Applied Animal Ethology, 1 (1975) 245-250 o Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

THE EFFECT OF LACK OF VISION ON SUCKLING BEHAVIOUR OF LAMBS

J. R. BAREHAM Universities Federation for Animal Welfare, South Mymms, Herts (Great Britain) Seconded to the Department of Animal Husbandry, Royal Veterinary College, Potters Bar, Herts (Great Britain) (Received September 23rd, 1974)

ABSTRACT

Bareham, J.R., 1975. The effect of lack of vision on suckling behaviour of lambs. Appl. Anim. Ethol.. 1: 245-250.

Lambs which had all previously suckled were taken from their mother between 2 h and 2 days after birth and deprived of food for a variable period. When one of a pair of twin lambs was blindfolded and put back either in or out of physical contact with its mother it did not suckle. Its twin with either no blindfold or a control blindfold did suckle during the test period. Lambs previously blindfolded suckled when the blindfold was removed. These results implicate the importance of an intact visual sense for successful teat location by lambs of this age. However, the possible involvement of other senses is discussed and other effects of blindfolding, which may account for the inability to suckle, are also con- sidered.

INTRODUCTION

In the majority of cases, lambs more than 2 h old move direct to the mother’s udder and suckle without previous contact with other areas of her body. (Bareham, 1974). From this observation, it was hypothesised that location of the udder depends primarily on an intact visual sense. This spec- ulation was tested in experiments in which the suckling behaviour of blind- folded lambs up to 2 days of age was compared with suckling by lambs fitted with either a control blindfold or no blindfold.

METHODS

Seven pairs of twin Clun lambs and seven Masham twins were used in Experiment 1. Five twin and three single Border Leicester lambs were tested in Experiment 2. The Cluns and Mashams were born in a covered, straw- bedded, indoor pen in December 1970, the Border Leicesters in March 1971. The blindfold used was made of a 5 X 10 cm strip of white terrycloth with

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elastic loops attached to the corners. The control blindfold was similar but with a rectangle cut from the centre of the blindfold so that no part of the lamb’s eyes was covered when it was in position.

EXPERIMENT 1

Pairs of twin lambs born to the Clun and Masham ewes indicated in Table I, were removed from their mother between 2 h and 1 day after birth. The lambs had all suckled prior to removal (Bareham, 1975) and were then held for 30 or 60 min in a pen similar environmentally to the pen in which they were born. The holding pen was out of sight and sound of the main sheep pen in which the mother remained. A heat lamp was provided in both pens. The test consisted of the experimenter introducing lambs at one corner of the sheep pen where they were held until the mother came and licked or smelled them. Each lamb was fitted with either a complete blindfold, a con- trol blindfold or nothing. After initial contact with the mother the pair of twins was released and the time in seconds recorded until suckling occurred. The test period ended after 5 min when the blindfolds were removed.

Results

The results are given in Table I. Seven Masham lambs fitted with a blind- fold did not suckle during the test period. One lamb which was tested after the blindfold was removed, then suckled. The seven twins without a blind- fold all suckled in the test period.

Of the five Clun lambs tested without a blindfold, three suckled. Two lambs with a control blindfold also suckled in the test period. Five of seven blindfolded Clun lambs did not suckle within 5 min of introduction but one of these then tested with the blindfold removed suckled within a few seconds.

Only two lambs suckled when fitted with a blindfold but in the case of C.205 the blindfold slipped off at the start of the test.

Two non-blindfolded lambs did not suckle. The lamb of C.153 sat down throughout the test and ewe 156, having nosed her lambs then refused to nurse and wandered round the pen.

In summary, lo/12 non-blindfolded lambs and 2/2 lambs with control blindfolds suckled during the five minute test period. 12/14 blindfolded lambs did not suckle, although 2/2 did so when their blindfold was removed. The difference in suckling response of lambs with and without an intact visual sense is significant (x2, 19.2; d.f., 1; P< 0.001; Siegel, 1956, p. 109.)

