Alien Lambs Research Articles

Use of birth fluids and cervical stimulation in lamb fostering.

Jackets soaked in birth fluids (BF) and cervical stimulation (CS) were used in a 2 X 2 factorial arrangement of treatments to determine their usefulness in fostering lambs. Subjects were 39, 3-d-old to 14-d-old lambs to be adopted by 39, 2-d to 7-d postpartum ewes rearing their own single lambs. Birth fluids were collected by drying newborn lambs with cloth jackets. Jackets were frozen for storage and were later thawed and placed on experimental alien lambs. Cervical stimulation was applied by attempting to insert a hand into the cervix of the ewe for 5 min immediately before presentation of an alien lamb. Maternal behavior tests, in both the absence and presence of the ewe's own lamb, were conducted twice daily in a small pen for 2.5 d. On d 3 and 4, lambs were tested in a large pen with three to four other ewes and their lambs. Aggression toward the alien lamb was greater during the first exposure in all treatments. Avoidance and nosing behaviors toward aliens were significantly less, and alien lambs were able to suckle more, when the ewe's own lamb was also present. Lambs receiving BF suckled more and were accepted more often. Cervical stimulation, in the absence of BF, improved acceptance compared with controls. The proportion of ewes accepting alien lambs were 100, 80, 60 and 10% for BF, BF-CS, CS and control treatments, respectively. Alien lambs that were accepted had similar growth rates to weaning as the ewe's own lamb. We conclude that fostering is facilitated by use of jackets soaked in BF and by CS.

Fostering lambs by odor transfer: the add-on experiment.

Lamb-specific odor is used by ewes to discriminate between their own and alien offspring. Recent studies have demonstrated that fostering can be facilitated by transferring own-lamb odor to alien lambs via cloth stockinettes. The objective of the present study was to investigate the effectiveness of the odor-transfer technique in enticing ewes with a single lamb to adopt an additional lamb ("add-on" procedure). Shortly after birth, nylon stockinettes were placed on the single offspring of 49 ewes and 49 additional alien lambs designated for fostering. Approximately 20 h following parturition, stockinettes were removed from 41 natural lambs and placed on alien lambs (experimental treatment). In the control treatment (eight ewes) own and alien lambs retained their own stockinettes. Four acceptance tests were conducted, 24 h apart, starting at the onset of fostering. Successful adoptions were attained for 21 of 31 experimental ewes (68%) exposed to add-on lambs similar in facial coloration to their own lambs. Only 2 of 10 experimental ewes (20%) with whiteface natural lambs adopted blackface add-on lambs. One of eight control ewes (12.5%) adopted an add-on lamb. Of the 24 ewes that adopted alien lambs 10 (41.7%) demonstrated immediate acceptance and 20 (83.3%) had adopted lambs by the second test day. A higher proportion of primiparous than multiparous ewes adopted alien lambs. The presence of own-lamb odor on stockinettes worn by add-on lambs appears to facilitate fostering. However, the presence of own-lamb odor may not be a significant-enough cue to override obvious differences in facial coloration between own and add-on lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Fostering in sheep. V. use of unguents to foster an additional lamb onto a ewe with a single lamb

This paper reports two studies in which lambs were liberally coated with oily materials (unguents) in an effort to induce ewes to accept alien lambs. In both studies ewes were left with their own treated lamb for 22 h, and those that rejected a similarly treated alien lamb at this stage were left with the alien for a further 18 h. Ewes accepting an alien lamb were left with their own and the alien in an attempt at additive fostering. In the first study, washing alien lambs prior to unction hastened their acceptance but did not increase the final proportion accepted. The acceptance rate was similar for Merino, Dorset and Corriedale ewes. Neatsfoot oil was superior to wool wax, vegetable oil and white soft paraffin in inducing acceptance of aliens. The second study incorporated application of various amounts of neatsfoot oil and showed that liberal application (60 ml/kg body weight) was required for maximal acceptance, and that the same application rate of a mixture of neatsfoot oil with three volumes of paraffin oil was less effective than 60 ml/kg of neatsfoot oil alone. Sixty-two ewes were given an additional lamb and new family groups were successfully established with 53 ewes; the success rate for rearing two lambs, amongst ewes that had previously accepted the alien in a test situation, did not appear to be influenced by the means of inducing ewes to accept the alien.

