On-Farm Castration: Techniques, Issues, and What’s Coming – Part Two
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Following last month’s introduction to beef calf castration I want to present some recently published research to establish “where we’re at” as an industry. Collectively, beef calf castration is a hot topic. In 2013, over 15 million bull calves were castrated in the US. The public expresses growing concern every year about how we treat beef animals. A query of the library database returned 381 articles published in last 5 years containing the words “cattle and castration.” The focus of these articles varies tremendously and what follows is a summary of a few “big ticket” recurring topics.
Stress perceived by castrated calves. There are many different published methods for quantifying “stress” or “pain” in beef calves. Most authors rely on either (1.) blood or saliva levels of stress hormones or proteins, such as haptoglobin, cortisol (adrenaline), or substance P, (2.) semi-objective visual scores based on observations of certain behaviors or actions, or (3.) pedometers or feed intake monitoring technology to document movement or feeding behavior dynamics. The variety of methods used across published studies makes an overall assessment of our body of knowledge difficult. Each methodology has its inherent flaws and we honestly lack a scientific definition of what stress/pain looks like in a beef calf.
Regardless of method, across all studies castrated animals show an immediate negative response to castration, which most often constituted the 2-4 weeks following procedure. It should not be a surprise to anyone reading this article that castration is painful and causes stress to the animal enduring it. Castration technique (banding vs. surgical castration) has a differential effect on the animal’s stress response. In a 2012 study, the stress response measured in a group of calves banded at weaning was delayed as compared to calves surgically castrated at weaning. The authors point out that the effects of the delayed stress response in a banded weaning calf could have significant detrimental effect on health in the post-weaning period. Certainly, weaning itself is stressful and predisposes calves to increased rates of illness. Stacking stressors on top of each other is a bad idea, and simultaneously prolonging the stressor’s effects (as is done in banding) is an even worse idea. Surgical castration methods evaluated in this study showed an immediate sharp rise in stress hormones, but by day 7 to 10 post-castration, hormone levels had returned to similar levels to control bull calves or steers. Banded calves had elevated levels as far out as day 14-21. A trial from Arkansas found treatment at surgical castration with NSAIDs quartered the measured levels of haptoglobin, an acute phase inflammatory protein found in the blood. This indicates that medical management of pain at castration may alter the decrease the stress response of the animal.
Pain control. Many recently published studies focus on strategies to mitigate pain associated with castration. The bulk of this work focuses on use of a long-acting non-steroidal anti-inflammatory drug (NSAID) called meloxicam. This orally-delivered product is approved for use in cattle for mitigation of pain in Canada, and many US veterinarians are prescribing it in an extra-label fashion for pain associated with dehorning, lameness, and castration. Understand that this drug is not approved for cattle in the US and there is currently debate as to the legality of its use in the US. The last few years of published data present a mixed message as to whether NSAIDs at the time of castration are beneficial from an animal welfare or economic performance standpoint.
One nicely done 2015 study involving 150 700-pound bulls compared the effects of band castration on receiving at the feedlot versus not, and also the provision of meloxicam to banded animals versus not. The authors found that banding had a negative effect on average daily gain when compared to non-banded bulls, and that meloxicam administration had no impact on performance, behavioral, or physiological parameters evaluated in the relatively short 28-day post-castration observation period. In a 2012 study out of Kansas, surgically castrated animals that received meloxicam 24 hours prior to their surgery did not show any positive performance traits over non-treated castrated controls, but they did have a decreased risk of treatment for bovine respiratory disease in the 50-day post-castration observation period. An Arkansas study involving 62 head from a single ranch followed study calves from birth to slaughter and monitored effects of castration + meloxicam in several different treatment groups. The authors found no difference in average daily gain or weaning weight between the groups castrated at birth and either treated with meloxicam or not. The authors then compared animals surgically castrated at weaning with or without meloxicam to the birth-castrated group. The group that received meloxicam at weaning-castration had significantly better performance for the first 60 days following castration than those that did not. The authors concluded that meloxicam treatment did provide some benefit towards supporting the castrated animal through the early post-castration phase, although they cautioned interpretation in light of the small numbers involved in the study (15 animals/treatment group).
