Hennovation partner Thea van Niekerk reported on a couple of interesting project results in Resource (article in Dutch):
Alpacas may protect free-range laying hens from birds of prey.
A custom-made trolley can substantially improve the welfare of spent laying hens.
Pecking blocks were tested in the Netherlands (cementblocks used for construction appeared best; see flyer).
Dutch_farmers are learning to live without beak trimming
Poultry World, Aug 22, 2018
Beak treatments will formally be banned in the Netherlands from next year, but the market has moved ahead of legislation. Poultry World discovers how farms are managing the change.
From the beginning of September, members of the Netherlands’ largest egg assurance scheme, IKB EI, will not be permitted to keep hens with treated beaks.
This also includes infrared beak trimming. To this end, Avined decided to anticipate market demands as much as possible.
The German KAT (Association for Controlled Alternative Animal Husbandry) monitoring system has already prohibited the restocking of hens with trimmed beaks with effect from 1 January 2017.
When research meets farming to lift welfare (article in Poultry World, dd 12-6-2018).
The EU-funded Hennovation project was an exercise in bringing egg farmers together with researchers to develop practical ways to improve welfare, as Tony McDougal discovers.
Researchers have partnered with farmers to draw up practical new measures for improving the health and welfare of farmed poultry.
The 2 ½ year EU-funded Hennovation project, which ended this autumn, has been finding ways to introduce practice-led innovation in sustainable animal welfare through the development of innovation networks.
Read more at the Poultry World website.
This is post 1. “Introduction” 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. Brackea, T. Bas Rodenburgb, Herman M. Vermeera, Thea G.C.M. van Niekerka
a Wageningen Livestock Research
b Wageningen University, Dept. of behavioural ecology
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:
The entire text (8 posts) can be downloaded as one pdf here.
Feather pecking (fp) in poultry and tail biting (tb) in pigs are among the most persistent animal-welfare problems associated with intensive livestock farming. Both problems have been studied and reviewed extensively (e.g. fp: (Rodenburg et al., 2008; Nicol et al., 2013; Rodenburg et al., 2013); tb: (Schrøder-Petersen and Simonsen, 2001; Bracke et al., 2004a; EFSA, 2007b; Taylor et al., 2010; D’Eath et al., 2014; Valros, 2017)). Legislation and policy initiatives have been discouraging the continued performance of routine mutilations (beak treatment and tail docking for fp and tb respectively). However, both poultry and pig farmers generally find it difficult to stop mutilations and prevent and/or treat these injurious behaviours in intensive farming systems. Comparing fp and tb may help address these problems. However, few papers have compared the two forms of abnormal behaviour in detail. One notable exception is the fairly recent Open-Access publication by Brunberg et al. (2016). These authors discussed similarities and differences between fp and tb, and presented a general model which looks somewhat like an envelope. This publication is written for a scientific audience, and it is not easy to read for farmers and others interested in solving fp/tb such as vets, other farm advisors and NGOs. Also the ‘envelope-shaped’ model presented by Brunberg et al. (2016) is not as appealing as we would (ideally) like it to be. It mainly says that by nature both pigs and poultry are omnivorous generalists that have (had to) become production specialists via genetic selection and rearing in large-scale intensive systems applying a one-size-fits-all principle. According to Brunberg et al. both the physical and social environment (‘where you are’ and ‘who is with you’), together with animal-related factors (‘who you are’) determines ‘what you become’ in terms of fp or tb, i.e. a performer (pecker/biter), victim/receiver or a neutral animal. The authors also hypothesise that the gut-microbiota-brain axis may play a crucial role which should be investigated further. This is in accordance with the common view that fp and tb are multifactorial problems associated with the substantial discrepancy between the natural and the commercial environment resulting in a (seriously) deprived foraging (and/or feeding) motivation that eventually leads to fp/tb (and worse, i.e. cannibalism, if not curtailed adequately).
It is not entirely clear, however, why the model (figure) in Brunberg et al. (2016) should look like an envelope. When looking a bit more closely at the figure, the model appears to encompass everything (the animal, its history and its entire, physical and social, environment). Only upon more careful examination and in particular when reading the text itself do the further ramifications underlying the model become more clear. Since we feel the text may be rather inaccessible for practical application in problem solving, one objective of these blog posts, therefore, is to compare this model to other models, esp. those developed in our own organisation (Wageningen University & Research), in order to see if we can better highlight the available knowledge that should be used to (eventually help) solve the problem in practice. To this end we have also tried to make the information presented by Brunberg et al. (2016) more accessible, and we supplemented it with our personal expertise on fp/tb. It is important to emphasise, however, that the primary aim of this publication is to improve on the available conceptual frameworks to facilitate practical understanding of fp and tb so as to support solving the problem in the future. We do not, however, aim to present a tool box or cook book for solving fp/tb.
This was blog post nr. 1 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:
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).
