Certain procedures implemented in the production of pigs for meat can cause immediate and prolonged pain in the animal, which makes these procedures controversial in the matter of animal welfare. Routine tail docking and teeth clipping are performed to control for certain damaging behaviours elicited in groups of pigs that are unable to express natural foraging and rooting and where competition for space and food is high.

It is argued that ongoing outbreaks of damaging behaviour are largely observed in barren, intensive systems, and are a symptom of whole-system issues: a theory to which modern swine welfare research can attest. The translation of such research into on-farm practices that are both cost- and time-efficient is a challenge, and something that academics worldwide are striving to achieve.

The Pig Site speaks to researchers, Dr Dale Sandercock (Scotland’s Rural College), Dr Mette S. Herskin (Aarhus University) and Dr Pierpaolo Di Giminiani (Newcastle University), about issues related to pain-inducing swine management procedures and the future of welfare science on farms.

What do you believe are the major issues with pig welfare in both intensive and extensive rearing systems?

Dr Herskin: I think one major issue in the pig industry is related to the pain experienced by pigs under production conditions, combined with the present lack of knowledge of, and opportunities to relieve, this pain. The pain is a result of management procedures involving tissue damage and pathological conditions observed in pig production, yet when it comes to pain, the pig is actually among the least studied of the domestic mammals, and that is a paradox to me.

Dr Sandercock: For me the most pressing welfare issues in pig production are tail docking and tail biting because ultimately, I think they reflect problems in systems where there is inappropriate management of the pigs and their behaviour. We really should be looking at rearing pigs with intact tails as the gold-standard for pig production.

When it comes to intact tails being the gold-standard for certain welfare measures, what does that show to you is working well in the system?

Dr Sandercock: You have to relate this back to some of the causes as to why tail biting occurs in the first place: the animals are redirecting their natural rooting behaviour into something that is adverse and inappropriate. Ultimately, this reflects animals that are bored and stressed which even at a sub-clinical level, is a key pre-disposing factor for the occurrence of tail biting.

If you look at recent work published by members of the FareWellDock consortium and others, it is possible to rear pigs with intact tails (Bulens et al., 2018; D’Eath et al., 2014; Valros and Heinonen, 2015; Wallgren et al., 2018). It doesn’t mean that you’re not going to get the odd outbreak, but these outbreaks are contained and manageable. The farmers of these systems have learnt to deal with that – they accept that it can happen, but they have contingency plans for it.

Tails are also bitten outdoors though it’s much rarer. Efficiently dealing with outbreaks requires vigilance and good management practice on behalf of the producers. That sounds like us dictating information, but that’s how it is. That’s what has proven to work.

What advice would you give to producers who are looking to manage tail biting better?

Dr Sandercock: There has been a lot of work done and plenty published online on environmental enrichment, and there’s ways that producers can rear pigs to mitigate this issue. One example is chopped straw which has proven a useful alleviator of tail biting and has shown to provide significant health benefits in pigs (Jensen et al., 2015; 2017)

However, straw as a solution being brought into an old system can be a problem. What I mean by that is if you look at the way producers remove slurry, they use slatted systems with a built-in system of pumping out the slurry. There is an immediate rejection to using straw because it causes issues with slurry removal.

We come up a lot against that response: “we can’t use that because we’ve got this system”.

This is a clear example of where there is a solution but to adopt it requires almost going back to the drawing board and deciding that if we want pig production systems that are fit for purpose into 2020 and beyond, we’ve got to review the whole system in order to implement those changes.

For me, there needs to be an evolution of the system in order to provide any meaningful progress on how to prevent issues such as tail biting.

A set of practical recommendations on tail docking and tail biting have been published as four fact sheets and translated into eight languages, and can be found on the FareWellDock website.

You have had a number of papers published on the short-term pain experienced by tail-docked pigs. Why is it important that you also investigate the long-term pain associated with tail docking?

Dr Di Giminiani: Research in pain has been limited to a few measures, both behavioural and physiological, and these indicators are limited to a few hours after docking occurs. Our involvement with FareWellDock was investigating the long-term effects and long-term causes of pain as we are still far from knowing exactly what happens beyond a few hours after tail-docking. From a welfare perspective, the long-term pain may be even more important than the acute.

Dr Sandercock: The term, ‘pain’, is used very ambiguously. Scientifically, pain is the aversive sensation that comes from higher processing of something that starts out as tissue damaging, such as tail amputation by docking. It is difficult to quantify so we tend to look for more practical ways of doing that as almost like a proxy measure to begin with. We, like a lot of other researchers, look for an evoked response in an animal by applying a quantifiable mechanical stimulus to an area that might be painful (Di Giminiani et al., 2016; 2017). We do recognise that there are limitations in interpretation using this approach. It tells us about the sensory discriminant component of pain but not necessarily the affective component of ongoing pain. Currently, methodological research is focussed on being able to include the affective component in farm animal pain as well.

The reason we think there are long-term pain issues relates to the development of traumatic neuromas that occur following tail docking and severe tail biting. These neuromas provide the potential for spontaneous or ongoing or long-lasting pain as part of the damage to the sensory nervous system long after the initial injury event (Sandercock et al., 2016; 2017). I would use, very cautiously, the analogy of human phantom limb pain. A lot more research needs to be done in that area for us to be 100 percent certain, but the early signs are that it is pretty similar.

What do you hope to achieve by communicating more with producers?

Dr Di Giminiani: There are producers who will share our concerns; there are other producers who are simply not as convinced by scientific evidence. It’s important to see what they believe are important issues – they might not see tail docking as a particularly urgent issue compared to transport or lameness.

I think for people on this side of the research it is always nice to get feedback from producers as they themselves know what is pressing in their industry.

We’d certainly like to reach out to producers about how our work is perceived.