APPLIED ANIMAL BEHAVIOUR

SCIENCE ELSEVIER Applied Animal Behaviour Science 48 ( 1996) 61-71

Effects of handling during temporary isolation after early weaning on goat kids’ later response to

humans.

X. Boivin *, B.O. Braastad Dept. of Animal Science, Agricultural Unioersity of Norway, P.O. Box 5025, N-1432 .& , Norway

Accepted 9 November 199.5

Abstract

The effects of brief isolation from peers and handling at two early ages on the relationship between humans and goat kids were investigated. Norwegian dairy kids were weaned at 1 week, penned together, fed from a multinippled bucket, and allocated into three groups: HO animals (n = 8) received no additional contact; H 1 animals (n = 9) were isolated and individually handled for 5 min twice a day for 10 days after weaning; H6 animals (n = 9) were handled similarly at 6 weeks of age. Kids were tested at 5 months and 7.5 months with two tests which were conducted twice on each goat. The ‘encounter test’ included social isolation (1 min), presence of a seated familiar person (1.5 min), and presence of a standing familiar person trying to touch the kid (1.5 min). The ‘choice test’ included social isolation behind solid walls (1 min), behind fenced walls (30 s) and a choice between tied familiar peers or a familiar seated human. Handled kids moved less (P < 0.05) than HO kids in the encounter test, especially with the moving human. They spent more time in contact with the human even if familiar peers were present in the test pen (P < 0.05) than did HO kids. At 5 months of age, they also vocalised less (P < 0.01) than HO kids, but not at 7.5 months of age. However handling appeared to be more effective at 1 week (Hl) than 5 weeks later (H6). Many more recorded variables differentiated significantly between Hl and HO than between H6 and HO. In addition, Hl spent more time close to the observer when alone in the encounter test at both ages (P < 0.05) and vocalised less alone behind solid walls in the choice test at 5 months of age (P < 0.01). In conclusion, artificial feeding is not sufficient to tame the kids. Kids only sought human contact if they had previously been isolated and handled. Handling

?? Corresponding author at: L.A.H.M., INRA de Theix, F-63122 St Genes Champanelle, France.

0168-1591/96/$15.00 0 1996 Elsevier Science B.V. All rights reserved SSDI 0168-1591(95)01019-X

62 X. Boioin, B.O. Braastad / Applied Animal Behaoiour Science 48 (I 996) 61-71

at weaning seemed to induce different effects compared with handling at a later age. The effect of weaning, age, isolation and handling on the later behaviour of the kids are discussed.

Keywords; Goat; Human-animal interaction; Taming; Early handling; Vocalisation; Choice test; Weaning; Social bond

1. Introduction

When modern husbandry changed from a traditional management with few animals per stockman to modem farming with a large number of animals, the contact between stockman and animal decreased markedly. Such changes may have affected the human- animal bond adversely. Several experiments with various species have shown that regular handling may tame the animals (Fordyce et al., 1985; Boissy and Bouissou, 1988; Sato et al., 1984; Heird et al., 1986; Jones and Faure, 1981; Hargreaves and Hutson, 1990) while no contact or minimal human contact may keep the animals fearful towards humans (Csermely et al., 1983; Lyons et al., 1988a) and hard to handle (Boivin et al., 1992a). Moreover, through the last 20 years, scientific evidence has revealed the influence of the human-animal relationship on the economical performance of farm animals. Hemsworth et al. (1986) observed negative effects of aversive handling on the growth rate and reproductive performance of pigs. Seabrook (1972) observed a signifi- cant relationship between the human psychological profile and the milk production of cows. Gross and Siegel (1979) showed that chickens were more resistant to a pathogen when regularly stroked than non-handled birds. Furthermore, the welfare of animals and their caretakers is also thought to be influenced by the quality of the human-animal relationship. Hemsworth et al. (1986) observed a higher free plasma corticosteroid level in the absence of humans in aversively handled pigs than in pigs handled non-aversively. Boivin et al. (1994) observed more aggression towards humans from range calves that had received little human contact than from calves that were suckled traditionally twice a day.

