The desired 1st response rate for mail surveys is 40% to 57% (11
). Mail surveys are considered reliable if they achieve a minimum response rate of 50% (12
). The veterinary survey represents a survey of the entire target population rather than a survey of a sample of the population. This gives the 49% response rate a high accuracy. The fact that nearly half of the practices surveyed indicated that they are no longer doing food animal practice is a reflection of both the current accuracy of the CVO database for veterinary practice activity and the ongoing trend in agriculture toward consolidation of enterprises.
To the authors’ knowledge, this is the first survey to investigate dehorning practices. It provides new information on dehorning methods and attitudes about the practice in Ontario. Previously, it has been stated that dairy calves in North America are commonly dehorned without local anesthetics (8
), but this statement was not quantified. The results of this study indicate that the proportion of calves receiving nerve blocks performed by producers is higher than expected. It may be that those producers who perform the procedure were more likely to answer the survey. The percentage of veterinarians dehorning calves for clients was more than the percentage of clients not dehorning calves (31% versus 21%). The confidence intervals around these estimates overlap and, therefore, are not statistically different. However, one possible explanation of the numeric difference is that although many producers dehorn most calves themselves, some producers have veterinarians dehorn some calves, especially those missed when calves were younger. This hypothesis is supported by the fact that 12% of the producers who indicated that they dehorned their own calves, actually dehorned less than 100% of their calves.
Electric dehorning was the most widely used method of dehorning, both in number of calves dehorned and in frequency of use. Roughly half of the veterinarians reported that they used gouge, a combination of gouge and electric cautery, and wire for dehorning, compared with relatively few producers that used these methods. However, only a small proportion of calves were dehorned by these methods. The most likely explanation of this discrepancy is that producers tend to use a particular method of dehorning because of experience and equipment with that method, while veterinarians carry tools and materials for several methods of dehorning. Veterinarians likely have a preference for certain methods and will tend to use these in conjunction with routine herd visits; however, they will occasionally either be asked by producers to dehorn with other methods or be forced to use other methods on some calves because of age or maturity of the horn. This view is supported by the differences in distribution of ages reported in for veterinarians and producers. While there is a tendency for producers to dehorn at specific ages, veterinarians predominately dehorn calves across all age categories. Age of calf and dehorning method are somewhat correlated. Therefore, although the most common method for dehorning for both veterinarians and producers is the electric hot iron, those producers who dehorn predominately young calves tend to use the methods appropriate for that age, such as paste and a portable butane dehorner. Producers who dehorn at predominately more than 8 wk of age tend to dehorn more often with gouging and also have a higher rate of wire use, because the horns are bigger at this age and the hot iron will not work. Exact reasons why producers choose method or age of dehorning were not part of this survey, but they would provide an interesting follow-up to this questionnaire. Dehorning at a young age (ideally < 4 wk of age) is preferred because of ease of handling the calf and reduced trauma (smaller bud, less traumatic procedure). However, over 25% of producers had a program in place to dehorn calves, starting after the calf is 8 wk of age. Clearly this is an area for future client education.
Among producers who did not perform a nerve block, 40% chose “other” as a reason for not doing so. The responses given in the “other” category were divided into common themes: eleven percent (15/134) felt the procedure was unnecessary, and 13% (18/134) were unaware of the options for pain management. The frequencies of these answers indicate that education for producers regarding pain at dehorning and the choices available for pain management is needed. It is interesting that age categories for dehorning (<4 wk, 4 to 8 wk, >8 wk, or selective across all age categories) were not associated with lidocaine use. One could interpret from this that producers might be motivated to use lidocaine, regardless of the current age they dehorn calves. Likewise, if producers can be convinced to use lidocaine on older calves, they could likely be prompted to change their herd dehorning program to a younger age group.
The perception persists that pain management drugs for routine procedures like dehorning are prohibitively expensive. Producers who did not use local anesthetics for dehorning were most concerned about their cost and time (22% for each). Similarly, veterinarians cited cost (40%) as a reason for choosing not to use xylazine. However, the price per calf for an average dose is approximately $0.46 for lidocaine, $1.17 for xylazine, and $2.50 for ketoprofen (an NSAID). This calculation is based on the purchase price of a 100-mL bottle (lidocaine, ketoprofen) and a 50-mL bottle (xylazine) (personal communication, CDMV customer service representative)). Even when overhead and dispensing fees are included, the cost is minimal compared with the estimated cost of raising a heifer calf to maturity (13
Other common reasons for veterinarians not using local anesthetics on some or all calves were age of the calf (22%) and method of dehorning (18%). However, multiple studies have shown that dehorning changes behavioral and physiological parameters indicative of pain, regardless of the age of the calf or method of dehorning (2
). Interestingly, 57% of veterinarians used xylazine for pain management. However, xylazine and other alpha-2 agonists alone do not provide sufficient analgesia during dehorning, they should be combined with local anesthetics for maximum pain relief (2
Based on the logistic regression analyses, advice to producers regarding the involvement of their veterinarian in dehorning is the most important factor in the use of local anesthetics and sedatives prior to dehorning. This suggests that a significant number of producer dehorning practices might be improved by veterinary input. Furthermore, 22% of veterinarians said that they did not use local anesthetics before dehorning at the request of the owner. Therefore, veterinarians need to be aware of their influence and responsibility and they should set a standard protocol for local anesthetic use on all farms where they dehorn calves.
The design of the survey had several potential limitations that may have decreased responses. Despite the assurance of confidentiality for respondents, the inclusion in the survey of the producer and farm name to identify respondents and to obtain DHI information may have been a deterrent for some people. Similarly, the survey topic is potentially sensitive. We attempted to keep the wording neutral, but some may still have been hesitant of revealing their practices. A time deadline was indicated to urge completion. However, this may have been a disadvantage, as, after the deadline had passed, people may have been less likely to finish it. The timing of the survey may also have contributed to producers not responding; the survey was sent during the time of spring planting and farmers may have been too busy. Finally, self-selection bias is the greatest disadvantage of this type of survey. The people who answered the survey may not be typical of all dairy producers and veterinarians in Ontario; perhaps those who answered the survey were more likely to consider pain management and, therefore, were less concerned about disclosing their methods.
We attempted to address some of these issues in our design. The mail survey prevented interviewer bias and allowed people to respond at their convenience. Including self-addressed, stamped envelopes, using a follow-up telephone reminder, and offering incentives for completion of the survey are all methods that have been described as increasing response rate to postal surveys (12
The results of this survey indicated that most veterinarians follow the Canadian Code of Practice by using a local anesthetic for dehorning, while only 22% of producers do. Almost half of producers feel that pain management is not necessary for dehorning or are unaware that medications could be used. Veterinary involvement in the producer dehorning decision is the main factor influencing producer medication use for dehorning. Based on these results, education for producers regarding dehorning pain management is indicated. CVJ