Hot-iron disbudding, a husbandry procedure performed in dairy calves in which horn bud growth is prevented through tissue cauterization, produces severe burns. Little is known about how long pain persists following disbudding or factors, such as age at the time of disbudding, that may influence animal welfare outcomes. Our objectives were (1) to evaluate whether disbudding age mediates healing, pain sensitivity, and weight gain in calves disbudded near birth (3 d) compared with at a later age (35 d); and (2) to examine how long wounds are sensitive during healing. Forty-eight calves were disbudded or sham-disbudded at 3 or 35 d of age (n = 12/treatment). We assessed pain sensitivity with a pressure algometer on d 3 and 7 after disbudding and then weekly thereafter until the wound had re-epithelialized. Sensitivity was measured at the lateral and caudal edges of each wound, as well as on the rump to test for systemic changes in sensory function. We evaluated healing by scoring the presence of 7 tissue types in the wound bed: attached necrotic tissue, detached necrotic tissue, burns outside the necrotic ring, exudate, granulation, crust, and epithelium. Tissue scores, surface temperature, and girth circumference as an estimate of weight gain were measured twice weekly until the wound had re-epithelialized. Disbudded tissue was more sensitive than nondisbudded tissue for at least 3 wk, after which time the sham calves were removed from the study to be disbudded. Wounds took 62 ± 10 d (mean ± SD) to re-epithelialize and were more painful than new epithelium throughout this time, regardless of whether the procedure occurred at 3 or 35 d of age. The surface temperature of disbudding wounds did not differ from that of non-disbudded tissue nor did disbudding affect weight gain at either age. Age at the time of disbudding did not affect latency to re-epithelialize or wound sensitivity. However, rump sensitivity was greater in calves disbudded at 3 versus 35 d of age on d 28, 42, and 56 after disbudding, in agreement with other studies showing increased pain sensitivity when painful procedures are performed at an early age. In conclusion, wounds remain painful throughout healing, raising animal welfare concerns about hot-iron disbudding. Performing the procedure near birth does not improve welfare outcomes; rather, some evidence suggests it may produce a generalized long-term increase in pain sensitivity.

Hot-iron disbudding, a routine procedure that prevents horn bud growth through cauterization, is painful for calves. The resulting burns remain sensitive to touch for weeks, but it is unknown whether calves experience ongoing, non-evoked pain. We evaluated conditioned place preference for analgesia in 44 calves disbudded or sham-disbudded 6 hours (Day 0) or 20 days (Day 20) before testing (n = 11/ treatment). Calves were conditioned to associate the effects of a lidocaine cornual nerve block with the location and pattern of a visual stimulus, and a control injection of saline with the contrasting stimulus. On Day 0, disbudded calves tended to prefer the lidocaine-paired stimulus over the saline-paired one, suggesting that they found analgesia rewarding. On Day 20, sham calves avoided the lidocaine-paired stimulus, consistent with humans' experience of this drug being painful. Disbudded calves on Day 20 did not show this aversion, suggesting that they traded off the short-term pain of the lidocaine with the longer-term analgesia provided. Day 0 sham calves did not avoid the lidocaine-paired stimulus, likely because they received less than half the dose of Day 20 calves during conditioning. Thus, higher doses of lidocaine are aversive to uninjured animals, but disbudded calves are willing to engage in this cost. We conclude that calves experience ongoing pain 3 weeks after disbudding, raising additional welfare concerns about this procedure.