Fostering in sheep: experiences with the use of neatsfoot oil

This paper reports the results of 3 studies on variables associated with the use of neatsfoot oil for substitutive or additive fostering of lambs. In the first study, neatsfoot oil was applied at the rate of 60 mL/kg of liveweight to 3-day-old lambs from Merino and Border Leicester x Merino ewes, and the lambs were exchanged between pairs of ewes of the same breed 3.5, 7 or 24 h later. The proportion of ewes accepting the alien lamb from the other ewe of the pair within 17 h generally increased with the period from application to exchange. Crossbred ewes accepted the foster lambs more readily than did the Merinos. Acceptance rates with batches of neatsfoot oil produced by different methods were similar. We found no advantage in smearing the ewe's nose with neatsfoot oil at the time the oil was applied to the lamb. Additive fostering in 20 ewes that accepted the alien lambs and were left with their own lambs was 95% successful and appeared permanent. In the second study using similar methods, with lambs of 28 crossbred ewes anointed 24 h prior to exchange, no advantage was found in presenting the foster lamb to the ewe at night over presentation during the day. Most foster lambs were accepted within 12 h, and all ewes reaccepted their own lambs after a 13 h absence. The acceptance rate of foster lambs by the crossbred ewes ranged from 70 to 83%. In the third study, 27 Merino ewes whose lambs were anointed with neatsfoot oil 7-40 h after birth, were presented with freshly anointed foster lambs 24 h later. The rate of acceptance of the foster lambs within the next 24 h was 74%,but many ewes required prolonged restraint before reaccepting their own lambs after 5-26 h separation. The results show that most ewes can be induced to accept foster lambs 1-2 days post partum, if their offspring have been liberally coated with neatsfoot oil for 24 h, and then substituted with neatsfoot-treated foster lambs. For additive fostering, the ewes' offspring should be returned within a few hours.

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

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 ewe's 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.

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

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 ewe's 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 ewe's 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. IV. Use of restraint

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.

The importance of olfactory bulb noradrenalin for maternal recognition in sheep

Herds of grazing mammals characteristically produce precocial offspring in synchrony, and it is therefore important for the mother to form a rapid recognition of her own offspring to distinguish them from others. In sheep, the ewe forms such a selective bond with her lamb within 2–4 hours of parturition, a bond which is primarily dependent on olfactory sensory recognition. Here we report that the neuronal mechanism whereby the olfactory “imprint” is made is dependent on the centrifugal noradrenergic projections to the olfactory bulbs. Lesioning of this neural pathway prevents the ewe from forming a selective bond with her own lamb, enabling her to adopt alien lambs.

Pheromones in farm animals

Although extracts from animals have been used for many years by humans to conceal natural pheromones, it has only recently been realised that pheromones can be used to improve the productivity of farm animals. Terrence Knight reviews the work on pheromones that has been done so far on farm animals. Oestrous sows have been identified for artificial insemination and ewes stimulated to ovulate by means of pheromones. In the future, it might be possible to get ewes to more readily accept foster lambs by masking the odours of the alien lamb by pheromones. A pheromone which induced early puberty in heifers could have commercial applications.

Fostering lambs by odor transfer: the substitution experiment.

Lamb-specific odor is used by ewes to discriminate between their own and alien offspring. The objective of the present study was to investigate the feasibility of transferring own-lamb odor to alien young to facilitate fostering. Shortly after birth, cloth stockinettes (body suits) were placed on the offspring of 37 multiparous ewes. At 48 to 72 h after parturition, a lamb from each ewe was replaced by an alien lamb. In 31 cases the odor-impregnated stockinette of the ewe's own lamb was placed on the alien lamb; in the remaining six cases the alien lamb retained its own stockinette (control condition). Lamb acceptance tests were conducted every 12 h for 2 d after fostering and once daily for the following 2 d. Twenty-six of the 31 experimental ewes (84%) adopted alien lambs using the odor-transfer technique. All of the control lambs were rejected. Of the 26 ewes that adopted foster young, 10 (38%) showed immediate acceptance and 22 (85%) were exhibiting acceptance behaviors by 36 h after fostering. There were no significant differences in the fostering success of ewes bearing single lambs and those with twins. The presence of own-lamb odor rather than the absence of alien lamb odor appears to be the salient cue for lamb acceptance. Lamb-specific odor transfer represents a relatively inexpensive and rapid technique to achieve maternal acceptance of alien lambs by postpartum ewes.

Behavior of ewes and lambs subjected to restraint fostering.

