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SAMANTHA E. C. ENGELDAL

GRADUATE SCHOOL

BOGOR AGRICULTURAL UNIVERSITY

BOGOR

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document entitled:

‘STRESS-INDUCED BEHAVIOUR IN RAMS OF THREE DIFFERENT SHEEP (Ovis aries) BREEDS: INDICATOR OF WELFARE?’

has been obtained and presented in accordance with academic rules and ethical conduct. I also solemnly declare that this thesis was composed by myself through guidance of my supervisory committee. This work has not been submitted for the awards of any other academic degree, diploma, certificate or other professional qualification except as specified. As required by academic rules, all material and results that are not original to this work have been clearly and fully cited and referenced.

      Bogor, December 2012

Samantha E.C. Engeldal

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RONNY RACHMAN NOOR and SUBANDRIYO.

Growing importance of and concern for the welfare of farm animals within production systems has been the basis for an enormous amount of scientific studies. The goal of the present study was to investigate whether both vocal and social behaviour of sheep, under specific stress-inducing situations, could be used as an indicator of the animals’ welfare status. Two separate experiments were carried out with 2-3 year old adult rams. The animals were of three breeds, namely Barbados Blackbelly Cross, Local Garut and Composite Garut. In the first experiment twelve clinically healthy animals, four from each breed, were subjected to three different levels of social isolation. The animals were held completely alone, in the presence of a human and alone in a group pen adjacent to a pen with conspecifics. During the isolation sessions both vocal and locomotive behaviour of each animal were recorded. The recorded calls were acoustically analyzed using specialized acoustic software. The results showed that the levels of isolation were characterized by very specific behavioural responses with an increased amount of locomotor activity and vocalization in partially isolated animals. The animals that were completely isolated showed a higher amount of inactive behaviour. No specific differences were found in the behaviour of animals that were held completely alone and the ones which were in the presence of a human observer. Acoustic analysis of the recorded calls showed significant differences in a number of temporal and structural features. Spectral analysis revealed the most notable differences in the amount of sound energy integrated in the calls. Differences were found in both locomotive and vocal behaviour based on isolation level and breed. The second experiment focused on the effect of stocking density on the social behaviour of newly regrouped rams. Thirty-six animals were subjected to three different stocking density levels, namely low (3.2 m2/ram), medium (1.6 m2/ram) and high (0.8 m2/ram). Recorded data consisted of frequencies of agonistic-, exploratory, locomotive-, aberrant-, inactive-, self-care-, mating- and vocal behaviour. The results of this experiment showed that the animals responded differently to the different stocking density levels. The highest stocking density level was characterized by the highest number of inactive behaviour and the lowest number of locomotor activity. There were also significant differences found in the frequency of displayed behaviours based on the amount of time the animals had spent within the new group settings. The amount of agonistic-, mating- and exploratory behaviour was found to be significantly higher on the day of regrouping as compared to the level of these behaviours on the day after regrouping. Significant differences were also found in the behavioural response of animals from different breeds. The results from both experiments thus lead us to conclude that both vocal- and social behaviour of rams are able to provide humans with important information on their affective state which may be helpful in the design of production systems that are beneficial to the animals their welfare.

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of RONNY RACHMAN NOOR and SUBANDRIYO.

Animal domestication has played a central role in the development of human civilization. Modern animal production systems are principally characterized by a larger number of farm animals which are kept together in reduced space. A great number of the management practices which are currently applied in intensive systems along with the conditions under which the animals are kept, are thought to have a negative influence on both physiological and production traits of the animals. The perception that humans have a moral obligation to ensure that the animals their welfare, which is thought to be the extent to which the animals are able to successfully adapt to their environment, is never excessively poor has become widespread. The attempts of an animal to cope to its environment and the results of failure to cope can be measured. This meaning that the welfare of an individual animal can be assessed in scientific ways using different types of indicators. An appreciation of how to handle animals appropriately necessitates knowledge of their behaviour.

The purpose of this study was to evaluate both vocal- and social behavioural response of different breeds of sheep to situations which have been found to be very stressful for this gregarious species, in an attempt to discover non-invasive ways that might reveal information on the animals’ affective state. It was also intended to discover whether the animals would differ in their behavioural response based on their breed.

The research consisted of two separate experiments. A total of forty-eight rams from three different sheep breeds were used throughout the entire study. The following breeds were included: Barbados Blackbelly Cross (BC) (50% Local Sumatera, 50% Barbados Blackbelly), Local Garut (LG) and Composite Garut (KG) (50% Local Garut, 25% St. Croix, 25% Moulton Charollais). In the first experiment twelve clinically healthy, 2-3 year old adult sheep were subjected to different levels of social isolation. Each individual animal was kept alone without visual- and tactile contact with conspecifics, kept in the presence of an observer without visual – and tactile contact with conspecifics, and kept alone in a group pen at a specific distance from conspecifics with whom visual-, acoustic- and olfactory contact was possible. During a maximum of 15 minutes both vocal and locomotive behaviour were recorded. High-pitched bleats were recorded using a Digital Voice Recorder after which the calls were acoustically analyzed using the acoustic software program Raven Pro 1.4. Thirty-six acoustic parameters were calculated after which their values were subjected to statistical analysis. Frequencies of locomotive behaviours were observed and recorded during 5 minutes per isolation session using a predefined ethogram.

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09.30 am, 12.00 pm and 14.30 pm.

The results from the first experiment showed that the animals were more active during partial isolation compared to complete isolation. The frequency of locomotive behaviours and vocalizations during partial isolation was also found to be higher compared to that during complete isolation. Significant effects of isolation level and breed on both temporal and structural acoustic properties were found. Amplitude, power and time acoustic properties were found to affect acoustic quality of vocal responses to isolation, whereas frequency related properties were also found to differ significantly (P < 0.05) between breeds. From spectrogram analysis, the patterns of energy distribution within the calls proved to offer the most distinctive difference between isolation levels and breeds. Calls uttered during complete isolation were all identified by a higher level of noise-energy compared to calls uttered during partial isolation. It was concluded that the acoustic analysis of calls uttered during social isolation of adult rams revealed information on the affective state of the animals. This was found to be predominantly expressed by both temporal and structural variations in acoustic cues within distress calls and to differ per breed.

The results of experiment 2 showed that agonistic behaviour was observed at the highest frequency throughout the entire study. Stocking density was found to have a significant effect on exploratory-, locomotive- and standing behaviour. The effect of breed caused significant differences in agonistic-, self-care-, aberrant- and mating behaviour. Significant differences were also found between day 1 and day 2 of regrouping for agonistic-, exploratory, self-care- and mating behaviour. These results led to the conclusion that the animals’ behavioural response to regrouping and space allowance was characterized by specific patterns and that the three breeds do differ in their reactions to novel situations. It is believed that the animals their welfare might be compromised by housing them at high stocking densities.

