Reducing aggressive behaviour among young piglets by an electronic feed reward system

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University of Veterinary Medicine Hannover

Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour

Reducing aggressive behaviour among young piglets by an electronic feed reward system

THESIS

Submitted in partial fulfilment of the requirements for the degree

DOCTOR OF PHILOSOPHY (PhD)

awarded by the University of Veterinary Medicine Hannover

by

Lília Thays Sonoda

Londrina – Paraná – Brazil Hannover, Germany 2014

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Supervisor: Prof. Dr. med. vet. Dr. h. c. Jörg Hartung / Dr. med. vet.

Michaela Fels

Supervision Group: Prof. Dr. med. vet. Dr. h. c. Jörg Hartung / Dr. med. vet.

Michaela Fels

Prof. Dr. rer. nat. Ute Radespiel Prof. Dr. Ir. Daniel Berckmans

1^st Evaluation: Prof. Dr. med. vet. Dr. h. c. Jörg Hartung / Dr. med. vet.

Michaela Fels

Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour, University of Veterinary Medicine Hannover, Foundation – Germany.

Prof. Dr. rer. nat. Ute Radespiel

Institute of Zoology, University of Veterinary Medicine Hannover, Foundation – Germany.

Prof. Dr. Ir. Daniel Berckmans

M3-BIORES: Measure, Model & Manage Bioresponses, Katholieke Universiteit Leuven – Belgium.

2^nd Evaluation: Prof. Dr. Hanno Würbel

Division of Animal Welfare, Vetsuisse Faculty of the University of Bern – Switzerland.

Date of the final exam: 08.05.2014

Sponsorship: EU Commission, Marie Curie Actions and CAPES Foundation of the Brazilian Ministry of Education and CNPq Brazil.

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Dedicated to my sweethearts Sofia, Sara and Luiza.

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Table of contents

Table of contents

Chapter 1

Introduction ... 1

Chapter 2 Tail Biting in pigs – Causes and management intervention strategies to reduce the behavioural disorder. A review ... 7

Chapter 3 Cognitive Enrichment in Piglet Rearing: An Approach to Enhance Animal Welfare and to Reduce Aggressive behaviour ... 9

Chapter 4 Kognitive Aufgaben als Umweltanreicherung im Abferkelstall – erste Ansätze einer Nutzung früher Verhaltenskonditionierung von Saugferkeln zur Verminderung aggressiver Verhaltensweisen während der Aufzucht ... 11

Chapter 5 General Discussion ... 15

5.1 Tail biting and aggressive behaviour ... 16

5.2 Training of piglets ... 19

5.1 Resident-Intruder test ... 23

Conclusions ... 27

Chapter 6 References ... 29

Chapter 7 Summary ... 47

Chapter 8 Zusammenfassung ... 51

Chapter 9 List of conferences with active participation ... 55

Chapter 10 Acknowledgments ... 59

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Chapter 1

Introduction

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Chapter 1: Introduction

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1 Introduction

In modern pig production, weaned and fattening pigs are usually housed in groups of similar age and size, therefore, a very common practice is to mix unfamiliar pigs in groups of uniform weight directly after weaning and at the beginning of the fattening period. After regrouping, the majority of pigs are fighting in more or less violent manor to establish a social hierarchy in the group experiencing social stress sufficient to cause a subsequent reduction in weight gain and growth performance (Beattie, 2000b). Also, fights among piglets during this period result frequently also in more wounded and seriously injured animals (McGlone & Curtis, 1985).

Apart from aggressive interactions, naturally noticed in pigs to establish the social hierarchy within a group, there are other injurious abnormal behaviours such as tail biting which is usually not executed as violent action but can result in serious skin and tissue damages followed by infection of tail and spine (Haarbo et al., 1966). Tail biting is more interpreted as response towards a boring and uninspiring environment or can be observed under stressful conditions (Beattie, 2000b). It is presently considered one of the largest welfare problems in modern pig industry in Europe (Zonderland, 2010).

Both tail biting and aggressive interactions affect the health and welfare of the affected animal and can lead to pain and increased risk of infection (Huey, 1996). Furthermore, aggression and tail biting can have considerable economic consequences as well as carcass condemnation at the slaughter house (Huey, 1996; Wallgren & Lindahl, 1996; Schrøder-Petersen & Simonsen, 2001; Busch et al., 2004; Zonderland, 2010). While tail biting has a multifactorial origin and

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occurs mainly in fattening pigs (Schrøder-Petersen & Simonsen, 2001), aggressive behaviour is expressed every time unfamiliar pigs are mixed, for the establishment of a new dominance order independent from their age or physiological state (Ewbank, 1976; Marchant-Forde & Marchant-Forde, 2005;

Puppe et al., 2008).

