Sedation With Xylazine Hydrochloride Decreases the Stress Response in Merino Meat Sheep During Routine Hoof Trimming in a Tilt Table

Abstract

We hypothesized that the hoof trimming in sheep in dorsal recumbency implicates a short but intensive stress situation and that the sedation with xylazine causes a decrease in the stress response in this situation. Ten healthy female merino meat sheep were randomly divided into two groups receiving either xylazine hydrochloride (0.1 mg/kg body mass (BM) applied intramuscularly) or a placebo treatment with 0.9% NaCl. Routine hoof trimming was performed in a tilt table and vital signs (rectal temperature (RT), heart rate (HR), and respiratory rate (RR)), 33 different behavioral traits and blood cortisol concentrations were recorded throughout the experiment at six different time points (total of 55 min). The procedure itself elicited a clear stress response (increase in the RR, RT, defensive movements, lip twitching, swallowing, and flight behavior). Parallelly, the blood cortisol concentrations were increased, reaching their maximum with 81.5 ng/ml in the control group when the sheep were tilted back into a standing position. In the sedated sheep, no increase in the RR and RT and a decrease in the HR were observed. In addition, the behavioral signs showed a decrease in flight, defensive, and general stress behavior (decrease in licking, movement of head and legs, and sitting on knees), complemented by the serum cortisol concentrations showing 2.28 times reduced concentration at the end of the procedure, compared to the control sheep. The results confirm our hypothesis and support the conduction of future trials investigating the feasibility and benefit of a sedation of sheep prior to routine hoof trimming under practical circumstances.

Effect of a targeted pain management protocol for the treatment of dermatitis interdigitalis contagiosa in Merino meat sheep in a tilt squeeze chute

“…Sheep that received xylazine and IVRA had significantly lower maximum blood cortisol concentrations, areas under the curve and cortisol concentration during the stress model than sheep that received a placebo. Claw treatment without pain management results in stress caused by the restraint (Fieseler et al, 2018;Amin et al, 2022) and handling (Wagner et al, 2021) and pain caused by treatment of the corium defect (Ley et al, 1989). The numerically higher cortisol concentration of the PLACEBO sheep compared with the HEALTHY sheep may suggest that the sheep of the PLACEBO group perceived perioperative paininduced stress.…”

“…After this procedure, sheep were moved back to the group pen. Two hours later, the sheep were restrained manually in a standing position in the group pen, and an indwelling Teflon catheter was placed in the external jugular vein (Figure 1; VWI Jugularis-Katheter, outer diameter 2.4 mm, length 10 cm, Walter Veterinär-Instrumente e.K., Baruth/Mark; Amin et al, 2022).…”

“…For sedation, xylazine hydrochloride is registered for use in food-producing animals in the European Union and other countries, but is not approved for livestock in many other parts of the world, for example the United States (Emmerich, 2011;Smith, 2013;Coetzee, 2013). Nevertheless, xylazine is often used off-label for sedation, analgesia and muscle relaxation in sheep (Hodgkinson and Dawson, 2007;Lizarraga and Chambers, 2012;Amin et al, 2022).…”

“…Bacteriologic culture of typical DINCO lesions yield Dichelobacter nodosus as the primary etiological agent, Fusobacterium necrophorum and different species of Treponema (Frosth et al, 2015;Zanolari et al, 2021). Lesions of DINCO and treatment involving a tilt squeeze chute are a useful model for the assessment of acute and chronic pain and stress in sheep (Ley et al, 1989;Fieseler et al, 2019;Amin et al, 2022). Acute pain associated with treatment has also been shown to increase the cortisol concentration in sheep (Fell and Shutt, 1989).…”

“…Acute pain associated with treatment has also been shown to increase the cortisol concentration in sheep (Fell and Shutt, 1989). Fixation in a tilt squeeze chute in dorsal recumbency elicits a clear stress response even in healthy sheep (Wagner et al, 2021;Amin et al, 2022).…”