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.     

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

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.     

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.     

Visual discrimination between ewes by lambs

Merino ewes that had been shorn shortly before lambing, or left unshorn, were run together from about 2 days after lambing. The behavioural responses of their lambs to alien shorn and unshorn ewes were observed in a test enclosure in which a ewe and lamb were released simultaneously from opposite ends. In lambs less than 1 week old, the responses were independent of whether the ewe was similar or dissimilar to the lambs' dams, but 3-week-old lambs were slower in their approach towards dissimilar ewes and showed less interest in them than in similar ewes.The results agree with previous indications, from studies where the ewe's appearance was changed suddenly, that visual clues provided by the appearance of the dam are used in maternal recognition by Merino lambs about 3 weeks old but not by lambs less than 1 week old.     

Effects of sex, litter size and periconceptional ewe nutrition on the ewe–lamb bond

Undernutrition restricted to the time around conception in sheep alters endocrine and metabolic responses in the offspring. Studies in rats suggest that such an early insult can also alter the behaviour of the offspring. We studied the effects of mild maternal periconceptional undernutrition (10–15% body weight reduction) on the lamb's response to separation from and reunion with the mother, and on the ewe–lamb bond, evaluated as the preference for each other over an alien ewe/lamb in a test enclosure, at 24 h, 1 and 4 weeks of age. Lamb birth weight was not affected by maternal nutrition. Maternal periconceptional undernutrition did not affect the lambs’ responses to separation and reunion (number of vocalisations, times to leave pen and achieve proximity with ewes) or the bond between ewes and lambs (percentage of time spent near their own dam/lamb). However, there were effects of sex, litter size and time on lambs’ responses to separation and reunion and on the ewe–lamb bond. Female lambs vocalised more during separation (P ≤ 0.01) and left the holding pen faster than males (P ≤ 0.05), and twins vocalised more than singletons (P ≤ 0.05). The time to leave the holding pen, achieve proximity with the ewes and number of vocalisations decreased with increasing postnatal age of the lamb (all P ≤ 0.001). Ewes showed a stronger preference for the lamb at 24 h and 1 week than at 4 weeks postpartum (P ≤ 0.001), whereas lambs followed an opposite trend, showing a lower preference for the mother at 24 h and 1 week and increased preference at 4 weeks of age (P ≤ 0.001). We conclude that periconceptional undernutrition does not affect offspring response to separation from the mother or the bond between ewes and lambs, but that these behaviours are affected by sex and litter size for up to 4 weeks after birth.     

Odour,and the recognition of lambs by Merino ewes

Ewes that had been separated from their lambs for several hours were each presented with a choice between three anaesthetized lambs, one of which was the ewe's own. Each lamb was in a separate cage adjacent to a passage-way in which the ewe was free to move. The ability of the ewe to select her own lamb was equally good whether the head or the tail region of the lamb was placed against the corridor for examination at close-quarters, but when the lamb was 0.25 m from the corridor, very few ewes appeared able to find their own lambs. Although the ewes displayed less interest in the lamb's head than in the tail region, the head, as well as the tail, appears to provide the ewe with close-quarter clues, presumably olfactory, to the identity of the lamb.     

Mother–young bonding in prolific D’man and Romanov sheep

The effect of prolificacy on mother–young mutual recognition is still largely unknown in sheep. The aim of the present study was to investigate the ability of prolific ewes to develop an exclusive bond with their neonate and to recognize each other from alien subjects. Observations were performed on 11 D’man and 16 Romanov ewes with, respectively, 19 and 37 of their lambs. Maternal selectivity was tested at 24 h postpartum during two consecutive periods of 3 min. All mothers accepted their own lambs at suckling, while 21 out of 27 (78%) rejected the alien, thus displaying mostly selective nursing. To assess mother–young recognition, a two-choice test was performed at 36 h postpartum. Ewes clearly preferred their own lambs to an alien lamb and behavioral differences were not found between mothers of small (singletons and twins) and large litters (triplets and quadruplets). Romanov ewes reached their own lambsmore rapidly and spent more time near them than D’man ewes. Lambs from small litters, in particular light lambs, clearly preferred their mothers to an alien dam; however, both light and heavy lambs in large litters did not discriminate between the two stimulus ewes. D’man lambs clearly preferred their mothers to an alien dam; in contrast, such a preference was not as clearly demonstrated in Romanov lambs.     

