Behaviour of the ewe and lamb at lambing and its relationship to lamb mortality

Postnatal maternal behaviour expression depends on lambing difficulty in Merino ewes

Dystocia, a prolonged or non-progressive birth event, is the main contributor to lamb mortality in Australia and across the world. Dystocia can cause neonatal hypoxia, central nervous system (CNS) damage leading to increased risk of starvation, exposure and mismothering, and death. These prolonged birth events can also cause fatigue, injury and death in the ewe. Dystocia may interrupt the expression of maternal behaviour and the strength of the ewe-lamb bond, and consequently lamb survival. This study focused on the effect of dystocia on ewe behaviour in the 2 h post-lambing. A total of 18 ewes were chosen for continuous behaviour annotation and analysis (dystocic (n = 9) and eutocic (n = 9)) based on the quality of video recordings, length of stage 2 parturition and classification by a single experienced observer. Dystocic ewes showed significantly lower expression of maternal behaviours and a significantly greater expression of avoidance behaviours compared to eutocic ewes. Additionally, dystocic ewes performed fewer behaviours in total compared to eutocic ewes. Dystocia can significantly affect the quality and quantity of ewe maternal behaviour expression, leading to increased avoidance of the lamb, increased risk of maternal disinterest, and increased risk of death for the lamb. If dystocic events can be identified quickly and accurately, measures can be taken to ensure the ewe and lamb recover successfully.

The Onset of Maternal Behavior in Sheep and Goats: Endocrine, Sensory, Neural, and Experiential Mechanisms

In sheep and goats, the onset of maternal behavior at parturition is characterized by a first phase called maternal responsiveness during which the mother is attracted to any newborn. In a second phase, called maternal selectivity, the mother establishes a selective bond with her young so that she only accepts it at suckling. After a description of the behavioral expression of both phases, this chapter reviews the physiological, sensory, and neural mechanisms involved. These two behavioral processes are synchronized with parturition by the vaginocervical stimulation induced by the expulsion of the newborn. Olfactory cues provided by the neonate are involved in maternal responsiveness and selectivity. Oxytocin supported by estrogens is the key factor for maternal responsiveness. The neural network involved in maternal responsiveness is mainly hypothalamic and is different from the circuitry involved in selectivity, which mainly concerns olfactory processing regions. Visual and auditory cues are necessary for offspring recognition at a distance. This multisensory recognition suggests that mothers form a mental image of their young. Maternal experience renders mothers more responsive to maternally relevant physiology and to young-related sensory inputs.

Regulation of maternal behavior, social isolation responses, and postpartum estrus by steroid hormones and vaginocervical stimulation in sheep

Periparturient ewes display several activities in addition to maternal behavior per se. They isolate themselves from the flock and, contrary to other mammals, do not show postpartum estrus. We investigated the possibility of a common hormonal control of maternal behavior, prepartum social isolation responses, and absence of postpartum estrus. We quantified responses to flockmate separation and incidence of sexual receptivity at several reproductive stages in intact ewes (Experiment 1). Responses to social isolation were lowest in preparturient ewes and at pregnancy day 149, intermediate at pregnancy day 147 and highest at day 136 and in non-pregnant ewes (P < 0.05 between the 3 levels). In a second experiment, we quantified the same parameters and maternal behavior in 1) ovariectomized ewes receiving medroxyprogesterone acetate only (ovxMPA); 2) ovariectomized ewes receiving MPA + estradiol benzoate (ovxSHORT); 3) intact ewes receiving a longer MPA + estradiol dipropionate treatment, before and after vaginocervical stimulation (VCS). Before VCS no steroid treatments decreased social isolation responses and maternal behavior was scarce or absent. Following VCS and interaction with lamb, maternal responses in the ovxSHORT group increased while social isolation responses decreased. Sexual receptivity occurred in non-pregnant ewes and in ovxSHORT group. Conclusion: some hormonal treatments +VCS can effectively induce maternal behavior and reduce social isolation responses. Long-term progestin treatment can inhibit postpartum estrus.