EXPERIMENT 2

Three pairs of twins and three single Border Leicester lambs either 1 or 2 days old were removed and held away from the sheep pen, which contained their mothers, for a time shown in Table II. The test consisted of placing the

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TABLE I

Time to suckle in lambs wearing either a complete or control blindfold or no blindfold (Blank space indicates no test)

Ewe Lamb Time lamb Time from Time to suckle (set) number, number was removed birth to Lamb wearing breed from ewe test time

(min) (h) No blind- Control Blindfold Blindfold fold blind- on then

fold removed

Cl53

Cl18

C287

Cl56

C205

Cl45

C206

M8

Ml8

M23

M7

Ml0

Ml3

Ml6

1 30 2 30

1 30 2 30

1 30 2 30

1 30 2 30

1 30 2 30

1 30 2 30

1 60 2 60

1 30 2 30

1 30 2 30

1 30 2 30

1 30 2 30

1 30 2 30

1 60 2 60

1 60 2 60

3 3

6 6

10 10

10 10

12 12

18 18

1 day* 1 day

2 2

5 5

12 12

18 18

18 18

1 day 1 day

1 day 1 day

NS 5 min

12

30

NS 5 min

3

115

24

20

55

22

5

10

NS 5 min

NS 5 min

NS 5min 10

NS 5 min

6

80 NS 5 min

5 60

NS 5 min

NS 5 min

NS 5 min 20

NS 5 min

NS 5 min

NS 5 min

NS5min

C = Clun. M = Masham. NS = No suckle in period shown. * 1 day = 18 to 36 h old. C = Uun. M = Masham. NS = No suckle in period shown. * 1 day = 18 to 36 h old.

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lambs 1.5 m in front of the mother who was physically restrained in a standing position facing her lambs. The time taken from release of the lambs until suckling started was recorded with a stopwatch. The test period was reduced to 2 min since in Experiment 1 a positive result had been obtained in that time.

Results

As shown in Table II, 5/6 lambs tested with a control blindfold reached the udder and suckled, whilst 7/7 lambs with the complete blindfold did not. Both the lambs of BL.423 when tested at 1 day old, sat inactive for 2 min. When the complete blindfold was remaved 4/4 of the lambs tested then suckled.

Again the difference in response of blindfolded lambs compared to those with an intact visual sense is significant (x2, 17.2; d.f., 1; P < 0.001).

TABLE II

Time to suckle in lambs wearing either a complete or control blindfold or no blindfold. (Blank square indicates no test given)

Ewe Lamb number, number breed

Time lamb was removed from ewe (min)

BL423 ‘z

BL429 ;

BL164 1

BL417 ;

BL423 ‘2

BL429 ;

BL426 1

BL438 1

60 60

60 60

250

60 60

195 195

235 235

285

165

Time from Time to suckle (set) birth to Lamb wearing test time -

No blind- Control Blindfold Blindfold fold blind- on, then

fold removed

1 day NS 2 min 1 day NS 2 min

1 day 40 1 day NS 2 min

1 day NS 2min 22

2 day 35 2 day NS 2 min

2 day NS 2 min 20 2 day 10

2 day 8 2 day NS 2min 45

2 day 20

2 day NS2min 16

BL = Border Leicester. NS = No suckle in period shown. lday =18to36hold. 2day -36to60hold.

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DISCUSSION

Stephens and Linzell (1974) report that the new-born goat kid makes random teat-seeking movements backwards and forwards along its mother’s flank. The kid shows no initial preference to move in one direction or the other and is not guided by the mother. Hence the neonate is equally success- ful in finding and suckling from an udder in the normal inguinal position or one grafted onto the neck of its mother. This pattern of teat-seeking is also shown by new-born lambs and there is slight evidence that at that stage blindfolding has no effect on teat location (Bareham, 1974).