Keywords: vocalization, behaviour, stress, sheep, animal welfare

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Copyright © IPB 2012

All Rights Reserved

This work is deposited at the university library to be made available to borrowers under rules of the library. Brief quotations from this thesis are allowable provided that accurate acknowledgment of the source is made. Request for this manuscript in whole or in part may be granted by Bogor Agricultural University when in its judgment the proposed use of the material will be beneficial for educational purposes. In all other instances, however, no part or all of this thesis may be reproduced or transmitted in any form or by any means.

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SAMANTHA E.C. ENGELDAL

 

 

 

 

A thesis sumbitted to the Graduate School of Bogor Agricultural University

in partial fullfillment of the requirements for the degree Master of Science

in the Department of

Animal Science and Production Technology

 

 

 

 

 

GRADUATE SCHOOL

BOGOR AGRICULTURAL UNIVERSITY

BOGOR

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External examiner: Prof. Dr. Ir. Cece Sumantri, M. Agr. Sc.

     

   

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motivation for investigating the way in which farm animals behave in stressful situations. By using animal behaviour as an indicator of the animals’ affective state, an attempt can be made to create such farming environments which support their overall welfare.

My journey in pursuit of a Master of Science degree has been very insightful, energized by numerous special moments. Each and every experience which I have had throughout these past two years has led me to view life in an entirely new light, of which an increased amount of respect for nature and its perfect natural order is just one result. In short, my time spent in Indonesia can be summed up by the words: ‘Without GOD, I am not’. Through HIS mercy I have been blessed with Spiritual Guides and Ancestors who provide me with divine insight, guidance and protection at all times. For this I am so grateful. THEY are the sole reason for this achievement.

My parents have always encouraged me to pursue my dreams. I have been blessed with a Mother who has always motivated and supported me throughout my educational journey. The example she has set for me through her own life fostered my enthusiasm and has also been the basis for all of the success I have been fortunate to experience so far. My father instilled in me two traits: a strong work ethic and to always strive for the best results. They have both taught me that final victory ALWAYS comes to the one who stays connected and perseveres. For this I am so grateful. I would not have reached this level had it not been for their uninterruptible love, care, encouragement and prayer.

Words of gratitude are due to my family and friends for always taking an interest in what I have been doing and offering me their much-valued support. I would thank you from the bottom of my heart, but for you my heart has no bottom.

I would also like to thank my head supervisor, Prof. Ronny Rachman Noor. Without his willingness to take me under his supervision I might not have had some of the wonderful experiences that I have had. He has provided me with supreme counseling while exploring a topic that I am very passionate about. I am thankful to him for his guidance, advice and encouragements throughout my study. I have learned a lot from him during my research, which greatly increased my skills in the field. His supervision challenged me intellectually and has helped enrich my knowledge.

I would also like to acknowledge, Prof. Subandriyo for his support and constructive criticism throughout this project.

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Indonesia will always be greatly valued.

I am very grateful to everyone I have met at the Indonesian Research Institute for Animal Production, especially the technicians who assisted me during the collection of my data. The support and assistance received from Bapak Sumantri, Pak. Koesma, Pak. Tohir, Pak. Njurjaja and Pak. Maplani in carrying out my research will always be greatly appreciated.

I would like to convey my gratitude to all the staff at IPB for their enormous and continuous support, patience and help throughout my study.

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After having finished all of the basic education levels, the author was admitted to

the Anton de Kom University of Suriname (ADEK). In the year 2009 the author

graduated with a Bachelor’s Degree in Animal Science.

In 2010 the author attained her teaching certificate for becoming a licensed

teacher. In that same year she was awarded a scholarship under the Developing

Countries Partnership Program to further her studies in Indonesia at Bogor

Agricultural University. The author successfully completed the Master’s program

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LIST OF TABLES ... xiii

LIST OF FIGURES ... xiv

LIST OF APPENDICES ... xv

GENERAL INTRODUCTION ... 1

Background to the Study ... 1

Purpose of the Study ... 4

Significance of the Study ... 5

Hypothesis ... 5

LITERATURE REVIEW ... 7

Systematics and Distribution of Sheep ... 7

Barbados Blackbelly Cross ... 7

Local Garut ... 8

Composite Garut ... 8

Importance of Animal Behaviour ... 9

Behaviour, Welfare and Environmental Design . ... 11

Motivation and Stress in Farm Animals ... 15

Relations of Vocalization to Animal Welfare ... 17

Vocalization Analysis ... 21

EFFECT OF DIFFERENT LEVELS OF SOCIAL ISOLATION ON THE ACOUSTICAL CHARACTERISTICS OF SHEEP VOCALIZATION ... 23

Abstract ... 23

INTRODUCTION ... 24

MATERIAL AND METHODS ... 27

Location and Time of the Study ... 27

Study Subjects and Housing ... 27

Isolation Procedures ... 27

Recorded Behaviour ... 28

Bleat Recordings ... 29

Bleat Analysis ... 29

Data Analysis and Statistics ... 34

RESULTS AND DISCUSSION ... 35

Behavioural Parameters... 35

Vocalization and Call Measures ... 41

Breed Differences of Acoustic Structure of High Bleats ... 45

CONCLUSIONS ... 53

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Abstract ... 61

INTRODUCTION ... 62

MATERIAL AND METHODS ... 65

Location and Time of the Study ... 65

Study Subjects and Housing ... 65

Experimental Setup and Procedure ... 65

Behavioural Parameters ... 66

Data Analysis ... 68

RESULTS AND DISCUSSION ... 69

Behavioural Budget ... 69

Effect of Space Allowance on Behaviour of Rams ... 70

Breed Effect ... 72

Impact of Day of Regrouping on Ram Behaviour ... 75

Vocal Behaviour ... 78

CONCLUSIONS ... 81

REFERENCES ... 83

GENERAL DISCUSSION ... 87

RECOMMENDATIONS ... 91

REFERENCES ... 93

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1 Values of acoustic parameters based on isolation level ... 105

