Factors of diversity of domestic behaviour in sheep

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Factors of diversity of domestic behaviour in sheep

V Lankin

To cite this version:

Original

article

Factors

of

_diversity

of

domestic

behaviour

in

_sheep

V

Lankin

Siberian

_{Department of}

the Russian

_{Academy of Sciences,}

Institute

_{of Cytology}

and

_Genetics,

10 Lavrentiev

_Avenue,

Novosibirsk

630090,

Russia

(Received

16

_January

1996;

accepted

19 November

₁₉₉₆₎

Summary - An

_ethological

test situation with stimuli that induce fear-motivated

with-drawal reactions, such as isolation from the

herd,

_presence of _man, and

change

of

feeding

and locomotion

_routine,

was used to measure domestic behaviour. The reactions of

with-drawal from man in

sheep

of various breeds were reduced

_{by increasing}

food motivation and vice versa. Withdrawal reactions decreased with

_ageing

and the rate of decrease was

higher

with

_increasing

food motivation. Interbreed

_{comparisons involving}

11 breeds have detected a breed

_specificity

of behavioural variation in

_{sheep. Lowly-specialized}

breeds are

characterized

_by

a

_large

number

(77.0-94.7%)

of animals of the ’wild’

_class,

with a

_high

prevalence

of man-withdrawal reaction and a low incidence of

_feeding

reactions in the

be-havioural test. In

_{highly-specialized}

commercial

_breeds,

the range of behavioural

diversity

is wider and the number of animals in domesticated classes is

_{larger, reaching,}

_eg, 86.0% in

the East-Friesian breed. It is

_hypothesized

that the

_polymorphism

of domestication-related behaviour in commercial breeds has

developed

under the influence of natural selection for

adaption

under stressful conditions of

_breeding

under the control of man and selection for

productivity.

sheep

/

behaviour

_/

breed

_/

domestication

Résumé - Facteurs de variation du comportement domestique chez le mouton. Le

comportement des animaux

_domestiqués

se caractérise par une absence de réaction de

retrait vis-à-vis de l’homme. Ce comportement est mesuré dans un test

_faisant

_appel

à

un

conflit

de motivation entre la réaction de peur induite par l’isolement du troupeau

et la

présence

de

l’homme,

et la réaction

d’approche

vers une _auge contenant de la

nourriture.

_{L’influence}

des

_facteurs

d’environnement et la variabilité du _comportement

ont été étudiées chez

₄₆₇

béliers et

_{plus de}

4 000 brebis appartenant à 11 races ovines.

L’augmentation

de la motivation

_alimentaire,

_{soit par} un

_jeûne

de durée variable

(12-14 h vs

_{2 h),}

soit en

_modifiant

la valeur nutritionnelle de la nourriture

_présentée

lors du

test

_(avoine

écrasée vs

_pellets

d’herbé),

réduit les réactions de retrait. Avec

_l’âgé

_augmente

également

le nombre des animaux

_{qui approchent}

de

_l’auge

pour se nourrir en

_dépit

de

la

présence

de l’homme. Cette diminution des

_réponses

d’évitement avec

_l’âge,

étudiée

chez la race Altaï entre 12 et 26 _mois, est

_{plus marquée lorsque}

la motivation alimentaire

grande proportion

d’animaux « sauvages»

qui

ne

_{s’approchent}

_pas de la nourriture en

présence

de l’homme

_(77,0%

pour la race de

_Mongolie

à

94,7%

_pour la race

Awassi).

Chez les races commerciales

_{spécialisées,}

la _gamme de variation est

_plus

importante et la

proportion des animaux «

_{domestiqués»}

atteint

_86,0%

dans la race de Frise orientale. Il est

_probable

_que ce

_{polymorphismé}

du comportement

caractéristique

de la domestication s’est

_{développé historiquement}

sous

_{l’influence conjointe}

de la sélection pour

l’adaptation

aux stress liés aux conditions

_{d’élevage imposées}

par l’homme et de la sélection pour la

productivité.

ovin

_/

_comportement

_/

race

_/

domestication

INTRODUCTION

One of the

_principal

results of domestication in animals is the

_hereditary

alteration of fear-motivated defensive reactions towards man

(Belyaev,

1969),

which is

con-sidered as the main characteristic of domestic behaviour

(Belyaev

and

_{Trut, 1964;}

Hale,

1969),

together

with the

_{reorganization}

of

_regulatory

neuroendocrine

_systems

such as the

hypothalamic-pituitary-adrenal

_system

(Naumenko

and

Belyaev,

_1981;

Naumenko et

_al,

_1987).

These

_aspects

of domestication were studied in

_breeding

ex-periments

of silver foxes

_(Belyaev

and

Trut, 1964;

Belyaev,

1972, 1979; Trut, 1981,

1987),

minks

_{(Trapezov, 1987)}

and wild rats

_(Dygalo

et

_al,

_1986).

Unlike these and other

_{comparative investigations}

of wild and domesticated animals as well as those

on domestication

_{(Bogolyubsky,}

1959;

Boice,

1973;

Baskin, 1976; Price,

1984),

in-traspecific

studies of domestic behaviour

_diversity

in

_species

of

productive animals,

such as

_sheep,

are

_practically

absent.

An

_impulse

to the

_development

of this

_type

of research has been the

_discovery

of

_polymorphism

in the domestic behaviour of

sheep

of the Altaian breed

_(Belyaev

and

_Martynova,

_1973).

This has led to a number of studies on the

_phenotypic

and

genetic relationships

between this behaviour and some characteristics of

_production

in

_sheep

of various breeds

_(Martynova

et

_{al, 1975;}

Kutz and

_{Hazratculov, 1977;}

Toshchev, 1980; Liev, 1983;

Yashunin and

_Svinchenko,

_1984).

_However,

in

_spite

of the demonstrated

_polygenic

inheritance of domestic behaviour in

_sheep

_(Stakan

et

_al,

_1976),

the task of

_studying

the motivational nature of this behaviour and the influence of environmental factors on its

_diversity

has not been tackled in this work. The

_{heterogeneous}

motivation of domestic behaviour was

_clearly

demonstrated

in domesticated

_foxes,

in that it includes not

_only

the absence of man-withdrawal

reactions,

but also the _appearance of a new trait of ’attachment and

_{sociability’}

towards man

(Belyaev

and

Trut,

_1982;

Vasilyeva,

1991).