Factors which are reported as important release triggers for both tail biting and excessive aggression seem to be very similar. For Moinard et al., (2003) increased levels of stress are the main reason for the observed behavioural disorders. The stress is caused by high stocking densities and poor environmental conditions which are common in modern intensive swine production systems, limiting the expression of behaviours such as pigs’ foraging and exploratory activity. Further factors such as genetic traits, bad air quality and type of feed can aggravate the problem (for reviews see EFSA, 2007;

Schrøder-Petersen & Simonsen, 2001; Sonoda et al., 2013a).

There are only few studies reporting a deeper understanding of the internal and external motivators of tail biting which is not reported in wild boars and rarely in more natural environments for pigs (Bilkei, 1994; Walker & Bilkey, 2006). Because of the lack of other efficient measures, for decades tail docking (amputation the distal part of the tail) was used to prevent tail biting and it worked quite successfully (Sutherland et al. 2009). However, tail docking is forbidden by current European animal welfare legislation. Exceptions are only allowed in individual cases approved by a veterinarian. Therefore, tail docking will not be any longer a routine practice in commercial farms. The most adequate approaches to avoid tail biting are seen in environmental enrichment to be introduced in pig farms (Feddes & Fraser, 1994; Beattie et al., 1996,

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2000a; Schrøder-Petersen & Simonsen, 2001) such as the provision of iron chains, various types of straw, toys made of hard plastic, car tires, pieces of wood, ropes made of natural fibres, salt blocks and supplementary food, however, pigs often lose interest in these objects as soon as they become familiar with them, leading to a low level of use and negligible effect (Grandin, 1989; Blackshaw et al., 1997).

Aggressive behaviour among unacquainted pigs when mixed is normal. They fight to establish a social hierarchy (Ewbank, 1976; Puppe et al., 2008). This natural process occurs among pigs of different ages and it has been described under natural, semi-natural as well as in intensive farming conditions (Cox &

Copper, 2001). Different from natural conditions, where an established hierarchy stays for a long period (Cox & Copper, 2001), in intensive production, since pigs with the similar size and growth rate are preferred to be housed together, the group composition changes regularly. Therefore pigs are exchanged between pens. Further, in pig production the space per animal in a pen is very limited, giving less chance for escaping from fights, which is also different from natural conditions.

In order to avoid or reduce aggressive interactions, several measures were tried in the past, such as odour masking agents, sedatives, regrouping pigs in darkness or equipping the pen with a hiding place (Petherick & Blackshaw, 1987; Arey & Edwards, 1998; Tan & Shackleton 1990; Francis at al., 1996;

Olesen et al., 1996; Amstutz et al., 2005). The effectiveness of these methods was rather limited and led mostly to a postponement of aggressive behaviour after mixing only without reducing it significantly. Methods to distract pigs from violent fighting by other strong or learned stimuli are rare (Sonoda et al.,

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2013b) but could be successful as examples shown by Manteufel et al.

(2009a,b) show. They were able to train sows individually on their name or on a specific sound. The sound was associated with food and only the called sow stands up and goes to the feeder when her specific sound is reproduced. The experiments show that tasks for pigs should be designed in a way that they have a natural interest in solving the task in order to reach the desired goal, food in this case. This keeps the animals motivated and facilitates learning the task (van de Weerd & day, 2009; Gieling et al., 2011).

Intentioned enrichment methods containing goal-directed learning behaviour have been tested using aversive or rewarding reinforcers. These methods have the potential to bring alternation and distraction, reducing boredom and abnormal behaviours (Meehan & Mench, 2007; Puppe et al., 2007; Tarou &

Bashaw, 2007; Manteuffel et al., 2009a,b). Enrichment devices which offer reinforcement as a reward (food, social access, etc.) have been proved to be effective. However, the efficiency in positive behavioural responses is not a stationary state which can be maintained for long, in this way, the applied reward must provide necessary feedback to guide behaviour, keeping a constant level of satisfaction (Spruijt et al., 2001).

For farm animals, cognitive enrichment is not yet used as a common practice, nonetheless, investigations about learning behaviour in various types of farm animals using e.g. acoustic cues to bring a desired reaction were already carried out (Kiley-Worthington & Savage, 1978; Ernst et al., 2005; Wredle et al., 2006;

Zebunke et al., 2011).

For verifying how cognitive environmental enrichment can be applied to young pigs raised in intensive commercial farms in this PhD project, it was necessary

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to primarily understand the scientific background of tail biting and aggressive behaviour (in group housed pigs). Later, in a second step, the knowledge about environmental enrichment, applying cognitive challenges, could be used to help to optimize a production system in regard both animal welfare and biological performance.

To achieve these objectives, a literature review was done on tail biting, followed by a summary of the causes and consequences of tail biting in pigs, a discussion of the importance and effectiveness of tail docking and the presentation of alternative management strategies focusing on environmental enrichment and applying Precision Livestock Farming (PLF) tools.