2 Values of acoustic parameters based on breed ... 106

3 ANOVA test results from the GLM procedure for comparison of acoustic parameters for isolation level and breed ... 107

4 Output of Duncan’s multiple range test for isolation level ... 117

5 Output of Duncan’s multiple range test for breed ... 122

6 Output of Kruskall-Wallis test ... 126

7 Output of Mann-Whitney U test ... 129

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1 An operational defination of animal welfare developed

in the Welfare Quality Project (Welfare Quality 2009) ... 12

2 Scheme for judging welfare indicators in animal management

and housing systems ... 13

3 Experimental design of isolation procedures ... 28

4 Frequencies of observed behaviours at different levels of isolation ... 35

5 Breed differences in frequencies of observed behaviours

at different levels of isolation ... 37

6 Comparison of acoustic parameters of high-pitched bleats

at different levels of isolation ... 42

7 Comparison of acoustic parameters of high-pitched bleats

from different breeds ... 46

8 Experimental design. Number of animals per breed group

and per stocking density ... 66

9 Ethogram used for studying behaviour of rams at various

stocking densities ... 67

10 Pooled behavioural categories ... 68

11 Frequencies of displayed behaviour at different

stocking densities ... 70

12 Influence of breed on ram behaviour ... 72

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1 Adult rams of the breeds Barbados Blackbelly Cross

and Local Garut ... 8

2 Adult rams of the breed Composite Garut ... 9

3 Assessment of welfare and consequences of lack of welfare ... 16

4 Neuronal, anatomical and functional elements of call

production in animals ... 19

5 Frequency of locomotor activity by animals from different

breeds at different levels of social isolation ... 39

6 Frequency of standing by animals from different breeds at

different levels of social isolation ... 40

7 Frequency of vocalizations per breed group at different levels

of social isolation ... 41

8 Representative spectrographs of high-pitched bleats from the same Barbados Blackbelly Cross ram while (A) completely alone,

(B) with observer and (C) partially isolated ... 48

9 Representative spectrographs of high-pitched bleats from the same Local Garut ram while (A) completely alone, (B) with observer

and (C) partially isolated ... 49

10 Representative spectrographs of high-pitched bleats from the same Composite Garut ram while (A) completely alone, (B) with observer and (C) partially isolated ... 50

11 Frequency of observed behaviours throughout the experiment ... 66

12 Frequency of vocalizations at different stocking densities

on day 1 and day 2 of regrouping ... 78

13 Frequency of vocalizations per breed group at different

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1 Values of acoustic parameters based on isolation level ... 105

2 Values of acoustic parameters based on breed ... 106

3 ANOVA test results from the GLM procedure for comparison

of acoustic parameters for isolation level and breed ... 107

4 Output of Duncan’s multiple range test for isolation level ... 117

5 Output of Duncan’s multiple range test for breed ... 122

6 Output of Kruskall-Wallis test ... 126

7 Output of Mann-Whitney U test ... 129

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Background to the Study

There is no better way of generating progress and development than by

looking beyond the boundaries of one’s current knowledge. For centuries

mankind has attempted to subject nature to obeying its rules in order to fulfill its

boundless needs. We are now, however, approaching an era in which change is

essential. Humans are becoming increasingly aware of the importance of

understanding and respecting both the animal and plant kingdom in order for us to

survive. In the development of human civilization the farming of animals has

played an important part. Animals have been used by humans for many purposes

including the production of food, clothing, draught power, companionship,

recreation, scientific research and education. In all cases some degree of

modification of genetics and/or environment of the species concerned has taken

place. According to Leaver (1999) those responsible for the animals and society as

a whole, have a duty to ensure that the welfare of animals is not unacceptably

compromised in these processes.

The feeling that man has a moral obligation to ensure that the welfare of

animals which are kept on farm is never poor has become widespread. At present

animals can no longer be considered machines that can be manipulated at will for

human purposes. It is believed by an increasing number of researchers (Duncan

1993; Whittaker et al. 2012) that because animals are sentient, their welfare matters. The welfare of an animal depends on how it perceives the situation with

which it is confronted and on how it perceives itself in that situation (de Jong et al. 2012). According to Fraser and Broom (1997) the attempts of an animal to cope and the result of failure to cope to its surroundings can be measured. Hence

welfare can be assessed in a precise scientific way using a variety of indicators.

Knowledge of animal behaviour may be more important today as intensive

husbandry systems place animals in environments far removed from those they

were originally selected for, and even more distantly removed from those their

wild ancestors were adapted to (Lawrence & Rushen 1993). It is believed by

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not soluble by investigating nutrition, body physiology, or disease control but

require investigations of the behaviour of the animals before progress can be made

towards a solution. Behaviour can be defined as that which animals do to interact

with, respond to, and control their environment. An appreciation of how to handle

animals thus necessitates knowledge of behaviour, which is generally the animal's

"first line of defense" in response to environmental change. As such, careful

observations of behaviour can provide us with a great deal of information about

animals' requirements, preferences, dislikes, and internal states (Mench & Mason

1997).

Over the last few decades, scientists have made huge progress in

understanding how animals perceive their environment and the feelings prompted

by this perception. Investigating the modern farming environments and

management strategies which livestock are subjected to might help determine

where mismatches exist (Leone & Estevez 2008). Substantial new knowledge of

the behaviour of livestock under intensive husbandry systems is therefore needed

to assess these systems of management. This knowledge can be applied in the

animal production industry in order to improve production and welfare. Whittaker

et al. (2012) stated that space provided to animals is one easily recognizable aspect of husbandry systems that is perceived by the public to imply that welfare

is poor. According to them features such as the structural characteristics of the

environment or social aspects of the group (such as group size or density) must be

considered to establish meaningful recommendations on how to create the most

beneficial environment for animals. Craig (1981) suggested that in many instances

it may be easier to modify an animal’s environment to provide or eliminate some

key stimulus than to use artificial selection to exploit a favorable behaviour or

eliminate an unfavorable one. When decisions are taken about methods in animal

husbandry, animals should be considered as individuals and their responses to

their environment should be evaluated and understood.

The vast majority of farmed animals is gregarious and reacts heavily to

being separated from group-mates. Much research has focused on the potential

role played by conspecifics in the elicitation of emotions. This is valid both for

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given a great deal of consideration in the design of housing systems and

equipment, even though behaviourally inappropriate design can lead to injury and

other welfare problems (NRAES 1995). A careful description of the behaviour

patterns or a sequence of behaviours of animals offers the possibility to identify

all of the relevant components and to link their performance to the wider context

of the physical and biological environment of the animal (Scott 2005).

Particular states of mood or emotion may be accompanied by specific

behaviours, vocalization being one of them. Hence, in farm animals vocalizations

may supply us with hints on their well-being in an easy way, given that the

meanings of the respective calls are well-established. Then, it is possible to judge

acoustically uttered current needs and impaired welfare by non-invasive, possibly

even automatized continuous monitoring in farm-housing. Vocalizations may also

modulate emotions of the receivers such that welfare may also be affected in

conspecifics hearing distress utterances. For these reasons, the analysis of farm

animal vocalization has gained increasing interest in the last years and a variety of

attempts to decode the meaning have been made. According to Manteuffel et al.

(2004) future bioacoustical research for welfare assessment should focus on

comprehensive studies of a broad spectrum of species specific distress

vocalizations.