Maternal and Neonatal Behaviour in Italian Mediterranean Buffaloes

The aim of this study was to describe the neonatal and maternal behaviour of Italian Mediterranean buffaloes. Thirty primiparous buffaloes were moved into individual pens 12.5 (±2.5) days before calving. Maternal and neonatal behaviours were recorded for 48 h after calving and the analysis was performed in continuous sampling with the software BORIS. Calves' clinical evaluations (temperature, weight, and heart and respiratory rates) were performed at different time intervals and correlated with behavioural data from the dam. Data were analysed with parametric and non-parametric methods after controlling their distribution. The maternal behavioural pattern found highlighted buffaloes' priorities during the post-partum period: firstly, they stand and start grooming to ensure proper care for the calf; it is only after this that they dedicate time to maintenance behaviours (feeding and lying). The dams mainly groomed the calf during the first six hours after calving (average time in the 1-6-h interval: 7.7 ± 2.5 min., F = (2.5, 60.2) = 75.0; p < 0.001) to ensure the formation of the mother-infant bond; thereafter, the behaviour decreased over time. As reported in the literature, inexperienced mothers could sometimes delay the calf's first suckling with aggressive or rejection behaviours. In this regard, 16 buffalo dams showed at least one maternal rejection behaviour, which was found to negatively correlate with calves' daily weight gain (DWG) at 14 (r_s = -0.5, p = 0.02) and 21 days (r_s = -0.7, p < 0.001). The calves took on average 212.0 ± 110.0 min to suckle, and this behaviour was mainly shown during the first six hours. Overall, suckling behaviour was correlated with standing: (r_s = 0.6, p < 0.001) and walking (r_s = 0.9, p < 0.001). The calves' live weight and DWG were consistently higher than the values reported in the literature. Our results present a detailed description of maternal and neonatal behaviour in the early post-partum period in Italian Mediterranean buffaloes. We also found that maternal rejection behaviours can negatively influence the calves' growth. Finally, we think that such results can improve the management of buffaloes during the period around parturition.

Developing a Simulated Online Model That Integrates GNSS, Accelerometer and Weather Data to Detect Parturition Events in Grazing Sheep: A Machine Learning Approach

Simple Summary

Near-real-time monitoring of livestock using on-animal sensor technology has the potential to improve animal welfare and productivity through increased surveillance and improved decision-making capabilities. One potentially valuable application is for monitoring of lambing events in sheep. This research reports on the development of a machine learning classification algorithm for autonomous detection of lambing events. The algorithm uses data from Global Navigation Satellite System (GNSS) tracking collars, accelerometer ear tags and local weather data. Overall, four features of sheep behaviour were identified as having the greatest importance for lambing detection, including various measures of social distancing and frequency of posture change. Using these four features, the final algorithm was able to detect up to 91% of lambing events. This knowledge is intended to contribute to the development of commercially feasible lambing detection systems for improved surveillance of animals, ultimately improving methods of monitoring during critical welfare periods.

Abstract

In the current study, a simulated online parturition detection model is developed and reported. Using a machine learning (ML)-based approach, the model incorporates data from Global Navigation Satellite System (GNSS) tracking collars, accelerometer ear tags and local weather data, with the aim of detecting parturition events in pasture-based sheep. The specific objectives were two-fold: (i) determine which sensor systems and features provide the most useful information for lambing detection; (ii) evaluate how these data might be integrated using ML classification to alert to a parturition event as it occurs. Two independent field trials were conducted during the 2017 and 2018 lambing seasons in New Zealand, with the data from each used for ML training and independent validation, respectively. Based on objective (i), four features were identified as exerting the greatest importance for lambing detection: mean distance to peers (MDP), MDP compared to the flock mean (MDP.Mean), closest peer (CP) and posture change (PC). Using these four features, the final ML was able to detect 27% and 55% of lambing events within ±3 h of birth with no prior false positives. If the model sensitivity was manipulated such that earlier false positives were permissible, this detection increased to 91% and 82% depending on the requirement for a single alert, or two consecutive alerts occurring. To identify the potential causes of model failure, the data of three animals were investigated further. Lambing detection appeared to rely on increased social isolation behaviour in addition to increased PC behaviour. The results of the study support the use of integrated sensor data for ML-based detection of parturition events in grazing sheep. This is the first known application of ML classification for the detection of lambing in pasture-based sheep. Application of this knowledge could have significant impacts on the ability to remotely monitor animals in commercial situations, with a logical extension of the information for remote monitoring of animal welfare.