In addition, experiments were carried out to test whether cognitive environmental enrichment using a sound signal followed by a food reward can reduce aggressive actions between pairs of piglets after weaning. For dispensing the food reward an electronic dog feeder was used. The feeder emits a “beep” sound immediately followed by the release of a sweet food reward attracting the piglets to stop fighting and eat the food (chocolate raisins).

Summarising, the objectives of this PhD project were:

1. Elucidate the causes of tail biting and the perspectives of the use of Precision Livestock Farming (PLF) technology in order to improve health and welfare of pigs.

2. Investigate whether cognitive environmental enrichment, using sound and reward as stimuli, has the potential to reduce aggressive interactions among weaned piglets raised in intensive production systems, particularly after mixing.

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Chapter 2

Tail Biting in pigs – Causes and management intervention strategies to reduce the behavioural disorder. A review

Sonoda, L.T.¹, Fels, M.¹, Oczak, M.^2,4, Vranken, E.^2,4, Ismayilova, G.³, Guarino, M.³, Viazzi, S.⁴, Bahr, C.⁴, Berckmans D.⁴, Hartung, J.¹

1Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.

2Fancom Research, Panningen, Netherlands.

3Department of Veterinary and Technological Sciences for Food Safety, Faculty of Veterinary Medicine, Università degli Studi, Milan, Italy.

4M3-BIORES: Measure, Model & Manage Bioresponses, Katholieke Universiteit Leuven, Leuven, Belgium.

Berliner und Münchener Tierärztliche Wochenschrift 126 (3-4), 104–112, 2013 (doi: 10.2376/0005-9366-126-104).

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Chapter 2: Tail Biting in pigs – Causes and management intervention strategies to reduce the behavioural disorder. A review

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2 Tail Biting in pigs – Causes and management intervention strategies to reduce the behavioural disorder. A review

ABSTRACT

One of the largest animal welfare problems in modern pig production is tail biting. This abnormal behaviour compromises the well-being of the animals, can seriously impair animal health and can cause considerable economic losses.

Tail biting has a multifactorial origin and occurs mainly in fattening pigs. High stocking densities, poor environment and bad air quality are seen as important factors. However, it is presumed that a plurality of internal and external motivators in intensive pig production can trigger this behaviour which is not reported in sounders of wild boars. The aim of this review is to summarize the causes and the effects of tail biting in pigs and present management strategies that are likely to reduce its incidence. In particular, management strategies by applying Precision Livestock Farming (PLF) technologies to monitor and control the behaviour of the pigs may be suitable to detect the outbreaks of tail biting at an early stage so that counter measures can be taken in time.

Keywords: pig, abnormal behaviour, tail docking, environmental enrichment, automatic monitoring.

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Chapter 3

Cognitive Enrichment in Piglet Rearing: An Approach to Enhance Animal Welfare and to Reduce Aggressive behaviour

Sonoda, L.T.¹, Fels, M.¹, Rauterberg, S.¹, Ismayilova, G.³, Viazzi, S., Oczak, M.^2,4, Bahr, C.⁴, ⁴Guarino, M.³, Vranken, E.^2,4, Berckmans D.⁴, Hartung, J.¹

1 Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour, University of Veterinary Medicine Hannover, Foundation, Bünteweg 17p, 30559 - Hannover, Germany.

2 Measure, Model & Manage Bioresponses (M3-BIORES), Katholieke Universiteit Leuven, Kasteelpark Arenberg 30, 3001 - Leuven, Belgium.

3 Department of Veterinary Science and Technologies for Food Safety, Faculty of Veterinary Science, Via Celoria 10, 20133 - Milano, Italy.

4 Fancom Research, Industrieterrein 34, 5981 - Panningen, the Netherlands.

ISRN Veterinary Science, Article ID 389186, 9 pages, 2013 (doi:10.1155/2013/389186).

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Chapter 3: Cognitive Enrichment in Piglet Rearing: An Approach to Enhance Animal Welfare and to Reduce Aggressive Behaviour

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3 Cognitive Enrichment in Piglet Rearing: An Approach to Enhance Animal Welfare and to Reduce Aggressive Behaviour

INTRODUCTION

It is known that pigs raised in enriched environments express less aggressive behaviour. For this reason, a new method of cognitive environmental enrichment was experimented at the University of Veterinary Medicine Hannover, Germany. In the first phase, 78 suckling piglets were trained to learn the link between a sound given by an electronic feeder and a feed reward in the form of chocolate candies during a period of 8 days. In the second phase, the same piglets were used in resident- intruder tests to verify the potential of the feeding system to interrupt aggressive behaviour. The analysis of all training rounds revealed that piglets learned the commands during 8 days of training and the interest of the piglets increased within training days (p<0.05).