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. Brackea, T. Bas Rodenburgb, Herman M. Vermeera, Thea G.C.M. van Niekerka
a Wageningen Livestock Research
b Wageningen University, Dept. of behavioural ecology
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:
The entire text (8 posts) can be downloaded as one pdf here.
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.
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:
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).
This is post 3 on “Overview of main similarities and differences between feather pecking and tail biting” 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. Brackea, T. Bas Rodenburgb, Herman M. Vermeera, Thea G.C.M. van Niekerka
a Wageningen Livestock Research
b Wageningen University, Dept. of behavioural ecology
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:
The entire text (8 posts) can be downloaded as one pdf here.
Table 1 shows an overview of similarities and differences between feather pecking (fp) in poultry (i.c. laying hens) and tail biting (tb) in pigs (i.c. weaned and growing/fattening pigs).
Table 1 is based primarily on Brunberg et al. (2016) and supplemented with our own (esp. MB and TvN) knowledge about fp and tb (also as presented on the henhub website www.henhub.eu). The table is intended to summarise the most relevant similarities and differences between fp (in hens) and tb (in pigs), and thus support decision making in dealing with fp/tb in practice.
The key risk in fp/tb is the fact that both laying hens and pigs are originally omnivorous generalists that have been become production specialists in feed intake and food conversion in intensive farming conditions. The motivation for fp/tb relates to a frustrated foraging need, which is modulated by a whole array of different risk factors, hence resulting in this multifactorial welfare issue. In addition to similarities the table also identifies a number of differences between fp in layers and tb in pigs, e.g. we don’t have genetically selected lines for tail biting comparable to the high and low fp lines in poultry. Hence, an experimental model to study tb in more detail is currently largely lacking (though pigs selected for social breeding value (high indirect genetic effects for growth) showed considerably less ear biting, tail damage, aggression and enrichment manipulation (Camerlink et al., 2015), and may thus in principle be suited to be used to study tb experimentally in more detail).
The table may perhaps be improved upon further by specifying relationships between the items specified as risk factors (in the left column) and the different responses identified in the process of fp/tb (in the right column; cf (Fraser, 1987a)).
Another suggestion relates to the many risk factors that may hamper practical problem solving. While scientific experiments necessarily vary only a few risk factors in order to reliably examine which factors may affect fp/tb, a tentative suggestion for solving the multifactorial fp/tb problem could be to try to formulate multifactorial solutions. This may be esp. relevant when monofactorial solutions fail to solve the problem. However, an important drawback of this approach is that it may essentially remain unclear which factors are accountable for any (positive or negative) results. When a multifactorial approach is working, it may be possible to tease out in subsequent research the relative contribution of the different risk factors. When it doesn’t work, that may be the end of the road for that particular type of farming (given the constraints imposed).
Table 1. Comparing risk factors and animal responses related to feather pecking (fp) in poultry (laying hens) and tail biting (tb) in pigs, taking Brunberg et al. (2016) as a starting point, supplemented with own author expertise (marked as *). Common risk factors (similar across species, specified between brackets when ‘unknown’) are followed by notable differences between Hens and Pigs (specified on the next lines). Black characters: risk increasing factors; green: risk decreasing factors (benefits); red (in the column ‘risk factors’): particularly welfare-reducing risk factors. ‘No’: means that the opposite reduced fp/tb.; behav.: behaviour; envir.: environment; decr.: decreased; incr.: increased; HFP: high fp line/breed; LFP: low fp line; TIM: tail-in-mouth; w: weeks; d: days; mo: months. The cells in column ‘Responses’ are not directly (horizontally) related to the risk factors. Responses are stacked: more positive behaviours are presented at the bottom; worst (form of escalation, i.e. cannibalism) is shown on top. Responses are related to ‘type of animal’ (victim, actor, neutral) (with welfare aspects specified at the level of the type-of-animal label). Poor welfare responses are shown in red (in the column ‘responses’). See the text for a more detailed description of how to read the table.
