Introduction

It is generally agreed that all mammals experience pain in a similar manner to humans. Some species such as pigs attempt to hide the effects of pain. Possibly, in the wild, this behaviour was protective because a pig showing signs of pain might attract the attention of a predator. Therefore, one problem in minimising pain in pork production has been the difficulty in detecting pain and assessing the severity of the pain.

A second challenge has been the scarcity of products licensed for use in food-producing animals that are effective in treating pain. This area of medicine has expanded greatly over the past decade but the pharmacological options approved for use in swine are still very limited.

There are other potential reasons that have limited the advancement of pain control in the pork industry including economics and labour requirements.

On the other hand, there are important reasons why we need to carefully examine this issue and determine where there are opportunities to improve pain control. There are circumstances on every farm where pain management will improve productivity, but in addition, as effective products become available pain control will be considered an essential part of good animal husbandry and expected by customers of the pork industry.

There are several categories of drugs that can be of use in reducing pain and stress.

In general, there are drugs that tend to block all pain sensation, the anaesthetics (general and local), and there are drugs which suppress pain, often referred to as analgesics or pain-killers. Under this latter general category, there are relatively new products available for swine that are classified as non-steroidal anti-inflammatory drugs (NSAIDs). They tend to be relatively long-acting and effective in reducing pain and inflammation. They include products such as Metacam (meloxicam), Anafen (ketoprofen) and Banamine (flunixin).

There are also drugs that primarily reduce inflammation, which is a major source of discomfort, for example, corticosteroid drugs.

Summary of Recent Pain Control Research at the University of Guelph

Researchers have used NSAIDs including meloxicam and ketprofen at the time of castration and tail docking to show that these products do appear to reduce pain during the 24-hour period following piglet processing.

Results are described in the following publications:

Tenbergen R., Friendship R., Cassar G., Haley D. Investigation of the use of meloxicam for reducing pain associated with castration and tail-docking and improving performance in piglets. J. Swine Health Prod. 2014. 22:64-70.

Cassar G., Amezcua R., Tenbergen R., Friendship R.M. Preoperative ketoprofen administration to piglets undergoing castration does not affect subsequent growth performance. Can Vet J. 2014. 55: 1250-1252.

The analgesics used in these studies were useful in reducing the post-operative pain but not the acute pain associated with the pull of the spermatic cord at the time of castration.

A study was performed to determine whether the use of a local anaesthetic (lidocaine) injected into the testicle three minutes prior to castration would block the acute pain at the time of castration. The results were inconsistent possibly because in some pigs the “freezing” did not penetrate far enough along the cord.

The conclusion from this study was that the extra handling and the injection of the lidocaine caused pain and stress that offset the advantage of using anaesthesia. It was also concluded that compliance by producers would be a problem because the procedure effectively doubled the time of processing.

Some current work involves trying to find techniques that will minimise the labour and costs associated with using analgesia at the time of processing. For example, Guelph researchers are looking at whether mixing NSAIDs with iron is an effective approach.

Although there has been a great deal of attention paid to providing pain control at castration, there are many other areas in production where analgesics may play an important role. Many of the pigs that are placed in a hospital pen are there because of painful conditions such as lameness, bitten tails and other trauma. Recovery may be greatly improved if analgesics and anti-inflammatory drugs are incorporated into the treatment protocols.

At Guelph, the use of analgesia given to sows after farrowing has been examined. In a study where sows were randomly assigned to treatment with meloxicam or to a control group, no difference was found in sow or piglet performance between the two groups. Details can be found in the following publication:

Tenbergen R, Friendship R, Cassar G, Amezcua MR, Haley D. Investigation of the use of meloxicam post farrowing for improving sow performance and reducing pain. J Swine Health Prod. 2014. 22:10-15.

This trial was repeated, treating only sows that had a difficult farrowing. In the second study, sows that received an analgesic recovered more quickly and did a better job nursing their litter than the control sows, illustrating that pain control should be a consideration following a difficult birthing process but is possibly not needed for routine farrowings.

Acknowledgments: These studies have been sponsored by Ontario Pork, OMAFRA-University of Guelph Research Partnership, and Boehringer-Ingelheim (Canada) Ltd.

Reference

Friendship R. 2015. Pain control in pigs. Proceedings of 34th Annual Centralia Swine Research Update. 28 January 2015. I27-I28.

May 2015