The Impacts of Waterproof Insulated Jackets on Lamb Performance on a UK Lowland Farm

The majority of lamb losses occur within the first two weeks of life, with cold stress being a major cause of lamb morbidity and mortality. This study investigated the effect of insulating lamb jackets on newborn lambs. One hundred and four newborn lambs were randomly allocated by birth date to two treatment groups, (a) non-jacketed (n = 52) or (b) jacketed (n = 52), for fourteen days after birth. The live weights of lambs were recorded regularly up to 21 days, and average daily weight gains were calculated from these data. For the first two days after recruitment to the study, surface and body temperatures of lambs were also recorded. The jackets significantly increased the lambs' surface temperatures, providing a warmer microclimate and reduced cold stress for jacketed lambs. There was no significant effect of the insulating jackets on estimated body temperatures, live weights or average daily weight gain of the lambs in this study. There were no detrimental effects of the jackets, and no rejection of lambs occurred.

Can accelerometer ear tags identify behavioural changes in sheep associated with parturition?

On-animal sensor systems provide an opportunity to monitor ewes during parturition, potentially reducing ewe and lamb mortality risk. This study investigated the capacity of machine learning (ML) behaviour classification to monitor changes in sheep behaviour around the time of lambing using ear-borne accelerometers. Accelerometers were attached to 27 ewes grazing a 4.4 ha paddock. Data were then classified based on three different ethograms: (i) detection of grazing, lying, standing, walking; (ii) detection of active behaviour; and (iii) detection of body posture. Proportion of time devoted to performing each behaviour and activity was then calculated at a daily and hourly scale. Frequency of posture change was also calculated on an hourly scale. Assessment of each metric using a linear mixed-effects model was conducted for the 7 days (day scale) or 12 h (hour scale) before and after lambing. For all physical movements, regardless of the ethogram, there was a change in the days surrounding lambing. This involved either a decrease (grazing, lying, active behaviour) or peak (standing, walking) on the day of parturition, with most values returning to either pre-partum or near-pre-partum levels (all P < 0.001). Hourly changes also occurred for all behaviours (all P < 0.001), the most marked being increased walking behaviour and frequency of posture change. These findings indicate ewes were more restless around the time of parturition. Further application of this research should focus on development of algorithms that can be used to identify onset of lambing and/or time of parturition in pasture-based ewes.

Potential for autonomous detection of lambing using global navigation satellite system technology

Context On-animal sensing systems are being promoted as a solution to the increased demand for monitoring livestock for health and welfare. One key sensor platform, global navigation satellite system (GNSS) positioning, provides information on the location and movement of sheep. This information could be used to detect partition in sheep, a key period of time when both ewes and lambs are at risk. The development of algorithms based on key behavioural features could provide alerts to sheep managers to enable intervention when problems arise. Aims To investigate the use of GNSS monitoring as a method for detecting behavioural changes in sheep in the period around parturition. Methods GNSS collars were attached to 40 late gestation ewes grazing a 3.09 ha paddock in New Zealand. Several metrics were derived: (i) mean daily speed, (ii) maximum daily speed, (iii) minimum daily speed, (iv) mean daily distance to peers, and (v) spatial paddock utilisation by 95% minimum convex polygon. Speed metrics and distance to peers were also evaluated at an hourly scale for the 12 h before and 12 h after lambing. Key results Minimum daily speed peaked on the day of parturition (P &lt; 0.001), suggesting animals may have been expressing more agitation and did not settle. Isolation was also evident during this time, with postpartum ewes located further from their peers than pre-partum ewes (P &lt; 0.001). Day of lambing was also evident by reduced spatial paddock utilisation (P &lt; 0.001). Conclusions This study demonstrates that GNSS technology can be used to detect parturition-related behaviours in sheep at a day scale; however, detection at the hour scale using GNSS is not possible. Implications This research highlights the opportunity to develop predictive models that autonomously detect behavioural changes in ewes at parturition using GNSS. This could then be extended to identify ewes experiencing prolonged parturition, for example dystocic birth enabling intervention which would improve both production and welfare outcomes for the sheep industry.

