The Pros and Cons of Caustic Paste
An estimated 94% of U.S. dairy herds perform disbudding or dehorning on their young animals, according to USDA data.
And yet there has not been a single, pain-free method for the procedure developed to date. It’s an area of dairying that can benefit from continuous improvement, according to Sarah Adcock, Assistant Professor of Animal Welfare in the Department of Animal and Dairy Science at the University of Wisconsin – Madison.
On a recent webinar hosted by the Dairy Cattle Welfare Council, Adcock explored the most common methods used today to remove horns, considering both pain management and long-term animal welfare. She also noted that current practices will continue to be modified based on the findings of additional research.
Adcock shared data from a 2021 collaborative study by researchers at the University of Wisconsin and the University of Guelph. In recent years, there has been a significant trend toward more producers using caustic paste to remove horn buds from calves less than one week old, versus removing them with a hot iron before 8 weeks of age, or dehorning with scoops, saws, or wires on calves older than 8 weeks.
As concern for animal welfare has grown and researchers have learned more about the pain calves incur from horn removal, pain management for the procedure has become a recommended practice. The American Association of Bovine Practitioners (AABP) declared in 2019 that pain management should be the “standard of care” for horn removal. Shortly thereafter, the National Dairy Farmers Assuring Responsible Management (FARM) program added the expectation of pain management to its continuous improvement plan for disbudding.
The FARM program also states a mandatory corrective action plan that all calves should receive disbudding treatment before the horn bud attaches to the skull at 8 weeks of age or less, making true “dehorning” an obsolete practice.
The shift toward disbudding helps to explain why more producers are choosing to use caustic paste. But they are not adopting pain management as rapidly as they are embracing the practice itself, as there is a perception that using caustic paste is not as painful as hot-iron removal.
“Both methods cause third-degree burns,” Adcock noted. “Hot iron causes a thermal burn, and caustic paste causes a chemical burn.”
In a 2016 study in Ontario, producers and veterinarians were asked to rate the pain associated with both caustic paste and hot-iron removal, on a scale of 0-10, with 10 being the most severe pain. They rated caustic paste at 4.8, versus 6.7 for hot iron. “However, there is no scientific evidence to support this perception,” said Adcock.
Further, producers surveyed in the Wisconsin-Guelph study were using pain management techniques less frequently for caustic paste versus hot iron. About half (51%) of hot-iron users were employing pain mitigation, while only 39% provided pain management support for caustic paste.
Compared to hot-iron disbudding, other characteristics of caustic paste include:
- Caustic paste pain is slightly delayed – The protracted pain response occurs because the chemicals in caustic paste burn slowly, versus the immediate burn of the hot iron. Combining a local anesthetic and non-steroidal anti-inflammatory drug (NSAID) is most effective at reducing the pain response.
- Healing takes longer with caustic paste – Comparing data from two research projects at the University of California-Davis, wounds from caustic paste require 16.2 weeks to heal, versus 9 weeks for hot-iron removal.
- Secondary injuries and errors can occur with caustic paste – One of the hazards of using caustic paste is that it can damage more than the horn bud. Adcock said this often is the result of applying too much paste. In such instances, it can cause secondary burns on the treated calf, as well as injury to herd mates in social housing situations.
- Early treatment does not mean less pain -- “There is a common assumption that newborns feel less pain, despite no scientific evidence to support this assumption,” noted Adcock. “We see pain responses in disbudded calves no matter how young they are.”
She added that studies in humans and rodents have shown that performing painful procedures on newborns can have adverse effects on their behavioral and physiological development later in life. “There even are arguments that infants feel more pain, because their nervous systems are not developed enough to have inhibitory control over pain responses,” she stated. “But in general, I think for now we should assume that calves feel the same degree of pain regardless of age.”
Given the challenges that caustic paste presents, Adcock said the next phase of disbudding management should be exploring ways to soothe the pain through additional pharmaceutical interventions; nutritional support; and/or social support like pair housing or cow-calf contact.
Substitute methods that incite less pain also should be explored. And suppressing the need for horn removal altogether through polled genetics – potentially accelerated via gene editing – could be another significant step in continuous improvement.