In the residentintruder test, 79.5% of aggressive interactions were broken by feeder activation. In interactions where either the aggressor or the receiver reacted, a high number of fights were stopped (96.7% versus 93.1%) indicating that it was not relevant if the aggressor or the receiver responded to the feeder activation.We conclude that the electronic feeding systemhas the potential to be used as cognitive enrichment for piglets, being suitable for reducing aggressive behaviour in resident-intruder situations.

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Chapter 4

Kognitive Aufgaben als Umweltanreicherung im Abferkelstall – erste Ansätze einer Nutzung früher Verhaltenskonditionierung von Saugferkeln zur

Verminderung aggressiver Verhaltensweisen während der Aufzucht

Rauterberg, S.¹, Sonoda, L.T.¹, Fels, M.¹, Viazzi, S.², Ismayilova, G.³, Oczak, M.^2,4, Bahr, C.², Guarino, M.³, Vranken, E.^2,4, Berckmans, D.⁴, Hartung, J.¹

1 Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour, University of Veterinary Medicine Hannover, Foundation, Bünteweg 17p, 30559 - Hannover, Germany.

2 Measure, Model & Manage Bioresponses (M3-BIORES), Katholieke Universiteit Leuven, Kasteelpark Arenberg 30, 3001 - Leuven, Belgium.

3 Department of Veterinary Science and Technologies for Food Safety, Faculty of Veterinary Science, Via Celoria 10, 20133 - Milano, Italy.

4 Fancom Research, Industrieterrein 34, 5981 - Panningen, The Netherlands.

Züchtungskunde 85, 376–387, 2013.

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Chapter 4: Kognitive Aufgaben als Umweltanreicherung im Abferkelstall – erste Ansätze einer Nutzung früher Verhaltenskonditionierung von Saugferkeln zur Verminderung aggressiver Verhaltensweisen während der Aufzucht

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4 Kognitive Aufgaben als Umweltanreicherung im Abferkelstall – erste Ansätze einer Nutzung früher Verhaltenskonditionierung von Saugferkeln zur Verminderung aggressiver Verhaltensweisen während der Aufzucht

ABSTRACT

Ziel dieser Studie war es, eine neue Methode der kognitiven Umweltanreicherung für

Saugferkel und damit verbundene Möglichkeiten zur Reduktion aggressiven Verhaltens nach dem Absetzen zu untersuchen. Zunächst wurden zehn komplette Würfe mit insgesamt 95 Saugferkeln ab einem Alter von 25 Tagen auf einen elektronischen Futterautomaten trainiert. Dabei lernten die Tiere, einen Signalton mit einer Belohnung in Form von Süßigkeiten zu verbinden. Das Training erfolgte in 8 Trainingseinheiten über einen Zeitraum von 10 Tagen. Am 3. Trainingstag zeigte sich bereits ein deutlicher Trainingserfolg, wobei sich 15 Sekunden nach dem Tonsignal 74,3% der Ferkel eines Wurfes am Futterautomaten aufhielten. Der zweite Teil der Studie erfolgte nach dem Absetzen und befasste sich mit der Möglichkeit der Beeinflussung aggressiven Verhaltens zwischen zwei Ferkeln mit Hilfe der im Saugferkelalter erlernten Reaktion auf den Futterautomaten. Dazu wurden in insgesamt 390 Resident- Intruder Konfrontationen aggressive Interaktionen zwischen je zwei trainierten Absatzferkeln ausgelöst. In 83,6% der Fälle konnten aggressive Auseinandersetzungen durch die Aktivierung des Automaten und der damit verbundenen Reaktion der Ferkel beendet werden. In 90% der Fälle reagierte zunächst eines der beiden Ferkel auf den Signalton, so dass der Kampf

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Chapter 4: Kognitive Aufgaben als Umweltanreicherung im Abferkelstall – erste Ansätze einer Nutzung früher Verhaltenskonditionierung von Saugferkeln zur Verminderung aggressiver Verhaltensweisen während der Aufzucht

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unterbrochen wurde. Während in 59% der abgebrochenen Kämpfe der Aggressor auf den Signalton reagierte, konnten 51% der Kämpfe durch die Reaktion des Receivers alleine oder gemeinsam mit dem Aggressor abgebrochen werden. Der Futterautomat lenkte die Tiere demnach effektiv von aggressivem Verhalten ab. Kognitive Umweltanreicherung kann somit bereits für Schweine im Saugferkelalter eingesetzt werden und könnte genutzt werden, um zu späteren Produktionszeitpunkten aggressive Verhaltensweisen zu reduzieren und das Wohlbefinden der Tiere zu verbessern.

Schlüsselwörter: Konditionierung, kognitive Umweltanreicherung, Ferkel, Aggressivität, Wohlbefinden.