It also involves

feeding

reactions,

including

motor

_feeding

_reactions,

which are known to be directed at the

signal

for manifestation of

_feeding

_activity

in animals

_(Karpicke

et

_al,

_1977),

in

the

_development

of defence behaviour in domesticated foxes.

_Taking

into account

the

_{alimentary dependence}

_upon man of domesticated animals and of those in the

process of domestication

(Price

and

King,

1968),

one _may think that the role of motivation for food can be found not

_only

in the modulation of

_expression

and

variability

of defense reactions

_during

_ontogenesis,

but also in the

_polymorphism

of

genetically

integrated feeding

and defensive reactions to man in domestic animals

and of

_farming

factors that influence the

_variability

of manifestation of

man-withdrawal

_reactions,

as well as

_ontogenetic

and

_populational

_diversity

of domestic

behaviour in

_sheep

remains unknown.

Breed

_genotype

is an

_independent

factor of

_diversity

of

_feeding

and

fear-motivated man-withdrawal reactions in

_sheep

_(Kroiter

and

_Akhatov,

_1980;

_Romeyer

and

_Bouissou,

_1992).

That is

_why

the correlations of domestic behaviour with the live

_weight

and wool

_yield

found in some breeds

(Belyaev

and

_Martynova,

_1973;

Stakan,

1987)

can

_point

both to the existence of interbreed differences in this

_type

of behaviour

_depending

on

_productive

characteristics and to the

dependence

of breed

_productivity

level on behavioural

_{polymorphism. Nevertheless,}

there have

been no interbreed

_comparisons

of domestic behaviour

_polymorphism

in

_sheep.

The

_objective

of the

_present

work was _{to compare} the influence of environmental

factors on the reactions of withdrawal from man and on the

_polymorphism

of

domestic behaviour in

_sheep

of different breeds.

MATERIALS AND METHODS

Animals and

_rearing

conditions

Four hundred and

_sixty

seven rams and 1617 ewes of the Soviet meat-and-wool breed at various _ages were used for the

_study

of the influence of environmental

factors on the manifestation and

_diversity

of withdrawal from man in

_sheep.

The influence of time after

_feeding

on the rate of

_{age-dependent changes}

of this reaction

was

_investigated

on 30 coeval ewes of the Altaian fine-fleece breed.

Polymorphism

of domestic behaviour was studied on 2783 ewes of 11

_breeds,

in-cluding

the

_{Altaian, Ascanian, Caucasian,}

North-East

_Bulgarian

fine-fleece

_breeds,

the White

_{Starozagorskaya,}

_{East-Friesian,}

Black-head Pleven and

_improved

Awassi

milk

_breeds,

the Ascanian

_type

of

_polycarpous

Karakul and

_pure-bred

Karakul

Astrakhan

_breeds,

as well as the native

_Mongolian

breed.

The

_sheep

of the Soviet meat-and-wool and Altaian breeds were

_kept

at the

Experimental

Farm of the Institute of

_Cytology

and Genetics

_{(Novosibirsk).}

The

sheep

of the North-East

_Bulgarian

and White

_{Starozagorskaya}

breeds were bred in

the farm of the Institute of Animal

_Breeding

and Livestock

_Raising

_(Stara

_Zagora,

Bulgaria);

the

_sheep

of three other fine-fleece and three milk breeds were

_kept

at the

_breeding

farm of the Institute of Animal

_Breeding

_(Razgrad,

_Bulgaria).

The

sheep

of the Ascanian

_type

of

_polycarpous

Karakul and

_pure-bred

Karakul were in

the

_breeding

farm of the Institute of Animal

_Breeding

of

_Steppe

_Regions

_(Ascania

Nova,

Ukraine).

The

_sheep

of the

_Mongolian

breed were in the

_breeding

farm of the Institute of

_Experimental

_Biology

_(Ulan-Ude,

_Buryat

_Republic).

Sheep breeding

conditions were characterized

by

a

_high

zootechnical level. In

all the

_farms,

lambs were reared

_together

with their mothers until the age of

90-100

_days.

After

_weaning,

ewes and rams were

_{kept separately.}

All the

_experimental

animals had ear marks

(numbers),

which made it

_possible

to

_study

their individual

Experimental

set-up

Estimation of reactions of withdrawal from man in

_sheep

_by

the method of

_Belyaev

and

_Martynova

₍₁₉₇₃₎

and its modification

_{(Lankin, 1988)}

was carried out in the

premises

where the

_sheep

were

kept

_{constantly during}

autumn,

winter and

_spring.

The device for estimation of this kind of behaviour consists of several

_joined

stalls

built of wooden sheets

_(1.0

x 4.0 m and 1.0 x 2.0

_m)

_including:

(1)

a

_{large pre-testing}

cage for

placing

all the animals under

_study;

(2)

a small

_pre-testing

_cage

(4.0

x 4.0

_m)

for

_keeping

30-50

_sheep;

(3)

the test cage

(4.0

x 4.0

_m);

(4)

a

_post-testing

_cage

_consisting

of the

_remaining

free _space.

In one corner of the test _cage is

_placed

a

trough

with food for the simultaneous

feeding

of 10-12

_sheep.

Behind the

_trough,

the

_experimenter

stands and marks with

a

_{long-handled paint-brush}

the

_sheep

that are

_eating

the food.

The movement of

_sheep

between the cages is done

through

a sheet

_gate

(1.0

x

2.0

_m).

Procedure

General

The

technique

to measure withdrawal reactions in

_sheep

at different farms was the

same.

_Testing

was

_performed

between 0900 and 1200 hours. For estimation of these

reactions in 10-12

_sheep

in the test cage, 9-12 min are _necessary. After

_completion

of the

test,

the

_sheep

are let out into the

_post-testing

cage, and the next group is let into the test cage. The animals move from one _cage to another

_{spontaneously}

and the

experimenter

only

controls the number of animals

entering

the test _cage.

In the

_original

_method,

each animal was tested

_only

_once, while in the modified

method each one is tested twice.

The

_experimental

conditions minimize uncontrolled stress in

_sheep.

This makes it

_possible

to estimate the

_sheep

behaviour in various farms _{without any}

_preliminary

habituation of animals to the

_experimental

conditions. A _necessary

_prerequisite

is the habituation of the animals to

_being

fed with concentrates.

