pregnancy rate in beef or dairy cattle. We conclude that the pregnancy rate was not affected by the supplementation of transforming growth factor beta-1 to semen at the time of insemination. Future studies should consider the effects of transforming growth factor beta-1 on other pregnancy outcomes, such as calving rate, birth weight, and postnatal growth.