| Type of factor | Risk factors (Multifactorial, related to the type of factor, i.e. environment-, group- & animal based) | Responses (behav., physiology, pathology & welfare, related to type of animal, i.e. victim, actor, neutral) | Type of animal |
| Envir.-based | Modern large-scale specialised farms | Victim: fear, pain (during outbreak), stress, sickness (during treatment, recovery) | Victim |
| Barren pen (no proper foraging material, straw), large discrepancy between intensive farming envir. and the natural envir./envir. of evolutionary adaptation | Cannibalism | ||
| (Partly) slatted floor Hens: (Litter) Pigs: Concrete |
(Wound) infection | ||
| Indoors* Hens: Range (may provide foraging opportunities and reduce stocking density) Pigs: – (Outdoor area may provide rooting substrate (soil), fibre (pasture), but not necessarily) |
Production loss (reduced growth) Hens: Egg laying (reproduction) Pigs: Growth (production) |
||
| One size fits all (food, climate*) | |||
| Standardised feed, optimised for average individual (vs indiv. needs); perhaps probiotics may treat fp/tb Hens: – Pigs: No phase feeding; decr. feeding frequency predicted tb outbreaks 9 w later; tb victims made more feeder visits 2-5w prior to tb |
Appearance Hens: Deteriorating feather cover Pigs: Tucked tails |
||
| Feed changes and ‘hiccups‘ in providing feed (unpredictable frustration) | Decreased tryptophan, serotonin levels | ||
| Feed type; Reduced feeding time, not ground, concentrated feed, less fibre Hens: Pellets give more fp than fine ground feed; no mash/pecking materials; high E diet; no feathers in diet (acting as fibre, incr. feed passage) Pigs: Contradictory results (liquid/pellets/meal) but straw reduces tb & is consumed |
(Fp/tb) Wound(s) Hens: Esp. tail, body (not back of head) Pigs: Tail (possibly ears, flanks, legs) |
||
| Protein, mineral (NaCl) deficiency; supra-nutritional NaCl may alleviate fp/tb Hens: Deficiency of crude protein, amino acids, minerals (Na, Ca) Pigs: Nutritional imbalance incr. tb |
|||
| Feeder space, feed competition (bite/peck to get access to feed) | Salivation (pH incr.; alleviate peptic ulcers) | ||
| Rearing conditions (both poor rearing conditions and a backdrop from enriched rearing conditions to deprived conditions later in life) Hens: Absence of litter around 5w, high stocking densities, rearing on wire floor Pigs: More piglets/stockperson, fostering, no straw in farrowing pen, reduced feeder space during rearing gives more tb later in life; multi-litter rearing decr. manipulative behav.; providing straw during rearing and then depriving pigs of straw later is also considered a risk factor |
[Microbiota composition?] Hens: HFP has different microbiota composition than LFP; feather eating changes gut microbiota; Pigs: Unknown |
||
| (Pen size, pen design) Hens: (Large) Pigs: (Small) |
Escalation of tp/tb (outbreak) | ||
| Group-based (envir.- & animal based) | Group housing Hens: (Very) large groups (10-100.000 birds) Pigs: Small (~10 pigs) |
Arousal, restlessness, excitement (positive), fear & avoidance (negative). Hens: Cut feathers increased fp Pigs: Blood tail model (rope) increased (tail) biting behav. |
|
| High stocking density Hens: More fp in largest groups (15-120 birds) Pigs: (Not uniform results) |
Cognition, (social) learning, (synchronisation; copy-behaviour; stimulus enhancement) | ||
| Farm health status (any (major) stressor/immune suppressor probably) Hens: Vaccination (specific immune stimulation) when young may incr. fp as adults; LFP have better immunocompetence; e.g. E. Coli incr. severe fp Pigs: Better health status reduces tb; straw reduces infections |
Prevalence/intensity: Hens: Fp on 86% of UK flocks; SFP esp. when adult; fp up to 135 bouts/bird/hr; 3 severe pecks/min Pigs: Tb on 30-70% of farms; fanatic biters bite 11-25% of time |
||
| Mutilation (3 aspects are relevant: 1. Method used; 2. Amount of tissue removed; 3. Age of treatment; esp. 2nd aspects is relevant as risk factor)
Hens: Beak treatment (previous beak trimming (may remove larger/smaller part of the beak), now infrared beak treatment) (Note: In poultry, as it were the (future) actor is mutilated) |
Severe fp (SEP)/tb
Hens: – Pigs: Three types of (severe/injurious) tb: two-stage (starting with TIM), sudden forceful, and obsessive (fanatic) |
||
| Pigs: Tail docking (longer or shorter part of the tail) (Note: in pigs as it were the (future) receiver is mutilated by removing the tail) | Actor: (Excitement, pleasure [during outbreak], pain, stress [during treatment]) Hens: Pecker Pigs: Biter |
Actor, performer | |
| History of fp/tb (once an outbreak has occurred, the likelihood of another outbreak increases; animals are never the same again after an outbreak; (irreversibly) changed set points) | Object-direction: Hens: Towards feathers Pigs: Towards the tail |
||
| Animal-based | (Bred for) very high production-efficiency (genetics, breeds) (esp. genetic motivation of feed-related behav.; behavioural need to species-specific foraging behav); fp/tb has moderate heritability (~0.2) | Neutral (in same pen)/control (on other pen): Neutral as a biter in spe: boredom, frustration, behavioural deprivation, esp. of foraging motivation |
Neutral / control |
| Hens: (Eggs) Pigs: Lean meat; neutrals have different genetics |
Gentle manipulation Hens: Gentle fp is prevalent in young birds, decr. with age Pigs: Tail in mouth (TIM), |
||
| Domesticated 5-6000 years ago; bred in 50 years of intensive selection from foraging generalists (omnivorous (variable diet; need to explore)) to meat & egg producing specialists; fp/tb not selected against; tb&fp are correlated to production, but not in the same way | Pen-mate directed exploration Hens: (Deteriorated) plumage condition Pigs: Wet tails |