Behavioural tests

The two behavioural tests used

_(Belyaev

and

_Martynova,

_1973;

_Lankin,

₁₉₈₈₎

involve mild stressful situations that enhance the

_phenotypic

manifestations of the

withdrawal reactions of

_sheep,

such as:

_(a)

isolation of 10-12 animals from the flock

during

the time of behavioural

_testing,

_(b)

_presence of a man who moves

_during

testing

along

the

_trough

and touches the

_sheep

with a

_paint-brush

stained with a

dye,

(c)

disturbance of the

_feeding

and

_gregarious

behaviour routines

provoked by

the two former stimuli.

The

_{experimenter’s}

actions and the behaviour of the

_sheep

in the _{test cage} can

be observed

_by

those

sheep

who are in the second

_pre-testing

_cage

_through

wide

Original

method

Experiments

(Belyaev

and

_Martynova,

₁₉₇₃₎

were carried out in

_{hungry sheep}

12-14 h after the

_{evening feeding.}

For

this,

all the

_sheep

were driven into the first

pre-testing

cage and 40-50

sheep

were let into the second cage. Into the test cage,

10-12 animals were admitted

_by

the

_{experimenter.}

_Being

seen

_by

the

_sheep,

he

_put

food

_(the

_feeding

_stimulus)

into the

_trough

_and,

while

_remaining

behind the

_trough,

stained the

_sheep

that were

_eating

the food with the

paint-brush. During

the first

3-4

_min,

he made the first marks on the heads of the animals.

During

the next 6-9

_min,

he

put

the second marks on the back of the

_sheep,

and in the last

9-12 min of

testing

he

_put

the third marks on the rear backs of animals

_eating

at the

_trough.

As a

result,

the

_sheep

that had

approached

the food

only

once

received one

_{staining mark,}

those who ate

_during

6-9 min received two

_marks,

and the

_sheep

who ate

_during

the whole

feeding

time received three marks.

This test was used for the

_study

of the influence of motivation for food and _age on the manifestation and

_variability

of withdrawal reactions.

Modification of the

_original

method

In the modified method

_{(Lankin, 1988),}

the influence of the

_feeding

drive level on

the withdrawal reactions in

_sheep

was taken into account. For

_this,

the animals

were tested twice:

first,

these reactions were estimated 12-14 h after

_feeding

_and,

3-4

_days

_later,

_they

were tested 2 h after

_feeding,

_ie,

in animals with a

_lowered,

but

not

_completely

absent,

feeding

motivation

_(Mamedov,

_1958;

_Segal,

_1977).

_During

the second

_testing,

the marks were made with a

_dye

of different colour. The

technique

was the same as in the

_original

method.

The modified method was used for the

_study

of domestic behaviour variation in

sheep

of different breeds.

Behavioural records and

_analysis

Reading

of stain marks for all the animals involved in an

_experiment

was

_performed

after

_completion

of the

_{given experiment.}

The ear number and the number of stain marks of different colours were recorded for each animal.

In the method of

_Belyaev

and

_Martynova

_(1973),

the number of marks

_varying

from 0 to 3 is the estimate of withdrawal reactions from man

_expressed

in scores.

Sheep

with a score of 3 are characterized

by

an absence of withdrawal reaction

and

_represent

the most domesticated animals in the flock. These

_sheep

are

_usually

among the

heading

animals and are the first ones to enter the test cage.

Sheeps

with a score of 0 show

_pronounced

withdrawal reactions and are

_represented

_by

the most fearful animals in the flock.

_During

_testing,

_they

do not

_approach

food.

Sheep

with scores of 1 and 2 have a withdrawal reaction intermediate between the

above-mentioned

_types

of animals.

In the modified method

_{(Lankin, 1988),}

behaviour estimates are

_{comprehensive,}

since

_they

include the score obtained

by

the animal 12-14 h and

_again

2 h after

feeding.

The method makes it

_possible

to

_distinguish

16 discrete behavioural classes:

manifestations of the withdrawal reaction and can be

_divided,

_depending

on the

character of their

_change,

into three groups.

Group

1 includes animals of the

’normal’ classes

_{3-2, 3-1, 3-0, 2-1,}

2-0 and

_1-0,

in which the decrease of the

_feeding

motivation enhances the withdrawal reaction. The second group includes the

sheep

of the ’stable’ classes

_{3-3, 2-2,}

1-1 and

_0-0,

with a consistent manifestation of the

withdrawal reaction

_independent

of

_changes

in their

_feeding

motivation. The third

group includes the animals of

’paradoxical’

classes

2-3, 1-3, 1-2, 0-3, 0-2

and 0-1

differing

in the character of ’conditioned

_reflectory

switch-over’

_(Asratian,

_1951,

1983)

of the order of manifestation of

_feeding

and defence reactions to man

during

the behavioural

_testing.

Protocols to

_study

the factors of variation

Repeatability

of behavioural scores

To estimate the

_{repeatability}

of the behavioural _scores, the same

_sheep

were tested

four times

_{consecutively. First,}

their withdrawal reactions were tested 12-14 h after

feeding,

and 3

_days

_later,

2 h after

_feeding.

After 10

_days,

_testing

was

_repeated

both 12-14 h and 2 h after

_feeding,

with a

_3-day

interval. The correlation _among

individual behavioural estimates determined in each of the four tests was studied.

In

_addition,

the correlation between the

_{comprehensive}

estimates obtained

_by

the

tests

_repeated

with the interval of 10

_days

was estimated.

In all these

_tests,

oats were used as the

_feeding

stimulus. In each

_test,

marks were made with a different

_dye.

Environmental influences

The influence of environmental

_factors,

such as time after

_feeding

or food

type

used as the

_feeding

stimulus on the man-withdrawal

_reactions,

was

_{investigated.}

It is known that

increasing

the time after

_feeding

or the caloric content of food

enhances,

whereas

_reducing

time after

_feeding

or caloric content of food reduces the

_feeding

motivation in cows and

_sheep

(Khrenov,

_{1965; Pyanov, 1975;}

Hutson

and

_Maurik,

_1981).

That is

_why,

for estimation of the influence of motivation for

food on withdrawal

_reactions,

manifestation and

_diversity

of these reactions were

observed in

_sheep

_{12-14, 7,}

2 and 1 h after

_feeding.