Sheep (Ovis aries) are a highly adaptable and versatile domestic species, which has made them a critically important resource in human societies around

the world (Meadows et al. 2005). According to statistical data on the Indonesian livestock sector, the amount of sheep raised for production purposes has increased

significantly in the past five to six years. The size of the national sheep population

was estimated at 8,979,849 animals in 2006. In 2010 this amount had increased to

10,915,000 (Direktorat Jenderal Peternakan 2010). It was reported by Johannes

and Budisatria (2011) that, in South East Asia, Indonesia has the largest small

ruminant population. According to them the rapid growth of the local population

serves as a major impulse for further increasing the number of small ruminants.

Although the welfare of farm animals has been of concern, and a focus for

research for decades, this has concentrated on those species generally farmed

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managed extensively, sheep have received relatively little attention from a welfare

perspective (Dwyer 2009). Recently, Veissier et al. (2012) found that the emotional responses of sheep to a threatening event are influenced by the animal’s

social environment. Therefore, sheep are likely to form social standards of

emotional responses according to their rank in hierarchy which makes them a

perfect candidate species for behavioural studies.

The general breeding strategy for any production environment is to match

genetic potential to the feeding and management system (Bradford 1993). In order

for farmers to increase the productivity of their livestock with the use of limited

resources, it is important for them to facilitate the needs of their animals as much

as possible. More precise welfare assessments need to consider specific

behavioural response of genetic lines, as different lines react differently when

facing environmental challenges (McGary et al. 2003). Behaviour, like physiology and anatomy, is part of the general functioning an make-up of an

animal. An interesting question in the context of animals’ genetical background

concerns how differences in genotype and in the environment result in differences

in behaviour (Broom 1981).

Farmers and the food industry have the responsibility of meeting the

demands of the consumers for high welfare products and quality products by

adjusting their farming systems. Research in the area of animal behaviour will

therefore be able to provide farmers with important information for developing

better livestock management systems and designing captive environments catering

to the specific needs of each breed, which will automatically result in an

improvement of the production level of the local animals.

Purpose of the Study

The purpose of this study was formulated as follows:

1. To discover whether, and if so, to what extend the vocal output of sheep is

influenced by the stressfulness of different levels of social isolation

2. To determine whether there are differences in the vocal behaviour of different

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3. To analyze the impact of farming practices i.e. regrouping and housing (space

allowance) on sheep behaviour

4. To assess the degree of variability in behaviour between sheep breeds

5. To discover amount of time needed for newly regrouped animals to establish

affinity and affiliative relationships

Significance of the Study

The output of this research is aimed at providing livestock farmers with a

valuable, less invasive and convenient method for assessing overall welfare of

sheep, in which behaviour can serve as a key indicator for the animals’

motivational state and welfare status. It is also hoped that the results of the study

will be able to provide valuable information about the optimum stocking density

and regrouping method for different breeds of sheep.

Hypothesis

The hypothesis that was tested during this study is that the acoustic output

of sheep is affected by their motivational state and that the quality of the vocal

repertoire differs per breed. The prediction was that the vocalizations of the sheep

would reflect the stress response induced by different levels of social isolation. It

was therefore thought that the quality of the vocal output would differ depending

on the intensity of the stressor and on the breed. It was also hypothesized that the

animals’ behaviour would be affected by the novelty of the new housing

conditions and amount of space available per animal. It was predicted that the

frequency of agonistic behaviour would be higher on the first day right after

regrouping and that the amount of agonistic behaviour displayed would differ per

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LITERATURE REVIEW

Systematics and Distribution of Sheep

Domesticated sheep (Ovis aries) belong to the tribe Caprini (Shackleton & Shank 1984). Following Mesolithic mans’ domestication of the sheep

approximately 8000–9000 years ago (Ryder 1984), selection has proceeded on

traits such as coat color, environmental tolerance, wool characteristics, and meat

and milk production. The result is a spectrum of phenotypic differences between

breeds (Meadows et al. 2005).

According to Sodiq and Tawfik (2004) Indonesia has various indigenous

sheep breeds distributed throughout its different tropical environments which are

well suited for intensive and extensive exploitation. Throughout the years

different crossbreeding programs have been used in the hope of creating the ideal

animal, one which is well adapted to the various environmental conditions and

thus able to produce optimally. It is believed that there are two distinct types of

sheep in Indonesia: thin-tailed - and fat-tailed sheep (Edey 1983). In the hope of

improving the production of local animals, certain temperate breeds such as

Merino, Suffolk, Suffas, Dorset and, more recently, Barbados Blackbelly and

St.Croix were introduced to Indonesia (BPPT 2007).

Barbados Blackbelly Cross

Barbados Blackbelly sheep are a breed of hair sheep. Although there can

be little doubt that the Barbados Blackbelly has African ancestry, there is

compelling evidence that the breed originated and evolved on the Island of

Barbados. The fleece color of these animals ranges from light tan to a dark mahogany red, with black breed markings on the face, legs, belly, inguinal region,

chin, and chest (BBAI 2011). The animals of this breed are believed to be more

tolerant than other sheep breeds to internal parasites (CARDI 2006). A composite

breed, named Barbados Blackbelly Cross was created by crossing Barbados

Blackbelly sheep with animals from the breed Local Sumatera. This composite

breed is believed to possess the combined attributes of adaptation to widespread

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Local Garut

Local Garut, a breed indigenous to Indonesia, is believed to have

originated from a crossing between Merino sheep, Kaapstad sheep and animals

from a breed local to Indonesia (Merkens & Soemirat 1926). Garut sheep possess

certain characteristics which make them very suitable for use in livestock

production systems, one of which is their adaptability to novel environments

(BPPT 2007). Under rural conditions, Garut sheep are generally raised on a small

scale as an additional source of income (Bradford & Inounu 1996). Due to its

rather dominant temperament, animals of this breed have been known to be used

for fighting purposes (Edey 1983).

Figure 1 Adult rams of the breeds Barbados Blackbelly Cross (left) and Local Garut (right). Source: private collection of the author

Composite Garut

St. Croix, a species of sheep known for its rather large size, high

adaptability to hot climates and ability to sustain a good production level under

poor feeding conditions together with Moulton Charollais, famous for its high

milk production, large body size and rapid growth rate, were used to create a

composite breed (Sodiq & Tawfik 2004). The before mentioned two breeds were

crossed with the previously described breed Local Garut to create the breed

Composite Garut. The animals of this composite breed are believed to have a very

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Figure 2 Adult rams of the breed Composite Garut Source: private collection of the author

Importance of Animal Behaviour

Farm animals are kept to produce food an other essentials for humans, and

the farmers need to make profit from their enterprises. It is therefore necessary

that the difference between the value of what animals produce and the costs that

the farmer incurs for this production is sufficiently high. By taking animal

behaviour into account, such optimization may be easier to achieve (Jensen 2009).