||
| Hens: Male peckers had higher body fat; female peckers had earlier onset of lay; HFP: Better growth, lower total egg mass, decr. feed efficiency Pigs: Lower backfat, lean tissue growth |
Consummatory behav.: Hens: Feather eating (more in HFP) Pigs: – |
||
| Being different Hens: Plumage colour (standing out from others; incidental pigmented birds were more often victims) Pigs: [Lame pigs get bitten] |
Object/substrate-directed exploration/foraging in accordance with nature, showing natural behav. (50-60% of time) Hens: Scratching, pecking Pigs: Rooting, biting |
||
| Personality Hens: Peckers appear more proactive, fearful (in open field), stress (cortisol shows variable results); more foraging & walking when young incr. fp as adults; HFP more active; mobility to get to the nestboxes (i.e. too calm birds are at risk for fp) Pigs: Low backtest responders showed less pen-mate manipulation; biters more sitting & kneeling 6d prior to tb; victims more posture changes 6 d prior to tb; tail posture (tucked) may predict tb 2-3d before outbreak |
|||
| Sex, probably females more active performers Hens: All females Pigs: Mixed/uni-sex; males receive more tb; uncastrated males are more likely to become fanatic biters (1 study) |
|||
| Age: Onset around sexual maturity (also then shifting nutritional needs) Hens: Adult (16-80wks); progesterone (& oestrogen) incr. up to 18w incr. fp; testosterone decr. fp; SFP ~20w in females, but not males Pigs: Young, prepubertal (<5-6mo); perhaps associated with teething* |
|||
| Body weight Hens: – Pigs: Biters are lighter; victims tend to be heavier before tb (later decr. growth) |
This was blog post nr. 3 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:
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).
This is post 5 on “Models” 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. Brackea, T. Bas Rodenburgb, Herman M. Vermeera, Thea G.C.M. van Niekerka
a Wageningen Livestock Research
b Wageningen University, Dept. of behavioural ecology
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:
The entire text (8 posts) can be downloaded as one pdf here.
Table 3 shows a list of various models/figures that have been proposed to clarify feather pecking (fp)/tail biting (tb), including the recent model proposed by Brunberg et al. (2016). Our focus here was to compare models, esp. models originating from Wageningen University Research, in search for potential improvements. Not all models have been included in Table 3. For example, Valros and Heinonen (2015) propose a modified bucket model where the bucket is filled with acute and/or chronic stressors (cf also Valros (2017)).
Since copy-rights are a problem for representing models, below a selection is given of models for which Wageningen UR (already) has the copy-rights. Other models can be obtained via the cited references or the internet. E.g. an example of the psychohydraulic model (Lorenz, 1950; 1978) can be found here.
Figure 7.3 below shows the tail biting (tb) model by Zonderland (2010a) (Fig. 7.3, p. 138).
The conceptual framework for tb originating from Bracke (2008) (reprinted in (Bracke, 2017)) is shown in Figure 1 below. This model was designed to construct the RICHPIG model (decision support system) to assess/calculate the welfare value of enrichment materials for pigs.
Figure 1. Schematic representation of the conceptual framework for assessing environmental enrichment for pigs. EMat: Enrichment material; AMI: animal-material interactions; I: Istwert, the environment as perceived by the animal; S: Sollwert, set point or norm (modified homeostatic model after Wiepkema (1987) and (Anonymous, 2001)). (Figure from Bracke (2008), permission granted by UFAW) (reprinted from (Bracke, 2017)).
Citation from Bracke (2017) relating the model to the principle of communicating vessels:
“Progressive feedback loops in the framework indicate that the animal’s welfare is good when proper enrichment satisfies the pigs’ need to explore and forage. When the enrichment is deficient, the animals will redirect their attention and show pen- and pen-mate directed behaviour. Note that this may imply a mechanism resembling the principle of communicating vessels (connected containers filled with liquid; see Wikipedia (2016c)). In accordance with this principle pigs may distribute their (motivation for) exploratory behaviour (the liquid) depending on the quality of the manipulable ‘materials’ available to them (cf Bracke et al. (2012)). Eventually, an outbreak of tail biting may occur, potentially evoking a positive feedback loop (an escalating outbreak) leading to cannibalism when no ‘proper enrichment’ is provided buffering and/or eliminating the (primary) cause/stressor.” (End of citation).
In the communicating-vessels model, for which we found some empirical evidence in pigs (Bracke, 2017), vessel size may change due to animal-properties like genetics; but also e.g. enrichment-based and other risk factors.
In the case of fp in poultry, in a classic paper Newberry et al. (2007) questioned the assumption of communicating vessels underlying the hypothesis that fp is redirected foraging behaviour as proposed earlier by Blokhuis (1986). Newberry et al. (2007) showed that birds with high levels of ground pecking as chicks were more likely to develop high levels of fp as adults compared to low ground pecking chicks. However, the high ground pecking chicks also continued to show high levels of ground pecking as adults, shedding doubt on the theory that fp would replace ground pecking.