In addition as the

_feeding

stimulus,

either oats or _grass

granulates

were

used,

which differ

considerably

in

the caloric content

_{(Modyanov, 1978).}

_Irrespective

of the kind of

_food,

the

_feeding

stimulus was

_always

_given

ad libitum

_during

testing.

Age

Beginning

from the

_post-weaning

age, and until the age of 60

months,

withdrawal

reactions were estimated in meat-and-wool

_sheep

both 12-14 h and 2 h after

_feeding.

The influence of motivation for food on the rate of

_{age-dependent}

_changes

in

withdrawal reactions was also

_investigated

in

_sheep

of the Altaian breed which

had,

at the age of 12

months,

zero behavioural scores both 12-14 h and 2 h after

Statistical evaluation

Distribution of

_sheep

with

_respect

to behavioural scores and classes was

_compared

by

means of

_chi-square

test

_{(Rokitski, 1978).}

Coefficients of correlation between behavioural scores in

repeated

_testings

were also calculated

(Snedecor

and

Cochran,

1967).

RESULTS

The influence of food motivation

The reduction of

_feeding

motivation

_by

_shortening

the time after

_feeding

influences

significantly

both the manifestation and the

_population

_variability

of withdrawal

reactions in

_1-year

old

_sheep

_{(table I).}

As

_compared

to the 12-14 h

_interval,

testing

2 h after

_feeding

resulted in an enhancement of

_expression

of withdrawal

reactions and a

change

of

population

distribution with

_respect

to behavioural scores

(behavioural

structure of the

_flock)

in rams

(x

2

=

_52.7,

P _<

0.001)

and _ewes

(

X

Z

=

15.8,

P _<

0.01).

The

_negative

correlation between food motivation and withdrawal reactions in

12-14 h interval.

_Probably,

when the test occurred 7-8 h after the

_{morning meal,}

it coincided with the usual time of the

_evening

meal and evoked a manifestation of

routine

_feeding

_behaviour,

which inhibited the reactions of withdrawal from man.

The influence of decreased food motivation on defensive reactions is

sex-dependent.

A

_comparison

of distributions

_by

behavioural scores shows

_that,

with

the

_exception

of

_testing

2 h after

_feeding

_(x2

=

_5.4,

P >

_0.05),

_testing

12-14 h

(x

2

=

23.8,

P _<

0.001),

7-8 h

(x

2

=

28.9,

P _<

0.001)

and 1 h

(

X

2

=

24.2,

P <

_0.001)

after

_feeding

resulted in a more

pronounced

enhancement of

manifesta-tion of defensive reactions in ewes than in rams.

Reduction of the caloric content of food influences

_{significantly}

the manifestation

and

population

diversity

of withdrawal reactions in rams

_{(table II).}

The use _{of grass}

pellets

instead of

_oats,

when

_testing

12-14 h after

_feeding,

enhanced the withdrawal reactions. The combination of factors

_(shortening

of the time after

_feeding

to 2 h

and use of grass

pellets)

resulted in an increase in the number of rams with scores

of 0 from 20 to

72%

_(P

<

_0.001)

and in a more than four-fold decrease in the

number of calm rams with a score of 3. The clear-cut

_additivity

of the effects of

these

_feeding

factors

_points

to the

_dependence

of the manifestation of withdrawal reactions on the

_changes

of food motivation in

_sheep.

Age

The

_regulatory

influence of food motivation on withdrawal reactions from man can

also be found in

_{age-dependent changes}

of this behaviour in

_sheep.

In meat-and-wool

ewes there is an

age-dependent

decrease of withdrawal reactions and enhancement

of

_feeding

reactions. From the age of 3-4 months to 12

_months,

the number of

ewes with a score of 0 when tested 12-14 h after

_feeding

decreased from 35 to

23%

_(P

<

_0.001),

and when tested 2 h after

_feeding,

from 58 to

32%

_(P

<

_0.001)

(table III).

Therein,

the number of ewes with a score of 3 increased from 34 and

12%

to 45 and

_30%,

12-14 h and 2 h after

_{feeding, respectively.}

_However,

unlike the _ewes, the number of rams with a score of 0 remained

_{unchanged during}

this

In meat-and-wool _ewes, further

_changes

with

_increasing

_age were of smaller

magnitude

(table III).

At the _age of 36

months,

the number of

sheep

with a

behavioural score of 3 when estimated 12-14 h and 2 h after

_feeding

increased

from 45 and

36%

to 53 and

52%

_(P

<

_0.05),

_{respectively.}

On the

_whole,

from the

age of 3-4 to 60

_months,

the number of ewes with a score of 0 decreased

_by

22 and

39%

_(P

<

_0.001),

and the number of ewes with a score of 3 increased

_by

36 and

55%

_(P

<

_0.001),

_{respectively.}

Food motivation and _age

The

_{significant dependence}

of the decrease of withdrawal reactions on food

moti-vation found in meat-and-wool

_sheep

before 12 months of _age

_(tables

III and

_IV)

prompted

us to

_study

in more detail the influence of this factor on the rate of

age-dependent changes

of these reactions.

In ewes of the Altai

_breed,

who had at 12 months a behavioural score of

0,

it was

turned out that the rate of decrease of withdrawal reactions with _age, as estimated

by

the increment in the number of

_sheep

that

_acquire

with _age a behavioural score

of 3 when tested 12-14 h after

_feeding,

was

higher

(during

the

_period

12-20 months

by

28%

_(P

<

_0.001),

and

_during

the

_period

20-26

_months,

_by

24%

_(P

<

_0.001))

than the increment for

_sheep

at the same _age

_periods

when tested 2 h after

_feeding

(table III).

It is

_only

from the _age of 26 months

_(ie,

after the

_completion

of formation

of

_adaptive

behavioural

_phenotype

to

82%

in

_sheep

with a

_high

food

_motivation)

that the rate of

_age-related

reaction decrease became

_higher

_{(by 20%)}

in

_sheep

with

a low food motivation

_(tested

2 h after

_feeding).

These data demonstrate that food motivation and its interaction with

_farming

factors is one of the mechanisms of environmental control of both manifestation

and

_ontogenetic

_variability

of the withdrawal reaction. An elevated level of food motivation not

_only

inhibits the manifestation of such

_reactions,

but is also

positively

correlated with a

_high

rate of

_{age-dependent}

decline of withdrawal

reactions from man in

_sheep.

Repeatability

of withdrawal reactions

The

_{repeatability}

of estimates of withdrawal reactions also

_depends

on the level of

food motivation.