Maternal selectivity suppression through peripheral anosmia affects neither overall nursing frequency and duration, nor lactation performance in ewes

The effects of prepartum peripheral anosmia on nursing activity, milk production and growth of the lambs, were assessed by comparing intact (n=10) and anosmic (n=10) multiparous Columbia and Rambouillet ewes and their single lamb during the first 2 months of lactation. Intact mothers only nursed their own lamb (98%) while most of the nursing activity in anosmic mothers concerned alien lambs (78%). On the other hand, the total duration and the frequencies of nursing did not differ significantly between groups (P>0.05). Nevertheless, the total percentage of nursing of own lamb by anosmic mothers (22%) was higher than expected at random (10%). Milk production or lambs' weights did not differ between groups. We conclude that prepartum anosmia resulted in the failure of ewes to develop true selective nursing up to the 8th week of lactation, although some preferential mother-young relationship yet developed. On the other hand, it did not affect significantly overall nursing activity.     

A comparison of the role of vision and hearing in ewes finding their own lambs

Ewes of Clun Forest, Finnish, Jacob, Dalesbred and Soay breeds of sheep quickly identified, and ran to their lambs when given a choice of three litters of lambs 16 m away from the gate by which the ewes entered the experimental area. When the lambs were hidden behind canvas, less than half the ewes ran to their own lambs and they took much longer to reach them. Most of the ewes which did not stay near their own lambs, went away and did not stay by alien lambs. There was no significant difference between the breeds of sheep and no definite change in behaviour which was related to the age of the lamb.     

Behavioral patterns of domestic sheep and their relationship to coyote predation

Activity patterns between individuals in a large herd of domestic sheep (Ovis aries) were examined to determine whether or not behavioral characteristics predisposed certain individuals to coyote (Canis latrans) predation. Coyotes killed 73 of 958 lambs and 6 of 624 ewes between 24 April and 15 August 1975. Twenty ewes and 19 lambs died from non-predatory causes. Coyote-kills accounted for 79.3% of the lamb losses. The amount of time ewes spent at various activities differed significantly by age or genotype, but the behavior of ewes whose lambs were killed was remarkably similar to that of other ewes. Single lambs were more active and were killed proportionately more often than twins. Within litters in which one of the lambs was killed, the killed sibling tended to be more active. Coyotes killed proportionately more disabled lambs and lambs from disabled ewes than healthy lambs or lambs from healthy ewes. Reduced mobility of either a lamb or a ewe increased the probability of a lamb's being on the periphery of the bed-ground and, hence, the probability that it would be noticed and attacked by a coyote. Coyote predation on domestic sheep was related more to the chance of an animal's being on the periphery of the bed-ground than to the animal's behavioral characteristics.     

A quantitative ethogram of behavior of yearling ewes during two hours post-parturition

A total of 2130 behaviors representing 24 behavioral categories were observed during the period from parturition to lamb nursing for seven ewe-lamb pairs. Both individual behaviors and behavioral sequences were counted. Ewes showed a high frequency of licking, especially directed at the head (41% of licks) and anterior body (30% of licks) of their lambs. Licking followed a specific, non-random pattern. Ewes licked from front to back of their lambs. Ewes licked their lamb's anterior body and head immediately before their lambs stood. When the lambs sought teats, ewes either presented their udder to their lamb which facilitated nursing, or moved away from the lamb which delayed nursing. This research identified behaviors and behavioral sequences that may be used in future studies seeking to select for improved maternal ability or to design improved lambing environments. Finally, this work may lead to the generation of hypotheses which may be tested in future work examining behaviors involved as causal factors in lamb survival.     

Relationship between male-male and male-female sexual behavior in 5-6-month-old male lambs