The concept of a sensitive period for the establishment of the human-animal relationship could be useful for the modern farm animal management. Although this phenomenon is well-known in birds (Lorenz, 1935) and Canidae (Scott, 1970; Belyaev et al., 19851, it has not been extensively studied in farm herbivores. Some evidence is reported in cattle. Non-aversive handling of cattle during early life (Boivin et al., 1994), parturition (Hemsworth et al., 1989) or weaning (defined as the complete separation from the mother; Boivin et al., 1992b) may improve the human-animal relationship. In particular, human contact in the period of artificial weaning results in a durable friendly human-animal relationship (e.g. in cattle: Boivin et al., 1992b; in foxes: Pedersen, 1993). Few reports are available on the other ungulates, however.

Dairy goats, like dairy cows, usually have close contact with humans throughout their life. Therefore human behaviour could have a great impact on the behaviour, welfare and productivity of the goats. Kids that were separated from their mother just after birth and petted during the 10 min suckling session twice a day for 2 months were less fearful towards humans than dam-reared animals until at least 55 weeks of age (Lyons et al.,

X. Boioin, B. 0. Braastad / Applied Animal Behauiour Science 48 (I 996) 61-71 63

1988a, Lyons et al., 1988b). Lyons (1989) also showed that the percentage of milk not extracted during the milking procedure after the first parturition (23 months of age) was higher in dam-reared goats than in human-reared goats. Goats are well-known for being easily attracted to humans, but very little is known about the establishment of the human-goat relationship. The present experiment investigated the effects of short periods of human contact at an early age on the reactions of goats to the human at later ages. Three questions were tested: Is artificial suckling with a multi-nippled bucket sufficient to tame (to reduce flight distance) the kid? Is a short period of daily handling of the kid at an early age enough to improve durably the human-goat relationship? Could such handling be more effective just after weaning (at 1 week) than 5 weeks later?

2. Animals, materials and methods

2.1. Animals

Twenty-six Norwegian dairy kids (half of each sex) were weaned one week after birth. They were put in four pens isolated from human activities, each pen containing kids varying less than 2 weeks in age. Each pen also contained non-experimental kids. This was done to give the kids opportunity to develop normal social behaviour. During l-9 weeks of age the kids were artificially fed with a multi-nippled bucket for 1 h twice a day. Three different people randomly brought milk in the bucket. The kids were taught to suckle the bucket for only 1 min on the first day. Rids in this experiment learned quickly to drink without assistance. After 9 weeks animals were fed twice a day with concentrate and ad libitum with hay. During 4-6 months of age, they were held on a pasture with little human contact. At 6 months of age, they were sent with their mothers to a mountain pasture. Animals had very little contact with humans except during milking of the adult goats twice a day. During milking (about 1 h), kids were separated quickly by the human and put together in a small pen without any further contact.

2.2. Treatments

The experimental kids were allocated to one of three treatments: HO animals (n = 8) received no additional contacts; Hl animals (n = 9) were individually handled for 5 min twice a day for 10 days after weaning. Each handled kid was caught from outside the pen, isolated from the others in a neighbouring empty pen, talked to and stroked by a seated human without being threatened or chased. This human did not feed the kids. H6 animals (n = 9) were handled similarly from 6 weeks of age. The treatment groups were equally represented in the four pens in order to avoid bias related to birth dates and rearing environment. Rearing several kids from each treatment group together in one pen might reduce, but not increase, differences in behaviour towards a human among these kids, since an unhandled kid might learn from observation that some kids do not avoid humans. This would give extra power to any differences in behaviour between treatment groups towards a human recorded during later tests.

64 X. Boiuin. B.O. Braastad/Applied Animal Behaviour Science 48 (19%) 61-71

2.3. Tests

At both S months and 7.5 months of age, two different tests were conducted twice on each kid to assess the effects of the handling. Repetition of the test allowed confirmation of the results. Rids from the three treatments were tested alternately. The first test called ‘encounter test’ consisted of three parts. In the first part called ‘alone behind solid walls’, the animal was placed alone for 1 min in the middle of a 10 X 2 m long pen with 2 m high solid walls (Fig. 1). This pen was divided into five equal squares drawn on the floor. In the second part of the test called ‘seated human’, the human who handled the kids entered and sat down in one end of the pen for 1.5 min. He tried to stroke the kid when it approached. In the last part of the test called ‘moving human’ (1.5 min), he stood up, walked if necessary to reach the kid and tried to stroke it.