_So,

estimates of behaviour obtained 12-14 h after

_feeding

are

62%

repeatable,

whereas estimates of withdrawal reactions obtained 2 h after

_feeding

are

79%

_repeatable

_(table

_V).

Comprehensive

estimates of behaviour take into account both the influence of the environment and of food motivation on withdrawal reactions and are therefore not

_only

more

_{representative,}

but also well

_repeatable

_{(table VI).}

These

_properties

of

_{comprehensive}

estimates demonstrate the

_objectivity

of the

_proposed

method of detection and measure of

_population

_variability

of

_coupled

_feeding

and withdrawal

Interbreed

_diversity

of domestic behaviour

With the

exception

of the Ascanian and Caucasian fine-fleece

_breeds,

the

_population

structure with

respect

to domestic behaviour in ewes is

significantly

different among

the 11 breeds studied

_{(table VII).}

This character is also

_{significantly}

different between the Black-headed Pleven and the

_polycarpous

Karakul breeds

_(x2

=

_18.30,

P <

_0.01),

_improved

Awassi and

_Mongolian

_(x2

=

_25.3,

P <

_0.001),

Ascanian and North-Eastern

Bulgarian

(x2

=

_13.2,

P <

_0.05)

breeds.

A distinctive character of behavioural

_polymorphism

in

_{low-specialized}

breeds such as the

_Mongolian

and Awassi

_(Esaulov

and

_{Litovchenko, 1963;}

Khinkovski

et

_al,

₁₉₇₉₎

is the low intrabreed

variability

of behaviour and

_prevalence

of ’wild’ class 0-0 animals. The number of animals of the 0-0 class is as

_large

as 77 and

94%

in these breeds and decreases to

3%

in the East-Friesian breed.

_Opposite

to this is the variation of ’domestic’ classes

_{3-3, 3-2,}

3-1 and 3-0 characterized

_by

prevalence

of

_feeding

reactions over the reactions of withdrawal from man. Characteristic of commercial breeds such as the Altaian and East-Friesian is the extension of

of animals in classes characteristic of domestic behaviour.

_Taking

the number of animals in the ’domestic’ classes

_(3-X)

as the criterion of interbreed

_differences,

it

is

_possible

to estimate the behavioural rank of breeds in the

_{following decreasing}

order:

_{East-Friesian,}

Pleven

_Black-head,

_{Askanian, Altaian,}

Caucasian,

North-Eastern

_{Bulgarian, Starozagorskaya, Polycarpous}

_{Karakul, Karakul, Mongolian}

and

improved

Awassi

_{(table VII).}

The number of

_sheep

of these classes was maximal

(86%)

in the East-Friesian breed.

The

_significance

of differences in the breed structure with

_respect

to domestic behaviour

_points

to breed

_specificity

of behavioural

polymorphism

and to the

dependence

of interbreed and intrabreed

_diversity

on breed

_genotype.

DISCUSSION

The data obtained in the

_present

_{experiments point}

to the existence of a

_negative

relationship

between the food motivation level and the manifestation of withdrawal reactions from man in

sheep

of various breeds.

Indeed,

a reduction of time after

feeding

and of food

_caloricity,

which lower the food motivation in

_sheep

_(Pyanov,

1975),

brought

about an enhancement of withdrawal reactions in rams and ewes

of meat-and-wool and Altaian breeds.

_Conversely,

an enhancement of food

moti-vation

_by

_increasing

the time after

_feeding

or food

_caloricity

resulted in a reduced

manifestation of withdrawal reaction in these

_sheep

_(tables

I, II,

V).

The

nega-tive

_dependence

of withdrawal reactions on food motivation

_points

to the existence of a

_{negative relationship}

between

feeding

and

passive-defensive

(or

withdrawal)

reactions in

_sheep,

which exists also in other animal

_species

_{(Kozlovskaya,}

_1974;

Petryaevskaya

and

_Andreev,

1974; Hind,1975;

Lozovskaya

and

Kassil, 1977;

reciprocal

relations between

_hypothalamic

centres of control of

_feeding

and

defen-sive behaviour in

_laboratory

animals

_(Kalyuzhny,

_{1962, 1964; Kozlovskaya,}

_1967).

The effect of such a

_{physiological relationship}

on the manifestation of

_coupled

feeding

and withdrawal reactions in

_sheep

is

_probably

limited

_by

the _age of the

animals and

depends

on the breed.

_So,

it turns out that in ewes of the

meat-and-wool

_breed,

from the age of 22-24

months,

the manifestation of the withdrawal

reaction does not

_depend

on

_changes

at the level of food motivation

_{(table III).}

On

the other

_hand,

the

_modulating

influences of food motivation on the manifestation of

withdrawal reactions in ewes of class 0-0 of the Altaian breed were

_clearly

_expressed

at 40 months of _age

_(table

_IV).

At the same

_time,

the data obtained show that the manifestation and

_population

variability

of withdrawal reactions in

_sheep

are under the influence of

_farming

factors which affect their

_feeding

behaviour.

_Depending

on the

_changes

in food

motivation which

_they

provoke,

these

_widespread

factors _may be divided into:

(a)

those

_enhancing

the withdrawal reactions in

_sheep

when their food motivation decreases due to

_shortening

of the time after

_feeding,

reduction of

_caloricity,

worsening

of food

taste,

or

during

_pasture

(Pyanov,

_1975;

Hutson and

_Maurik,

1981),

and

_(b)

those

_decreasing

the withdrawal reactions when the food motivation is enhanced. The effectiveness of

_modulatory

influences of food motivation on the

manifestation and

_variability

of withdrawal reactions

_permits

one _{to suppose} that food motivation _may

_play

the

_key

role in the environmental control of variation of

negatively

correlated

_feeding

and withdrawal reactions to man in

_sheep.

Finding

a

_{regulatory interdependence}

between food motivation and withdrawal reactions demonstrates that domestic behaviour in

_sheep

has a two-factor

motiva-tional basis.

_However,

one _may think that this conclusion is the result of the method

of

_estimating

the

_behaviour,

which includes the effect of the

_feeding

stimulus in

com-bination with the presence of man

(Belyaev

and

_{Martynova, 1973; Lankin,}

1988),

who induces fear in them

_(Leopold,

_1944;

_Krushinsky,

_1991).