To characterize male–male sexual behavior during lamb development, to relate it with lamb body and testicular growth, and with sexual behavior toward estrual ewes, 40 Milchschaf male lambs, weaned at 45 days of age, were kept with ewes that were nursing younger lambs. Experimental lambs were weighed and scrotal circumference was measured every 2 weeks. Male–male sexual behavior was observed during 1–2 h every 2 weeks after birth until 7 months of age. Observations were recorded more intensively (3–4 h on five different days) for 2 weeks (5–6 months of age) as male–male sexual behavior increased during that period. Both mounting and mounted lambs were identified. An individual mounting index (MI) was calculated. To study male–female sexual behavior, lambs were individually located with two estrual ewes, and during 5 min the number of ano-genital sniffing, lateral approaches, mounts, and mounts with ejaculation were recorded. From those data, a libido index was also calculated. Male–male mounts (n = 308) were observed. Courtship behavior was displayed in 25% of interactions; mounts were accepted in 72.1% of attempted mounts. Mounts without previous courtship were accepted more frequently than mounts with previous courtship (P = 0.002). Lamb weight and scrotal circumference were not different according to MI groups. Lambs that mounted more times estrual ewes (first tertile) had greater (P = 0.04) MI (0.61 ± 0.10) than lambs with medium (0.27 ± 0.09) and less (0.30 ± 0.10) MI. The regression between MI and heterosexual libido index was r = 0.33 (P < 0.05). In summary, intensive male–male sexual activity during a short period of male lamb development was observed. There was a positive relationship between sexual behavior of male lambs towards other male lambs and towards estrual ewes.     

Breed, litter and parity effects on placental weight and placentome number, and consequences for the neonatal behaviour of the lamb

Lamb survival is impaired in low birth weight lambs, and those that are slow to stand and suck. Many of the factors that influence lamb vigour, such as parity, litter size, and breed, may exert their effects, at least partially, before birth by influencing placenta development. Our hypothesis was that retarded lamb behavioural development was due to differences in placentation in these animals. Data were collected from Blackface and Suffolk lambs in the first 2 h after birth and placentas were collected when delivered. Suffolk lambs, which were behaviourally slower and had lower rectal temperatures than Blackface lambs, were associated with larger but less efficient placentas (placental efficiency defined as foetal weight supported per g placenta) with fewer foetal cotyledons than Blackface placentas. Triplet lambs were significantly slower than twin or single lambs to suck and had lower rectal temperatures. Although placenta efficiency increased with litter size, placenta and cotyledon weight, and cotyledon number increased with twinning but not thereafter. It seemed likely that triplet lambs suffered some placental insufficiency in comparison to other litter sizes. Lambs born to first parity mothers were slower to stand and reach the udder than lambs of more experienced ewes, and first parity ewes also had smaller and less efficient placentas although cotyledon number was not affected. Male lambs tended to be slower than female lambs for most behaviours, although rectal temperatures were not affected. The sire of the lamb also influenced lamb behaviour and rectal temperature. Both lamb sex and lamb sire influenced the average weight of placental cotyledons, thus some of the sire effect on the behaviour and birth weight of his progeny might be mediated through placental development. Lamb neonatal vigour was correlated with placental efficiency suggesting that lamb behaviour immediately after birth is related to placental development and function.     

Ewe and lamb contact at lambing is influenced by both shelter type and birth number

A significant number of lambs born each year in Australia die within 72 h of birth. Periods of high wind, combined with rain and low temperatures can lead to marked increases in the mortality level. Under these climatic conditions mortality levels may be reduced with the provision of shelter. This study used contact loggers to compare interactions between ewes with twin lambs across two shelter types (Hessian and shrubs), while also comparing ewes with single and twin lambs in a single shelter type (Hessian). The contact loggers record the time of the initial contact (within approximately 4 to 5 m) between collared animals and the duration of each contact. Contact levels between ewes immediately after lambing were only 10% of the initial levels (1 h/day). For single-born lambs, lambs averaged 11 h contact per day with their mother, while for twinborn lambs, each lamb averaged 9.25 h/day with its mother and 14.7 h/day with its sibling. The level of contact between ewes and each of their offspring in the Hessian was 24% lower (P < 0.05) for ewes with twin lambs than with singles. For ewes with twin lambs the level of contact was 17% lower (P < 0.05) in the Hessian shelter compared with shrub shelter. We conclude that shelter type and birth number can affect the level of contact between ewes and their offspring.     

