Evaluation of Dairy Heifer Calves Submitted to Hot-Iron Branding: Behavior, Infrared Thermography, and Mechanical Nociceptive Threshold

In Brazil, hot-iron facial branding marks brucellosis-vaccinated heifers. Given its welfare impact, we assessed acute and chronic pain in branded dairy heifers. Twenty-four female calves, allocated into control (CG) and branded (BG) groups, were evaluated for acute pain through UCAPS scale and facial grimaces, and for chronic pain, from the 8th to the 24th week after branding, through pressure algometry. For inflammation, temperature in the lesion region (TLR) and in contralateral ocular region (ORT) was assessed. Animals were weighed during all the experiment. UCAPS indicated acute pain for at least 48h after branding (<i>p</i> < 0.05). Unit facial grimace activation occurred in BG (<i>p</i> < 0.05). TLR indicated active inflammation for at least 120h in BG (<i>p</i> < 0.05); ORT did not differ between groups (<i>p</i> > 0.05). Pressure algometry could not detect chronic pain in this study (<i>p</i> > 0.05). The weight gain was similar in both groups (<i>p</i> > 0.05). Although chronic pain has not been demonstrated, its occurrence cannot be excluded. Furthermore, hot-iron branding causes acute pain and compromises calf welfare, reinforcing the urgent need for less invasive identification methods.