Effect of a single subcutaneous injection of meloxicam on chronic indicators of pain and inflammatory responses in 2-month-old knife and band-castrated beef calves housed on pasture

Abstract

One hundred and thirty-one 2 mo. old pasture housed Angus cross bull calves were evaluated for 62 d over two years (Year 1: n = 69, 134.1 ± 20.37 kg BW; Year 2: n = 62, 118.1 ± 15.49 kg BW) to determine 1) the effects of a subcutaneous (s.c) injection of meloxicam on indicators of long term pain after castration and 2) the potential use of cow-calf proximity and home range as indicators of pain. Calves were randomly assigned to treatments using a 3 × 2 factorial design including castration - sham (CT; n = 47), band (BA; n = 46) or knife (KN; n = 38) castration and medication – s.c. meloxicam (M; n = 66) or s.c. lactated ringers solution (NM; n = 65). Measurements included performance, scrotal temperature, swelling (WS) and healing (WH) scores, and pain sensitivity, collected on d -1, 6, 13, 20, 34, 48, and 62 post-castration. Suckling, lying, standing and walking duration, and head-turning, lesion-licking, foot-stamping and tail-flick frequencies were collected immediately following and up to 2-d after castration. Cow-calf proximity and home range were obtained from d 0 to 2 and from d 14 to 16. With the exception of suckling, no medication (P > 0.05) effects were found. Greater (P < 0.05) pain sensitivity was observed in KN from d 6 to 34 and on d 62, and in BA from d 6 to 62 compared to CT calves. Knife calves showed an earlier (d 20) absence of inflammatory responses (WS; P < 0.05) than BA (d 34) and overall, KN calves had greater (P < 0.05) standing, walking, and head turning than BA and CT. Knife and BA had greater (P < 0.05) foot stamping than CT for the first 2 h post-castration, but KN exhibited greater (P < 0.05) frequencies between 9 and 11 h (d 0) compared to BA and CT, and had greater (P < 0.05) tail flicks from d 0 to 2 than CT. Banded calves were closer to their dams on d 15 while KN calves and their dams had a reduced home range on d 0 than CT cow-calf pairs. Although meloxicam did not reduce indicators of pain (with exception of suckling behavior), our results suggest that knife castration causes greater acute pain, while band castration resulted in greater chronic-pain. Cow-calf proximity and home range have some potential to be used as pain indicators post-castration.