Conditioning ewes and lambs to increase consumption of spotted knapweed

Spotted knapweed (Centaurea maculosa Lam.) is an invasive plant that alters species composition and grazing value of rangelands in the northwestern United States. The spread of invasive plants may be reduced by using livestock as a biological control. We determined if mature ewes and their lambs (n = 34 ewe/lamb pairs) consume more spotted knapweed when ewes and/or lambs are conditioned to fresh-cut spotted knapweed. Ewe/lamb pairs were randomly assigned to one of four conditioning treatments: ewes and lambs not conditioned to spotted knapweed (N), conditioned ewes with non-conditioned lambs (E), non-conditioned ewes with conditioned lambs (L), or conditioned ewes and lambs (both—B). Then, ewes and lambs were observed together for 5 days (Trial 1); 11 days later, lambs were observed for 4 days without their mothers (Trial 2). During conditioning, intake by conditioned and non-conditioned ewes and lambs varied over time (as-fed basis, treatment by day interaction; ewes P = 0.03; lambs P = 0.05). Overall, non-conditioned lambs (N, E) consumed more than conditioned lambs (L, B; P = 0.02). In Trial 1, N ewes consumed similar amounts of spotted knapweed and bromegrass (Bromus inermis Leyss.) as the E, L, and B ewes (P = 0.67). E ewes spent more time eating spotted knapweed than L ewes (P = 0.001), and E ewe/lamb pairs consumed more spotted knapweed than L ewe/lamb pairs (P = 0.02). In Trial 2, N lambs consumed less spotted knapweed than E, L, and B lambs (P = 0.06). L lambs consumed more than E lambs (P = 0.007). Conditioning ewes, lambs, or ewes and lambs did not increase time spent eating spotted knapweed when both grazed together in a drylot, but conditioned lambs, without their mothers present, consumed more spotted knapweed 11 days later than non-conditioned lambs. Conditioning lambs only in a group setting with their peers may have the greatest potential to enhance consumption of spotted knapweed, because of social facilitation and the predilection for young animals to try novel feeds.     

Pair association between lambs of different breeds born to Jacob and Dalesbred ewes after embryo transplantation

Seven pairs of lambs, each pair consisting of one Dalesbred and one Jacob lamb born to either a Dalesbred or a Jacob ewe following embryo transplant, were observed for 5 weeks in a field. The association of the lambs with their sibling and with other sheep in the field was recorded. The lambs were seen to be with their dam 53% of the time at 10 weeks and this fell to 42% in weeks 11 and 12. They spent more than twice the amount of time near to a sibling than with any other lamb (54% and 25%). When the ewes were removed from the field, the lambs bunched together and the association with siblings and with other lambs increased. There was no breed identity amongst the lambs, but the Jacob ewes mixed more with other Jacobs and Dalesbred ewes mixed more with other Dalesbreds. Comparisons were made with pairs of genetically related Jacob lambs. It is concluded that association between lambs born to the same ewe is the result of that birth and subsequent upbringing and not due to genetic inheritance.     

A Hereditary Skin Defect in Sheep

Some years ago a lamb with abnormal skin was received at the State veterinary research station for small ruminants (SVRS), Stavanger, from a farm in Ryfylke. The lamb had apparently been normal at birth, but by normal activity and contact with its mother, extensive wounds developed, with large, loose skin areas. The lamb’s condition had deteriorated so much that it was killed when it was two days old. Two ewes sired by the same ram had given birth to similar lambs the same year, while some years earlier, lambs with the same defect had been born by other ewes in the flock.     

Reproductive costs of sons and daughters in Rocky Mountain bighorn sheep

Differential maternal investment theory predicts that in sexuallydimorphic and polygynous species mothers should invest morein sons than in daughters. We tested the hypothesis that bighornewes that raise sons incur greater reproductive costs than ewesthat raise daughters. Although ewe mass gain during lactationand subsequent winter body mass loss were independent of lambsex, lambs born the year following the weaning of a son hadlower survival than lambs born after a daughter. The effectsof lamb sex on subsequent reproductive success of ewes becamemore evident at high population density. Lamb sex did not affectmaternal survival. Population density, weather, and ewe agedid not alter the relationship between lamb sex and subsequentreproductive success of the ewe. The year after weaning a son,ewes were more likely to have a daughter than a son, while ewesthat had previously weaned a daughter had similar numbers ofsons and daughters. Our results show that for bighorn sheepewes, sons have a greater life-history cost than daughters,suggesting a differential maternal investment in the sexes.     

