PS2-7. Increasing Supply of omega-6 Fatty Acids to Beef Cows During the Early Embryonic Period: Effects on D 16 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 16 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 = 17), 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 = 16). 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 and 14. Cows diagnosed without the presence of a CL on d 0, but with a CL greater than 0.38 cm3 in volume on d 7 and 14, were assigned to conceptus collection via transcervical flushing on d 16. Data were analyzed as a 2 × 2 factorial arrangement using cow as experimental unit. Fatty acid (FA) source × dose interactions (P ≤ 0.05) were detected for plasma concentrations of linoleic, arachidonic, and total omega-6 FA in plasma, 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 ≥ 0.34) for plasma progesterone concentrations and CL volume during the experiment, as well as proportion of cows with a conceptus and length of the flushed conceptus. Within cows that had a conceptus, cows supplemented with CSSO had greater (P = 0.04) concentrations of interferon-tau in the uterine flushing media compared with CON cows (FA source effect), whereas a dose effect was not detected (P = 0.75). Fatty acid (FA) source × dose interactions (P ≤ 0.05) were detected for concentrations of prostaglandin F2α and prostaglandin E2 in the uterine flushing media, which were greater (P ≤ 0.04) in cows supplemented with CSSO at 250 g/d compared with all other treatments. In summary, post-AI CSSO supplementation increased plasma concentrations of omega-6 FA and improved factors associated with maternal recognition of pregnancy on d 16 of gestation.