Initially, before animal domestication, man used his knowledge of wild animal

behaviour to hunt them successfully. Later, whether by design or accident, he used

behaviour traits, particularly social ones, as key criteria in his selection of and

success with domestic animals (Tennessen & Hudson 1981).

Broom (1981) believes that behaviour, like physiology and anatomy, is

part of the general functioning of an animal. The term ethology is often used for

the observation and description of behaviour with the objective of finding out how

biological mechanisms function (Fraser & Broom 1997). Behaviour is the aspect

of an animal’s phenotype that involves the presence or absence of definable motor

activities, vocalizations and odor production by means of which it conducts its

daily affairs of self-maintenance and social interaction. Like other phenotypic

traits, behaviour is the outcome of environmental and genetic causal agents

(Banks 1982). Fletcher (1992) explained that research on animal behaviour has an

inherently integrative nature, for it gathers together questions and methodologies

across levels of analysis, across levels of explanation and across diverse taxa.

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appreciation of animals. In addition to providing knowledge about the diversity

and complexity of behaviour in nature, such studies also provide information

crucial to improvements in the welfare of animals maintained in laboratories,

agricultural settings and zoos, and as companion animals (The Association for the

Study of Animal Behaviour 2003).

According to Fraser and Broom (1997) there are two types of questions

which can be asked when trying to understand a particular kind of behaviour.

These are: “How does it work?” and “Why does it happen?” The answers to the

first question refer to the mechanisms underlying the behaviour which cause it to

occur at the time of observation and with the form which is seen. The answers to

the second question refer to the way in which this behaviour has arisen in the

species under observation. The authors have suggested that since all behaviour

depends on the genetic information in an animal and environmental factors will

always affect the expression of genes, it is not useful to try to distinguish between

instinctive and innate behaviour and which is environmentally determined. The

questions of interest here, concern how differences in genotype and in the

environment result in differences in behaviour.

It was mentioned by Arney (2009) that sheep are an attractive animal for

scientific research on behaviour due to the facts that they are docile, have a

(relatively) short flight distance and are gregarious. In sheep, several studies have

been carried out concerning the behavioural reactivity of animals to a novel

environment. Breed differences are known to exist in several behaviours, such as

selection of lambing sites (Alexander et al. 1983; Poindron et al. 1984), open-field behaviour and reaction to the presence of a dog (Torres-Hernandez &

Hohenboken 1997). It is possible that the breed differences found in open-field

tests reflect genotypic variations in reactivity of animals to various stressful

situations according to Le Neindre et al. (1993).

Abnormal behaviour may be the first indicator that there is a problem with

an individual sheep, or the whole flock. Such abnormal behaviours observed in

sheep include: lethargy, becoming uninterested in feeding, increased vocalization,

isolation of individuals from the flock, restlessness and an increased respiration

(39)

irrespective of professional expertise, observers' interpretation of animals'

behavioural expressions, including their emotional state, are in close agreement.

This includes assessments of sheep.

In an attempt to emphasize the importance of behavioural studies Fraser

and Broom (1997) even stated that every farmer, every veterinary surgeon and

indeed all those who have an interest in livestock production need to know about

farm animal behaviour in order for them to carry out their job properly. Research

on the behaviour of farm animals is thus relevant and needed for animal

production enterprises to be carried out effectively and economically.

Behaviour, Welfare and Environmental Design

It has been stated by Rollin (1995) that society is currently demanding that

agriculture be modified to reduce suffering and to accommodate the physical and

psychological needs of animals, as determined by their biological natures.

According to the author the aim of research into animal welfare that will be

undertaken in the future therefore, must be primarily to improve the well-being of

animals, presumably within the constraints of economic reality. This, in turn,

means that research should be directed toward making production systems

“animal-friendly”, so as to alleviate suffering and increase animal happiness. To

date there is no consensus on the definition of welfare, however definitions have

been proposed based on the ability of the animals to perform natural behaviour,

the animals’ subjective experiences, or the biological functioning of the animals

(Dwyer 2008).

Table 1 gives an operational definition of animal welfare developed in the

Welfare Quality Project (2009). At present the innovations in management are

principally characterised by larger livestock numbers kept together in markedly

reduced space. Such conditions have effects on disease transmission and they

require considerable physological and behavioural adaptation. It has been

assumed that farm animals are, in certain cases, able to adapt to the environmental

restrictions, but that both adaptation and failure to adjust are recognisable in the

(40)
[image:40.595.53.502.72.825.2]

Table 1 An operational definition of animal welfare developed in the Welfare Quality Project (Welfare Quality 2009)

Principle No. Welfare criterion Example of potential measures

Good feeding 1 Absence of prolonged hunger Body Condition Score

2 Absence of prolonged thirst Access to water

Good housing 3 Comfort aroused resting Frequency of different lying

positions, standing up and lying down behaviour

4 Thermal comfort Panting, shivering

5 Ease of movement Slipping or falling, possibility

of exercise

Good health 6 Absence of injuries Clinical scoring of integument,

carcass damage, lameness

7 Absence of disease Enteric problems, downgrades

at slaughter

Evidence of routine mutilations such as tail docking and

dehorning, stunning effectiveness at slaughter

Appropriate behaviour

8 Expression of social behaviours Social licking, aggression

Expression of other behaviours Play, abnormal behaviour

Good human-animal relationship Approach or avoidance tests

Positive emotional state Novel object test

Adapted from Rushen et al. (2011)

The welfare of different farm animal species has been a scientific issue for

a relatively long time, generating a significant quantity of information related to

welfare of different farm animal species in the scientific literature (Fregonesi

1999). Behaviour has been of great importance as an indicator of animal welfare.

It can be recorded without complicated equipment under field conditions and it

does not have the same difficulties and limitations associated with all other

indicators (Duncan & Poole 1990). The welfare of managed animals relates to the

degree to which they can adapt without suffering to the environments designated

by man. So long as a species remains within the limits of the environmental range

to which it can adapt its well-being is assured (Carpenter 1980).

In addressing the issue of how we can use behaviour in the assessement of

animal welfare, we next need to ask what behaviour can tell us about animal

health and also what it can tell us about what animals want. Behaviour has a

number of major advantages in welfare studies. Not only is it non-invasive (does

not include breaking the animal’s skin), but it is also in many cases

(41)

Table 2 gives an overview of commonly used indicators for judging the

suitability of management and housing systems for animals based on their

[image:41.595.113.517.190.315.2]

welfare.