Under ‘mechanism’ Van Niekerk (2015) presents both a balance model and a tipping-bucket model for fp (see also Van Niekerk (In prep.)). The bucket model was modified from a tb model originally proposed by Vermeer in Bracke et al. (2012). The main problem of the tipping-bucket model is that it suggests that fp/tb cannot stop, cannot be made undone (or perhaps only via an external ‘force’, e.g. a farmer taking adequate measures to correct the problem). Perhaps the model could be improved, e.g. by making a tumbler-type tipping bucket, such that it can be emptied, and then may restore its original position. However, this revised tumbler model would still be deficient in that post fp/tb set points are not the same as before (as a tumbler would suggest). Another option might be a series of buckets. Once tipped, the next bucket could stay down, with the next bucket being smaller, such that the next tipping point would be reached sooner, with preventive measures reducing the flow of water into the bucket. This would solve the issues just mentioned, but it would seem to be a somewhat ‘artificial’/non-parsimonious model.
Figure 2. Tipping-bucket model of feather pecking (Van Niekerk (2015); modified after Bracke et al. (2012)).
Figure 3. Balance model (Van Niekerk (2015), from http://www.henhub.eu/fp/mech/).
Perhaps the balance model could be modified to a balance between ‘fixed’ risk factors on the one scale and management (farmer effort) to reduce tb/fp risk on the other scale of the balance. However, the symmetry in disbalance suggested by the model does not seem to make sense: too much pressure on one side does not have the same effect as too much pressure on the other side. Also, fp/tb does not seem to be (totally) reversible: inducing fp/tb by removing a bit of enrichment cannot be undone by adding the same bit of enrichment (at least not shown). Also, to date no studies are available showing reversibility by adding other factors (e.g. inducing tb/fp by poor litter quality and then ‘treating’ this problem by adding e.g. better feed, etc.).
The next figure (Figure 4 below) shows a newly developed ‘face’ model aimed at incorporating the different types of animal involved (actor, victim, neutral), as well as emphasising the role of the farmer (as a kind of ‘actor’) in dealing with a fp/tb problem. The farmer is important for prevention and treatment of fp/tb. The emergence of an animal-actor is necessary to start fp/tb, but the responsiveness of the victim also plays a roll. For example, a victim may more or less effectively avoid becoming a victim and respond more or less in a way that leads to escalation of an outbreak. While a learning process may have transformed actors into individuals predisposed to show the abnormal fp/tb behaviour again at a later stage, similarly, at some point victims may show learned helplessness (which may also more or less permanently alter their behavioural predisposition).
Figure 4. New ‘face’ model of feather pecking (fp)/tail biting (tb), showing its multifactorial nature (‘left ear’), the role of different types of animal (actor & victim (‘eyes’), neutral (‘mouth’)), array of responses (‘right ear’), as well as the role of the farmer (‘nose’) in dealing with the problem. Both positive and negative feedback loops (‘glasses’ around the eyes of the face) are involved. Evolution and life history (‘hairs’) determine the set points of the individuals (animals and farmer). The comparators (‘pupils’ etc.) are (more or less) equivalent to welfare (smiley, balance, bucket and marble run) as indicated in the ‘necklace’ below the face. TIM: tail in mouth; OCTB: obsessive-compulsive tail biting; p.m.: pen mate; i.r.t.: in relation to. (Modified after (Bracke, 2017), and incorporating elements of the other models shown above, i.c. the balance and bucket models).
This was blog post nr. 5 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:
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).
This is post 7 on “Evolution and Domestication” 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. Brackea, T. Bas Rodenburgb, Herman M. Vermeera, Thea G.C.M. van Niekerka
a Wageningen Livestock Research
b Wageningen University, Dept. of behavioural ecology
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:
The entire text (8 posts) can be downloaded as one pdf here.
This final post/section aims to emphasise that adopting a disease framework for feather pecking (fp)/tail biting (tb) does not imply discarding the common science-based and evolutionary perspective on fp/tb. In order to show why this may be important we will first consider non-scientific reasoning to deal with fp/tb.