From this

_point

of

view,

the involvement of

_feeding

motivation in the modulation of instinctive with-drawal reactions in

_sheep

is not

_typical

of domestic

_behaviour,

which is

_usually

con-sidered as

_unitary

fear reactions to man in animals of various

_species

(Belyaev

and

Trut, 1964;

Belyaev

and

_{Martynova, 1973; Romeyer}

and

_Bouissou,

_1992).

Neverthe-less,

the

_plausibility

of the

_concept

of two-factor motivational nature of domestic behaviour is corroborated

by

the

_opinion

of Manteufel

_(1987),

who believed that behaviour of wild animals in

_interspecies

contacts is determined

_by

an interaction

of defensive

_(D)

and

_feeding

_(F)

reactions. If the mutual

_proportion

of these factors

in normal conditions is 1

_(D/F

=

1),

it becomes less than _{one as} the

feeding

mo-tivation is enhanced

_(D/F

«

₁₎

and it exceeds

_unity

_(D/F

»

₁₎

_{during danger.}

It follows from this notion that:

₍₁₎

domestic

behaviour,

as a

_typical

form of

inter-specific activity

(McBride, 1984),

has a

_{heterogeneous}

motivational

determination,

and

₍₂₎

there exists a

_{physiological}

_{regulatory relationship}

between defensive and

feeding

reactions that compose this kind of behaviour. The correctness of these deductions is confirmed

_by

our own data and

_by

results from the literature

The

_{heterogeneous}

motivation of domestic behaviour was

_clearly

manifested in

silver foxes in the _process of

_breeding

for absence of withdrawal reactions from man

(Belyaev

and

_{Trut, 1982;}

_Vasilyeva,

_1991).

This domestication

_phenomenon,

that has not been

explained

so

far,

_clearly

demonstrates that the nature of the behaviour of domestic animals towards man remains

_obscure,

as well as the laws of

_diversity

and evolution of animal behaviour in domestication.

Our data

_point

to the level of

_feeding

motivation

_being

an

_independent

fac-tor of control of the rate of

_{age-dependent}

modification of withdrawal reactions

in

_sheep

_{(table III).}

At the same

_time,

the common direction of

_development

of

adaptive

domestic behaviour in different breeds _presupposes the existence of a uni-versal

_{physiological}

mechanism of

_ontogenetic

inhibition of fear of man in animals.

It is

_possible

that such a mechanism _may be the

_{age-dependent}

enhancement of

feeding

drive caused

_by

animal

_growth

and

_development

of

_{productive properties,}

pregnancy and lactation

(Aminov,

1956;

Modyanov,

1978),

which inhibits the

man-ifestation of withdrawal reactions in older

_sheep.

This _process can be

_supplemented

by feeding

motivation-dependent

development

of

_positive

conditioned reflexes to stimuli associated with

_{feeding, including}

man as a

_key

stimulus in controlled

feed-ing,

which also inhibits the manifestations of fear reactions in animals

_(Sudakov,

1971; Karpicke, 1978; Hutson, 1985;

Grandin,

1989; Vasilyeva,

1991).

The laws of

_ontogenetic

variation of domestic behaviour in

_sheep

can be

_expressed

in the

_{following hypothetical diagram}

_{(fig 1).}

The

_diagram

takes into account the existence of ten basic behavioural classes

_representing

more than

90%

of animals in

the

_population

_{(table VI).}

The arrows indicate the most

_{probable age-dependent}

changes

of

_phenotypes

determined

by:

(a)

a common direction of

_development

of

adaptive

behavioural

_phenotypes

and

_(b)

a

higher

rate of extinction of withdrawal reactions in

_sheep

with

_high

_feeding

motivation

_(when

tested 12-14 h after

_feeding,

horizontal

_arrows)

than in those with lowered

_feeding

motivation

_(when

tested

2 h after

_feeding,

vertical

_arrows).

The rank values

_{corresponding}

to the more

probable

age-dependent phenotype changes

reflect at the same time the increase in

the ’share’ of

_feeding

reactions and decrease in the ’share’ of withdrawal reactions

in the behavioural

_phenotype.

As a result of realization of the above-mentioned _age

_pattern,

it is found

that there exists an

_organized

_ontogenetic

and

_{populational diversity}

of domestic

behaviour. It is characterized

_by

the absence of

_simple

linear

_{relationships}

between behavioural

_phenotypes,

there

_being

a

_special

discreteness of classes

_{0-0, 1-1,}

2-2

and 3-3. Direct

_{age-characteristic}

transitions between these

_classes,

that

_require

a simultaneous increase of the first and the second values of the

comprehensive

behaviour

estimate,

turn out to be ’forbidden’. The

_diagram

_points

to the existence of an environmental control of behaviour which

_brings

about an

_{age-dependent}

modification of the ’wild’ 0-0

_phenotype

into its

_opposite

domestic

_phenotype

_3-3,

with

_respect

to the state of

_feeding

and withdrawal reactions.

The data

_obtained,

that

_point

to the

_obligatory

involvement of

_feeding

reactions

manifestation in domestic animals not

_only

of

_fear,

but also of

_feeding

reactions. In this

_connection,

one _{may suppose} that the

_bisignal

_ecological

_significance

of man is a

_unique

_property

that arose from the first

_stage

of domestication as a _consequence

of a new ’domestic’

_feeding

chain of animals which made them

_dependent

on man to the

_degree

of

_possible

_starving

_(Kislovsky,

_1937;

_Bogdanov,

_1977).

_Having

created

an artificial

_feeding

chain which has

_rigidly

attached the animals’ defensive and

feeding

reactions towards man, the latter has created a new ’domestication’ vector

of natural selection

_acting

on the

_adaptation

of animals to stressful man-controlled conditions of

_feeding

and

_keeping.

Under these

conditions,

the effectiveness of

ontogenetic

and

_{evolutionary adaptations}

of behaviour could be determined

_by

the above-mentioned

_patterns

of

_{physiological}

interaction between

_feeding

reactions and the fear of animals towards man, who was transformed into a constant

_ecological

signal

for a combined manifestation of these

_{heterogeneous}

behavioural activities

in domestic animals and animals in the process of domestication.