The second test called ‘choice test’ was adapted from Tomlinson and Price (1980) and also consisted of three parts. At first (‘alone behind the walls’), the kid was put alone for 1.5 min in the central area (2 X 2 m> of a 10 X 2 m pen closed by solid walls (Fig. 2). In the second part lasting 30 s, called ‘alone behind fenced walls’, the solid walls were removed and the fenced walls allowed the animal to see three familiar kids tied in one end and the experimenter in the other end. The last part of the test, called ‘seated human’ (3 min) allowed the tested animal to walk freely in the whole pen divided in five equal squares as in the encounter test. The three tied kids were selected from 12 non-experimental kids previously habituated to be tied and were generally not restless during the test. They were exchanged every six animals tested. An experimental animal was always tested with the same three kids that had approximately the same age and were very familiar to it, as they were reared together in the same pen.

The time spent in contact with the human, the time spent immobile and the number of vocalisations were recorded with a micro-computer (home-made software). For all the tests, the observer was not hidden and sat on a table just outside the middle square of the test pen. Since his presence might influence the animal’s behaviour, the time spent in the square near the observer was recorded. For the choice test, the time spent in the square close to the human or close to the peers was also recorded.

At 5 months of age, the four tests on each kid were performed once a week during 1 month. Rids were allocated in groups of six from each treatment before the tests in order to be caught more easily. Two encounter tests were performed first and then the two choice tests. For the repetition of the choice test, the position of the tied kids and the experimenter were exchanged to counteract side preferences. To save time, the four tests at 7.5 months of age were performed on four successive days. One kid from the HO and

t----*ml

T‘ 2m

Observer

Fig. 1. Test pen for the encounter test.

X. Boiuin, 8.0. Braastad/Applied Animal Behauiour Science 48 (19%) 61-71 65

I w 2m . . II

Observer

Fig. 2. Test pen for the choice test.

one from the H6 group died after the encounter tests at 5 months of age. One Hl kid and one H6 kid died between 5 months and 7.5 months of age.

2.4. Statistical analyses

The percentage of time spent in each behavioural activity was calculated for each test part. Because most of the variables showed similar results in the two repetitions, analyses for each variable were performed on the individual average between the two repetitions of each test at each age. Generalised linear models (GLM; Statistical Analysis System Institute Inc., 1989) for repeated data were used to analyse the effects of treatment, part of the tests and interaction between both. If necessary square-root transformations were used on some variables prior to analyses of the data to homogenise the variances. However non-transformed means and standard errors are presented in the results. Effect of the sex was analysed but never found to be significant and hence excluded from the results. Student t-tests were used to compare least-squares means given by the GLM procedures.

3. Results

3.1. The encounter test

Hl kids spent a greater proportion of the test time in contact with the human motionless or moving (P I 0.05) than non-treated kids (HO) (Table 1). In contrast, H6 kids were only significantly different (P < 0.05) from HO kids with the moving human at 7.5 months of age. No significant interaction between part of the test and treatment was found for this variable.

The differences between HO and Hl kids were consistant on nine of 14 occasions (P < 0.07) for the other three variables analysed in each component of the test and at both ages (Table 1). Such results are in contrast to the inconsistent differences between HO and H6 kids. H6 kids were different from HO kids on only three of 14 occasions (percentage of time spent immobile with the moving human, P < 0.01; number of vocalisations with the seated and the moving human, P < 0.05; Table 1).

The variance analysis showed an interaction between the treatment and the part of the test. At 5 months of age, the Hl and H6 animals were immobile for a similar percentage of time with the seated or with the moving human. In contrast, HO animals were much

Tabl

e 1

Perc

enta

ge

of t

ime

spen

t in

con

tact

w

ith

the

hum

an

and

imm

obile

an

d vo

calis

atio

n ra

te d

urin

g th

e en

coun

ter

test

s at

5 a

nd

7.5

mon

ths

of a

ge

(LSm

eans

an

d St

anda

rd

Dev

iatio

n)

5 m

onth

s ol

d 7.

5 m

onth

s ol

d

HO

(n=S

) H

I (n

=9)

H6(

n=9)

SD

Si

gnif.

H

O(n

=7)

HI

(n =

8)

H6(

n=7)

SD

Si

gnif.

