Post-AI Supplementation with Ca Salts of Soybean Oil Increases Pregnancy Success in Bos Taurus Beef Cows.

Two experiments investigated the effects of supplementing Ca salts of soybean oil (CSSO) during early gestation on reproductive function and pregnancy rates to timed-AI in B. taurus beef cows. In Exp. 1, 771 lactating multiparous Angus cows were divided into 22 groups of approximately 35 cows/group, and timed-AI on d 0. After AI, groups were randomly assigned to receive (as-fed basis) 200 g/cow daily of a corn-based supplement and: 1) 100 g/cow daily of CSSO (n = 11; Essentiom; Church and Dwight Co., Inc., Princeton, NJ) or 2) 100 g/cow daily of prilled SFA (CON, n = 11; EnergyBooster; Milk Specialties, Eden Prairie, MN). Groups were maintained in individual pastures with free-choice access to forage, and offered treatments from d 0 to 21. Pregnancy status was determined on d 30 via transrectal ultrasonography. Cows receiving CSSO had greater (P = 0.01) pregnancy rates to timed-AI compared with CON cows (60.2 vs. 51.7%; SEM = 4.2). In Exp. 2, 90 lactating multiparous Angus cows housed in 18 drylot pens (5 cows/pen) were assigned to the same timed-AI program and treatments from Exp. 1 (9 pens/ treatment), receiving 20 kg/d (DM basis) of grass-alfalfa hay. Transrectal ultrasonography was performed to verify ovulation and corpus luteum (CL) volume immediately prior to AI, d 7, and 15. Within each treatment, 22 cows diagnosed without the presence of a CL on d 0, but with a CL greater than 0.38 cm3 on d 7 and 15, were assigned to conceptus collection via transcervical flushing with saline followed by endometrial biopsy on d 15. Both procedures were performed in the uterine horn ipsilateral to the CL. Blood samples were collected for whole blood RNA extraction (d 20) and pregnancy diagnosis (d 30; BioPRYN; Gold Standard Labs, Bowling Green, KY). Conceptus from cows receiving CSSO had greater (P ≤ 0.05) mRNA expression of interferon-tau vs. conceptus from CON cows (21.3 vs. 12.1 fold effect; SEM = 3.4). Within cows diagnosed as pregnant on d 30, blood mRNA expression of interferon-stimulated gene 15 and 20,50-oligoadenylate synthetase on d 20 were greater in CSSO vs. CON cows (43.1 vs. 29.8 fold effect, SEM = 4.6; 26.8 vs. 18.3 fold effect, SEM = 2.7; respectively). Hence, post-AI CSSO supplementation to beef cows increased pregnancy rates to timed-AI compared with non-supplemented cows, which can be attributed to increased mRNA expression of interferon-tau by the conceptus when CSSO is supplemented during early gestation. [ABSTRACT FROM AUTHOR]