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Chapter 5

General Discussion

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Chapter 5: General Discussion

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5 General Discussion

5.1 Tail biting and aggressive behaviour.

Since the advent of intensive pig production, some serious behavioural disorders are described, such as tail and ear biting, among fattening pigs as well as massive and injurious aggressive actions among unfamiliar young pigs (Hughes & Duncan, 1988; Zonderland, 2010) leading to serious health and welfare problems (Weiss, 1971; Wiepkema & Schouten, 1990; Stookey &

Gonyou, 1994; Varley & Stedman, 1994; De Jonge et al., 1996). There is clear evidence that such problems preferentially occur when the natural behaviour of the animals is impeded, and they are bored and/or deeply dissatisfied with their environmental living conditions (Zayan & Dantzer, 1990).

One of the situations when increased aggressive actions are observed is the mixing of piglets after weaning in production groups. This sorting according to body size creates balanced groups of animals with approximately same weight and food uptake. It is a very common procedure in intensive swine production systems and can occur several times during an animals’ life. Mixing with unacquainted conspecifics usually results in fighting to re-establish group hierarchy leading to stress and possible impairments of health and welfare of the pigs. The situation can trigger excessive aggression but also stereotypies, immunosuppression, decreased food intake, and suppressed growth (Fraser et al., 1994; Hyun et al., 1998; Robert et al., 1999).

As it may be impossible to eliminate all the stress at mixing from a production environment, it is necessary to apply management practices to reduce stress or distract pigs’ attention from each other by appropriate measures such as

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environmental enrichment tools. Cox & Cooper (2001) postulate that providing young pigs with an environment that requires spatial learning and memory, allowing them to perform biologically relevant behaviours, may be a strategy that simultaneously stimulates cognitive development and adaptive stress response. However, in intensive indoor production settings piglets are not given the opportunity to root, play with items in their environment or search for food during longer periods.

In a natural context, aggressive interactions among pigs happen mostly when they are introduced to unfamiliar conspecifics to determine their social hierarchy status, or to gain access to resources such as feed (Mendl et al., 1992; Marchant-Forde, 2002; D’Eath & Turner, 2009). Also, in modern pig production, ordinarily, in a stable group, levels of aggression are relatively low (Marchant-Forde, 2002). However, deficiencies in system design or repeated changes in group composition can result in persistent and high aggression levels, which may lead to physical injury, including lameness and significant acute stress (Straw et al., 2006). If unresolved, persistent aggression may cause chronic stress with negative consequences such as increased disease susceptibility and impaired productivity (Straw et al., 2006).

On the other hand, even when there is no competition for resources and most of the physiological necessities are well supplied, which is common in intensive pig farming, detrimental and unwanted behaviour, tail biting for instance, can be seen (Hughes & Duncan, 1988; Zonderland, 2010).

The outbreak of tail biting, this important and detrimental misbehaviour most often seen in fattening pigs is influenced by a variety of factors including diet, feeding methodology, stocking density, ventilation and humidity (Schroder-

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Petersen & Simonsen, 2001, Sonoda et al., 2013a), and besides all the knowledge accumulated up to now, each specific farm can have a different background cause for its occurrence. In this case, when outbreaks of tail biting are analysed, every case must be verified separately, and still, the best alternative is to rely on the close look of an expert.

The overall aim of this dissertation was to seek for technological solutions, by the development of a method or system which could stop violent aggressive actions between pigs. Furthermore, it should become a commercial product that could be applied in many farms to recognise and stop aggressive behaviour.

The most promising approach seemed to be the combination of a cognitive environmental enrichment element and a reward. As enrichment, a sound was chosen and the reward was chocolate raisins.

The suckling piglets were already trained in their farrowing pens to learn the link between the sound given by the feeder and the feed reward (chocolate raisins). Eight days of training were sufficient that 73,5% of the piglets understood the link between sound and sweet reward.

After weaning the trained piglets were transferred to new pens, and mixed in groups of 12 piglets sorted by similar weight and sex. Four days after mixing, the electronic feeder was used to measure the reaction of two piglets on the sound stimulus combined with a sweet reward (the same chocolate raisins used during the training) in a resident-intruder test, when aggressive interactions such as fighting, biting and mounting behaviour were expressed.

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5.2 Training of piglets.

It is proven that pigs can learn at multiple levels and in different forms.

However, apart from learning simple stimulus–response links, an animal can also learn at a cognitive level that a specific action leads to a reward, like the training with a Skinner box, in which is a bar pressed and a food pellet is dispensed (Bolles, 1972; Berridge, 2001; Dickinson, 1985). Such representation is different from trainings using responses to various stimuli, in which the animal accomplishes a task ‘blindly’, generating a targeted desirable behaviour leading to a reward.

