Effects of lidocaine-plus-meloxicam treatment on behavioral and physiological changes, and leukocyte heat shock protein 90 gene expression after surgical castration in Hanwoo bulls

This study examined the effects of surgical castration and lidocaine-plus-meloxicam treatment on growth, physiology, behaviors, and leukocyte heat shock protein 90 (HSP 90) gene expression in Hanwoo (Korean cattle) bulls. Twenty Hanwoo bulls (body weight 248.8 ± 28.5 kg, age 9.4 ± 1.04 months) were assigned to three treatments: surgical castration with lidocaine injection (5 mL in the scrotum) and oral meloxicam administration (1 mg/kg body weight; LM; <i>n</i> = 7); surgical castration with placebo injection (5 mL of 0.9% NaCl) and oral placebo administration (lactose, 1 mg/kg body weight; CAS; <i>n</i> = 7); and shame castration (SHAM; <i>n</i> = 6). Meloxicam and lactose were administered 3 h before castration, and lidocaine and NaCl were injected immediately before castration. Surgical castration was performed with a Newberry knife and a Henderson castration tool. Wight was measured the day before and 14 d after castration, and behavior was observed from 0.5 h to 4.5 h post-castration. Blood was collected at -1 d, 0.5 h, 6 h, 1 d, 3 d, 7 d, and 14 d after castration to measure plasma cortisol, haptoglobin, and leukocyte HSP 90 mRNA. Castration tended to decrease average daily gain (<i>p</i> = 0.06), but the LM treatment did not affect weight gain. Bulls in CAS showed higher cortisol concentration (<i>p</i> < 0.05) at 0.5 and 6 h after castration compared to SHAM, with no difference between CAS and LM. Castration increased haptoglobin concentration at 1 and 3 d after castration (<i>p</i> < 0.05) while LM bulls showed decreased haptoglobin concentration (<i>p</i> < 0.05) than CAS bulls at these times. HSP90 mRNA was increased at 6 h post-castration while LM did not reduce its expression, suggesting HSP90 may serve as an acute stress marker in castrated bulls. Castration increased (<i>p</i> < 0.05) frequencies of drinking, lying, walking, leg lifting, kicking, and stiff gait, while decreasing (<i>p</i> < 0.05) eating frequency. LM alleviated (<i>p</i> < 0.05) drinking, leg lifting, kicking, and stiff gait. Collectively, castration resulted in physiological changes, increased leukocyte HSP90 gene expression, and altered behaviors. These findings suggest that lidocaine-plus-meloxicam treatment partially mitigates pain and inflammation in the castrated bulls.