Pain sensitivity and healing of hot-iron cattle brands1

Abstract

Hot-iron branding is painful for cattle, but little is known about the duration of or effective methods to control this pain. This work quantified pain sensitivity and healing in branded and unbranded animals. In addition, the effects of a single injection of nonsteroidal anti-inflammatory drug (NSAID) were also considered; this has been suggested as practical method of mitigating pain in the hours after the procedure. Calves (mean±SE, 126±2.2 d and 112±2.8 kg) were hot-iron branded and allocated to 1 of 4 treatments: branded with or without flunixin meglumine (intravenous; 1.1 mg/kg) and unbranded with or without this NSAID (n=12/treatment). Pain sensitivity was assessed by applying a known and increasing force with a von Frey anesthesiometer in the center of the brand (or equivalent area in nonbranded treatments) until animals showed a behavioral response. Healing was measured with a 6-point scale (1=fresh brand and 6=no scabbing and fully repigmented). These measures, along with weight gain and surface temperature, were recorded 1, 2, 7, 14, 21, 28, 35, 42, 56, and 71 d after branding. Lying behavior was recorded with loggers from the day before to d 27 after branding. Brand wounds were more painful than nonbranded tissue (P<0.001). These differences were most pronounced in the days immediately after branding (e.g., d 7; 113±36 g of force for Brand vs. 449±23 g force for No brand, mean±SE) but persisted until d 71 (380±37 g force for Brand vs. 453±23 g of force for No brand, mean±SE); only 67% of brands were fully regimented or healed by this time. The first fully healed brand was identified 8 wk after the procedure. Giving a single injection of flunixin had no brand-specific effects on sensitivity, surface temperature, or healing but improved weight gain in the days after branding in all treated groups (flunixin×brand×day, P<0.001). Flunixin-treated animals also spent 0.7 h less time lying down on the day of branding but tended to spend more time lying on d 15 and 26 after the procedure. The magnitude of these differences is small, less than the day-to-day variation, and not brand specific. In summary, brand wounds take at least 8 wk to heal. These wounds remain painful for a least this long, and a single injection of NSAID has no measurable effect in mitigating pain associated with branding, even in days immediately after the procedure.

Effect of a single dose of subcutaneous meloxicam before knife castration alone or combined with hot-iron branding on scrotal healing, inflammatory response, and behaviour in 2-mo-old beef calves over 42 d post procedure

“…When the evaluation extended beyond 7 d, Molony et al (1995) and Marti et al (2017a) did not find changes in lying time in 1 wk and 2-mo-old calves compared with noncastrated calves. Furthermore, Tucker et al (2014b) reported that the time branded calves spent lying was not different from nonbranded calves. Note: NM, single s.c. injection of lactated ring at castration time; M, single injection of s.c. meloxicam (0.5 mg kg −1 ) at castration time; Med, medication effect; n, number of animals observed at each score; Median, median days to reach each healing score relative to days of castration and castration and branding; FCL, 95% confidence limits distribution free of the days to reach each healing score.…”

“…However, it was expected that the combination of castration and branding would increase the deposition of cortisol within the hair. This hypothesis was based on the findings of Tucker et al (2014aTucker et al ( , 2014b who reported greater pain sensitivity values (g force) in hot-iron-branded calves using a Von Frey anesthesiometer applied to the brand site for at least 10 wk after the procedure. However, as discussed previously, pain sensitivity of the brand site might not be sufficiently intense to result in increased hair cortisol concentrations, or pain sensitivity may be poorly correlated with other indicators of stress and (or) pain.…”

“…For example, plasma cortisol was shown to be greater in branded compared with nonbranded calves for up to 40 min after the procedure (Schwartzkopf-Genswein et al 1997c), in contrast no differences were observed in the reluctance to enter into the handling facility between branded compared with nonbranded calves (Schwartzkopf-Genswein et al 1997a). In addition, the lack of treatment differences in ADG, hair cortisol, and acute phase proteins (APP) may indicate that the greater pain sensitivity of the brand site observed by Tucker et al (2014b) at the time of palpation does not necessarily mean that the calves experienced continual pain, but rather it was only experienced for short periods of time during palpation.…”

“…Hot-iron branding is a method used to permanently identify cattle, and it is still commonly used in countries where no electronic identification is required or in areas where producers comingle animals on community pastures. The few studies that have evaluated the welfare implications of hot-iron branding have reported several indicators associated with pain (Lay et al 1992;Schwartzkopf-Genswein et al 1997a, 1997b, 1997cTucker et al 2014aTucker et al , 2014b. For example, hot-iron branded calves had greater tail-flick, kick, and fall frequencies at the time of branding (Schwartzkopf-Genswein et al 1997a), as well as greater heart rate (Lay et al 1992) and plasma cortisol concentrations (up to 40 min post branding) (Lay et al 1992;Schwartzkopf-Genswein et al 1997c), than freeze or unbranded control calves.…”

“…For example, hot-iron branded calves had greater tail-flick, kick, and fall frequencies at the time of branding (Schwartzkopf-Genswein et al 1997a), as well as greater heart rate (Lay et al 1992) and plasma cortisol concentrations (up to 40 min post branding) (Lay et al 1992;Schwartzkopf-Genswein et al 1997c), than freeze or unbranded control calves. In addition, the use of a von Frey anesthesiometer indicated that branding wounds remain sensitive for at least 10 wk after branding (Tucker et al 2014a(Tucker et al , 2014b. Broom and Johnson (2000) suggested that two noxious stimuli potentially generate greater physiological and behavioural responses than either one alone when performed at the same time.…”