The effect of aspirin on prostaglandin F2α secretion in lactating dairy cows

Early embryonic loss may be related to untimely secretion of prostaglandin F2α. The objective of this study was to examine the effect of aspirin, a nonsteroidal anti-inflammatory drug (NSAID), on prostaglandin F2α secretion and luteal function in lactating dairy cows by characterizing plasma prostaglandin metabolites (PGFM) and progesterone (P4) during the luteal phase. Estrous cycles were synchronized in 23 lactating Holstein cows using a 5-d CIDR-Ovsynch protocol. Transrectal ultrasonography was performed to confirm ovulation and formation of a corpus luteum. On d 14, after after the second injection of gonadotropin-releasing hormone, cows were assigned randomly to receive aspirin (n = 11, 46.65 g/dose) orally on d 14 (2×) and d 15 (1×), 12 h apart, or no aspirin (n = 12, control). On d 15, hourly blood samples were collected for PGFM, and daily blood samples were collected (d 14 to 22) for P4 concentrations. Mean P4 concentrations before treatment (d 14) did not differ between groups. There was an effect of treatment and treatment × time on PGFM (P < 0.05). Mean PGFM concentrations decreased (P < 0.05) after treatment and remained low for 11 h after last aspirin dose, whereas in the control PGFM remained unchanged. For cows that underwent luteolysis (n = 16), P4 concentrations were greater (P = 0.05), and the days to luteolysis tended (P = 0.09) to be longer for the aspirin compared with the control. This study indicated that oral administration of aspirin may suppress prostaglandin F2α secretion during d 14 to 15 after estrus and may prevent early luteal tissue regression.