Towards a common conceptual framework and illustrative model for feather pecking in poultry and tail biting in pigs – 2. Terminology

This is post 2 on “Terminology” of:

Towards a common conceptual framework and illustrative model for feather pecking in poultry and tail biting in pigs – Connecting science to solutions

Marc B.M. Bracke^a, T. Bas Rodenburg^b, Herman M. Vermeer^a, Thea G.C.M. van Niekerk^a
a Wageningen Livestock Research
^b Wageningen University, Dept. of behavioural ecology

Reading guide

This is one of 8 blog posts under the heading of: “Towards a common conceptual framework and illustrative model for feather pecking in poultry and tail biting in pigs – Connecting science to solutions”. It contains the following sections/posts:

1. Introduction, specifying the need to compare feather pecking (fp) in layers and tail biting (tb) in pigs
2. Terminology, specifying the various concepts involved in fp/tb.
3. Overview of main similarities and differences between feather pecking and tail biting
4. Farmer as a risk factor, emphasising, perhaps for the first time, that the farmer is a kind of ‘animal’ that is part of the problem (and the solution).
5. Models, reviewing available conceptual models of fp and tb, as well as presenting a new ‘face model’.
6. Disease framework, arguing that fp/tb may be regarded as a medical disorder, over and above being an abnormal behaviour per se.
7. Evolution and domestication, emphasising the need to view fp/tb as a phenomenon an evolutionary and genetic background.
8. References

The entire text (8 posts) can be downloaded as one pdf here.

2. Terminology

In the next posts we will summarise similarities and differences between feather pecking (fp) in laying hens and tail biting (tb) in pigs, taking Brunberg et al (2016) as a starting point. We will also characterise the different models that have been proposed before on fp/tb. Building on this we will argue why we think that fp/tb may/should be regarded as a medical/mental disorder, provided the medical framework maintains an evolutionary and scientific perspective on fp/tb.

This post aims to characterise the underlying concepts and criteria, so as to illustrate that giving crisp definitions may not be as easy as it may seem to be at first sight.

Note: We will use the label ‘fp/tb’ in the remainder of these related posts to refer to the communal problem. It is difficult to provide an overarching term for fp and tb together. Most existing terms are too wide: Abnormal behaviour, injurious behaviour and harmful-social behaviour, e.g. because there are other forms of abnormal behaviour and because there are other forms of injurious behaviours like aggression (e.g. vulva-biting in sows) and abrasive behaviours (injuries resulting from making contact to flooring or pen fittings; cf fin injuries in farmed fish (Noble et al., 2012; Stien et al., 2013; Pettersen et al., 2014; Folkedal et al., 2016)).

An outbreak of injurious fp/tb requires a specification of the start and end point, i.c. presence of injuries. Here, again, the observer may play a significant role: the detection of injuries depends e.g. on the inspection frequency and quality (e.g. method & expertise) of the observer. The observer also plays a role in so-called early-detection and in decision-making as to when and what treatment is to be started to counteract an on-going outbreak.

It should also be emphasized that fp/tb is a process, where different types of animals are involved. In order to start, one ‘neutral’ animal must become an actor (pecker/biter) showing fp/tb behaviour towards a victim/receiver resulting in a fp/tb wound. When the outbreak escalates more and more individuals become involved and/or wounds become progressively severe, potentially leading to the death of the victim (such that the fp/tb may at some point be called ‘cannibalism’). Wounds may also get infected, thereby aggravating the impact on productivity and welfare. Some animals in a fp/tb pen may not get involved. These may be labelled ‘neutrals’. In addition, Brunberg et al. (2016) use the term ‘controls’ for animals in neighbouring pens which are not affected by fp/tb. These different types of individuals involves are not fixed over time. E.g. both neutrals and controls are labels that may changes over time (Daigle et al., 2015), i.e. animals that were neutrals/controls today, may become actors or victims tomorrow, and individuals may be both actor and victim at some point in time (or even at the same time). When an outbreak ends, both actors and victims may return to being ‘neutrals’, even though it is generally recognised that the probability of recurrence is much bigger in groups that have previously experienced fp/tb problems, as if the ‘set points’ of such animals have changed irreversibly. Because of this rather irreversible state-change it is important to differentiate between prevention, what is done to prevent an outbreak, and curative treatment, what is done to stop an outbreak that has occurred.

A final term used in these posts is the word ‘model’, by which we primarily mean a figure intended to explain fp/tb. Ideally, the model should not only illustrate the mechanism and the types of individuals involved, and where/how it goes wrong (e.g. that fp/tb is a multifactorial problem), but also provide answers to the other 3 why questions (evolution, function, ontogeny). Ideally, also the model should explain anomalies (i.e. apparently ‘strange’ facts) and generate testable predictions. The ideal model should also be effective in communicating what is the (e.g. welfare or production) problem associated with fp/tb and provide suggestions regarding prevention and/or treatment. Also, a model is better if it uses a stronger, more intuitively appealing metaphor, such that it is easily remembered, not only by scientists, but also by other stakeholders, i.c. farmers, their advisors, and NGOs (see e.g. cartoons at http://www.featherwel.org/). However, besides addressing all of these aspects, a good model should not be complex, but rather explain fp/tb in the most parsimonious way possible.

Reading guide

This was blog post nr. 2 under the heading of: “Towards a common conceptual framework and illustrative model for feather pecking in poultry and tail biting in pigs – Connecting science to solutions”. It contains the following sections/posts:

1. Introduction, specifying the need to compare feather pecking (fp) in layers and tail biting (tb) in pigs
2. Terminology, specifying the various concepts involved in fp/tb.
3. Overview of main similarities and differences between feather pecking and tail biting
4. Farmer as a risk factor, emphasising, perhaps for the first time, that the farmer is a kind of ‘animal’ that is part of the problem (and the solution).
5. Models, reviewing available conceptual models of fp and tb, as well as presenting a new ‘face model’.
6. Disease framework, arguing that fp/tb may be regarded as a medical disorder, over and above being an abnormal behaviour per se.
7. Evolution and domestication, emphasising the need to view fp/tb as a phenomenon an evolutionary and genetic background.
8. References

The entire text (8 posts) can be downloaded as one pdf here.

Acknowledgements

These blog posts have been made possible by the Hennovation project (HORIZON 2020 ISIB-02-2014 project, Grant no. 652638).