The learning of a simple relationship between a sound followed by a food reward appears to be mediated by a direct process (Toates, 2002). However, the extinction of this relationship (the loss of response when the food reward is omitted but the tone still applied) is associated partly with a high-level hierarchical architecture of the brain (Toates, 2002). Evidence suggests the basis of extinction is the animal’s utilization of cognition in the control of a behaviour (e.g. the food reward is no longer dispensed after the tone).

In our project, the piglets had to learn the link between a sound given by the feeder and a feed reward in form of chocolate raisins for a period of eight days.

The results of the experiments show that 25 days old suckling piglets understood the link between the sound and the sweet reward after 5 stimuli during one hour training per day (10:00 – 11:00 a.m.) for eight days. For the tested pigs 40 events were sufficient that they memorised the connection between the “beep” and the food reward. The video recordings showed that most of the piglets were attracted by the feeder within 2 seconds after the activation of the feeder (Figure 1).

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Figure 1: Identification of the piglets around the feeder during the image analysis.

Most of the piglets learned the training commands on the period of eight days, reaching reaction levels of 74,3% and 73,3% at 15 and 30 seconds after activation of the feeder, respectively (Figure 1). Similar results were obtained by Manteuffel et al. (2010) who trained 36 sows to respond to a call-feeding station, in 6 rounds of experiments, and concluded that on average after 8 days of operant conditioning the animals reached the learning criterion with 80% of success. When Zebunke et al. (2011) worked with 24 German Landrace pigs at the age of 16 weeks they reported the same time of 15 seconds from the time of the call until the pigs approached the feed, dispensed by an automatic feeding station, even after 7 weeks of training. Kirchner et al. (2012) trained sows for 15 days using a call-feeding station and obtained response times around 60 seconds from the call until the animal reached the trough. In

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another study, the same authors (Kirchner et al., 2014) found that after 7 days of training the 62 tested sows obtained 60% of successful response when called by an electronic call-feeding station.When the response to a stimulus is followed by a reinforcer, the probability of having a positive result is increased.

This is called operant conditioning or instrumental learning and its application to pigs has been first reported decades ago (Noble & Adams, 1963; Baldwing &

Stephens, 1973; Baldwing & Meese, 1979). For this type of test, food rewards such as pieces of apple, chocolate raisins, commercial pellets, dog biscuits, or milk replacer (for piglets) were most commonly used (Tanida & Nagano 1998;

Laughlin et al. 1999; Held et al. 2001; Croney et al., 2003; Hagl et al. 2005;

Moustgaard et al. 2005; Siegford et al. 2008).

In our experiments the piglets received the food reward every time the feeder was activated. In this way, we could not only maintain their interest in the training, but also increased their reaction along the training days, in accordance with the results of Puppe et al. (2007), Manteuffel et al. (2010) and Kirchner et al. (2012).

Although we took the precaution of providing enough treats when the feeder was activated, in order to make sure that every piglet which approached the feeder got at least one chocolate raisin, we did not reach 100% of piglets approaching the feeder at the same time. This was also observed by Puppe et al. (2007), who evaluated the learning behaviour of 112 castrated German Landrace male pigs starting at the age of seven weeks, and found that the animals could reach a success rate of 80% even after 20 weeks of training using an acoustical signal to the release of food by a call-feeding station.

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Another explanation for not having 100% of piglets around the feeder can be the presence of the sow. As we trained piglets in the farrowing unit in the presence of a sow, it was expected not to observe all the piglets around the feeder, since the sow represents the main and strongest source of food during this period (Jensen & Redbo, 1987; Pluske et al., 2003).

Although pigs can compete for food and switch their behaviour towards a favourable situation (Laughlin & Mendl, 2000; Moustgaard et al., 2002, 2004, 2005), during the training period of our experiments no aggression caused by competition was observed, perhaps due to the well-defined social hierarchy within the group.

The good training results obtained in our experiment were posteriorly confirmed by a high efficiency of the feeder in interrupting aggressive interactions during the resident-intruder test.

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5.3 Resident–Intruder test.

Aggressive behaviour among pigs is natural and conflicts and fights can last for periods of 24 to 72 hours. The frequency of aggressive interactions falls at the same time as a stable social hierarchy emerges (Guy et al., 2009; Li et al., 2011;

Fels & Hoy, 2008, 2013).

At weaning for example, when piglets are mixed into groups of non-littermates, an initial intensive period of aggression lasting approximately two hours is commonly observed (Meese & Ewbank, 1973). The animal that eventually becomes top-ranking deals out most of the aggression. Various factors influence the speed with which a social hierarchy is established and aggression during mixing decreases.

When aggressive behaviour exceeds the period of 72 hours for the establishment of the rank order, a chronic and less intense number of fights occurs, making necessary the application of management measures to solve this issue.

The resident-intruder test is a common test to measure individual aggressiveness in pigs. Many researchers have attested its efficiency, and one important point of this test is not to allow long confrontations, being the pair of pigs separated immediately after they engage into a fight (Forkman et al., 1995; De Jong et al., 2000; D’Eath & Pickup, 2002; D’Eath, 2004; Koolkas et al., 2013).

