Fostering in sheep. IV. Use of restraint

Applied Animal Behaviour Science, 14 (1985) 355--364

355

Elsevier Science Publishers B.V., Amsterdam - - P r i n t e d in The Netherlands

FOSTERING IN SHEEP. IV. USE OF RESTRAINT

G. A L E X A N D E R and L.R. B R A D L E Y

CSIRO Division of Animal Production, Sydney (P.O. Box 239, Blacktown, N.S.W. 2148) (Australia) (Accepted for publication 27 February 1985)

ABSTRACT Alexander, G. and Bradley, L.R., 1985. Fostering in sheep. IV. Use of restraint. Appl. Anita. Behav. Sci., 14: 355--364. Fostering an additional lamb on to a ewe with a single lamb of her own was attempted in Dorset, Corriedale and Merino ewes restrained by the neck in pens for up to 12 days. Fostering occurred more rapidly in Dorsets than in Merinos, and success rates tended to be higher in Dorsets (81%) than the other breeds (73% in Corriedales and 69% in Merinos). The use of screens at the level of the ewe's neck to limit her olfactory examination of the lambs was more successful than when full olfactory contact was allowed. The prevention of any close olfactory contact resulted in an intermediate rate of acceptance, even though acceptance was apparently based on olfaction, as shown by universal rejection of strange alien lambs. Acceptance tests done within a few minutes of release from restraint were found not to reflect accurately the final level of acceptance, since some lambs came to be accepted within a day of being released. Further acceptances, that developed several days after release into a flock of ewes and lambs, emphasize an important role of the lamb in maintaining contact with the ewe. With few exceptions, lambs accepted when released from the pens were still accepted after a week or so in the flock. Dorset ewes given one or two foster lambs in the absence of their own lamb accepted the fosters within 9 days. Restraint fostering had no apparent harmful effects on the ewes or lambs, but had the disadvantages of being laborious and of soiling the ewes' wool. It has the advantage of providing lambs with an assured milk supply, and could prove useful for ewes that have failed to accept lambs under other methods.

INTRODUCTION

Fostering is useful in practical sheep husbandry and in research into lactation and lamb growth (Langlands, 1972; Doney et al., 1981}, but since ewes can distinguish their own lambs from aliens within a few hours of birth, and suckle their own lambs exclusively, foster lambs are not readily accepted (Alexander et al., 1985). Numerous fostering techniques are in use in practical farming (Lamond, 1949), b u t there are few scientific reports on their short- or long-term effectiveness, or on the principles on

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356

which they are based. This paper deals with a study that examined the principles and permanence of restraint fostering. Farmers have long realized that close confinement, sometimes coupled with the use of a halter and leg rope, may lead a lactating ewe to accept a foster lamb if the confinement and restraint are continued for days or even weeks (Close, 1979). Collias (1956} recorded that locking a ewe with twins into a " s t a n c h i o n " resulted in the rejected twin being accepted after some days. In a more controlled, laboratory situation, Hersher et al. (1963) successfully fostered lambs or kids on to ewes by harnessing the ewe to a stanchion within 12 h of parturition, to prevent the young being driven from the udder; success was invariably achieved within 30 days. Today, restraining pens, variously known as " m o t h e r i n g " , "fostering" or "twinning" crates or pens, or as "grafting stanchions", are widely used in the British Isles and North America and more rec.ently in New Zealand. They are available commercially, but published data on their use and application are limited (Wallace et al., 1979; Hulet et al., 1979). Restraint fostering, in its conventional commercial form, consists of restraining the ewe by the neck between a pair of vertical bars (stanchion) that are too close to allow the ewe to withdraw her head (Fig. 1), but (a)

Ib)

"SCREENS~

"PLASTIC COLLAR.

PLAN VIEW

(c) .

.

.

NO SCREENS"

ISOOmm u...o.i

I.

1000mm ......