% o

f rim

e in

con

tuct

with

the

hum

an

Seat

ed

hum

an

14.0

a

64.0

b

Mov

ing

hum

an

50.0

a

84.0

b

% I

# tim

e im

mob

ile

Alo

ne

61.1

69

.5

Seat

ed

hum

an

82.4

a

93.2

b

Mov

ing

hum

an

51.1

x

91.4

y N

umbe

r of

oocu

lisut

ions

pe

r m

inut

e A

lone

29

.3 a

19

.6 b

Se

ated

hu

man

13

.9 a

x 5.

1 y

Mov

ing

hum

an

7.3

a 1.

9b

% o

f tim

e in

the

squ

are

close

to

the

obs

erue

r A

lone

23

.8 x

55

.4 y

44.0

ab

35

.6

P <

0.05

30

.0

a 82

.8

b 59

.0

ab

40.3

P

< 0.

06

81.0

ab

30.0

P-

CO.0

6 68

.8

a 98

.3

b 93

.5

b 22

.5

P <

0.05

71.0

9.

6 N

S 67

.5

71.7

66

.8

15.0

N

S 90

.3

ab

8.4

P <

0.07

83

.4 a

98

.2

b 92

.5

ab

11.2

P

< 0.

06

84.6

y

19.3

P

< 0.

01

65.1

a

97.3

b

88.6

ab

20

.7

P <

0.05

25.5

ab

8.

2 P

= 0.

05

18.6

20

.2

19.9

7.

9 N

S 8.

3 b

5.9

P <

0.05

8.

1 3.

5 6.

9 6.

2 N

S 3.

3 b

4.1

P <

0.05

2.

3 1.

9 3.

9 3.

0 N

S

29.3

x

19.4

P

< 0.

01

25.5

a

42.7

b

27.2

a

13.5

P

< 0.

05

Stud

ent

r-te

st:

resu

lts

with

diff

eren

t le

tters

ar

e sig

nific

antly

di

ffer

ent:

a, h

:, P

I 0.

05;

x, y

: P

< 0.

01.

HO

non

tre

ated

an

imal

s;

HI

isol

atio

n an

d ha

ndlin

g at

1

wee

k of

ag

e;

H6

isol

atio

n an

d ha

ndlin

g at

6 w

eeks

of

age

.

Tabl

e 2

Perc

enta

ge

of t

ime

spen

t in

con

tact

w

ith

the

hum

an

and

voca

lisat

ion

rate

du

ring

the

choi

ce

test

s at

5 a

nd

7.5

mon

ths

of a

ge

(LSm

eans

an

d St

anda

rd

Dev

iatio

n)

5 m

onth

s ol

d 7.

5 m

onth

s ol

d

HO

(n=7

) H

I (n

=9)

H6(

n=8)

SD

Si

gnif.

H

O(r

r=7)

H

l (n

=8)

H6(

n=7)

SD

Si

gnif.

% o

f tim

e in

cont

act

with

the

hum

un

3.1

x 60

.4

y 52

.3

y 24

.1

P <

0.01

11

.9

a 60

.4

b 48

.6

ab

37.0

P

= 0.

05

% o

f tim

e in

fhe

hum

cm .

syuu

re

22.8

x

73.9

y

79.0

y

34.5

P

= 0.

01

29.1

a

75.4

b

61.0

a

38.6

P

= 0.

09

% o

f rim

e in

the

syuu

re

clos

e to

the

pee

rs

57.8

a

15.3

b

17.0

b

28.0

P

= 0.

07

57.6

a

15.4

b

33.8

ab

33

.5

P =

0.07

Nu

mbe

r of

uoc

ali.~

utio

n.~

per

min

ute

Beh

ind

solid

wal

ls

24.3

x

15.9

y

24.8

x

5.2

P <

0.01

12

.5

11.5

11

.8

4.6

NS

Beh

ind

fenc

edw

alls

11

.4

14.1

15

.9

6.5

NS

3.1

x 12

.6 y

7.

1 xy

5.

6 P

= 0.

01

Seat

ed

hum

an

3.4

2.4

2.8

1.9

NS

1.3

3.2

2.3

2.9

NS

Stud

ent

l-tes

t: R

esul

ts

with

diff

eren

t le

tters

ar

e sig

nific

antly

di

ffer

ent;

a, b

: P

5 0.