The effects of pasture availability for twin- and triplet-bearing ewes in mid and late pregnancy on ewe and lamb behaviour 12 to 24 h after birth

This experiment was conducted to evaluate the effect of offering ewes two different feeding levels, during mid and late pregnancy, on ewe and lamb behaviour 12 to 24 h after birth. Romney ewes, bearing twin (n = 80) or triplet foetuses (n = 56), were allocated to a pasture sward height of 2 or 4 cm between 70 and 107 days of pregnancy. In late pregnancy (day 107 to 147), half of the ewes were reallocated the alternate sward height, which produced four treatments: 2-2, 2-4, 4-2 and 4-4. Ewes were weighed on days 65, 92, 107 and 130 of pregnancy and lamb live weights were recorded 12 to 24 h after birth. Twelve to 24 h after birth the maternal behaviour score (MBS) of the ewes were determined, whilst their lambs were tagged. After the lambs were released, the behaviour of each ewe and her lambs was observed for 5 min. Ewe treatment and litter size had no effect on ewe MBS. However, as MBS increased (ewes stayed closer to lambs during tagging), ewes bleated less in a high-pitch and were quicker to make contact with their lamb. During the observation period, ewes in the 4-4 treatment had a greater percentage of their bleats in a low pitch (P < 0.05) than ewes in the 2-2 and 4-2 treatment (61.3% v. 41.3% and 38.8% low bleats, respectively) and more lambs born to 4-4 ewes (95%) bleated than lambs born to 2-2 ewes (84%; P < 0.05). However, lambs born to ewes in the 2-2 treatment bleated earlier than lambs in all other treatments (P < 0.05). Lambs born to 4-4 ewes were less likely (P < 0.05) to move towards their dam in order to make contact than lambs born to 2-2 or 4-2 ewes (3.1% v. 16.9% and 16.7%, respectively). These findings suggest that under the conditions of the present study, ewe nutrition had little effect on maternal behaviour. However, lambs born to ewes offered 2 cm pasture sward heights during mid and/or late pregnancy (2-2, 2-4 and 4-2 treatments) displayed behaviour that demonstrated greater 'need' whereas lambs born to ewes offered 4 cm during mid and late pregnancy sought less attention from their dam.     

Mob size of single-bearing or twin-bearing Merino ewes at lambing may not influence lamb survival when feed-on-offer is high

Limited research has suggested that higher lambing densities increase interference from foreign ewes at lambing which disrupts the ewe-lamb bond and compromises lamb survival. This may be particularly evident in mobs of twin-bearing ewes compared to single-bearing ewes because a greater number of lambs are born per day. Therefore, we hypothesised that; (i) decreasing the mob size of ewes at lambing has a greater impact on the survival of twin-born lambs than single-born lambs; (ii) the relationship between mob size and lamb survival can be explained by differences in the rate of interaction with foreign ewes and lambs at lambing; and (iii) ewes will utilise a limited area of the paddock at lambing and thus lambing density will be defined by the distribution of ewes in the paddock rather than the paddock area. Merino ewes were allocated into a 2×2 factorial combination of ewe pregnancy status (single- or twin-bearing) and mob size (high (n=130 ewes) or low (n=50 ewes)) on day 140 from the start of joining. Each treatment had two replicates excepting the low mob size for twins which had a third replicate. Ewes lambed at a stocking rate of 11 ewes/ha. Feed-on-offer during lambing exceeded 2400 kg dry matter (DM)/ha. Ewe-lamb behaviour was observed and dead lambs were autopsied over 11 days during the peak of lambing. The distribution of ewes in each paddock was recorded every 2 h during daylight hours by counting the number of ewes occupying 2500 m² grids. The proportion of ewes and their newborn progeny which interacted with foreign ewes at lambing did not differ between the high and low mob sizes for single- (24.9% v. 20.8%) or twin-bearing ewes (14.3% v. 19.6%; P=0.74). Similarly, interaction with foreign lambs did not differ between the high and low mob sizes for single- (14.5% v. 25.2%) and twin-bearing ewes (34.5% v. 26.4%; P=0.44). The distribution of ewes within the paddock did not differ between treatments (P=0.95). On average, single-bearing ewes which lambed at the high and low mob sizes occupied 34% and 36% of the paddock during daylight hours, and the corresponding values for twin-bearing ewes were 40% and 43%. Survival of twin-born lambs was lower than single-born lambs (75.3% v. 87.9%; P<0.01), however, lamb survival was not influenced by mob size regardless of birth type. These results suggest that higher mob sizes may not compromise lamb survival when feed-on-offer during lambing exceeds 2400 kg DM/ha.