1

J Weldmesh pen

Choin

/

Collar

Steel posts

FRONT

EVELATION

mm

Fig. 1. P e n c o n f i g u r a t i o n s t h a t p r o v i d e d varying degrees o f visual a n d o l f a c t o r y c o n t a c t . S c r e e n s (a) allowed a small degree o f c o n t a c t via t h e n e c k space; screens plus collars ( b ) p r e v e n t e d a n y visual c o n t a c t or close o l f a c t o r y c o n t a c t ; p e n s w i t h o u t screens or collars (c) allowed a l m o s t n o r m a l c o n t a c t . T h e sides o f t h e p e n s were s c r e e n e d w i t h hessian.

357

permit her to stand up or lie down. The fostering pen is divided into two sections by vertical screens, placed at the level of the ewe's neck (Fig. 1), with the apparent purpose of restricting her visual or olfactory investigation of the lambs (Hulet et al., 1979), but some investigation of the lambs may occur through the neck space, and some lambs pass to and fro through this space. The present study examined the efficacy of this procedure in each of three breeds of sheep given a foster lamb in addition to their own lamb. The effectiveness of the conventional configuration was also compared with one that provided much freer olfactory and visual contact between the ewe and the lambs, and another that completely eliminated the possibility of visual or close olfactory investigation o f the lamb by the ewe. The main study was concerned with additive fostering, i.e. fostering an additional lamb on to a ewe with a lamb of her own, but substitutive fostering was also attempted. METHODS

Sheep Additive fostering was done with aged multiparous Dorsets, Corriedales and Merinos that lambed in September, October and November, respectively, on pasture, and that were supplemented with oat grain and lucerne hay. They were brought into the fostering pens 24--72 h after parturition; 18 had produced multiples and 34 had produced singles. Substitutive fostering was confined to another 15 Dorsets.

Fostering pens Restraint within the 1.5 X 1 m pens was provided by two steel posts, 100 mm apart, driven into the earth floor to leave 920 m m exposed (Fig. 1). Ewes were lifted into position and the 100 mm X 900 mm neck space was closed at the top with a chain. Hessian attached to the wire-mesh wall prevented ewes from seeing lambs in adjacent pens. Water was provided in a bucket, and approximately 750 g oat grain and 1 kg lucerne hay were placed in front of the ewe daily. In the conventional pens (Fig. la), a vertical screen extended from each steel post to the side o f the pen, leaving the neck space open except for the portion occupied by the ewe's neck. In one variation of this configuration, no screens were used (Fig. lc), but in the other, screens were used and flexible polyethylene sheets, in the form of a flattened tube 350 m m wide and 500 mm high, were placed over the restraining posts concertinafashion, one below and one above t h e neck o f the ewe (Fig. lb). These were attached at the top and b o t t o m o f the posts and to a collar round the ewe's neck to ensure that the neck space remained closed when the

358 ewe stood up or lay down. Ewes were allotted to the three pen-types at random, and remained in the pens at least 9 days (9--12 days depending on the fall of week-ends). Straw bedding was provided in the pens, and soiled straw and manure were removed daily.

Foster lambs Foster lambs of the same breed as the ewe were used. They ranged from 1 to 6 days old when presented to the foster ewes, together with one of the ewe's own offspring (1--4 days old). However, with some Dorsets, one or two foster lamb(s) were presented in the absence of the ewe's own lamb. All foster lambs had previously been suckled by their own mothers.

Tests o f acceptance and release from the pens Acceptance tests were made at intervals of approximately 3 days. The lambs were removed from the fostering pens 2--3 h before the tests and the ewe was released about 15 min before testing. Tests were usually made in a 1-m wide passage-way in which the ewe's own lamb, the foster lamb and another alien lamb were presented to the ewe individually in random order. If the ewe's own lamb and the foster lamb were accepted separately, then they were also tested together, and any lambs that were allowed to suck only if the "foster-twin" was also sucking were recorded as merely tolerated. Lambs were regarded as being accepted if they were allowed to suck unhindered by the ewe moving. Ewes and their lambs were released into a 1-ha paddock containing other ewes and lambs after a nominal period of 9 days (9--12 days) in restraint, or earlier if both lambs were fully accepted at a nominal 3 (3--4) or 6 (5--7) days after fostering began. However, many ewes were first released with their lambs into a 10 × 10 m enclosure, and were re-tested on the following morning before being released into the paddock. Each ewe was re-tested in a 5 X 5 m enclosure 3--10 days later. Lambs were weighed daily during fostering and at the time of the later tests.