The objective of this study was to investigate the development of maternal-filial social attachments between ewes and alien lambs using the technique of "restraint fostering." Forty-eight to 72 h after parturition, 22 Targhee -type ewes were separated from their natural lambs, placed in restraining devices ( stanchions ) and each exposed to a single alien lamb. After a period of 1 or 4 d of restraint, the ewes were subjected to five 10-min lamb acceptance tests over a 48-h period. The observer recorded butts and butt attempts by the ewe and successful and unsuccessful suckle attempts by the lamb. The ewe-lamb pairs were then housed in pens with other groups of ewes and lambs and observed intermittently for acceptance behaviors. Six of the 14 ewes restrained for 4 d and none of the eight ewes restrained for 24 h met the criterion for successful adoption within 48 h. After being housed in group pens, adoptions were achieved by three ewes in the 1-d group and an additional four ewes in the group restrained for 4 d. Ewes restrained for 24 h were significantly more aggressive toward fostered young than ewes restrained for 4 d. In addition, the proportion of successful suckling attempts was significantly lower for lambs fostered on ewes in the 1-d group. Both groups showed a decline in butts and butt attempts over successive acceptance tests, but while the proportion of successful suckling attempts declined for lambs housed with 1-d ewes, they increased over time for lambs fostered on ewes restrained for 4 d.(ABSTRACT TRUNCATED AT 250 WORDS)

Bleating Behaviour of Dalesbred and Jacob Ewes in Sight of Lambs

The number of bleats made by Jacob and Dalesbred ewes during 120 sec were counted after separation from their lambs, when they could see their own and alien lambs 4 m away, and after the lambs had been removed. The Jacob ewes bleated more than the Dalesbred ewes except when the Dalesbreds could see their own lambs and for 30 sec after the lambs were removed. Both breeds increased their bleating more to own lambs than to alien lambs, but the difference was significantly greater throughout the 120 sec for the Dalesbred ewes bleating at lambs of either 10 or 20 days of age. The Jacob ewes differentiated more between own and alien when the lambs were 20 days old. When their own 10 day old lambs were removed, both breeds bleated more than after removal of alien lambs. When lambs were removed at 20 days, only Dalesbreds bleated more to their own. It is suggested that different breeds of sheep use vocalisation in different ways and that Jacob ewes bleat more in any situation, whereas Dalesbreds bleat more to communicate with their own lambs.

Washing lambs and confinement as aids to fostering

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 ewe's own lamb also tended to facilitate fostering, but not to any marked extent. Where the ewe's 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 ewe's memory for lamb odour is transient and/or that the odour changes with time.

Vaginal Stimulation: An Important Determinant of Maternal Bonding in Sheep

The immediate induction of the full complement of maternal behavior in nonpregnant ewes primed with estrogen and progesterone has been obtained after 5 minutes of vaginal-cervical stimulation. A similar period of such stimulation given to recently parturient ewes, after the development of selective bonding to their own lambs, reversed their rejection behavior of alien lambs and produced a state of plasticity in maternal behavior, such that ewes receiving vaginal stimulation would accept and adopt alien lambs. These findings implicate vaginal-cervical stimulation as playing a role in the onset of maternal behavior.

A Statistical Analysis of Vocal Communication Between Ewes and Lambs

Recordings of ewes and lambs bleating to each other, while separated by a canvas barrier, were analysed into categories based on the definition of an answer as being a bleat made within 2 sec of the first bleat. The number of answers were counted when: (a) the ewe answered the lamb; (b) the ewe answered the lamb's reply to its first bleat; (c) the lamb answered the ewe; (d) the lamb answered the ewe's reply to its first bleat. The number of bleats made by the lamb or ewe with no answer was also counted. The time interval between bleats was recorded for each of these categories. The percentage occurrence of each category was similar for all breeds tested. Lambs bleated more often with no answer from an alien ewe than from their dams. Analysis of the ewes answering bleats showed that the Dalesbred ewes had the greater tendency to answer their own lambs rather than aliens, and Soay ewes had the least tendency to answer all lamb bleats. All breeds answered their own lambs more than alien lambs. Analysis of the lambs answering bleats showed the Soay lambs answered less than other breeds and Dalesbred responded most. The Dalesbred also responded more to own ewes than aliens. All lambs answered their dams more quickly than alien ewes in the first minute of the records. Breed differences showed most in the third minute of the records, as the Jacob and Dalesbred lambs slowed in their response time and the Border Leicester lambs showed little temporal change. The ewes showd no difference in response time for own or alien lambs. When lamb bleats were not answered, their frequency increased more in the presence of their dams than in the presence of alien ewes. These results suggest that vocal recognition occurs quickly and that sheep may use frequency of bleating for identification of their own ewes and lambs. The variation between breeds in the speed with which ewes and lambs vocalise may reflect the rate in which they recognise each other or their degree of alertness.

