Center for Animal Welfare, Department of Animal Science, University of California, Davis 95616.
Center for Animal Welfare, Department of Animal Science, University of California, Davis 95616.
J Dairy Sci. 2018 Nov;101(11):10361-10373. doi: 10.3168/jds.2018-14987. Epub 2018 Aug 23.
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.
热铁烙角，一种在奶牛犊牛中进行的畜牧业操作，通过组织烧灼来阻止角芽生长，会造成严重的烧伤。关于烙角后疼痛持续的时间，以及年龄等因素对动物福利结果的影响，人们知之甚少。我们的目的是：（1）评估在出生后 3 天（3 d）与稍后（35 d）进行烙角的犊牛，烙角年龄是否会影响愈合、疼痛敏感性和体重增加；（2）研究愈合过程中伤口的敏感持续时间。48 头犊牛在 3 日龄或 35 日龄时进行烙角或假烙角（n = 12/处理）。我们使用压力测痛计在烙角后第 3 天和第 7 天评估疼痛敏感性，然后每周评估一次，直到伤口重新上皮化。在每个伤口的外侧和尾侧边缘以及臀部测量敏感性，以测试感觉功能的全身变化。我们通过评估伤口床中 7 种组织类型的存在来评估愈合情况：附着的坏死组织、分离的坏死组织、坏死环外的烧伤、渗出物、肉芽组织、结痂和上皮组织。每周两次测量组织评分、表面温度和周长，以估计体重增加，直到伤口重新上皮化。烙角组织比未烙角组织敏感至少 3 周，此后，假烙角的犊牛被从研究中移除进行烙角。伤口需要 62 ± 10 d（平均值 ± 标准差）才能重新上皮化，并且在整个过程中都比新上皮组织更痛，无论烙角是在 3 日龄还是 35 日龄进行。烙角伤口的表面温度与非烙角组织的表面温度没有差异，并且烙角在两个年龄段都不会影响体重增加。烙角时的年龄并不影响重新上皮化的潜伏期或伤口敏感性。然而，在烙角后第 28、42 和 56 天，3 日龄烙角的犊牛的臀部敏感性大于 35 日龄烙角的犊牛，这与其他研究结果一致，即当在早期进行疼痛处理时，疼痛敏感性会增加。总之，在整个愈合过程中，伤口仍然疼痛，这引起了人们对热铁烙角的动物福利的关注。在出生后不久进行该操作并不能改善福利结果；相反，有证据表明，它可能会导致长期的全身性疼痛敏感性增加。