Statistical comparisons Fisher's exact test was used in all non-parametric comparisons; weight changes were compared by conventional t-test. RESULTS

Additive fostering Acceptance after the various periods o f restraint The proportion of ewes fully accepting both their own lamb and the

359 DORSET Screens (n:?)

SF

Plastic collars (n=71

CORRIEOALE

(.=5,

MERINO

5

(n=5)

(n=6)

(n--S)

~s

d

No screens (n=7}

3

6

9

Later

3 6 9 Later DAYS FROM START OF RESTRAINT

3

6

9

Later

DOWN LAMB ~FOSTER ~BOTHLAMBS

Fig. 2. Cumulative numbers of lambs accepted by ewes of three breeds after various nominal periods of restraint in pens that restricted olfactory and visual contact with lambs to varying degrees (Fig. 1) (note that vertical scales differ). The number of lambs still accepted by ewes after a further 3--10 days in a flock of ewes and lambs is also shown. The number of lambs known to have been accepted within 24 h of release, following 9 days of restraint, is indicated by the portion of the columns labelled "L". The number of lambs only partially accepted is likewise indicated by "P". Reversals from full acceptance to partial acceptance or rejection are indicated by " t " in the column for the time of full acceptance. f o s t e r lamb s h o w e d a general increase with the p e r i o d o f restraint (Fig. 2). With b r e e d and t r e a t m e n t p o o l e d , the p r o p o r t i o n o f ewes accepting b o t h lambs was 1 3 / 5 2 b y D a y 3, 1 9 / 5 2 b y Day 6 and 2 4 / 5 2 b y Day 9 ( 1 3 / 5 2 v. 2 4 / 5 2 , P = 0.04). A n o t h e r 10 ewes a c c e p t e d b o t h lambs w i t h i n 3 - - 1 0 days o f release into t h e flock. Seven o f these were k n o w n to have a c c e p t e d t h e lambs w i t h i n 24 h o f release f r o m restraint. T h r o u g h o u t , the n u m b e r o f lambs a c c e p t e d b y ewes t e n d e d to increase with time, and in o n l y five ewes was full a c c e p t a n c e at some stage replaced b y partial acc e p t a n c e or r e j e c t i o n o f o n e o r b o t h lambs (Table I, Fig. 2). E x c e p t f o r 3 D o r s e t s (Table I) f r o m t h e no-screens t r e a t m e n t , all ewes a c c e p t i n g b o t h lambs at the t i m e o f release, still fully a c c e p t e d t h e m w h e n tested a f t e r being in t h e flock. T h u s at the final test, 3 1 ( = 2 4 + 10 - 3) o f the 52 ewes still fully acc e p t e d b o t h lambs. In addition, partial a c c e p t a n c e or t o l e r a n c e o f b o t h lambs, or full a c c e p t a n c e o f o n e lamb b u t o n l y partial a c c e p t a n c e o r tolerance o f the o t h e r , was s h o w n b y t w o Dorsets, t w o Corriedales and f o u r Merinos at t h e final test a f t e r being in the flock (Fig. 2). Only 25% o f ewes r e j e c t e d o n e lamb (9 ewes) or b o t h lambs (4 ewes). No ewe a c c e p t e d a f o s t e r lamb and r e j e c t e d her o w n lamb. N o ewe fully a c c e p t e d a strange, alien lamb at the t i m e o f a c c e p t i n g b o t h h e r o w n and t h e f o s t e r lamb. H o w e v e r , t w o D o r s e t ewes w i t h collars,