The

_specificity

of breed structure with

respect

to the domestic behaviour that

was found and the differences in characteristics between

_{lowly-specialized}

and commercial breeds make it

_possible

to

_put

forward some

_hypotheses

on

_evolutionary

factors of

_development

of

_polymorphism

of this behaviour in domestic

_sheep

_{(fig 1).}

The common direction of the

_ontogenetic

and interbreed variation of domestic

behaviour

_points

to the

_existing

_pressure of selection for fitness

_(Kislovsky,

_1937;

Lobashov, 1955; Mair,

1968)

of

sheep

to

_farming

conditions

_including

the ’domes-tication’ vector of selection for absence of withdrawal from man and enhancement

of feed-motivated

_approach

to man in these animals.

_However,

it has been directed

to the

_opposite

direction of the vector of selection

_by

_negative

environmental fac-tors that have been dominant

_by

their

_intensity

under

_primitive

_farming

conditions

(Price

and

_King,

₁₉₆₈₎

thus

_{’protecting’}

the ’wild’ behavioural

_phenotype

in

low-specialization

breeds

_(such

as

_Mongolian

and Awassi shown in

_fig

_2).

An

evolu-tionary

result of the

_disruptive

action of these vectors of natural selection could

have been the

_development

of

ecological

polymorphism

with

_respect

to a

_complex

of

_{coupled viability}

and fitness characteristics

_(Mettler

and

_Gregg,

_1972),

_including

defensive and

_feeding

_behaviour,

in domestic

_sheep.

At the same

_time,

the increased number of more

_adaptive

and more

_productive

sheep

of domesticated classes

_(Belyaev

and

_{Martynova, 1973;}

_Stakan,

₁₉₈₇₎

in commercial breeds

_suggests

that their behavioural structure has been formed under the influence of

_coinciding

selection

_{(Schmalhausen,}

_1940):

the domestication vector of natural selection and selection for

_productivity

_(such

as Altaian and East-Friesian shown in

_fig

_2).

The influence of these selection vectors on

_adaptation

to

increasing

pressure of stressful ’domestication’ conditions

(Kislovsky,

1937, 1965;

Ovsyannikov,

1969;

Belyaev,

1983)

must have resulted in the formation of the behavioural

_polymorphism

characteristic of commercial breeds. It is

_possible

that the effect of this form of selection has reached its ’limit’ result in the

_historically

ancient East-Friesian breed

_conspicuous

with its

_productivity

and characterized

not

_{only by}

the _very low incidence of the ’wild’ 0-0

_class,

but also

_by

the loss of

gregarious

behaviour

_(Maimone

et

_{al, 1965; Novitsky,}

_1981).

The

_{proposed hypothesis}

of

_development

of

_ecological

behavioural

_polymorphism

in commercial breeds assumes

_logically

that the domestic behaviour _may be an

morphophysiolog-ical features

_coupled

with it and determines

_viability

and

_adaptation

in domestic

sheep.

In this _case, the domestic behaviour may be a factor

_controlling

the _range

of intrabreed

_diversity

of the

_complex

of

_{coupled adaptive}

_{physiological}

and

pro-ductive characteristics that _compose the ’constitutional

_type’

of

_animals,

and the

behavioural structure of breeds

_being

a

_specific

trait of

_adaptability

and

ACKNOWLEDGMENTS

The author thanks Ts

_Khinkovski,

D

Nedelchev,

D

_Dochevsky

and Yu Ubeev for their

help

in

_organization

and

_performance

of

_experiments,

and S

_Boikovski,

I Tsenkov and I Alexiev for technical assistance. He is

_grateful

to VG

_Kolpakov

for his

_help

in the translation and discussion of the paper and to P Morm6de

_(Laboratoire

de

G6n6tique

du

Stress, INRA,

Bordeaux,

France)

for

_editing

the

manuscript.

REFERENCES

Aminov SA

₍₁₉₆₅₎

On

_reflectory

influence of mammary

gland

on the

_digestive

_{organs in}

sheep.

In: Metabolism and

_{Productivity of}

_Agricultural

Animals

_(NA

_Baryshnikov,

_ed),

Nauka, Moskow-Leningrad,

24-33

_{(in Russian)}

Asratian EA

_(1951).

Switch-over

principle

in the conditioned

_{reflectory activity.}

Zhurn

Vysshei

Nervnoi

_Deyatelnosti

1, 47-54

_{(in Russian)}

Asratian EA

₍₁₉₈₃₎

_{Reflex Theory of the Higher}

Nervous

_Activity.

Selected Works.

_Nauka,

Moscow

_(in

_Russian)

Baskin LM

₍₁₉₇₆₎

Behaviour

_{of Ungulate}

Animals.

_Nauka,

Moscow

_{(in Russian)}

Belyaev

DK

₍₁₉₆₉₎

Domestication of animals. Sci J 5, 47-52

Belyaev

DK

₍₁₉₇₂₎

Genetic _aspects of animal domestication. In: Problems

_of

Animal and Plant Domestication

_(DK

Belyaev,

ed),

Nauka,

Moscow, 39-45

_{(in Russian)}

Belyaev

DK

₍₁₉₇₉₎

Destabilizing

selection as a factor in domestication. J Hered

70, 301-308

Belyaev DK, Martynova

VN

₍₁₉₇₃₎

Behaviour and

_reproductive

function in domestic

sheep.

In: Problems

_of

Theoretical and

_{Applied Genetics,}

380-401

_{(in Russian)}

Belyaev DK,

Trut LN

₍₁₉₆₄₎

Behaviour and

_reproductive

function in animals. II.

Correl-ative

_changes

in

_breeding

for

_tameability.

Bull MOIP

_{69, 5-14}

_{(in Russian)}

Belyaev DK,

Trut LN

₍₁₉₈₂₎

From natural to artificial selection. Nauka v SSSR 5, 24-64

(in Russian)

Bogdanov

EA

₍₁₉₇₇₎

Doctrine

_of

Livestock

_{Raising. Kolos,}

Moscow

_{(in Russian)}

Bogolyubsky

SN

₍₁₉₅₉₎

_Origin

and

_{Transformation of Domestic}

Animals.

_Nauka,

Moscow

(in Russian)

Boice R

₍₁₉₇₃₎

Domestication.

Psychol

Bull 80, 215-230

Dygalo NN,

Shishkina

_GT,

Borodin

_PM,

Naumenko EV

₍₁₉₈₆₎

The role of neurochemical brain _systems and

_changes

of

_reactivity

of the

_{pituitary-adrenal complex}

in

_Norway

rat

during

selection for behaviour. Zhurn Evolutsionnoi Biokimii i

_Fiziologii

_21, 342-347

(in Russian)

Esaulov

_R,

Litovchenko V

₍₁₉₆₃₎

_Sheep

_Breeding.