Table 2 Scheme for judging welfare indicators in animal management and housing systems

Behavioural indicators Non-behavioural indicators Meeting requirement Behaviour Fitness of facility

quality form measurements clinical

quantity frequency space allowance pathological

duration social integration physiological

intensity type of material biophysical

modification hygienic and reproduction

climatic

characteristics

production

Adapted from Zeeb (1983)

Farm animals are social species with a strong tendency to form groups.

Living in groups has associated costs and benefits. Variation in the size of a group

in natural populations is self-regulated through cost–benefits balance and can be

considered a byproduct of the environmental conditions, as animals will join or

leave the group depending on the overall benefits. This possibility does, however,

not exist in the farm environment, as animals will have no opportunities to leave a

“costly” group setting, creating a situation of increased aggressive interactions

that may favor despotic behaviour, with negative consequences for some

individuals in the group (Estevez et al. 2007). Group size in sheep varies widely within species in response to local environmental conditions and to population

characteristics according to Shackleton and Shank (1984).

In confinement, animals are constrained by the space and conditions

provided for them; they cannot disperse or abandon the group when conditions

become adverse, as they are restrained within the limits of the enclosure.

Inadequate physical and social features of the captive environment can therefore

be considered a source of discomfort and stress that can lead to serious

physiological, behavioural and welfare problems (Estevez & Andersen 2007;

Würbel 2001; Morgan & Tromborg 2007). Enclosure size is a feature of critical

importance for captive animals, because they are willing to work actively to gain

(42)

size, animal movement in captive environments may be limited by specific

features such as environmental complexity.

The European Commission (2005) believes that group size has to be

manipulated when testing for density effects in enclosures of equal size, leading to

confounding between density and group size. Yet a clear understanding of the

effects of each factor is critical to improve the quality of the environment for

captive animals. It is believed that this is particularly relevant in production

systems in which space is a precious commodity. Scott (2005) mentioned that

recommendations on minimum space requirements cannot be based on the

simplistic view of mere units of space per animal. According to the author

features such as the structural characteristics of the environment or social aspects

of the group must also be considered to establish meaningful recommendations. A

careful description of the behaviour patterns or a sequence of behaviours of

animals offers the possibility to identify all of the relevant components and to link

their performance to the wider context of the physical and biological environment.

In designing an environment for domestic or captive animals, it is common

to consider one feature at a time: a feature such as space allowance. According to

Jensen (2009) the essence of keeping animals in captivity is to control their

behaviour by preventing their escape, controlling their breeding and making them

adapt to the housing environment. The way in which animals behave in different

environments has been used informally in modifying those environments or in

designing new ones ever since animals have been kept in captivity. With the

development of behavioural science, however, particularly in the second half of

this century, this process has been made more formal (Appleby 1997). Dethier and

Stellar (1964) mentioned that the assertion that an organism maintains relations

with its evironment, whether nonliving or living, implies that an organism

changes in response to changes in the environment.

Whenever animals have to be grouped or decisions have to be taken about

the housing and density of animals, information about social behaviour is

important (Fraser & Broom 1997). Social behaviour, by definition, implies the

interaction of two or more individuals, the influence of one individual on another

(43)

various behavioural disorders. Aggression levels may become excessively high

and dramatic behaviour such as cannibalism and several other types of abnormal

behaviour may develop (Lawrence & Rushen 1993).

By using ethological knowledge environmental conditions can be created

that best suit the needs of the animals. This thus leading them to produce

optimally (Jensen 2009). Ethological indicators are believed to permit statements

about whether housing and management conditions of the animals fit their needs

and therefore also their welfare (Duncan 1993).

Motivation and Stress in Farm Animals

It is recognized that a reliable assessment of stress cannot be made solely

with the aid of hormonal variables (Toates 1995). Even if there is no consensus

about the precise meaning of the word ‘stress’, its frequent usage suggests that it

captures some essential features of the reactions of animals to harmful stimuli.

Stress, as described by Burchfield (1979), is an environmental effect on an

individual which overtaxes its control systems and reduces its fitness or seems

likely to do so. The relationship between stress and welfare is very clear using this

definition of stress. Since welfare refers to a range of states of the animal from

very good to very poor, whenever there is stress, welfare is poor.

The physiological responses of animals to aversive situations are complex

and often inconsistent according to (Mason 1975). In addition, different

individuals may react consistently differently to the same challenge and in

situations of unambiguous stress there can either be a sympathetic or

parasympathetic/HPA dominance, due to constitutional differences between

individuals of the same species (van Holst 1985; Benus et al. 1991). Broom (1996) believes that stress concerns situations when there is failure to cope, but

poor welfare includes the state of an animal both when there is failure to cope and

when the individual is having difficulty in coping.

When the assessment of welfare is related with the coping definition there

are a considerable number of scientifically acceptable indicators. The following

groups of indicators are commonly used in research according to Smidt (1983):

(44)

Veissier et al. (2000) have created a model which shows the relationship between an animal, its surroundings and its welfare status.

Figure 3 Assessement of welfare and consequences of lack of welfare Adapted from Veissier et al. (2000)

Kilgour (1983) suggested behaviour, stress and production as means to

assess welfare of housed animals. Behavioural responses are first used to cope

with an arousal. If with behavioural changes the individual is unsuccessful in

coping with the problem, physiological mechanisms of coping might then be used.

(45)

stressed and with this its welfare becomes an issue. Production may also be

adversely influenced. The primary experimental research linking the social

environment with disease has tied ‘stress’ to biological intermediaries of disease

(e.g. reduced immunity and resistance to infection) and consequent disease risk.

The concept of ‘stress’ in mammals has been reviewed extensively (Proudfoot et al. 2012). Consequently, stress can induce a malfunction of the immune system having negative repercussions on animal health and welfare. The effect of

stressors on the immune response to foreign antigens like ovalbumin has been

tested in several species by measuring the level of antibody in the serum in sheep

(Cockram et al. 1993).

Relations of Vocalization to Animal Welfare

Communication can broadly be defined as “the sharing of information

between A and B”. In the context of animal behaviour, communication is the

sharing of information between two or more individual animals (Scott 2005). One

question that arises from this statement is: ‘What information is shared when

animals communicate’? Vocal communication is believed to play a central role in

animal societies. Animals rely upon their acoustic and vibrational senses and

abilities to detect the presence of both predators and prey and to communicate

with members of the same species (Fletcher 1992). It is accepted that calls provide

various types and amounts of information (Setchell & Curtis2011).