Hot-iron disbudding, the process of cauterizing the horn buds of calves or goat kids at an early age to prevent horn growth, is routinely practiced in dairy production. The wounds take weeks to heal and are painful to touch throughout this time. Possible strategies to hasten the healing of disbudding wounds are not well understood, but the type of iron used may be an important factor to consider. When evaluating strategies to hasten healing, a within-subjects design may be preferable, but laterality effects might act as a potential source of variation and confounding in this type of experiment. Our objectives were to compare healing after disbudding with 2 commercially available irons, and to determine whether wounds healed differently on the left versus the right side of the head. Ten Holstein calves 4 to 10 d of age were disbudded using the Rhinehart X50A electric disbudder (Rhinehart Development Corp., Spencerville, IN) on one horn bud and the Portasol gas disbudder (Portasol USA, Elmira, OR) on the other; side (left vs. right) was balanced between treatments. We scored wounds daily for the presence of 6 tissue types: attached necrotic tissue, detached necrotic tissue, exudate, granulation, crust, and epithelium. Surface temperature and size of the wound were measured twice-weekly using thermal and digital photographs, respectively. The type of iron used did not affect latency to re-epithelialize, which took on average (mean ± standard deviation) 53 ± 3 d and 55 ± 3 d for Portasol and Rhinehart wounds, respectively (range: 40-70 d). However, compared with Portasol wounds, those from the Rhinehart had fewer days of granulation tissue and tended to have more days of detached necrotic tissue. The Portasol tip had a smaller total surface area than the Rhinehart, which may have resulted in a less severe burn, causing the necrotic tissue to fall off sooner. The left side tended to re-epithelialize faster than the right side (mean ± standard error: left 51 ± 3 d; right 57 ± 3 d) and have fewer days of crust. Left-sided wounds were also cooler and tended to be smaller than those on the right. To assess the external validity of these laterality effects in our primary experiment (experiment A), we analyzed wound healing data from 2 other disbudding studies, one on calves (experiment B) and one on goat kids (experiment C). We observed laterality effects in the opposite direction in Experiment B, but negligible effects in experiment C, indicating that the differences in laterality had low external validity; the biological meaning of this asymmetry is unclear. Nonetheless, if using a within-subjects design, asymmetries in wound healing should be considered to avoid confounding effects. In conclusion, wounds from both irons took 7 to 8 wk to heal, on average; other strategies to accelerate healing should be explored.

Dairy calves are routinely administered medicines, vaccines, and anesthesia via injection. Although injections are painful, little is known about methods to alleviate this pain. The aim of this study was to determine whether lidocaine-prilocaine cream, a topical anesthetic, reduced calves' pain response to a subcutaneous injection around the cornual nerve. Calves were assigned 1 of 2 treatments: lidocaine-prilocaine cream at the sites of injection (n = 10) or no cream (n = 9). Thirty minutes after treatment, calves received a subcutaneous injection of 2% buffered lidocaine hydrochloride around the left and right cornual nerves. Contrary to our hypothesis, calves that received anesthetic cream beforehand displayed more escape behaviors during the injections than control calves. Both treatments had similarly low amounts of head-related behaviors afterward. Maximum eye temperature did not differ between the calves that received anesthetic cream and control calves, although eye temperature increased over time for both treatments. Heart rate increased during the 30 s following the first injection in both treatments. There were no treatment differences for any heart rate measures over the 5-min period after the first injection (mean heart rate, root mean square of successive differences, high-frequency power, and the ratio of low-frequency power to high-frequency power). These results suggest that cornual nerve blocks with buffered lidocaine are painful and that a lidocaine-prilocaine cream was not only ineffective in reducing this pain but that it may also worsen it.