_{Selkhozizdat,}

Moscow

_{(in Russian)}

Grandin T

₍₁₉₈₉₎

_Voluntary

acceptance of restraint

_{by sheep. Appl}

Anim Behav Sci

_23,

257-261

Hale EB

₍₁₉₆₉₎

Domestication and the evolution of behaviour. In: The Behavior

_of

Domestic Animals

_(ESE

Hafez,

ed),

Williams and

_{Wilkins, Baltimore,}

22-42

Hind R

₍₁₉₇₅₎

Animal Behaviour.

_Mir,

Moscow

_{(in Russian)}

Hutson GD

₍₁₉₈₅₎

The influence of

_barley

food rewards on

_sheep

movement

_through

a

handling

system.

Ap

P

L

Anim Behav Sci

_14,

263-273

Hutson

_GD,

Maurik SC

₍₁₉₈₁₎

Food

_preference

of

_sheep.

Aust J

_Exp

Anim Husb

_21,

575-582

Kalyuzhny

LV

₍₁₉₆₄₎

On chemical mechanisms of some forms of behaviour.

_Uspekhi

S’ovremennoi

_Biologii

57, 232-244

_{(in Russian)}

Karpricke

J

₍₁₉₇₈₎

Directed

_approach

responses and

positive

conditioned

_supression

in

the rat. Anim Learn Behav

_6,

216-224

Karpricke J, Christoph G,

Peterson

G,

Hearst E

₍₁₉₇₇₎

_Signal

location and

positive

versus

negative

conditioned

_supression

in the rat. J

Exp

Psychol

Anim Behav Processes

_3,

105-118

Khinkovski

Ts,

Donchev

P,

Dochevski D

₍₁₉₇₉₎

Milk

_{Sheep Breeding}

and

Sheep

Mainte-nance

_{Technology. Zemizdat, Sophia}

_{(in Bulgarian)}

Khrenov II

₍₁₉₆₅₎

Reaction to various kinds of food in cows. In: Metabolism and

Productivity of

Agricultural

Animals

_(NA

_Baryshnikov,

_ed),

_{Nauka, Moscow-Leningrad,}

24-33

_{(in Russian)}

Kislovsky

DA

₍₁₉₃₇₎

Problem of

_mastering

the _process of evolution of domestic animals.

Izvestiya

AN SSSR 1, 121-173

_{(in Russian)}

Kislovsky

DA

₍₁₉₆₅₎

_{Origin of Animal Breeding}

and Initial Domestication. Selected Works.

Kolos,

Moscow

_{(in Russian)}

Kozlovskaya

MM

₍₁₉₆₇₎

_Analysis

of mechanisms of the

_feeding

reaction

provoked by

hypothalamus

stimulation. Fiziol Zhurnal SSSR 53, 650-656

_{(in Russian)}

Kozlovskaya

MM’(1974)

Detection of

_{psychotropic activity}

on a model of

experimentally

provoked changes

in emotional state. In:

_{Nevropharmacological Regulation of Systemic}

Processes

_(AV

Waldman,

ed),

Nauka, Leningrad,

12-29

_{(in Russian)}

Kroiter

_MK,

Akhatov Zh S

₍₁₉₈₀₎

_Consumption

of _pasture fodder

_depending

on the

_sheep

breed. Ovtsevodstvo 6, 30-31

_(in

_Russian)

Krushinsky

LV

₍₁₉₉₁₎

_Evolutionary

Genetic

_{Aspects of Behaviour.}

Selected Works.

_Nauka,

Moscow

_(in

_Russian)

Kutz

_GA,

Hazratkulov N

₍₁₉₇₇₎

Types

of

_higher

nervous

_activity

and their association with

_productivity

in the Precoce breed. Selkhoz Biol 12, 388-392

_{(in Russian)}

Lankin VS

₍₁₉₈₈₎

Method of

_estimating

stress resistance in

_sheep.

Bull Izobret i

_Otkrytii

45,

1-12

_{(in Russian)}

Leopold

AS

₍₁₉₄₄₎

The nature of heritable wildness in

_turkeys.

The Condor

_46,

133-197 Liev M

₍₁₉₈₃₎

Behaviour of ewes in stressful situations. Ovtsevodstvo

_{2, 30-31}

_(in

_Russian)

Lobashov ME

₍₁₉₅₅₎

Studies on animals’

_{adaptation by}

the method of conditioned reflexes.

Zhurn Obshchei

_Biologii

16, 95-105

(in Russian)

Lozovskaya RG,

Kassil VG

₍₁₉₇₇₎

Development

of

_{food-procuring}

conditioned reflex in

dogs

with

passive-defensive

behaviour. Zhv,rn

Vysshei

Nervnoi

_{Deyatelnosti 27, 635-637}

(in Russian)

McBride

G

₍₁₉₈₄₎

Feral animal studies in animal science: The uses and limitations of feral

animal studies to contemporary animal science. J Anim Sci

_58,

474-481

Maimone

_{B, Harring F,}

Linnenkol K

₍₁₉₆₅₎

Local

sheep

breeds. In: Manual

of

Livestock

Raising

(F

Harring,

ed),

Kolos,

Moscow, 170-192

_{(in Russian)}

Mair E

₍₁₉₆₈₎

_{Zoological Species}

and Evolution.

Mir,

Moscow

_{(in Russian)}

Mamedov DM

₍₁₉₅₈₎

_{Complex reflectory regulation}

of _energy metabolism in

_sheep

depending

on

_feeding.

Fiziol Zhurn SSSR

_45,

976-981

_{(in Russian)}

Manteufel BP

₍₁₉₈₇₎

_Ecological

and

_{Evolutionary Aspects of}

Animal Behaviour.

_Nauka,

Moscow

_(in

_Russian)

Martynova VN,

Stakan

_GA,

Soskin

_AA,

Chernov LL

₍₁₉₇₅₎

Formation of individual behaviour of

_sheep

in the course of

ontogenesis

and its

relationship

with certain characteristics of

productivity.

Genetika 11, 31-39

(in Russian)

Mettler L,

Gregg

T

₍₁₉₇₂₎

_Population

Genetics and Evolution.

Mir,

Moscow

_{(in Russian)}