D. Stevens

Separation of ewes from twin lambs: Incidence in several sheep breeds

Abstract The ability of ewes and their lambs to keep together during the first day or two of life, when the mother—offspring bond is consolidating, was examined in fine-wool Merino, Dorset Horn and Crossbred (Border Leicester × Merino ewes mated to a Suffolk ram) sheep, lambing on a sparse pasture in the Armidale district of N.S.W., and in a Romney flock, lambing on good pasture in the Mangakino district of New Zealand. Ewes in the N.Z. flock had been selected for their ability to rear more than one lamb. 46% of the twin-bearing Merinos became permanently separated from a lamb, mostly on the day after giving birth, and in at least 54% of these cases these was no obvious precipitating factor such as birth difficulties or interference by other sheep. In addition, a further 34% of twin-bearing Merinos experienced temporary separation from one lamb. By contrast, in the other flocks, permanent separations were 17, 0 and 8%, respectively, and some precipitating factor could always be identified. Few separations were associated with human interference. The sheep at Armidale moved from the birth-site much more rapidly than the Romneys (means of 2 h versus 6.5 h), possibly due to sparse pasture conditions. In the Merinos, the proportion of separations decreased as the time that ewes remained near the birth-site increased. The observations indicate that fine-wool Merino ewes are slow to recognize the size of their litters and inherently poor at maintaining contact with more than one lamb in the neonatal period.

Lamb mortality due to inadequate care of twins by Merino ewes

Abstract One hundred and three fine-woolled Merino ewes and their twin lambs in four 12-ha paddocks, carrying 12.5 sheep per ha, were observed during daylight for 2–4 days immediately following parturition. Fifty-one ewes became permanently separated from one twin due to the ewe moving and leaving the lamb behind, mostly on the day of birth; the ewes appeared unconcerned if followed by only one lamb. Only two ewes became separated from both lambs. Human interference appeared to play only a minor role in these separations. Low vigour of one twin, as assessed within several hours of birth, usually resulted in its early separation from the ewe, but more than half of the lambs separated from the ewes were vigorous and mobile. Regardless of separation, all lambs of low vigour died. In this flock, the inability of the ewes to keep twins together, and maintain contact with both, contributed largely to the higher mortality in the twin lambs than in singles in the same birth-weight ranges; overall, 37.4% of twins died compared with 9.6% of singles. These figures indicate there could be a problem of high mortality in twin lambs from fine-wool Merino flocks under commercial conditions where lambing takes place in paddocks that are usually well in excess of 12 ha.

Recognition of washed lambs by Merino ewes

Abstract Ewes in six groups each of 12, that had been separated from their 2- to 8-day-old lambs for several hours, were individually presented with a choice between their own and two alien lambs. Each lamb was in a separate cage contiguous with a passageway in which the ewe was free to move. Ewes, with lambs anaesthetized to remove auditory cues and reduce visual cues to recognition, mostly chose their own lamb, whether it was dry or sprayed with a detergent solution, but in groups in which lambs had been scrubbed in the detergent solution, few ewes chose correctly. Thus, scrubbing appeared to reduce or remove the olfactory cues. By contrast, ewes in a group with scrubbed lambs that were not anaesthetized almost all correctly selected their own lambs. However, when these lambs were given access to the ewes and attempted to suck, 6 of the 12 were actively but temporarily repelled by their own mothers, and one was permanently prevented from sucking. It seems that ewes can recognize their lambs from auditory and visual cues alone, but that the correct olfactory cues are required for sucking to be permitted; only 2 of 12 ewes allowed one or two scrubbed alien lambs to suck. This unwillingness to suckle in the absence of olfactory cues contrasts with the indiscriminate suckling reported to occur in ewes made anosmic before lambing. Ewes with 4-week-old lambs likewise correctly chose their own scrubbed, conscious lambs, but only 1 of the 12 temporarily prevented the lamb from suckling. Thus, the importance of olfactory cues in maternal acceptance appears to decline with increasing age of the lamb. The odour of lambs does not appear to be closely associated with the smell of the faeces because ewes in another group displayed little or no interest in a scrubbed alien lamb which had been smeared with fresh faeces from the ewes own lamb. Nevertheless, ewes appear to be more interested in the tail-region than in the head-region of lambs. It is concluded that attempts to foster lambs through elimination of olfactory cues by scrubbing lambs are unlikely to be successful.