From a non-scientific and non-welfare perspective it may make perfect sense to farmers and veterinarians to prevent or treat fp/tb using respectively beak treatment (i.e. removing the means for fp) and tail docking (i.e. removing the object of tb). Similarly, measures like spectacles to prevent accurate vision (preventive measure in poultry) and teeth cutting (treatment measure in pigs) have been used, as has been the keeping of animals in the dark (thus blocking the animals’ vision). Along these lines one may also propose breeding poultry without feathers and pigs without tails, hens with blunted beaks, and pigs without incisor teeth, or perhaps blind animals (Ali and Cheng, 1985) (e.g. without eyes). Similarly, physical restrictions may be imposed in theory, e.g. solitary confinement/individual housing would be highly effective in stopping fp/tb. A related ‘solution’ is a limited physical ability to move (rather than lack of motivation (Bokkers and Koene, 2004)), as appears to be the case in heavily selected broilers. In fact, this may (partly) explain why fp is much less of a problem in broilers compared to laying hens. When comparing broilers to pigs, another reason, besides the limited physical activity, may be age. Broilers are slaughtered at 5-6 weeks of age, while egg-laying (puberty) starts at around 17 weeks (when severe fp normally develops). In pigs slaughter age and puberty are around 6 months and tb may be seen roughly in the period between 4 weeks and 6 months. Perhaps the situation in pigs, where tb is frequently seen in weaned and young growing pigs, and in rearing gilts but not in pregnant/farrowing sows, is somewhat more comparable to turkeys, where fp is a problem (5-8% in untreated turkeys; 10-16% in beaktreated turkeys) at around 4 days of age and around 8-10 weeks of age, at which age egg-laying/puberty may also start, while slaughter age is around 16-20 weeks (Van Niekerk and Bracke, 2016; van Niekerk and Veldkamp, 2017). Turkeys, like pigs, have been bred less intensively for muscle growth compared to broilers (Van Niekerk and Bracke, 2016). However, it may also be noted that fp in turkeys does not seem to respond as favourably to enrichment as does fp in laying hens (Van Niekerk and Bracke, 2016) and tb in pigs. In line with these considerations, the comparison between fp in poultry (laying hens and broilers) and tb in weaned/growing pigs, would raise the tentative suggestion that while fp is less prevalent in fast-growing broilers because of their very young age and limited physical activity, slower-growing broilers, in virtue of the older age and enhanced physical activity, should be expected to have an enhanced propensity to show fp behaviour. An anonymous poultry-welfare expert (pers. comm.) indicates that this may indeed be the case.
A risk of using breeding for inactivity to reduce fp/tb, of course, could be that in addition to reducing the propensity of the actor to show harmful social behaviour, inactivity may also reduce the propensity of the victim to avoid being pecked/bitten. Another breeding goal may thus be to select for animals that do not have the (cognitive) capacity to ‘discover’ fp/tb, and/or to breed against the ability to acquire the behaviour through social transmission (i.e. to learn from conspecifics who have become actors). Such selection for ‘stupidity’ is also unlikely to be effective, because both laying hens and pigs need a certain level of cognitive functioning and synchronisation, e.g. to regulate access to limited resources like nest boxes and feeders (Boumans, 2017).
A major factor in causing fp/tb is the animals’ motivation to explore/forage. Would it then make sense to select against this motivation per se?
In applied ethology it is commonly assumed that fp/tb are caused or at least mediated by a deprived motivation to forage. The idea is that poultry and pigs still have behavioural needs originating from evolution in a natural environment. Domestication is not perceived to have had a major attenuating effect, i.e. modern pigs and poultry are not (yet) adapted to intensive farming. The motivation to forage is still considerable because it was essential to survive in a natural environment spending considerable periods of time searching for food. Being generalist omnivores also implied these animals had relatively inquisitive natures to investigate a wide variety of potential food items under variable circumstances encountered in nature.
In fact, this attraction to novelty and eagerness to learn may well be sufficient to explain one of the most characteristic features of fp/tb, namely that a kind of irreversible state change occurs once the first fp/tb has taken place, and also that the problem has a certain tendency to escalate and is much more difficult to counteract later than it is to prevent it from occurring in the first place. A normal learning process can thus explain the difference in set point between animals who have never experienced fp/tb and those that have. No pathology need to be involved here.
Esp. pigs that are provided with novel enrichment materials clearly show ‘fanatic’, almost compulsive behaviours, except that the behavioural intensity tends to wear off readily (it is mostly a matter of a few quarters rather than hours that pigs spend on interacting with new enrichment materials). However, when the enrichment is slowly destructible (like soft wood), designed to fit the needs of the animal (e.g. branched chain design, (Bracke, 2017)) or provides (irregular) food rewards, e.g. as in the case of the Edinburgh foodball in pigs (releasing food pellets upon being rooted and thus moved around the pen (Young et al., 1994)), much more persistent (and less fanatic) interest may be observed. Pigs and poultry also clearly appreciate the taste of blood and (tail/feather/skin) tissue.
Note also that in addition to being potentially explained as a cognitive (learning) process, the escalation of fp/tb and (subsequent) state change may also be related to cognition and a tendency to show synchronised (feeding/exploration/activity) behaviour. A related potentially-involved mechanism could be the supposedly powerful tendency to show conformism, as suggested by De Waal in the case of primates (De Waal, 2016).