My summary of these studies leads me to believe that the benefit of meloxicam treatment at surgical castration is situationally-dependent, and the decision to use it should be made in light of other management practices that will occur simultaneously with castration. There is not enough supportive data available for me to recommend treatment with band castration. Perhaps studies looking at prolonged treatment with meloxicam (1-2 weeks after band placement) would convince me otherwise, but that practice would likely not be practical from a labor efficiency standpoint.
Performance Effects of Castration Pre- vs. Post-Weaning. Much has been published on the effects of castration in the immediate post-castration period. Fewer data exist on the long-term effects of different castration timings. From the few published studies, the body of evidence indicates that castration prior to enrollment in the stocker period or feedlot is beneficial to individual animal performance in that segment. In a 2015 published study, 3 groups of animals differing by castration method were compared to intact bulls and pre-weaning castrated steers in a GrowSafe® system. Regardless of castration technique, ADG was decreased as compared to steers or bulls in the 2 weeks following castration, but not in the overall 84-day performance test. Gain to feed intake ratios did not differ among the five groups. However, residual feed intake (defined as the difference between actual feed intake and the expected feed intake; lower numbers = more efficient animal) tended to be more negative for pre-weaning castrated animals when compared to post-weaning castrated animals. In the previously mentioned 2015 study out of Arkansas, bulls castrated close to birth performed better than animals castrated at weaning in the 60-day backgrounding period. Interestingly, non-castrated calves performed similarly to the birth-castrated animals, suggesting that the muscle growth benefits of testosterone are not experienced until well after the typical weaning age. After the initial 60-day backgrounding period, all calves performed similarly during a 111-day grazing period and on through slaughter, suggesting that the effects of castration are somewhat transient. It is important to note that the group castrated at birth did not show the same significant back-slide as did the weaning-castrated group. This differential suggests higher resiliency in the pre-weaning beef calf, and the importance of early castration as compared to late castration.
Alternatives to castration. In my opinion, castration is not a good thing to do as defined by its effects on the animal. If research into alternate techniques and pain-mitigation practices has netted zero in improving the situation, are there alternatives on the horizon? One could argue for simply stopping the practice if it is seen as unfavorable. Many studies have compared carcasses of uncastrated animals to castrated animals and unanimously agreed that steer carcass quality is superior to that from a bull. Unless consumers change the requirements of their beef-eating experience or we can more tightly control carcass quality genetic selection, we cannot just stop castrating calves. There is a growing body of evidence supporting use of a “castration vaccine.” These vaccines direct the animal’s immune system against hormones that are responsible for the negative attributes of intact bulls. A 2015 Canadian study compared the use of Bopriva®, an anti-GnRH vaccine manufactured by Zoetis, to traditional banding at receiving to a feedlot. The trial involved initial vaccination on day -35, banding or booster vaccination on day 0, and an observation period ending on day 56. Both groups were compared to intact bulls, which acted as controls. Vaccine-castrated calves had higher final body weights than did banded calves, but both groups were lighter than control bulls. Both vaccine-castrated calves and banded calves had higher carcass quality than did intact bulls. Vaccinated calves had transiently decreased ADG for the week following both injections while banded calves had lower ADG and daily feed intake for the duration of the study. Average daily gains for banded calves came to 1.04 kg/day while vaccinated calves gained at 1.23 kg/day over the 56-day observational period. The problems cited in the literature pertaining to vaccine castration are similar to any vaccine program: vaccines are not 100% effective. In regards to a castration vaccine, this means that 10-20% of calves would not be “castrated” by a standard vaccine protocol. This has been documented in several large-scale studies across many different species using similar products.
Our current management practices seem to compensate for the long-term effects of castration, assuming we can support the calf through the critical stress period of transitioning between industry segments and processing. Currently, we rely on good nutrition, adequate housing, competent labor, and pharmaceutical technology to meet these demands. We still see significant morbidity and mortality in stocker yards and feedlots, much of which ultimately boils down to our inability to overcome the stress those animals experience. Our ability to manage calves efficiently is important to our consumers indirectly, as is evidenced by their willingness to pay current prices for our product. Regardless, the immediate effects of stress on an animal’s experience of life and our reliance on technology to overcome those stressors are what consumers are telling us is important to them directly. This public opinion influences how they choose to spend their money. Until we have better management techniques such as highly effective vaccines or less stressful/painful alternatives to common management practices, we have to work diligently to align these two somewhat opposing forces. This will be will only be achieved through open communication and proactive addressment of these problematic areas of management.