Page 184 - The Welfare of Cattle

PaIn MItIGatIon In CattLe 161

surgical castration following arrival to the feedlot resulted in lower pull rates and respiratory dis-
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ease treatment rates. Furthermore, calves receiving meloxicam following surgical castration had a
reduced inflammatory response compared to placebo controls. 35

DehOrNING

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Dehorning occurs on more than 90% of the dairy farms in the United States. In the beef
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cattle sector, it occurs less than half the time due to the use of polled genetics. The purpose of
dehorning is to lower risk of injury to humans and other animals, and to minimize carcass bruising.
Additionally, cattle without horns require less bunk space compared to their horned counterparts.
The removal of horns can be accomplished one of three ways: disbudding prior to the horn tissue
attaching to the skull; removal of the horn after horn tissue has adhered to the skull; and the use of
polled genes, in which cattle are born without horns. Both disbudding and dehorning are associated
with pain and activation of the neuroendocrine system.
The use of polled genes is an alternative to dehorning cattle. In cattle, the polled gene is domi-
nant, meaning only one chromosome must carry the gene for the phenotypic expression. Use of
polled genetics is prevalent in the beef cattle industry due to the use of Angus genetic lines that
typically carry the polled gene. Utilization of polled genetics has not gained significant ground in
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the dairy industry due to its negative relationship to milk production. It is estimated that the use
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of polled genetics may reduce the herd’s genetic merit and predicted net merit. The use of polled
genetics in the Jersey breed may be less than those seen in Holsteins. 38
There are differences in invasiveness of the various dehorning methods, but all methods are con-
sidered painful. The American Veterinary Medical Association (AVMA) and American Association
of Bovine Practitioners (AABP) both recommend disbudding or dehorning to be accomplished as
early in life as possible. The use of caustic paste in calves younger than 1 week of age has been
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shown to be less invasive of a procedure compared to cautery dehorning. Although less invasive,
caustic dehorning does result in pain and discomfort to the animal. This discomfort can be attenu-
ated using local anesthetic blocks. 40
The effects of local anesthesia in dehorning or disbudding studies are similar to castration. The
acute pain and distress associated with dehorning is attenuated compared to untreated controls
as determined by cortisol concentrations. 41,42 This effect is primarily observed for the duration of
the local anesthetic activity for up to 5 hours post-dehorning. Moreover, evaluation of the auto-
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nomic nervous system through heart rate variability and ocular temperatures indicate an imbalance
2–3 hours post-dehorning with lidocaine administration, coinciding with the time associated with
loss of lidocaine activity. 43
The use of NSAID therapy in conjunction with local anesthetics has been shown to have a positive
impact on pain biomarkers, but this practice is not widely used by veterinarians and producers. 44,45
Flunixin meglumine is a commonly studied NSAID. Flunixin administration provided benefits
to calves during the acute distress and painful phase following dehorning. Flunixin meglumine
administered to calves following a cornual nerve block reduced cortisol concentrations compared
to untreated controls in calves undergoing chemical and amputation dehorning, respectively.
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Recently, a transdermal flunixin meglumine was released in the European Union and approved
in the United States. Due to its novel pharmacokinetic properties, it has the potential to be a needle-
less method of providing analgesia to calves. When administered at the time of dehorning, calves
treated with the transdermal flunixin meglumine had significantly lower cortisol at 1.5 hours post-
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dehorn. Cortisol levels remained lower in treated calves for up to 12 hours post-dehorning, but
these levels were not significant. The transdermal flunixin had no effect on substance P con-
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centrations or MNT at the dehorning site. However, there was a significant improvement in the
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MNT at a control site, indicating improvement in central sensitization. Further research on how this