0.5;

x,

y:

P 5

0.01

; H

O n

on t

reat

ed

anim

als;

H

I is

olat

ion

and

hand

ling

at I

wee

k of

ag

e;

H6

isol

atio

n an

d ha

ndlin

g at

6 w

eeks

of

age

.

68 X. Boivin, B.O. Braastad/Applied Animal Behaviour Science 48 (1996) 61-71

less immobile with the moving than with the seated human (interaction: F4+ = 4.83; P < 0.01, Table 1). The same was observed at 7.5 months of age (interaction: F4,38 = 2.58; P = 0.05).

The vocalisation rate also indicated an effect of the treatment on the animal’s reaction to the test, In the whole test at 5 months of age, HO kids vocalised more than Hl and H6 ones (16.8 vs. 8.8 vs. 12.4 vocalisations per minute, respectively, SD = 4.1; F2 23 = 8.03; P < 0.01). Differences were recorded in each part of the test (Table 1). In addition, there was a trend for Hl kids to vocalise less than H6 when alone at five months of age but this was not significant. No difference in vocalisation rate was observed at 7.5 months of age. The number of vocalisations per minute decreased through the parts of the test both at 5 months of age (F2,46 = 19.56; P < 0.01) and at 7.5 months of age (F2,38 = 5.58; P < 0.05). No significant interaction was observed between treatment and part of the test. It is interesting to note that Hl kids spent more time in the square close to the observer when alone than HO and H6 kids both at 5 months of age (P < 0.01) and at 7.5 months of age (P < 0.05, Table 1).

3.2. The choice test

Results from the choice test confirmed those obtained with the encounter test (Table 2). The most prominent differences between treatments in this test were those between HO and Hl kids. HO kids were different (P < 0.09) from Hl on 8 of 12 occasions while HO kids were different from H6 on three of 12 occasions. Hl and H6 kids spent more time in contact with the human (P < 0.01) than HO kids at 5 months of age. Hl and H6 kids also spent much more time in the human square (P < 0.01) and less time in the peer square (P < 0.07) than HO kids did. The same tendencies were observed at 7.5 months of age, but only Hl was different from HO (P < 0.05). H6 was intermediate between the two other groups. Similar to the tendency noted in the encounter test, the vocalisation rate when alone was lower for Hl kids (P < 0.01) compared with HO and H6 kids. As with the encounter test, the vocalisation rate decreased through the three parts of the test (at 5 months, F2,42 = 133,84, P < 0.01; at 7.5 months of age, F 2,38 = 37,87, P < 0.01, Table 2). An interaction was found between treatment and parts of the tests both at 5 months of age (F4,42 = 5.17, P < 0.01) and at 7.5 months of age (F4 3s = 3.55, P < 0.05). In both ages HO and H6 decreased their vocalisation rate significantly more than Hl from the part ‘alone behind solid walls’ to the part ‘alone behind fenced walls’ (Table 2).

4. Discussion

Clear differences in behaviour appeared between handled kids and controls both at 5 months and 7.5 months of age. When isolated, handled animals approached and interacted much more with the human than controls. They were also more immobile than controls especially with the moving human. The test with the moving human revealed that control kids were not only uninterested in approaching the human, but were also avoiding him, a trait that is undesirable during handling. Similar taming effects of early

X. Boivin, B.O. Braastud/Applied Animal Behaviour Science 48 (19%) 61-71 69

handling has been clearly demonstrated in several species (e.g. dogs, Scott, 1970; pigs, Hemsworth et al., 1986; cattle, Boivin et al., 1992a and goats Lyons et al., 1988a). However, the experiment by Lyons et al. (1988b) differed from our experiment in several respects. Their additional handling included no isolation and was associated with suckling for 2 months. Furthermore, they compared handled kids separated from the mother with dam-reared kids with very little contact with caretakers. In our experiment the handling treatment was shorter (only 2 weeks), not associated with feeding, and the handled kids were compared with artificially suckled kids. Thus it seems that a short period of isolation and handling in early age is sufficient for the development of very tame animals, at least until 7.5 months of age. Artificial suckling with a multi-nippled bucket is not sufficient to tame the animal despite the fact that caretakers brought the milk. However nothing is known about the interaction between artificial suckling, handling and isolation. Our handled kids were also artificially fed. Whether handling alone is enough to improve the human-animal relationship when kids are fed by their mother or by an automatic feeder without any association with a human, and to what extent feeding and handling together are required to obtain very tame animals remains to be tested. It is also possible that early social isolation as during our handling treatment could habituate the animal to test situations including isolation. Many experiments, especially on rodents, have shown an influence of early environmental changes like isolation in a box (‘handling’) on the adaptability of the animals (see Chevins, 1990 for review). Isolation could have been more stressful for animals that previously had not been isolated, such as HO kids. However personal observations (X. Boivin) of the kids’ behaviour towards humans suggest that HO animals were, in general, harder to approach even when in a group.