Mammalian vocalization consists of a varied number of different call types

and contexts in which these calls typically occur. While it is now well established

that vocalizations carry information about the emitter such as its species, its sex or

its identity, few studies have thus far focused on how vocalizations could hold

information about the emotional state of the sender. Nevertheless, some recent

studies in mammals revealed that physiological stress is often associated with

modified vocalizations, implying that an emotion of stress could be expressed

(46)

It has been demonstrated that isolation is a strong stressor in many species,

which is assumed to provoke a raise of stress hormones and/or a change in

behaviour such as emission of stress-induced vocalization (Perez et al. 2011). It is therefore of great importance to gain understanding in the process of vocal

production. According to Brandbury and Vehrencamp (1998) the starting point of

an approach to understanding the vocal repertoires of non-human mammals is a

thorough evaluation of the physics and physiology of their vocal production

system. This is essential to the study of animal behaviour and ecology, as the

progression of interactions between individuals is mediated by visual, olfactory

and vocal signals

The ability to produce calls depends on the existence of a vocal tract which

is constituted by specialized elements of the tracheal tract and, in mammals, the

pharyngeal cavities. The anatomy and function of the acoustical elements

determine the range, the acoustic characteristics and the limits of sound

production in a species. Regarding aspects of animal welfare, however, they may

be of less importance than the trigger and vocalization control systems within the

central nervous system which determine the onset, the character, and the intensity

of vocalization (Manteuffel et al. 2004).

The function of animal utterances is probably in most cases directed to

conspecifics and signals attraction or warning (in a double sense: warning against

a predatory threat or of the warner himself as a habitat resident). In domestic

animals, where some original ultimate causes of vocalizations may have vanished,

it can be hypothesized that the respective repertoire has survived in other contexts.

In farm animals, vocalization characteristics and releasers have not changed much

during the process of domestication (Andersson et al. 2001).

Results from research (Fraser 1974; Von Borell & Ladewig 1992; De

Passillé et al. 1995) have shown that an increased vocalization rate is indicative of the excitement of pigs and calves and their degree of fearfulness to novelty and

social separation. It has also been discovered that vocalizations can be elicited by

the injection of drugs that stimulate neuronal circuitries involved in mood and

(47)

homeostatic factors influencing mood, are perceived by limbic centres of the

forebrain. Signals are then transferred via centres of the midbrain (periaqueductal

grey) and the lower brainstem to effector muscles of the vocal system (Figure 4).

Figure 4 Neuronal, anatomical and functional elements of call production in animals. Adapted from Manteuffel et al. (2004)

Sheep is a mammalian species which produces a number of different

vocals. Some of the specific vocalizations that may be discriminated within this

species are, a low-pitched bleat usually produced by lambs, and high-pitched

bleats usually produced by ewes, considered to be “protest” or distress bleats. The

fact that sheep are a prey species causes these animals to use less vocal

communication in comparison with other social animals. As a result, there is

likely to be little vocal "redundancy" (Krause & Ruxton 2002). Dwyer et al.

(1998) believe that this offers the advantage that a functional and

situation-specific analysis of bleating behavior in this species, has an increased chance of

being fruitful.

Social isolation is known to be particularly stressful for gregarious species.

Among farm animals, sheep are known to be very sensitive to social isolation

(Price & Thos 1980). Sheep, being gregarious animals, are very sensitive to the

stress of becoming separated from the flock. Minton and Blecha (1990) and

Coppinger et al. (1991) have shown that subjecting sheep to restraint and isolation stress (RIS) caused robust increases in plasma concentrations of ACTH and

cortisol. The strong stressful effects induced by social isolation in sheep have also

Amygdala Cingulate Cortex

Periaqueductal Grey

Brainstem and Cervical Cord

(48)

been characterized by behavioral (Poindron et al. 1997) or endocrine responses (Apple et al. 1993) but rarely by concomitant behavioral and endocrine responses (Cockram 2004). The results found by Viérin and Bouissou (2003), however,

concluded that distress in sheep, is also characterized by increased number of

vocalizations, pawing the ground, decreased time of lying down, feeding,

locomotion and increases in plasma cortisol or heart rate.

Understanding negative animal responses and observing and recognizing

animals in distress is a key skill to implement appropriate practices in order to

reduce the stress effects. A possibility toward this goal is applying sound analysis,

in livestock farming compartments, as a tool for early detection of disease and

distress from continuous recording and automatic processing of animal sounds

(Ferrari et al. 2011). Grandin (1998) defines vocalization as being the active generation of sounds with specific organs as an expression of a distinctive inner

state of an animal that may occur spontaneously or may be the result of an

external event. Recent studies in mammals revealed that physiological stress is

often associated with modified vocalizations, implying that an emotion of stress

could be expressed through vocalizations (Briefer 2012). According to Dawkins

(1998) animal calls have partly evolved as communication signals to indicate

some types of “need” and they are relatively easy to record. It therefore seems to

be reasonable to regard vocalizations as easy indicators of an animal’s state of

welfare.

In the ideal case, a given animal’s vocalization can be clearly attributed to a

distinct inner state (or a class of inner states) which - sometimes context

specifically - defines the subjective meaning of the utterance. Weary and Fraser

(1995) reported that alterations of the inner state of an animal may result in

physiological and/or behavioural reactions which can be measured and used to

draw conclusions on the intra-individual and intra-specific meaning of the

vocalization (its semantic content). The dependence of animal vocalizations on

inner states thus makes them useful tools for judgments on the state of well-being

or stress in an individual. According to these authors vocal signals are particularly

useful in the assessment of animal welfare when they reflect aspects of the

(49)

occur (“honest signaling”). Judgments on welfare require that, in a given

environment, the physical and physiological conditions of the vocalizing animal

can be clearly attributed to its state of welfare. The vocalization by itself is not an

indicator because forms of utterances are arbitrarily attributed to the carried

message (Guilford & Dawkins 1995).

According to the Motivation Structural Rules (Morton 1977) almost all

sounds used for close-range communication follow a certain pattern reflecting the

motivational state of the caller. Whereas high-pitched, tonal sounds are thought to

signal appeasement in fear-associated contexts, low-pitched, harsh sounds are

attributed to more aggressive emotions. Although there is some evidence

supporting this concept (Seyfarth & Cheney 2003), clearly designed systematic

studies to test this concept in farm animal species are lacking up to now.

Vocalization Analysis

Animal acoustic behaviour can be termed as being rather complex due to

its variability. The distinction and scientific communication of various types of

farm animal vocalizations requires formal description based on physical

parameters. Frequently the majority of vocalizations is initially recorded in

common environments (e.g. in a husbandry system) and / or behavioural contexts.

The recorded calls are subsequently open to any kind of analysis to find and

describe specific acoustic parameters. Digital signal processing now allows more

diverse numerical descriptions and statistical examinations (Hopp et al. 1997) that can be applied for the analysis of vocal utterances of farm animals. It is of utmost

importance to find an approach to the causal links between welfare-relevant

stressors and respective vocalizations.

