Effect of the non-steroidal anti-inflammatory drug, carprofen, on weaned sheep following non-surgical mulesing by intradermal injection of cetrimide

Abstract

Objective: To assess in weaned lambs the palliative effects of the non-steroidal anti-inflammatory drug, carprofen, following intradermal injection of cetrimide to induce non-surgical mulesing. Procedures: We allocated 40 weaned lambs (20-22 weeks old) to four groups of 10 animals: (1) control, 2) conventional surgical mules, (3) intradermal treatment and (4) intradermal treatment + carprofen. Non-surgical mulesing was induced by intradermal injection of 4% (w/w) cetrimide + 3% (w/w) polyvinylpyrrolidone in water. In group 4, carprofen (4 mg/kg, SC) was administered 1 h before intradermal treatment. Five weaners, including an animal from each treatment, were run in each pen. Neutrophil to lymphocyte ratio, cortisol, beta-endorphin and haptoglobin levels and rectal temperature were monitored at least daily for the first 7 days after treatment, then weekly until day 28. Body weight was measured weekly and behaviour was measured every 15 min for 12 h on the day of treatment, then on days 1, 2, 4, 6, 12, 21 and 28 following treatment. Results: The intradermal treatment resulted in high fever and elevated blood cortisol by 12 h. Rectal temperatures were significantly elevated until 5 days after treatment, cortisol was elevated until 3 days after treatment, haptoglobin for at least 7 days after treatment and the neutrophil to lymphocyte ratio until 4 days after treatment. Average daily gain was depressed in the week following treatment. Abnormal behaviours (hunched standing, stiff walking, pawing, lateral lying and lying intention) were increased on the day of treatment and for 6 days post treatment. Carprofen reduced the time spent in abnormal behaviours by approximately two-thirds but did not ameliorate the physiological responses to the intradermal treatment. Conclusions: In weaner sheep, carprofen ameliorated the behavioural responses, but was unable to provide relief from the intense and sustained physiological responses to non-surgical mulesing by intradermal injection of cetrimide. Systemic side-effects may be unavoidable with formulations based on quaternary ammonium compounds that are designed to reduce the risk of fly strike in sheep by remodelling breech tissue through induction of tissue necrosis.