A lamb less than 1 hour old, teat seeks in other areas of the mother’s flank before moving to the udder, even though by then it has usually suckled several times. With time, both the lamb (Bareham, 1974) and the kid (Stephens and Linzell, 1974) move direct to the udder and suckle without prior teat-seeking. The goat kid will move to the udder on the neck or in the inguinal region of the doe, depending on its previous preference. This suggests that within a few hours of birth the kid and lamb have learnt to discriminate the udder from other areas of the mother, a process reinforced by the milk reward.

At first sight, the present results implicate the importance of an intact visual sense in making this discrimination since non-blindfolded lambs moved direct to the udder and suckled whether starting in or out of physical contact with the mother. Generally the blindfolded twins did not suckle during the test period.

Other interpretations may be valid. It is suggested that individual recognition in groups of pigs depends on pheromones, with receptors on the face and jaws (Ewbank et al., 1974). It can be argued that just as the blindfold used in the pig work may have masked pheromone receptors, the complete blindfold used here may have had a similar effect, possibly blocking out stimulation from the inguinal glands on the ewe. The same may apply if the lamb responds to a temperature gradient, locating the udder which is warmer than other areas of the ewe’s flank.

However, these points whilst not invalidated appear less likely explanations when it is noted that lambs in Experiment 2 moved direct to the udder from out of contact with the ewe, and also in the observations by Stephens and Linzell (1974) goat kids moved direct to the udder transplanted to the mother’s neck. In this position the udder may be isolated from any possible pheromone producing areas.

Complete blindfolding may however have had other effects accounting for the lambs’ inability to suckle. It was noted that the balance of younger lambs was particularly affected and this led to a decrease in teat-seeking efforts. Lack of vision may also decrease levels of arousal and again lead to a decrease in teat-seeking effort, as is known to be the effect if lambs are held in a non- stimulator-y environment (Baron in Blauvelt, 1954; Alexander and Williams, 1966).

The other factor involved is the effect on the mother’s behaviour of blind-

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folding the lambs. Although in the new-born lamb the guiding and orienting responses of the ewe play an important part in ensuring suckling by the lamb, they are not crucial (Alexander and Williams, 1964). It is feasible that blind- folding makes the lamb a less active and hence a less attractive stimulus to the mother. She may not recognise it because of an interference with phero- mones to which she may respond or because of its altered visual appearance. Although in only one case a nursing was refused, the mother may give differ- ential help to her lambs depending on their appearance and vitality.

Apart from its theoretical interest, the present results, if the importance of the visual sense is confirmed, may enable provision of more adequate artificial rearing devices for lambs. (Stephens and Baldwin, 1971).

ACKNOWLEDGEMENTS

This research forms part of studies on the behavioural development of sheep and artificial rearing of lambs. I am grateful to the Council of the Universities Federation for Animal Welfare for a grant, to Professor Laing for giving facilities in his department, and to Dr N. Blurton-Jones for his critical advice.

REFERENCES

Alexander, G. and Williams, D., 1964. Maternal facilitation of the sucking drive in new- horn lambs. Science, 146: 655-656.

Alexander, G. and Williams, D., 1966. Teat-seeking activity of lambs in the first few hours of life. Anim. Behav., 14: 166-176.

Bareham, J.R., 1974. Studies on behavioural development in sheep. Thesis, University of London, unpublished.

Bareham, J.R., 1975. The behaviour of lambs on the first day after birth. Br. Vet. J., in press.

Blauvelt, H., 1954. Group processes. Trans. Conf. Josiah Macey Jr., Foundn. 1, 221-229. Ewbank, R., Meese, G.B. and Cox, J., 1974. Individual recognition and the dominance

hierarchy in the domestic pig. The role of sight. Anim. Behav., 22: 473-480. Siegel, S., 1956. Non-parametric statistics for the behavioural sciences. McGraw-Hill,

New York, N.Y., 312 pp. Stephens, D.B. and Baldwin, B.A., 1971. Observations on the behaviour of groups of

artificially reared lambs. Res. Vet. Sci., 12: 219-224. Stephens, D.B. and Linzell, J.L., 1974. The development of sucking behaviour in the goat.

Anim. Behav., 22: 626-633.