Effects of xylazine hydrochloride on hormonal, metabolic, and cardiorespiratory stress responses to lateral recumbency and claw trimming in dairy cows

Abstract

To investigate the hormonal, metabolic, and cardiorespiratory effects of xylazine hydrochloride on dairy cows undergoing lateral recumbency and claw trimming. Prospective crossover study. 6 healthy Holstein-Friesian cows. Cows were treated with xylazine (0.05 mg/kg [0.023 mg/lb], IM) or an equal volume of saline (0.9% NaCl) solution 15 minutes before being placed in lateral recumbency for claw trimming. As a third treatment, cows also received xylazine (0.05 mg/kg, IM) but underwent no further manipulation. At preset time intervals, heart rate (HR), respiratory rate (RR), systolic arterial blood pressure, diastolic arterial blood pressure, mean arterial blood pressure (MAP), blood gas values, and plasma concentrations of cortisol, insulin, glucose, lactate, and nonesterified fatty acids (NEFA) were measured, and signs of sedation and ruminal bloat were recorded. Saline solution treatment resulted in a temporary significant increase in SAP, diastolic arterial blood pressure, MAP, RR, and cortisol, lactate, and NEFA concentrations and a significant decrease in arterial oxygen saturation (Sao(2)). Xylazine treatment induced significant decreases in HR, RR, MAP, insulin and NEFA concentrations, and Sao(2) and induced significant increases in glucose concentration. Compared with saline solution treatment, HR, RR, MAP, Sao(2), and cortisol, lactate, and NEFA concentrations were significantly decreased with xylazine treatment. Xylazine treatment resulted in mild signs of sedation as well as clinically negligible ruminal bloat. Xylazine administered in a low dose to cows preceding lateral recumbency for claw trimming decreased hormonal and metabolic stress responses, but augmented the respiratory depressive effect of lateral recumbency reflected by a decreased Pao and increased Paco(2).