The effect of aspirin on prostaglandin F2α secretion in lactating dairy cows during the luteal phase of the estrous cycle

Abstract Text: Approximately, 70-80% of total embryonic loss in dairy cattle occurs between days 8 and 16 after artificial insemination (AI).  Early embryonic loss may be due to the premature secretion of prostaglandin F_2α (PGF_2α) during days 14-16 after fertilization.  The objective of this study was to examine the effect of Aspirin, a non-steroid anti-inflammatory drug (NSAID), on PGF_2α secretion in lactating dairy cows by characterizing blood plasma prostaglandin metabolites (PGFM) and progesterone (P₄) during the luteal phase of the estrous cycle.  Twenty-four lactating Holstein cows were synchronized to ovulation. The ovulation was confirmed by ultrasonography (d 1).  On d 14 and after detection of corpora lutea, cows were assigned randomly to receive Aspirin (total of 140 g) or no Aspirin (control) and the blood sample was obtained from each cow.  Aspirin was given orally on d 14 (2×) and d 15 (1×), 12 hours apart.  On day 15, 6 h after the last dose of Aspirin, hourly blood samples were taken for 6 h for PGFM concentrations.  Daily blood samples were also collected (d 15 to 23) to examine P₄concentrations. One cow was eliminated from the study for having < 1 ng/mL P₄ on d 15.  Analyses of repeated measures, using the mixed model procedure of SAS were utilized.  The model included treatment, the repeated factor time, and treatment × time interaction. Cow was the random effect. On d 14, mean P₄ was > 1 ng/mL for all cows and it was similar between groups. Before treatment, there was no difference in mean PGFM concentrations between the groups, (203 vs 224 ng/mL; SE ± 39 for Aspirin and control, respectively). There was an effect of treatment and treatment × time on mean PGFM (P < 0.05). Mean PGFM concentrations were decreased (P < 0.05) 30 h after initiation of treatment and remained low for 5 h after last treatment, whereas they remained unchanged in the control. Overall, mean PGFM concentrations were 106 and 190 ng/mL (SE ± 33) for Aspirin and control, respectively. Blood P₄ concentrations post-treatment were similar between the two groups (3.6 vs. 3.2 ng/mL; SE ± 0.6), but declined from d 15 to d 23 (P < 0.01).  The study indicated that oral administration of Aspirin treatment may suppress PGF_2α during d 14 to 15 after estrus and prevent early luteal tissue regression; however, no effect on P₄ was observed.

Keywords: dairy cows, NSAID, prostaglandin F_2α