Rids vocalised more when alone than when with the human, as Price and Thos (1980) have shown. Vocalisation could be a good indicator of social isolation. As Price and Thos (1980) suggested, a human could serve as an effective social substitute when goats are isolated from their social group. Like a pet animal, tame goats could spend several hours with a human without appearing distressed by the social isolation from peers (X. Boivin, personal observations).

Real differences appeared between animals separated from their mother and handled at 1 week (Hl) and animals separated at one week but handled at 6 weeks (H6) relative to the HO animals. The effect of handling treatment was more pronounced when imposed from weaning than at 6 weeks of age. In addition, Hl kids seemed more interested in the observer when alone in the encounter test than H6 kids. Hl kids also had a tendency to vocalise less when alone in the encounter test at five months of age. This tendency was confirmed when ‘alone behind solid walls’ in the choice test at 5 months. If vocalisations are an indicator of perception of isolation, it could be postulated that HI animals felt less alone at 5 months of age because of the observer’s presence. In contrast, Hl animals did not decrease their vocalisation in the choice test from ‘alone behind solid walls’ to ‘alone behind fenced walls’ at both ages. The sight of the familiar human in the pen through the fenced walls could elicit calls because of the physical hindrance to join the human.

Both age effects and the association with weaning could explain the differences between Hl and H6 kids. One hypothesis could be that the effectiveness of handling is

70 X. B&in, B.O. Braastad/Applied Animal Behaviour Science 48 (19%) 61-71

age dependent: the earlier the treatment is performed, the more effective it is. Lickliter (1987) observed that kids of the Toggenburg breed spent their first week of life lying down, interrupted only by the regular visit of the mother. From the end of the second week of life, close associations with the other peers were established. Our Hl kids might have received the human handling exactly when they started to establish social affinities. At 6 weeks handling could be less effective, because the social group was already created. The second hypothesis concerns the relation to weaning. Bateson (1979) has proposed that socialisation effects are more effective at birth and weaning, because these are periods of rapid reorganisation when the animal is easily destabilised by deprivation or environmental disturbance. All kids in our experiment were calling just after weaning even though they were with their peers. It is shown in cattle (Boivin et al., 1992b) and in foxes (Pedersen, 1993) that the weaning period could be used favourably for establishing a good human-animal relationship. At this period kids could be more susceptible to form new social bonds, motivated either by the need for peers or the need for being adopted by a new mother. One observation suggested that the human might serve also as a surrogate mother. At the beginning of the study the experimenter who handled the kids also surveyed the artificial suckling. Three kids handled at weaning had to be removed from the experiment because they would not drink alone. They were just looking at the familiar experimenter. Thereafter, the experimenter stayed away from the feeding session and no other kids had problem with drinking.

In conclusion, the behaviour towards humans by the handled kids in our tests might be a result of habituation to the test situation and to humans. However, the close contact between handled kids and the human during our tests indicate strongly that a process beyond mere habituation had occurred. A social bond seemed to exist, suggesting an imprinting-like process.

Further experiments are needed to investigate more precisely the role of age and weaning in the socialisation of goats to humans. The treatment procedure (isolation or in a group, with or without a human feeding them) and the testing procedure (alone or in a group, in a new environment or in the familiar one, with the familiar caretaker or with a stranger) have to be explored more fully. As with pets, goats tame easily and could be a good model for a more detailed investigation of the mechanisms of the human-animal socialisation.

Acknowledgements

Thanks to Anne Walle, Kari Eikanger and Asbjem Westre for good management of the kids, to Kari Eikanger and Qurban Hussain for help with observations and to H%kon Tangen for building the test pens. We are grateful to Jan Ladewig for reviewing the manuscript. The project was made possible by a postdoctoral fellowship to X. Boivin from the Norwegian Agricultural Research Council.

References

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