360 TABLE I R e s u l t s f r o m t h e five ewes s h o w i n g reversals o f a c c e p t a n c e ~ Breed

Pen

No. o f

configuration

ewes

Results o f t h e v a r i o u s t e s t s "3" days

"6" days

"9" days

"9"+1 days

Ex-flock 3--10 days later

O

O

O

O

O

F

F

F

Dorset

No screens

3

Tol Acc Acc Rej Acc Rej

Rej Rej Acc Acc A c c Rej

Acc Rej

Corriedale

Screens No screens

1 1

Acc Rej Acc Rej

Rej Rej

Rej Rej

Rej Rej

F

Acc A c c

Rej Rej

Acc A c c

F

Tol Acc A c c Rej Acc Tol Acc A c c Acc Rej

i O = O w n l a m b ; F = f o s t e r l a m b ; A c c = e w e a c c e p t s l a m b ; Rej = e w e r e j e c t s l a m b ; Tol = e w e tolerates lamb in presence of " c o - t w i n " .

and one with screens, partially accepted an alien lamb in addition to accepting own and foster. Acceptance rates were similar in single- and twin-bearing ewes, both within breeds and in the pooled data (20/34 v. 11/18). Most lambs sucked in the normal, so called "inverse parallel", position (Poindron, 1976), but in the Dorsets with screens, one accepted foster lamb sucked in the posterior position, and in the Merinos with collars, one ewe rejected both at 9 days, but freely allowed them to suck from the posterior position at the final test. In the pens with screens, lambs were occasionally seen in front of the screens, but whether they were own or foster lambs was not recorded.

Acceptance o f own lamb In all treatments within each breed, some ewes failed to accept fully their own previously accepted lamb even when tested after only 3--4 days of restraint (Fig. 2). This was more marked amongst ewes with collars than those with screens (13/17 v. 6/18, P = 0.018) or amongst ewes with neither screens nor collars (13/17 v. 3/17, P = 0.0016). However, the proportion of own lambs re-accepted by ewes with collars, and by ewes with screens, increased with successive tests, so t h a t by the final test no more than one ewe in any group still rejected its own lamb (Fig. 2). Breed comparison In the pooled results for the treatments, 15/21 Dorsets, 9/15 Corriedales and 7/16 Merinos fully accepted both lambs at the final test, but these differences were not statistically significant (Dorsets v. Corriedales, P -0.50; Dorsets v. Merinos, P = 0.11). The same trends were seen at 3 days; both lambs were fully accepted by 10/21 Dorsets, 3/15 Corriedales and 0/16 Merinos (Dorsets v. Corriedales, P = 0.6; Dorsets v. Merinos, P = 0.0017).

361

Effects of treatments In the pooled results for the breeds, 15/18 ewes from the foster pens with screens fully accepted both lambs in the final test, compared with 10/17 ewes from pens with screens and collars (15/18 v. 10/17, P = 0.15) and 6/17 ewes from pens with neither screens nor collars (15/18 v. 6/17, P = O.OO59).

Substitutive fostering All five Dorsets given two foster lambs and all 10 given a single foster in the absence of the ewe's own lamb came to fully accept the foster lambs before the final test. Eight of the 15 ewes had accepted the lambs within 5--7 days of being confined, another three accepted the lambs within 24 h of release, and the remaining four accepted the lambs during the period in the flock.