E.g. van de Waal et al. (2013) showed that green monkeys that had been trained to prefer maize of one colour, would unlearn their previous colour preference and acquire the colour preference of the group they had been introduced into. Similarly, mixing a less friendly primate species with a more friendly species, made the former much (4 times) more friendly (De Waal and Johanowicz, 1993). Uitdehaag et al. (2009) found that mixed housing of a more and less fearful strain of laying hens negatively affected fp and fear-related behaviour. Perhaps conformism may play a role in fp/tb in that once more and more individuals start to show the behaviour, other individuals may have a strong tendency to do the same. Thus conformism may explain (part of the escalation) by potentiation, but it cannot explain its origin (though it may explain why there is a reluctance to show fp/tb in a group that has never experienced it before). (Note: the origin may also be more or less accidental, e.g. McAdie and Keeling (2000) showed that (artificially) damaged feathers may trigger (outbreaks of) fp in laying hens.)
Counteracting the motivation to show fp/tb by genetic selection may simultaneously counteract the animals’ motivation to consume feed and thus (efficiently) produce under commercial conditions. Pigs and poultry need to be eager to consume food and they must readily accept novel feeds (e.g. when moved from rearing farm to finishing/egg-laying farm).
Thus, the motivation to forage may not only be a remnant of evolution in a natural environment, it may also be a product of selection for maximised production efficiency. In other words, domestication and genetic selection may have been co-shaping the current problem underlying fp/tb in intensive pig and poultry farming.
Traditionally, pigs and poultry have been selected using individual selection, i.e. the fastest growing individuals were selected to breed the next generation, perhaps even when individuals were showing high levels of production at the expense of pen mates (e.g. due to excessive aggression or the performance of fp/tb). In particular, when fp/tb occurred the (most heavily affected) victims were unlikely to be used for reproduction, but the actors in a pen could partly go unnoticed (unless they were detected and eliminated from the group). Group selection has been proposed as an alternative to individual selection, where the production efficiency of pen mates is also taken to load on an individual’s selection potential (Muir, 2003; Bijma et al., 2007a; Bijma et al., 2007b). Group selection has thus been suggested as a potential solution for fp/tb by selecting for peaceful pigs/poultry. Such peaceful pigs, however, may be less motivated to forage, and thus be less efficient for production.
Genetic selection probably has made use of the evolutionary tendency of animals (esp. males) to grow fast so as to have a higher likelihood of reproduction (as the largest individuals of a generation tend to win fights for access to females). Fast growth (as required for pigs and broilers), however, requires a persistent appetite to sustain growth. Compared to egg-laying in hens, which similarly require a substantial appetite to be able to sustain a high egg production, the biological prioritisation is different. Resource allocation theory suggests that animals make adaptive adjustments in the allocation of resources to different life processes when facing changed selection pressures (Beilharz et al., 1993). Hens must prioritise allocating energy to their offspring (eggs), whereas pigs and broilers must (i.e. have been selected to) allocate energy to their own growth (so as to produce meat). Thus, both types of farm animals are also likely to have been selected to prioritise (as much as possible) those processes that are preferred by man (be it the production of meat or eggs). Thus, when dealing with (mild) disease states it is possible that farm animals have been selected to (tend to) prioritise production over the (energetically costly) activation of the immune response. Farm animals that continue ‘functioning’ in an economic/zootechnical sense, however, may not be the most productive overall, e.g. when enhanced appetite has a negative side-effect in increasing the likelihood of fp/tb.
Several observations may be in line with the suggestion that in modern farm animals appetitive foraging motivation may have originated in a discrepancy with the natural environment, but may also have been co-determined by genetic selection for maximised production efficiency. A main indicator is that adult animals, esp. pregnant sows and broiler breeders, are known to experience high levels of feeding motivation and a tendency to become obese when given ad lib access to feed. (In laying hens, however, fp rather seems to be associated with hyper-mobility, also called a hyperactivity disorder (Kjaer, 2009), perhaps related to an (over-)activated foraging motivation.) In addition, when growing pigs are feeding they seem to be focussed so much on feed intake that vaccinating them with a rather painful (large diameter) needle seems to go (largely) unnoticed. Also, growing pigs whose front teeth have been cut so as to counteract an outbreak of tail biting don’t seem to show a clear reduction in feed intake. When their teeth have been cut, however, the pigs are much less inclined to continue tail biting and they also show much less interest in manipulating enrichment materials like chains, wood and ropes, suggesting that they do feel pain while maintaining a relatively high motivation to feed.