Do MERINO EWES SEEK ISOLATION OR SHELTER AT LAMBING

Abstract Fine-wool Merino ewes, lambing in four adjacent 12-ha paddocks, were observed between 09.00 and 16.00 h daily for 18 days. Ewes in two of the paddocks had recently been shorn; ewes in the other two were unshorn. There were small areas of contrived shelter in two paddocks and the sites at which ewes lambed were recorded in relation to the shelters and to the position of other sheep. About 90% of ewes appeared to lamb at the site where the flock was grazing or resting at the time labour started; only 2% appeared to move from the flock when labour commenced, and a maximum of about 9% could have left the flock deliberately prior to the onset of obvious labour. The use of shelter for lambing closely reflected the preference of the flock for shelter; there was no evidence that ewes sought shelter in which to lamb.

Importance of the first hour post-partum for exclusive maternal bonding in sheep

Abstract Newborn lambs wet with amniotic fluid or partly dried were confined to double wire cages that prevented grooming or suckling, and were placed in a pen with their mothers at 0 or 1 h post-partum. At 12 h post-partum, the lambs were released and each ewes behaviour towards her own lamb and various classes of alien lambs, presented separately, was examined. More ewes accepted their own lamb and rejected a 12-h-old alien when the period of separation was 0 h than when it was 1 h. Also, more ewes that were exposed to a wet lamb as opposed to a partly dried lamb at the time of caging remained maternal and were able to discriminate between their own and alien lambs. More ewes accepted 12-h-old aliens than 24–60-h-old aliens. The findings emphasize the importance of the first hour after birth in the development of discriminatory maternal behaviour, and suggest that odour associated with amniotic fluid plays a role in this process and in the maintenance of maternal behaviour.

WASHING LAMBS AND CONFINEMENT AS AIDS TO FOSTERING

ABSTRACT Alexander, G., Stevens, D. and Bradley, L.R., 1983. Washing lambs and confinement as aids to fostering. Appl. Anim. Ethol., 10: 251–261. The effects on maternal behaviour, of washing lambs and of confining ewes with alien lambs for several days, were examined in groups of Merino ewes that had lambed approximately 1, 3, 9 or 27 days previously. In the 1-, 3- and 9-day groups, 25–43% of ewes refused to allow their own washed lambs to suck and 7–47% permitted a washed alien to suck, though most were able to distinguish their own washed lamb from 2 washed aliens in a multiple choice test. In the 27-day group, all ewes permitted only their own washed lamb to suck. Similar results were obtained in the 4 age groups with the same lambs when only the hind half was washed, indicating that odour from this region is responsible for releasing suckling behaviour. When ewes were penned together with washed alien lambs for at least 2 days, 73–100% of lambs in the 1-, 3- and 9-day groups either gained weight progressively or were seen to suck freely from the foster mother, while only 33% of lambs in the 27-day group were similarly accepted. With unwashed lambs, the acceptance rate was approximately half that of washed lambs. Labelling the alien lamb with wool from the tail region of the foster ewes own lamb also tended to facilitate fostering, but not to any marked extent. Where the ewes own lamb was also present in the flock after fostering, foster ewes tended to revert to suckling their own lamb at the expense of the foster lamb, especially in the 9- and 27-day groups. The use of washing coupled with close confinement appears to be an effective method of fostering lambs on to ewes, especially within the first day or two after birth. Fifty-five % of ewes in the 1- and 3-day groups failed to accept their own unwashed lamb after being separated from it for only 40–48 h, indicating that the ewes memory for lamb odour is transient and/or that the odour changes with time.

Washing lambs and confinement as aids to fostering

Abstract The effects on maternal behaviour, of washing lambs and of confining ewes with alien lambs for several days, were examined in groups of Merino ewes that had lambed approximately 1, 3, 9 or 27 days previously. In the 1-, 3- and 9-day groups, 25–43% of ewes refused to allow their own washed lambs to suck and 7–47% permitted a washed alien to suck, though most were able to distinguish their own washed lamb from 2 washed aliens in a multiple choice test. In the 27-day group, all ewes permitted only their own washed lamb to suck. Similar results were obtained in the 4 age groups with the same lambs when only the hind half was washed, indicating that odour from this region is responsible for releasing suckling behaviour. When ewes were penned together with washed alien lambs for at least 2 days, 73–100% of lambs in the 1-, 3- and 9-day groups either gained weight progressively or were seen to suck freely from the foster mother, while only 33% of lambs in the 27-day group were similary accepted. With unwashed lambs, the acceptance rate was approximately half that of washed lambs. Labelling the alien lamb with wool from the tail region of the foster ewes own lamb also tended to facilitate fostering, but not to any marked extent. Where the ewes own lamb was also present in the flock after fostering, foster ewes tended to revert to suckling their own lamb at the expense of the foster lamb, especially in the 9- and 27-day groups. The use of washing coupled with close confinement appears to be an effective method of fostering lambs on to ewes, especially within the first day or two after birth. Fifty-five % of ewes in the 1- and 3-day groups failed to accept their own unwashed lamb after being separated from it for only 40–48 h, indicating that the ewes memory for lamb odour is transient and/or that the odour changes with time.