Well-being of animals Most ewes struggled or lay down when first restrained, but appeared to habituate to restraint rapidly. All appeared to eat normally within 24--48 h. There were no injuries during the restraint, but the flanks and udders of ewes in pens with screens, or screens and collars, tended to become soiled and moist from the ewe lying in excreta. Two lambs in pens with collars died, apparently from the effects of being lain upon; consequently their mothers were removed from the trial. Almost all lambs gained weight steadily while in the fostering pens (Table II). T A B L E II Weight changes o f l a m b s in the f l o c k according t o degxee of a c c e p t a n c e

Breed

Both a c c e p t e d Foster 0.20 -+0.04

0.25 -+0.06 5

0.13

0.18 -+0.02

0.35 -+0.03 3

-0.22

0.06 -+0.03

0.21 +0.04 8

0.06

Mean -+ SEM ( k g / d a y ) n

0.22 -+0.04

Corriedale

Mean +- SEM ( k g / d a y ) n

0.20 -+0.02

Merino

Mean + SEM ( k g / d a y ) n

0.11 -+0.02

Mean + SEM ( k g / d a y ) n

Only o w n accepted

Own Dorset

Pooled

Tolerated lambs I Rejected l a m b s 1

Accepted lambs

15

9

6

1 (1)

2 (0)

6 (2) 0 . 0 8 3 P ~ 0.01 -+0.039 9

-0.05 3 (0) -0.11 3 (0) -0.11 4 (0) -0.093 +0.023 10

i T h e n u m b e r o f o w n l a m b s i n c l u d e d is s h o w n in parentheses; t h e r e m a i n d e r w e r e f o s t e r l a m b s .

362

Only four foster lambs failed to suck the foster mother during the first 24 h or so. These lambs were given 300 ml of a milk formula by stomacht u b e daily for 1--3 days until they were observed to be gaining weight. Although soiled with the ewes' excreta, lambs showed no ill-effects from confinement, b u t showed a high level of running, jumping and playing behaviour when first released from the pens. Accepted lambs continued to gain weight while in the field prior to the final acceptance test (Table II). The weight of lambs rejected at the final test usually declined during the period in the field, while partially-accepted lambs usually gained a little weight (Table II); this difference was significant in the pooled data (P < 0.01). DISCUSSION

The results show that a proportion of ewes restrained by the neck from 1--4 days post-partum for up to 9--12 days will come to accept a foster lamb, up to 6 days old, in addition to their own. This result conforms with other limited data on the m e t h o d (Hulet et al., 1979; Wallace et al., 1979), but in the present study screens were clearly advantageous (83% acceptance with screens, 35% without screens) which is in discord with the findings of Hulet et al. (1979). Whether all ewes could be induced to accept foster lambs by restraint b e y o n d 9--12 days is not clear from these several studies. The success rate showed some evidence of being breed-dependent, as already reported for other fostering methods (Alexander et al., 1985). Dorsets tended to be superior to Corriedales and Merinos in the proportion accepted and in the speed and completeness of acceptance. However, these aspects require further study in the absence of any confounding influences, such as differing previous history of the breeds. Breed differences could account for the conflicting evidence a b o u t the use of screens. Breeds that foster easily might n o t require limitation of olfactory and/or visual contact by the use of screens. In the present study, the o p p o r t u n i t y for full olfactory or visual contact, in the absence of screens, appeared to p r o m o t e continued full acceptance of o w n lamb and hence to prejudice acceptance of foster lambs, especially in Corriedales and Merinos, breeds that do n o t foster readily (Alexander et al., 1985). It is not clear w h y three ewes rejected their o w n lambs under this treatment, but frequent olfactory examination of lambs could be limited by the difficulty of the restrained ewe turning her head to sniff sucking lambs under the tail, as is c o m m o n in unrestrained ewes. It is also unclear w h y some ewes, deprived by means of collars of any opportunity for close olfactory examination of the lambs, came to accept lambs including their own. Most of these ewes appeared to forget the odour of their own lamb within 3--4 days of restraint and olfactory deprivation, b u t thereafter acceptance of o w n lamb increased progressively while acceptance of the foster increased more slowly. Since no ewe accepted a