Hot-iron disbudding in goat kids causes acute pain and tissue damage. However, the duration of healing and wound sensitivity is unknown. We assessed wound healing and pain sensitivity in 18 female dairy goat kids disbudded with a heated iron at 10 d of age (range: 5-15 d). Pressure algometry was carried out twice a week from d 1 after disbudding to determine the mechanical nociceptive threshold (MNT) in 4 locations on each bud (front, lateral, caudal, and middle). At the same time, digital and infrared images of the wounds were used to visually and thermally describe the healing process. Wounds were visually scored daily for the presence of 7 tissue types: attached necrotic tissue, detached necrotic tissue, burns outside the necrotic ring, exudate, granulation, crust, and epithelium. All data were taken until epithelium was present for 4 consecutive days. Necrotic tissue detached completely from the scalp 26 ± 5 d after the procedure (mean ± SD; range: 17-43 d), and wounds took 50 ± 8 d (35-63 d) to re-epithelialize. Wounds were more sensitive at all stages of the healing process compared with re-epithelialized tissue. The caudal and middle locations were the most-and leastsensitive test sites (1.24 ± 0.10 and 1.90 ± 0.10 N, respectively; mean ± SE). Goats became less responsive to stimulation as their wounds decreased in size. Sensitivity did not differ between left and right sides of the head. Maximum surface temperature of necrotic tissue, when present, tended to be higher than that of epithelium (38.8 ± 0.2 vs. 38.1 ± 0.2°C); temperature did not differ among other tissue types. Our results indicate that hot-iron disbudding wounds in goats take, on average 7, wk to re-epithelialize (35-63 d) and are painful throughout this time, raising additional welfare concerns about this procedure.

Farm animals routinely undergo painful husbandry procedures early in life, including disbudding and castration in calves and goat kids, tail docking and castration in piglets and lambs, and beak trimming in chicks. In rodents, inflammatory events soon after birth, when physiological systems are developing and sensitive to perturbation, can profoundly alter phenotypic outcomes later in life. This review summarizes the current state of research on long-term phenotypic consequences of neonatal painful procedures in rodents and farm animals, and discusses the implications for farm animal welfare. Rodents exposed to early life inflammation show a hypo-/hyper-responsive profile to pain-, fear-, and anxiety-inducing stimuli, manifesting as an initial attenuation in responses that transitions into hyperresponsivity with increasing age or cumulative stress. Neonatal inflammation also predisposes rodents to cognitive, social, and reproductive deficits, and there is some evidence that adverse effects may be passed to offspring. The outcomes of neonatal inflammation are modulated by injury etiology, age at the time of injury and time of testing, sex, pain management, and rearing environment. Equivalent research examining long-term phenotypic consequences of early life painful procedures in farm animals is greatly lacking, despite obvious implications for welfare and performance. Improved understanding of how these procedures shape phenotypes will inform efforts to mitigate negative outcomes through reduction, replacement, and refinement of current practices.

Simple SummaryBranding cattle with hot irons is a painful procedure, inflicting severe burns that take weeks to heal. Although Sri Lanka prohibits hot-iron branding, the practice is still common in some areas of the country but has not been described. We observed branding practices on four smallholder farms and identified welfare concerns and challenges impeding adoption of alternative methods of identification, such as ear tags. Farmers used multiple irons to mark their initials and, in some cases, their address, with the largest brands extending across the ribs and hip. Farmers did not consider ear tags a viable alternative to hot-iron branding because of issues with security and tag retention. Hot-iron branding raises serious animal welfare concerns and efforts to introduce more welfare-friendly alternatives are needed.AbstractHot-iron branding is illegal in Sri Lanka, but is still commonly used to identify dairy herds in extensive farming systems, which are primarily located in the country’s Dry Zone. Despite the negative welfare implications of this practice, there is no written documentation of branding in this region. We observed branding on four smallholder farms in Kantale, Eastern Province to understand the welfare implications associated with the procedure and challenges limiting the uptake of more welfare-friendly alternatives, such as ear tagging. Areas of welfare concern included the duration of restraint, the size and location of the brand, and the absence of pain relief. Animals were restrained with rope for an average duration of 12 min (range 8–17 min). Farmers used multiple running irons to mark their initials and, in some cases, their address, with the largest brands extending across the ribs and hip. Three farmers applied coconut or neem oil topically to the brand after performing the procedure. No analgesics were given before or after branding. Farmers reported that poor ear tag retention in extensive systems and theft were the main factors impeding the uptake of alternative forms of identification. Branding is also practiced as part of traditional medicine in some cases. Given the clear evidence that hot-iron branding impairs animal welfare and there is no evidence that this can be improved, alternative identification methods are needed, both in Sri Lanka, as well as in other countries engaging in this practice.

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