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.     

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.     

Phenotypic and genetic relationships between udder morphology and udder health in dairy ewes

The aim of this paper was studying the phenotypic and genetic relationships between udder morphology traits and udder health in dairy sheep. From 2000 to 2008 udder traits, somatic cell count (SCC) and clinical mastitis cases were recorded in an experimental flock consisting each year of around 900 ewes. A logistic regression was performed to evaluate the risk for a ewe of showing either a mastitis or at least 2 daily SCC records greater than 1 × 10⁶ cells/ml in one of its lactations as function of udder traits scored in 1st lactation. 1587 individual udder scores and 39,950 SCC daily records were used for the analysis. Secondly, genetic correlation between lactation mean of somatic cell score and udder traits were estimated by a REML method applied to four bi-trait animal models, using data from 2251 primiparous ewes. Logistic regression results indicated that the risk of mastitis or high SCC values during the productive life increased as the cistern height increased and the degree of udder suspension and udder depth decreased. This suggests that the appraisal of the udder is a useful tool for culling decision aimed at increasing the sanitary status of the flock. The genetic correlation between lactation SCS and udder traits were favourable for udder depth (−0.50 ± 0.12), teat placement (0.39 ± 0.011) and degree of udder suspension (−0.42 ± 0.011) and closed to zero for the degree of separation of the two halves. Thus selection for udder morphology, already implemented in some dairy sheep breeds with the aim of improving machine milkability, will lead to a favourable correlated genetic response on SCC.     

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.     

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.     

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.     

Survival of fertilized ova from ewe lambs and adult ewes in the uteri of ewe lambs

The cause of fertility differences between ewe lambs and adult ewes following natural oestrus were studied in Romneys. Insemination was determined by anterior vaginal swabbing. Fertilized ewe-lamb ova were returned to donor animals along with one matched fertilized adult ewe ovum and lambings were recorded. Ewe-lamb ova were less likely (P<0.01) to survive to term compared with adult ewe ova. Insemination failure, fertilization failure and anovular oestrus were minor sources of reproductive wastage.It is concluded that reduced ovum quality appears to be the major cause of the lower fertility in naturally ovulating ewe lambs compared with adult ewes.     

Sister-chromatid exchange in cultured lymphocytes of ewes and their newborn lambs

The incidence of sister-chromatid exchange (SCE) in cultured lymphocytes of ewes and their newborn lambs was determined using the BrdU-Giemsa technique. In all ewe-lamb pairs, the SCE rate in the lambs was less than that of the ewes. The mean SCE frequencies per chromosome of the ewes after lambing and of the newborn lambs were 0.1909 and 0.1581, respectively. The statistical analysis shows that a significant difference exists between SCE in the adult female sheep and their lambs. At the same time, a negative correlation was observed between SCE rate and cell proliferation. The results of this study are compared with those of previous reports on age-dependency of SCE.     

Distance recognition in ewes and lambs kept permanently indoors or at pasture

We tested the ability of Merino and Merino × Romanov ewes and lambs to recognise each other at a distance when given the choice between an alien partner and their own. Two groups of animals were studied. In the first group, multiparous ewes and their lambs were housed permanently indoors at a stocking-rate of 1 ewe/2 m². In the second group, ewes and lambs were run permanently outside in a paddock at a stocking rate of 1 ewe/500 m². Of animals living outside, 87% of ewes recognised their own lamb (100% of multiparous dams versus 84% of primiparous ones, P = 0.02). This differed significantly from a random choice. By contrast, the proportion of correct choices by ewes living inside (all multiparous) was significantly lower (64%) and did not differ from a random choice at the 5% level. Lambs reared outside recognised their dam in 95% of cases, versus 72% in lambs reared indoors (P = 0.01). Both frequencies differed significantly from a choice at random. It is concluded that the environmental conditions in which ewes and lambs are maintained can influence their ability to select their partners at a distance with the help of auditory and visual cues.     

