Effect of fish meal supplementation on luteal sensitivity to intrauterine infusions of prostaglandin F2α in the bovine.

Progesterone is a steroid hormone secreted from the corpus luteum (CL), which is responsible for establishment and maintenance of pregnancy. Early embryonic mortality often occurs due to inadequate regulation of uterine prostaglandin (PG) F2α secretion, leading to a decrease in progesterone and loss of pregnancy. The objective of the current study was to determine the effects of fish meal supplementation on luteal sensitivity to intrauterine infusions of PGF2α. Nonlactating beef cows received corn gluten meal or fish meal supplementation for 60 days. Cows were administered four intrauterine infusions of 0.25 mL saline at 6-h intervals (n = 6 corn gluten meal; n = 5 fish meal) or two doses of 0.5 mg PGF2α in 0.25 mL saline at 12-h intervals (n = 11 corn gluten meal; n = 11 fish meal) commencing on days 10 to 12 of the estrous cycle. At time of each infusion, luteal biopsies were collected to determine the effects of supplementation on expression of immediate early and steroidogenic genes involved in cholesterol transport and progesterone biosynthesis. Transrectal ultrasonography was performed to measure diameter of CL, and blood samples were collected to determine serum progesterone. Intrauterine infusion of PGF2α resulted in upregulation or no change in FOS, NR4A1, and 3BHSD and downregulation in LDLR, STARD1, and CYP11A1. Although CL diameter decreased, infusion of PGF2α resulted in functional regression in 91% of cows supplemented with corn gluten meal, and only 46% for fish meal supplemented animals. Results demonstrate that fish meal supplementation alters luteal sensitivity to PGF2α, which may affect fertility.