A final aspect where a science-based evolutionary understanding of fp/tb behaviour has clear added value over a classic medical framework may be the observation that not all kinds of stressors are equally likely to contribute to fp/tb. This may be an important aspect of the pathophysiology/mechanism underlying fp/tb. In laying hens, for example, organic farmers say that pullets with access to an outdoor range are less fearful later in life (e.g. in using the outdoor range), and therefore are less likely to develop fp (TvN, pers. comm.). Also in laying hens, the stressor of being moved from the rearing farm to the layer facility appears to be a trigger of stress and fp (even though it may also be a ‘revival’ of fp that originated at the rearing farm). In pigs, by contrast, mixing is not typically eliciting tail biting, despite the fact that it is highly stressful for the pigs. E.g. Holinger (2017) found no effect of mixing and isolation stress on tail and ear manipulation in pigs. Note also that mixing in pigs typically occurs at 25kg body weight (10-12 weeks of age), which is long before puberty at slaughter age, i.e. about 5-6 months of age, whereas laying hens are transferred to the laying facilities shortly before egg-laying starts (i.e. puberty). In pigs this compares to the rearing of breeding gilts, who are also particularly prone to tb (probably because they are fed on more restricted diets than slaughter pigs are), but only at a younger age (i.e. before the gilts are inseminated). Tb in pigs is hardly seen in (first or older parity) pregnant sows and in this respect tb in pigs differs from fp in laying hens. Such differences must be kept in mind, but they should not overrule the striking similarities between fp in poultry and tb in pigs, nor should they be regarded as a counterargument to the proposition that fp/tb would certainly benefit from being regarded as a medical/mental health disorder, provided the existing science-based and evolutionary framework is maintained to understand the behavioural as well.
This was blog post nr. 7 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:
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).
By Isabelle C Pettersson, Claire A Weeks, Christine J Nicol. 2017. Applied Animal Behaviour Science 195: 60-66.
The effect of a resource package designed to reduce inter-bird pecking and increase range use was tested on fourteen free-range farms in the UK. The package comprised two types of objects intended to attract pecking behaviour: ‘pecking pans’ containing a particulate pecking block, and wind chimes; plus long, narrow shelters placed just outside the popholes, bridging a barren area 2–10 m from the house, with the aim of improving bird distribution on the range. We predicted that if the resource package succeeded in these aims, overall bird welfare would also be improved. Fourteen commercial farms were enrolled for this two-year study. Flocks were assessed for pecking behaviour, range use and general indicators of welfare at 40 weeks in Year 1 without the resource package. The resource package was then added to the same houses at the start of the next flock cycle in Year 2. The new flocks were assessed in the same way at 40 weeks with additional observations taken of their use of the resource package at 25 and 40 weeks. These additional observations showed that most aspects of pecking behaviour directed at the pecking pans remained consistent from 25 to 40 weeks although a reduction in substrate pecking frequency was seen (p < 0.001) and birds perched on the pan for longer (p = 0.033) and more often (p = 0.010) at 40 weeks. Although consistent within houses, wind chime use was very variable between houses, with pecking observed in only 8 of the 14 houses. The number of birds under the shelters increased from 25 to 40 weeks (p = 0.018), as did the proportion of birds that went under a shelter within 5 min of entering the range area (p = 0.021). Birds were more likely to use a shelter within 5 min if they exited the shed via a pophole within 10 m of the shelter rather than a pophole more than 10 m away at both 25 weeks (p < 0.001) and 40 weeks (p = 0.001).
A reduction in gentle feather pecking (p = 0.001) and severe feather pecking (p = 0.018) behaviour was seen when the resource package was provided in Year 2. Range distribution also improved, with a greater proportion of birds seen 2–10 m from the house (p = 0.023). Additionally, the proportion of abnormal eggs (p = 0.010), headshaking behaviour (p = 0.009) and the percentage of wet/capped litter (p = 0.043) decreased in Year 2.
Management tips to stop feather pecking
By Tony McDougal. Poultry World, 2 Oct., 2017.
The UK branch of the World’s Poultry Science Association held its annual conference in Cambridge this summer. Scientists looked at poultry feathers and skin – the past, present and future of poultry integument.
Management risk factors and genetic influences have an effect on feather pecking, according to the University of Bristol’s Christine Nicol.
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Thea van Niekerk, from the Wageningen Livestock Research centre, Netherlands, adds prevention is most important as once feather pecking begins, the behaviour is very hard to stop.
Ms van Niekerk explains that optimising rearing conditions to prevent injurious pecking was the first step: “The most important strategy in rear is a continuous presence of good substrate to stimulate foraging behaviour and to teach the pullets to direct their pecking towards the litter.”
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Esther Ellen and Piter Bijima, of Wageningen University Research Animal Breeding and Genomics centre, assessed genetic solutions to injurious pecking.
They argued that, while behavioural observations can be used to select against feather pecking, they were expensive, time consuming and difficult to apply in animal breeding. Instead, a solution could come from quantitative genetic methods that took into account both the direct (DGE, victim effect) and indirect genetic effect (IGE, actor effect).
“For the survival time, we found that the victim effect contributes 35-87% of total heritable variation. Together, they explain 15-26% of total phenotypic variation in survival time.
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Professor Nicol’s joint paper with Dr Claire Weeks, ‘Provision of a resource package reduces feather pecking and improves ranging distribution on free-range layer farms,’ was published in the Applied Animal Behaviour Science in July.