Manteuffel et al. (2004) have listed the following procedures which have

been applied in distinguishing various types or individual characteristics of

vocalizations:

¾ Standard statistical methods (e.g. ANOVA, t-test, Wilcoxon test) if few

selected features (e.g. fundamental frequency, duration, rate) are sufficient

for discrimination

¾ Complex statistical methods to compare groups of features (e.g.

(50)

quality of a call, described by a set of features is important (Schrader &

Hammerschmidt 1997)

¾ Neural networks (NN) allow applications in noisy environments because

they tolerate variations of a trained feature set (Schön et al. 2001)

¾ Hidden Markov Models (HMM) allow an arbitrary number of different

vocalizations to be classified, but this demands a specific HMM for each

type of vocalization. A given utterance is then attributed to the best fitting

HMM (Jahns 2002).

One of the latest methods in analyzing animal vocalizations is the

interpretation of non-linear phenomena. The vocalizations of animals range from

periodic vocal-fold vibration to completely atonal turbulent noise. Between these

states non-linear dynamics appear in the sounds. It has been hypothesized that an

increased appearance of non-linear phenomena is correlated with a worsened

condition of an animal (Riede et al. 2001; Tukoda et al. 2002) or with the effort that was put in the vocalization production. If that can be proven, the search for

non-linearities in an utterance will be a suitable additional indicator of welfare

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EFFECT OF DIFFERENT LEVELS OF SOCIAL ISOLATION

ON THE ACOUSTICAL CHARACTERISTICS OF SHEEP

VOCALIZATION

ABSTRACT

It is commonly accepted that social isolation represents a stressful challenge to gregarious species and is able to impair welfare. Vocalization is believed to be a form of commentary by an animal on its own internal state. Animal vocalizations are therefore thought to be useful for determining the emotional state of an animal. In farm animals, vocal analysis is accepted as a non-invasive method forassessing animal welfare in comparison to most physiological measurements. The aim of this study was to investigate the influence of different degrees of social isolation on the acoustic characteristics of stress-induced bleats from three different breeds of sheep. A total of twelve adult male sheep, 2–3 years old, divided in three equal groups based on breed, were used. The animals were subjected to three different degrees of social isolation. At the first isolation level each animal was kept completely alone. At the second level each animal was kept in a room in the presence of a human. At the third level the animal was only partially isolated from conspecifics. Both locomotive and vocal behaviour were recorded during 15-minute sessions on three consecutive days. The locomotive behaviour was subjected to descriptive analysis while the vocal data were first visualized using the acoustic software Raven Pro 1.4, after which a total of thirty-six acoustic parameters were measured. Statistical analysis of the measured parameters was done using the software program SAS 9.2. The descriptive analysis of the observed behaviour showed that the animals were more active during partial isolation compared to complete isolation. The number of bleats during partial isolation was also found to be higher compared to the number of bleats during complete isolation. The application of two-way analysis of variance showed a significant effect of isolation level and breed type on both temporal and structural acoustic properties. Amplitude, power and time acoustic properties were found to affect acoustic quality of vocal responses to isolation, whereas frequency related properties were also found to differ significantly (P < 0.05) between breeds. From spectrogram analysis, the patterns of energy distribution within the calls proved to offer the most evident difference between isolation level and breed. Calls uttered during complete isolation were all identified by a higher level of noise-energy compared to calls uttered during partial isolation.

In conclusion the acoustic analysis revealed that the affective state of the animals was expressed by both temporal and structural variations in acoustic cues within distress calls and that this differs per breed.

(52)

INTRODUCTION

Communication, as reported by Hauser (1996), can occur through a range

of modalities- by sound, smell, sight and touch. Acoustic communication has been

found to play an important role in the social life of many animals. Communicative

behaviour occurs in any form of social interaction and implies an exchange of

information between at least two individuals: a signaler and a receiver. The

acquisition and the use of information helps animals to anticipate and respond

appropriately to events, and therefore to increase their survival (Owings et al.

1997). Through communication, for example, social dominance hierarchies are

established without dangerous fights occurring, members of groups warn each

other about potential danger, and recognition occurs between mothers and their

young (Halpin 1991; Huntingford et al. 2000).

Vocalizations are essential in communication and social interactions,

conveying the speaker’s identity, gender, intentions, and emotional state (De

Lucia et al. 2010). Dawkins (2004) suggested that vocalizations may perhaps be a rather special case of an indicator of what an animal wants because they are

signals, that is, behaviours that have specially evolved to alter the behaviour of

another animal, and which can therefore be “listened in on” by humans. In

communication, information is made available by signals that vary in relation to

the type of information delivered and to the surrounding environment (Vannoni et al. 2005).

The passing of more restrictive animal welfare laws has caused the

detection of stress, especially in domesticated animals, to become an important

issue. One suggested method of detecting stress has been through monitoring the

vocalizations of the animals (Clemins et al. 2005). The vocalizations produced by an animal species can be categorized from both structural and functional

standpoints, and the relationship between the two may take many forms (Soltis et al. 2005).

It is possible to assess welfare using some animal signals shown when they

need certain resources. Weary and Fraser (1995) have reported that vocal and

other natural signals provide reliable indicators of the signaller’s needs. However,

(53)

of a signal before invoking this as a measure of welfare. Acoustic signals can vary

in their duration, pitch (vibration frequency), or amplitude. These features can be

described and studied with the aid of spectrograms which give a visual

representation of a sound (Hauser 1996).

Regardless of how the communication occurs, it is important to understand

how animals can benefit from producing signals, and how others can benefit from

responding. It has been found,for example, that some animals vocalize in response

to pain while other animals are stoic. This difference in behaviour probably

reflects differences in potential audience (Briefer 2012).

Bioacoustics is the study of sound in animals and includes, but is not

limited to, animal communication with associated behaviour (Waring 1975;

Bradbury & Verencamp 1998; Mulligan et al. 1994), sound production anatomy and neurophysiology, auditory capacities and auditory mechanisms, and animal

welfare (Manteuffel et al. 2004). Bioacoustics is extremely important to animal welfare and potentially may be used to monitor and boost livestock and other

agricultural productivity (Dantzer & Mormede 1983; Morton & Page 1992). The

main goal of this field of study is to determine the role of animal vocalizations in

the communication process. Knowledge of the value of vocal parameters may be

of great importance within the field of animal production (Brudznski 2010)

Animal acoustic behaviour can be termed as being ra

Gambar

Table 1 An operational definition of animal welfare developed in the Welfare
Table 2 Scheme for judging welfare indicators in animal management and              housing systems                                Behavioural indicators      Non-behavioural indicators
Table 5 Breed differences in frequencies of observed behaviours at different levels of isolation
Figure 7 clearly shows the highest frequency of vocalizations for the breed
+7

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