9 EFFECTS OF MECLOFENAMIC ACID ON LUTEAL FUNCTION OF BEEF CATTLE

Abstract

The objective of this study was to determine the effects of meclofenamic acid, a nonsteroidal anti-inflammatory, on luteal function of beef cattle. A total of 18 Angus cows, aged between 2 and 3 years old, were enrolled in the experiment. All cows were synchronized using a 5-day CIDR protocol. Briefly, cows received 100 μg of gonadorelin diacetate tetrahydrate (GnRH; Cystorelin^®, Merial, Athens, GA, USA) and a controlled internal drug release insert (CIDR; Eazi-Breed^TM CIDR^®, Pfizer Animal Health, New York, NY, USA). Five days later, the CIDR was removed and 50 mg of dinoprost (Lutalyse^®, Pfizer Animal Health) was administered intramuscularly. Oestrus was determined by twice daily observations of mounting behaviour and tail painting scores (day of oestrus = Day 0). At 72 h after dinoprost, a second dose of gonadorelin (100 μg, IM) was administered. On Day 14, cows were randomly assigned to the following treatment groups: 1) control: 10 mL of saline solution administered IM; 2) systemic: 2 g of meclofenamic acid administered IM; and 3) oral: 2 g of meclofenamic acid administered orally. Cows were treated once daily for 11 days (i.e. until Day 24) and no adverse reactions were observed. Blood sampling and ovarian ultrasonography were performed every 72 h from Day 0 until Day 12 and then every 48 h until the end of the study. Serum progesterone concentrations were determined by radioimmunoassay and were used to determine functional luteolysis (i.e. progesterone <1 ng mL^–1). Ovaries were evaluated for the presence of a corpus luteum and to evaluate follicular growth and subsequent ovulation. One-way ANOVA was used to compare the day of peak progesterone concentration, lifespan of the corpus luteum and the length of the oestrous cycle between groups. Significance was set at P < 0.05 and data are presented as means ± standard error of the mean (Table 1). There were no effects of meclofenamic acid administration on any of the parameters evaluated (P > 0.05). In conclusion, meclofenamic acid administration did not affect luteal function in our study. Potentially, higher doses of meclofenamic acid may be necessary to inhibit prostaglandin synthesis and prevent luteolysis.

Table 1.  Effects of meclofenamic acid administration on the day of peak progesterone concentration, lifespan of the corpus luteum (CL) and the length of oestrous cycle in beef cows (mean ± standard error of the mean)

Funding was provided by The Ohio State University, College of Veterinary Medicine, USDA-Animal Health Formula Funds. The authors are also grateful to the staff at the OSU Beef Center Facility for helping with animal handling and care.