363

foster w i t h o u t also accepting her own, acceptance of o w n was clearly a prerequisite for acceptance of foster lambs under additive fostering. The acceptance of foster lambs by ewes was n o t due to indiscriminate acceptance of lambs, because almost all of these ewes rejected other alien lambs. The acceptance of foster lambs therefore appears to be based on olfaction, and could be due to own and foster lambs developing c o m m o n odours through enforced close association and close contact with the ewe and her excretions, as Hulet et al. (1979) have suggested. The influence of c o m m o n odours in facilitating fostering has already been observed in studies on fostering by the use of odorants (Alexander and Stevens, 1985a), and maternal labelling of kids has been reported for goats (Gubernick, 1981). The increase in acceptance of lambs within 24 h of release from the fostering pens, and the erratic results shown by a few ewes, raise questions about the significance of acceptance behaviour when the ewe has been released for only 15 min or so and is confronted by the lambs for the first time after several days of confinement. Hulet et al. (1979) suggested that a trial period of 1 day may be necessary for the relationship to stabilize. The increase in acceptance that occurred during the period in the flock is likely to have been the result of continued close association between the ewe and rejected, or merely tolerated, lambs. This emphasises the important role of the lamb in maintaining contact with the ewe, either directly or via bonding with the foster twin, and conforms with the weight gains in the field shown by lambs that were not fully accepted. Restraint-fostering has the disadvantages of being laborious and of soiling the ewe's wool, but it could prove useful with ewes for which other methods of additive or substitutive fostering (Alexander and Stevens, 1985a,b) have failed. It also has the advantage that lambs are provided with an assured supply of milk during the fostering process. ACKNOWLEDGEMENTS

The study was made possible by the ready cooperation of Bill Dwyer of CSIRO, St. Mary's Field Station, who managed the flock. Denise Stevens o f CSIRO provided valuable help at week-ends.

REFERENCES Alexander, G. and Stevens, D., 1985a. Fostering in sheep. III. Facilitation by the use of odorants. Appl. Anita. Behav. Sci., 14: in p r e s s . Alexander, G. and Stevens, D., 1985b. Fostering in sheep. II. Use of hessian coats to foster an additional lamb on t o e w e s with single lambs. Appl. Anita. Behav. Sci., 14: in press. Alexander, G., Stevens, D. and Bradley, L.R., 1985. Fostering in sheep. I. Facilitation by use of textile lamb coats. Appl. Anim. Behav. Sci., 14: in press.

364 Close, W.L., 1979. Lambing time - - hints on fostering. Australian Poll Dorset Journal, March--June, p. 38. Collias, N.E., 1956. The analysis of socialization in sheep and goats. Ecology, 37: 228-239. Doney, J.M., Peart, J.N. and Smith, W.F., 1981. The effect of interaction of ewe and lamb genotype in milk production of ewes and on growth of lambs to weaning. Anita. Prod., 33: 137--142. Gubernick, D.J., 1981. Parent and infant attachment in mammals. In: D.J. Gubernick and P.H. Klopfer (Editors), Parental Care in Mammals. Plenum Press, New York, pp. 243--305. Hersher, G., Richmond, J.B. and Moore, A.U., 1963. Modifiability of the critical period for the development of maternal behaviour in sheep and goats. Behaviour, 2 0 : 3 1 1 --320. Hulet, C.V., Dahman, J.J., Shupe, W.L. and Duren, E., 1979. How to Graft Lambs. University of Idaho, College of Agriculture, Current Information Series, No. 269. Lamond, H.G., 1949. Mothering a lamb. Sheep Goat Raiser, San Angelo, TX, 29(9): 36--38. Langlands, J.P., 1972. Growth and herbage consumption of grazing Merino and Border Leicester lambs reared by their mothers, or fostered by ewes of other breeds. Anim. Prod., 14: 317--322. Poindron, P., 1976. Mother--young relationships in intact or anosmic ewes at the time of suckling. Biol. Behav., 2: 161--177. Wallace, M.H., Lewis, J.M. and Hinds, F.C., 1979. Adopting extra lambs on extra udders. Shepherd, 24(12): 16--17.