In our experiment, the resident-intruder test was used four days after weaning.

In a pen two trained but unacquainted piglets were placed and subjected to the sound of the electronic feeder followed by the sweet reward (the same

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chocolate raisins as during the training), when aggressive interactions such as fighting, biting and mounting behaviour occurred.

The vast majority of trained piglets reacted to the auditory stimuli followed by the reward. On average 79% of aggressive interactions could be interrupted and the attention of the animals was redirected to the food reward. In 3.5% of cases the piglets did not make any aggressive movement against each other and in 17.5% the started aggressive interactions did not stop, resulting in violent fighting. This is in agreement with earlier results e.g. from Olsson et al.

(1999), who offered sand to piglets in the farrowing unit in order to reduce aggressive interactions. Aggression could never be completely reduced but piglets raised in environments with no bedding materials inflicted more wounds on each other during a dyadic resident-intruder confrontation. All experiences show that aggressive interactions between pigs cannot be stopped totally, also not by the activation of our sound feeder apparatus, since fighting is part of the animals’ normal behaviour being necessary for establishing a winner/loser relationship or a hierarchy in a group (Olsson et al., 1999; Erhard et al., 2007; Andersen et al., 2004).

A more detailed study of our group (Rauterberg et al., 2013) analysed 390 aggressive interactions of trained piglets in resident-intruder confrontations.

About 83.6% fights could be stopped in initial stage by the activation of the feeder, confirming earlier results that the sound-feeder system can effectively distract the animals from aggressive behaviour.

Interesting was to observe that in 59% of all fights which stopped after the sound, the aggressor pig reacted first and rushed to the feeder. 51% of fights were first stopped by the receiver or both (receiver and aggressor) stopped at

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the same time, although there was no significant difference. The results show that not always the most aggressive pig reacts first competing for resources as assumed by Andersen et al. (2000) and Keeling et al. (2001). It seems that the sound–reward system used in our experiments is attractive enough for both, aggressors and receivers, to stop fighting.

The results of our experiments do not indicate that there is a habituation of the animals to the stimulus or a learning effect that aggression is related to the reward. Such phenomenon can be assumed because pigs are known to learn quickly from other pig’s behaviour (Held, 2000). The resident-intruder test was repeated only three times for a period of maximum seven minutes. There was not enough time for the animals to make a link between aggressive behaviour and the food reward. Several authors report that pigs normally need on average three days to be accustomed to a novel situation and approximately the double of the time to express considerable learning of a different task in stressful situations (Lien & Klopfer, 1978; Mendl et al., 1999; Toates, 2002;

Bolhuis et al., 2004). Therefore, we can be rather sure that the results of the experiments were not influenced by a shift of behaviour caused by learning of the pigs within the tests. Furthermore, all pigs had access to the chocolate raisins in the training phase, independent from their behaviour when the feeder was activated. Thus, it seems not probable that they learned the connection between “being aggressive” and “receiving a food reward”.

This conclusion is not in conflict to the high potential of pigs to use cognition for solving problems in food competition in farm situations (Ernst et al., 2005;

Puppe et al., 2007; Manteuffel et al., 2009a,b; van de Weerd & Day, 2009;

Zabunke et al., 2011). However, until the present moment, there are few

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researches relating the effect of cognitive environmental enrichment with the aim of reducing aggressive interaction in pigs (Sonoda et al., 2013b).

The results presented in this PhD thesis give an example how PLF technology can reduce aggressive behaviour in young piglets and helps to improve the living conditions of the animals using their cognitive abilities and natural intelligence.

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Conclusions

1. Tail biting and excessive aggression are issues of great importance in modern pig production and have significant influence on health, welfare and performance of the animals.

2. The origin and nature of tail biting is multifactorial as our extensive literature review reveals. Violent aggressive attacks between unfamiliar pigs in order to establish a hierarchy can be avoided or eased by using the cognitive abilities of young pigs.

3. The results of the here performed experiments show that young piglets can learn within 3 to 8 days of training to recognise the relationship between a sound and a food reward. For this purpose PLF technology was used to develop an electronic feeder which releases attractive sweet feed (chocolate raisings) after a specific sound signal. The sound – reward system reduces aggressive interactions between pigs in a Resident-Intruder situation by nearly 80%.

Trained pigs respond to the stimulating sound even 5 days after training.

4. The sound – reward system represents a cognitive environmental enrichment for piglets kept in groups. It has the potential to reduce aggressive interactions among pigs. The system should be tested under practical conditions on commercial farms. The sound – reward system may have also some potential to prevent or reduce tail biting outbreaks.

