Is there an optimal age and method of castration for calves under 6 months of age?
K.Schwartzkopf-Genswein, D. Melendez, E. Janzen, E.Pajor and S. Marti
Producers typically castrate their bull calves anywhere between 1 week and 5 months of age and less commonly between 6 to 9 months of age with the exception of bulls destined for breeding. The most common methods used are band castration that restricts blood flow to the testicles and knife castration that involves immediate removal of the testicles by cutting. We know that both methods cause acute and chronic pain, increase stress and discomfort, and can reduce immune function and weight gain. In some instances these methods can cause infection or death due to complications. It is because of this that there is heightened interest by the public and legislators regarding management of pain in food animals.
The Canadian beef industry has made a consistent and concerted effort to promote and implement science informed, welfare conscious production practices.A prime example of this is the revised Code of Practice for the Care and Handling of Beef Cattle (www.nfacc.ca) that was completed in 2013. The new Code specifies that as of January 1st 2016, bulls older than 9 months of age must be castrated using pain control, and as of January 1st 2018, pain control will be mandatory for bulls older than 6 months of age. Currently, there is no requirement for pain control in calves castrated under 6 months of age. Instead, there is a recommendation that calves be castrated as young as possible to reduce pain and possible complications. Although veterinarians and animal scientists agree and recommend that castration be done as early as possible, there are no studies in calves < 4 months of age identifying the best age, method and pain mitigation strategy (in terms of animal welfare) to castrate beef cattle. As a result, the Beef Cattle Research Council (BCRC) identified such a study as a high priority for funding. In 2013 the BCRC approved a 5 year study lead by Drs Karen Schwarzkopf-Genswein of AAFC in Lethbridge and Ed Pajor at the University of Calgary and in collaboration with Dr.Eugene Janzen (U of C) with the main goal of identifying the best age, method and pain mitigation strategy for the castration of young calves (4 months of age or less).
The study helped to fund PhD student Dr. Daniela Melendez, who is working on assessing the acute effects of castration while postdoctoral fellow Dr. Sonia Marti is assessing the chronic effects.Some preliminary findings from their work are presented below.
The research team conducted three experiments at the Lethbridge Research Centre to evaluate the effects of band and surgical castration on indicators of stress and pain in beef calves at three different ages (36 calves/age group): newborn (Experiment 1, calves were 5 ± 1.1 d of age, and weighed 43 ± 6.61 kg); 2 months of age (Experiment 2, calves were 62.5 ± 1.0 d of age, and weighed 91.5 ± 11.93 kg); or 4 months of age (Experiment 3, calves were 131.3 ± 1.34 d of age and weighed 157.6 ± 22.5 kg). In each experiment calves were randomly assigned to a control group (bulls left intact; CT), band (BA) or surgical (SU) castration. Experiments 1, 2 and 3 ended when the testicles of all banded calves had sloughed-off (68, 49, and 42 d, respectively).
In terms of acute pain, newborn and 2-month old surgically castrated calves tended to have higher cortisol (stress hormone) levels compared to band and non-castrated control calves. However, 4-month old calves had higher cortisol levels after band castration compared to surgical and non-castrated calves. Surgical calves at 2 and 4 months of age stood and walked more, but at 2 months of age calves lied down and ate less compared to band and non-castrated calves. At 4 months of age, surgical calves tail-flicked more and had shorter stride length (indicators of pain) than band and non-castrated calves. Scrotal lesion scores (used as an indicator of the amount of healing observed on the scrotum as an indicator of chronic pain) were higher (less healing) in banded calves compared to non-castrated calves for a longer period of time compared to surgical calves at all three castration ages. In addition, lesion scores increased as age increased dependent on the castration method. For example, in older calves, band castration produced more severe lesions than in surgically castrated calves, while in young calves, surgical castration produced more severe lesions than in banded calves. Only newborn weaning weights were affected by castration method with intact and banded calves having weaning weights 23 and 16 kg heavier, respectively, than surgically castrated calves.
The combined results of the acute and chronic welfare assessments suggest that newborns showed fewer signs of pain compared to 2 and 4 month old calves. In terms of method, surgical castration produced more pain related behaviours and physiology compared to band castration. However, band castration resulted in more signs of pain in older calves. Lesions caused by band castration take longer to heal than those caused by surgical castration, indicating that band castration may cause discomfort for a longer period of time. Overall, our preliminary results suggest that newborn calves that are band castrated show the fewest signs of acute pain and have higher weaning weights compared to the other combinations of age and castration methods assessed.
The results presented here are just a portion of the entire body of work being conducted as part of this study. The team has recently completed several other experiments assessing different pain mitigation strategies including the comparison of single and multiple drug combinations, time of drug delivery, and the effect of single or multiple procedures on pain relative to the age and castration methods being evaluated. The final conclusions from the completed study will be available in late 2018.