Fostering in sheep. I. Facilitation by use of textile lamb coats

Abstract Transfer of odour between lambs less than 1 week old was attempted by the use of rectangular coats of hessian (a jute textile) worn for 24 h by a ewes own lamb and then transferred to a potential foster lamb. In the absence of their own lamb, 50–60% of ewes accepted the foster lamb immediately and more than 90% accepted the foster after confinement together over the next 2 days. Without exchange of coats, 12% of ewes accepted alien lambs immediately, and 50% after confinement. Breed differences in the success of fostering were observed, and a higher proportion of primiparas than multiparas accepted foster lambs. Foster lambs of similar appearance to the ewes own lamb were more readily accepted than lambs of different appearance, and lambs 1–2 days old were more readily accepted than older lambs. There was a low level of success with fostering several weeks after lambing. Ewes that had accepted a foster lamb and then had their own lamb returned within 24 h of fostering initially tended to favour their own lamb. The success of the fostering method used in these studies appears to depend on both transfer and masking of lamb odour. The method should prove useful as an experimental tool, and as a practical means of saving lambs.

FOSTERING IN SHEEP. II. USE OF HESSIAN COATS TO FOSTER AN ADDITIONAL LAMB ON TO EWES WITH SINGLE LAMBS

Abstract Hessian coats were used to induce ewes to accept a foster lamb in addition to their own lamb. The study involved 39 multiparous Merino ewes and their lambs and 38 Merino lambs from other ewes. When lambs were 2–3 days old, a coat worn by the ewes own lamb for 24 h was placed on the foster lamb at the time of introduction to the foster ewe. The ewes own lamb was either left coat-less with its mother, or treated in one of several ways to prejudice its maternal acceptance. During the following 2 days, the rate of acceptance of foster lambs declined rapidly if the ewes own lamb was returned coat-less. Highest success rates ( 7 9 ) were achieved where the ewes own lamb wore the coat of the foster lamb. Removal of the ewes own lamb for 24 h, without feeding, from the time of introduction of the foster resulted in a high acceptance rate of the foster lamb but a high rejection rate of own lamb, especially if it had been disguised by a new coat, by washing in a small volume of detergent solution or by smearing with neatsfoot oil. Additional coat exchanges after 48 h restored acceptance of previously separated own lambs without obvious prejudice to acceptance of the foster lamb, so that many ewes now accepted both lambs. However, this intervention had little effect on acceptance of previously rejected foster lambs. In a control group in which no coats were used and own lamb was removed for 24 h, none of the 6 ewes accepted both lambs within 2 days. The method, using exchange of coats between the ewes own lamb and the foster lamb, coupled with temporary removal of the ewes own lamb, should have widespread application for additive fostering in sheep.

Fostering in sheep. III. Facilitation by the use of odorants

Abstract Lambs were thoroughly anointed with various odoriferous substances to test the facilitatory effects on substitutive fostering on to multiparous Merino ewes held in individual pens. The ewes were first familiarised with an odorant by anointing their own lamb with it 24 h before a similarly anointed foster lamb was presented. The odorants were neatsfoot oil, wool wax, vegetable oil, butyric and propionic acids, mercaptoethanol, vanillin, methyl salicylate and eucalyptus oil. Acceptance of foster lambs was assessed over the next 48 h. Odorants were not applied to the ewes. All eight foster lambs treated with neatsfoot oil were accepted within 24 h; seven immediately. There were few immediate acceptances with the other odorants, but from two to five lambs out of groups of six were permanently fostered by 48 h. Only one foster lamb was accepted in the control group of 12 in which no odorant was used. Fostering was most successful with neatsfoot oil and wool wax, both substances that originated from ruminant skin. Fostering was less successful in tests that omitted pre-exposure of the ewes to their own lambs treated with neatsfoot oil, wool wax or vegetable oil. Toxicity problems were encountered with ethanol solutions of mercaptoethanol, methyl salicylate, eucalyptus oil and neatsfoot oil.