Comparison of the survival of fertilized eggs from adult ewes in the uteri of adult ewes and ewe lambs

Fertilized eggs, obtained from mature donor ewes, were transferred into the uteri of adult ewes and ewe lambs (1 or 2 eggs per recipient). The survival rate to term of the transferred eggs was similar in the two classes of recipients. The percentage of adult ewe and ewe lamb recipients which gave birth to twins was 45.3 and 41.1 respectively. Gestation length was shorter (P less than 0.01) and lamb birth weight lower (P less than 0.01) for ewe lamb recipients. The results indicate that the generally lower lambing rate of ewe lambs compared to adults is unlikely to be due to unfavourable uterine conditions.     

Length of gestation in ewes carrying lambs of two different breeds

Length of gestation was studied in pregnancies established by intrabreed, interbreed, and mixed-breed embryo transfers of Finnish Landrace (Finn; mean gestation: 144.9 days) and Targhee (mean gestation: 150.4 days) embryos to Finn cross and Targhee recipients. At least one lamb of each breed comprised mixed-breed pregnancies. There was a significant effect of the breed of lamb (Finn, Targhee, or Finn and Targhee) on the length of gestation (P < .01), but not of breed of recipient. Mixed-breed pregnancies had a mean gestation period intermediate between those for pregnancies which contained only one breed of lamb. The mean gestation period for mixed-breed pregnancies was 2.10 +/- .70 (x +/- S.E. ) days longer than for pregnancies with only Finn lambs (P < .01) and 2.99 +/- .73 days shorter than for pregnancies with only Targhee lambs (P < .001). The delay in parturition in mixed-breed pregnancies beyond the normal gestation period for Finn lambs occurred even in litters with a majority of Finn lambs. These results demonstrate an interaction between fetuses in the processes leading to parturition. Possible mechanisms by which the Targhee lamb delayed parturition in mixed-breed pregnancies are discussed.     

Low pasture allowance until late gestation in ewes: behavioural and physiological changes in ewes and lambs from lambing to weaning

Low pasture allowance during gestation affects ewes’ BW at parturition, the bond with their lamb, lamb development, and thus also may affect their responses to weaning. The objectives were to determine if native pasture allowance from before conception until late pregnancy affects ewe–lamb behaviours at lambing, ewes’ milk yield, lambs’ BW, and the behavioural and physiological changes of ewes and lambs at weaning. From 23 days before conception until 122 days of pregnancy, 24 ewes grazed on two different native pasture allowances: high (10 to 12 kg of dry matter (DM)/100 kg of BW per day; HPA treatment; n=12) or low (5 to 8 kg of DM/100 kg of BW per day; LPA treatment; n=12). Thereafter, all ewes grazed on Festuca arundinacea and received rice bran and crude glycerine. Ewes’ body condition score (BCS) and BW were recorded during pregnancy and postpartum periods. Milk yield was determined on days 32, 41 and 54 after lambing. Lambs’ BW was recorded from birth until 72 days after lambing. Latency from parturition until the ewe licked her lamb, maternal behaviour score (a test that evaluates maternal attachment to the lamb) and latency for lamb to stand up and suckle were determined. The behaviour of the lambs and ewes was recorded before and after weaning (at 65 days). The ewes’ serum total protein, albumin and globulin concentrations were measured before and after weaning. The HPA ewes presented greater BW (P<0.005) and BCS (P<0.005) than the LPA ewes during pregnancy and postpartum (P<0.04), and had a greater milk yield than the LPA ewes (P<0.03). Treatments did not influence any behaviour at lambing, lambs’ BW, neither the ewes’ behavioural and physiological changes at weaning. HPA lambs paced and vocalized more than LPA lambs (P<0.0001). The variation of albumin concentration before and after weaning was greater in the HPA lambs than in the LPA lambs (P<0.0001). In conclusion, although ewes’ BW, BCS and milk production were affected by pasture allowance until late pregnancy, this did not affect the behaviours that lead to the establishment of the mother–young bond, nor the ewes’ behavioural responses at weaning. Lambs reared by ewes that grazed on low pasture allowance during pregnancy presented fewer behavioural changes and a lower decrease of albumin concentration after weaning. Lambs’ BW was not affected by the feeding received by their mothers.