Preferences for sibling or mother in Dalesbred and Jacob twin lambs

Twin lambs of Jacob and Dalesbred breeds (12 and 13 pairs, respectively) were tested in a T maze and given the choice of running to (1) a sibling or an alien lamb, and (2) a sibling or dam. Lambs were tested 3 times before, and twice after, enforced weaning at 80 days. The choices made by the lambs and the time spent at each choice were recorded. Three-week-old Jacob (but not Dalesbred) lambs, and all older lambs, chose to run to the sibling first more than to the alien lamb. Eighty-two percent of Dalesbred lambs, before weaning, chose to go to their dam first rather than the sibling, but Jacob lambs before weaning, and all lambs after weaning, showed no significant preference for dam or sibling. Lambs which ran to the sibling first often moved over to the ewe, but fewer lambs moved from ewe to sibling. All lambs stayed near to the sibling for a longer time than near to the alien lamb. Before weaning, the lambs of both breeds spent a longer time near their dam than near the sibling. After enforced weaning, the Dalesbred lambs still did this but the Jacobs spent longer with their siblings. Short tests allowing ewe and lambs to meet showed that more of the Dalesbred than Jacob lambs tried to suck from their dams over 7 weeks after weaning. The variation between breeds and the strength of the ewe—lamb bond compared with the sibling bond is discussed in relation to cohesion of social grouping in sheep.

Odour cues to maternal recognition of lambs: An investigation of some possible sources

Samples that might carry lamb-specific odour were tested in a three-choice system in which the ewe's interest in samples from herself or her own lamb, or samples from two other ewes or their lambs, were assessed. Each sample was suspended near the tail of an anaesthetized lamb from a ewe that was not under test. Since ewes showed no more interest in samples of their own milk, inguinal wax, saliva, faeces, urine or wool than expected by chance, it appears that lamb-specific odour is not derived directly from the ewe. Similarly, ewes displayed no interest in faeces of their own lamb, and there was a weak interest only in their lamb's urine. By contrast, ewes showed significant interest in swabs that had been rubbed around the rump, tail and anal region of their own lambs, as well as in wool clipped from these areas. There was also marked interest in wool clipped from the trunk and head of the ewe's own lamb, indicating that the anal region may not be the only source of lamb odour. A basis for collection of lamb odour for future chemical study, and a possible means of facilitating fostering of alien lambs, are indicated.

Responses of tranquilized post-partum ewes to alien lambs

The objective of this study was to determine the effect of tranquilization on the responses of ewes to alien lambs substituted for own lambs 48–72 h after parturition. Eleven ewes whose young had been taken away, and nine ewes with a lamb of their own, were penned with alien lambs following a single injection of the tranquilizer perphenazine. Seventeen control ewes, including 15 whose only young had been taken away, were also exposed to alien lambs after receiving placebo injections of normal saline. The responses of the ewes to the alien lambs were studied over a four-day period. All ten tranquilized ewes exposed to a single alien lamb without their own young present readily accepted the strange offspring. All of the tranquilized ewes accompanied by one of their own offspring, and a single ewe that was given an alien set of twins in place of her own single lamb, subsequently rejected the strange young. Six of 15 control ewes, with own young removed, accepted alien lambs. The remaining 11 control ewes rejected alien lambs. The success of fostering appeared to be positively related to the persistence of sucking attempts by the lamb, and inversely related to the aggressiveness of the ewe. Tranquilization under the conditions employed can be an efficient technique for fostering single alien lambs on post-partum ewes that have lost their own lambs, but does not facilitate fostering on ewes with their own young present.

Vocal Communication Between Ewes and Their Own and Alien Lambs

Abstract Vocal communication and consequent recognition between ewes and their own lambs or alien lambs was investigated by recording the bleating of one ewe and one lamb separated by a canvas barrier. Border Leicester, Dalesbred, Jacob and Soay, ewes were tested once when their lambs were 20-27 days and once when they were 70-80 days old. The number of bleats made by ewes and lambs over 3 min. was recorded, and the number of times they answered each others bleats within 2 sec. of hearing the first bleat, was calculated. Both ewes and lambs bleated more and answered more bleats when they were bleating to own rather than alien animals. Vocalisations were less with older lambs, particularly in the Soay sheep. The Dalesbred ewes answered significantly more of their own lambs' bleats than alien lambs, compared with other breeds. The Dalesbred lambs answered more of their own ewes' bleats when they were 70-78 days old. It is concluded that this vocal behaviour of answering bleats may help the lambs to identify their ewes more easily.

Recognition of washed lambs by Merino ewes

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 ewe's 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.