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Chapter 6

References

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Chapter 6: References

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Summary

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7 Summary

Lília Thays Sonoda (2014)

Reducing aggressive behaviour among young piglets by an electronic feed reward system

Excessive aggressive behaviour and tail biting are currently important behavioural problems in intensive pig farming. Both issues have great impacts on the welfare and life quality of the animals, they also affect their health causing major economic losses along the production chain.

In order to enhance animal health and welfare, since 2008 it is required by EU legislation that pigs should have sufficient material for rooting in order to engage them in exploratory activities to maintain the animals occupied.

Although there are various materials known to be suitable as environmental enrichment such as straw, not all the farms are willing and able to deal with additional costs for supply and the manure management generated by these substrates.

Additionally, it is important that the enrichment not only entertains but also involves the animals in cognitive tasks making use of their natural intelligence.

In this regard, there were many studies attesting that pigs are able to learn the most varied types of tasks with different levels of difficulty. However, the understanding about how a cognitive task can redirect pigs’ behaviour when

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expressing aggressive behaviour or tail biting with long lasting effects is still limited.

In this PhD thesis, the results of a new approach of environmental enrichment using the learning abilities of suckling piglets with the potential to reduce aggressive interactions at a later production stage are reported. This study is part of a European project called BioBusiness that aimed to find answers based on technology to solve behavioural problems of pigs in intensive production farms.

To achieve the general objective of the BioBusiness project, first it was necessary to get an overall view about these different problematic behaviours.

For this reason, a literature review was done to verify the state of the art regarding research on aggression as well as on tail biting and the current alternative management strategies focusing on environmental enrichment. In addition, the potential of Precision Livestock Farming (PLF) technologies, that are likely to monitor and control the behaviour of the pigs by the detection of outbreaks of tail biting at early stage, was described.

As a second step, environmental enrichment based on training of suckling piglets still in the farrowing unit was tested.

The goal was to verify whether the cognitive environmental enrichment using sound and food as reward can be a tool for reducing the level of excessive aggression among pigs, especially after weaning.

For testing this hypothesis, suckling piglets were trained in their farrowing pens to react to the activation of an electronic feeder filled with chocolate raisins.

The piglets had to learn the link between a sound given by the feeder and a feed reward during a period of eight days. As a result, it was shown that the

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piglets were able to learn the training commands in the given training period, reaching a level of response in the order of 68% of reaction between 15 and 30 seconds after the activation of feeder.

After ten days from the beginning of the training (eight days of training with one weekend without training between the 5th and the 6th day), as a second step of the study, the same piglets used in the training were weaned, transferred to new pens, and mixed in groups of 12 piglets. Four days later, the electronic feeder was used to interrupt aggressive interactions expressed during confrontations of pairs of piglets in a test called resident-intruder test. It was shown that 84% of aggressive interactions in initial phase such as mounting, biting or head knocks could be interrupted by the sound followed by the chocolate raisins when the feeder was activated. It can be concluded that the used training method is suitable as environmental enrichment for suckling piglets and has the potential to reduce the length of aggressive interactions after weaning, by distracting and redirecting the attention of the piglets from fighting.

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Chapter 8

Zusammenfassung

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8 Zusammenfassung

Lília Thays Sonoda (2014)

Reduzierung aggressiver Verhaltensweisen zwischen Ferkeln mit Hilfe eines elektronischen Futter-Belohnungssystems

Übermäßiges aggressives Verhalten und Schwanzbeißen stellen derzeit bedeutende Verhaltensprobleme in der intensiven Schweinehaltung dar.

Beides hat großen Einfluss auf das Wohlbefinden und die Lebensqualität der Tiere, beeinträchtigt die Tiergesundheit und verursacht bedeutende ökonomische Verluste entlang der Produktionskette. Um Wohlbefinden und Gesundheit der Tiere zu verbessern, wird seit 2008 durch die EU-Gesetzgebung gefordert, dass Schweinen ausreichende Mengen an Beschäftigungsmaterial zur Ausübung ihres Erkundungsverhaltens zur Verfügung gestellt werden müssen. Obwohl verschiedene Materialien zur Anreicherung der Haltungsumwelt bekannt sind, wie beispielsweise Stroh, werden diese oftmals wegen der zusätzlichen Kosten sowie aufgrund ihrer Unvereinbarkeit mit bestehenden Güllesystemen, nicht verwendet. Weiterhin ist wichtig, dass die Materialien die Tiere nicht nur beschäftigen, sondern auch kognitive Aufgaben beinhalten, die sich die natürliche Intelligenz der Tiere anregt. Diesbezüglich gab es bereits einige Studien, die zeigten, dass Schweine in der Lage waren, die verschiedensten Aufgaben mit unterschiedlichen Schwierigkeitsgraden zu bewältigen. Jedoch ist das Wissen darüber, inwieweit eine kognitive Aufgabe