PS2-6. Increasing Supply of omega-6 Fatty Acids to Beef Cows During the Early Embryonic Period: Effects on D 22 Pregnancies.

Abstract This experiment compared hormonal, uterine, and conceptus factors associated with pregnancy establishment in beef cows supplemented with different levels of Ca salts of soybean oil (CSSO) for 22 d beginning after artificial insemination (AI). Sixty-six multiparous, non-lactating Angus-influenced cows were allocated to 11 pens equipped with Calan-gate feeders (6 cows/pen), and timed-inseminated on d 0. After AI, cows were ranked by expression of estrus, body weight, and body condition score, and assigned to receive 1 of the 4 treatments: a) 100 g/d of CSSO (n = 16), b) 250 g/d of CSSO (n = 17), c) 100 g/d of Ca salts of palm oil (CON; n = 16), d) 250 g/d of CON (n = 17). Treatments were mixed with 0.5 kg of corn, and individually fed to cows daily using the Calan-gate feeders. Cows received ad libitum access to hay, mineral mix, and water. Blood samples were collected and transrectal ultrasonography was performed to verify ovulation and corpus luteum (CL) volume immediately before AI (d 0), on d 7, 14, and 21. All cows were slaughtered on d 22 for collection of conceptus and uterine luminal flushing. Fatty acid (FA) source × dose interactions (P ≤ 0.05) were detected for plasma concentrations of linoleic and total omega-6 FA, which were similar (P ≥ 0.55) between CON at 100 or 250 g/d, greater (P ≤ 0.05) in CSSO at 100 g/d compared with both CON treatments, and greater (P ≤ 0.05) in CSSO at 250 g/d compared with all treatments. No FA source nor FA dose effects were detected (P ≥ 0.12) for plasma progesterone concentrations and CL volume during the experiment, as well as proportion of cows with a conceptus. Within cows that had a conceptus, cows supplemented with CSSO had heavier (P = 0.04) conceptuses, and tended to have greater concentration of prostaglandin F2α in the uterine flushing media compared with CON cows (FA source effect), whereas dose effects were not detected (P ≥ 0.22) for these variables. No FA source nor FA dose effects were detected (P ≥ 0.17) for concentrations of prostaglandin E2 in the uterine flushing media from cows that had a conceptus. Within cows that had a conceptus, CSSO-supplemented cows had greater (P ≤ 0.05) mean mRNA expression of myxovirus resistance 2 and interferon-stimulated gene 15 in whole blood, whereas a tendency for a similar outcome was observed for mean mRNA expression of 20,50-oligoadenylate synthetase compared with CON-supplemented cows. No dose effects were detected (P ≥ 0.37) for mRNA expression of these genes in whole blood. In summary, post-AI CSSO supplementation increased plasma concentrations of omega-6 FA and improved factors associated with maternal recognition of pregnancy on d 22 of gestation.