Do calcium and magnesium deficiencies in reproducing ewes contribute to high lamb mortality?

High lamb mortality continues to be a significant economic and welfare problem within the Australian sheep industry, with 20–30% of lambs born in commercial flocks dying mostly within 3 days of birth. Clinical hypocalcaemia and hypomagnesaemia cause ewe mortality, and, subsequently, either fetal or lamb death, but it is not known whether subclinical deficiencies of calcium (Ca) and magnesium (Mg) compromise lamb survival. This review considers the potential mechanisms through which Ca and Mg deficiencies may influence lamb survival, and factors influencing the risk of deficiency. Pastures grazed by lambing ewes may be marginal in calcium (Ca; &lt;4 g/kg DM) and magnesium (Mg; &lt;0.9 g/kg DM) but also have a high dietary cation–anion difference (&gt;12 meq/100 g DM) and high concentrations of potassium (K; &gt;30 g/kg DM) and nitrogen. In young cereal crops, sodium concentrations are also often low (&lt;0.9 g/kg DM). This combination of minerals and other nutrients creates an imbalance in supply and increases susceptibility to acute Ca (hypocalcaemia) and Mg (hypomagnesaemia) deficiency. Calcium is required for smooth muscle function and has a direct role in uterine contraction, so may influence the duration of parturition. Low Ca and Mg intake both influence insulin release and sensitivity, low Mg results in poor glycaemic control and insulin resistance by impairing both insulin secretion and its action on peripheral tissues, also potentially altering the duration of parturition as well as risk of metabolic disease. Magnesium is also a neuroprotectant that slows the neuronal damage during hypoxia and has been linked with thermogenesis in offspring and increased immunoglobulins in colostrum. These functions indicate potential importance in improving the ease of parturition and improved ability of the newborn lamb to thermoregulate and survive after birth. Subclinical Ca and Mg deficiencies commonly occur in 20% of lambing ewes grazing temperate pastures, so further studies are warranted to investigate whether correction of these deficiencies can improve lamb survival.

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&lt;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.

Survival of lambs from maiden ewes may not be improved by pre-lambing exposure to mature lambing ewes

The survival of lambs born to ewes at their first (maiden) lambing is generally lower than for those born to ewes which have previously lambed, and poor maternal behaviour is a contributing factor. This study examined whether pre-lambing exposure of maiden ewes to multiparous lambing ewes would improve the survival of lambs born to maiden ewes. Pregnant maiden (n = 333, 2 years of age) Merino ewes were allocated to three replicates of two treatments: exposed – maidens were grazed with multiparous Merino ewes (n = 111, 5 or 7 years of age), which were due to lamb during the 2 weeks before the start of maiden lambing, with mature ewes comprising 50% of the mob size; and non-exposed – maiden ewes grazed in paddocks without mature ewes. The total number of ewes per paddock (74), number of ewes per hectare (14.0) and paddock size were the same in both treatments. The number of lambs born per ewe was similar between treatments, indicating a similar proportion of multiple births. The proportion survival of lambs from maiden ewes exposed to adults (0.53) tended to be lower (P = 0.091) than the survival of lambs born to maiden ewes grazing alone (0.61). The number of lambs marked per ewe lambing was similar (P = 0.284) in exposed (0.71) compared with non-exposed (0.78) maidens. The survival of lambs from maiden ewes was not improved by lambing in the same paddock with adults, even where the adults had largely completed lambing before the maidens commenced.

Vigour of lambs newly born to outdoor wintering ewes

The aim of the present investigation was, to examine whether outdoor wintering of lambing ewes is a successful and animal friendly production system. The welfare and growth performance of winterborn lambs in outdoor husbandry were assessed in two winter periods (1995/96, 1996/97) when a total of 353 lambs were born into three different husbandry systems. System 1 consisted of 75 lambs from 26 (winter 1) and 29 (winter 2) ewes and was wintered outdoors with access to a lambing shelter with a straw bedded floor. System 2 included 120 lambs from 52 (winter 1) and 54 (winter 2) ewes which were born in an uninsulated barn with access to an outdoor yard. System 3 was kept in an uninsulated barn with no access to the outside and consisted of 158 lambs from 52 (winter 1) and 54 (winter 2) ewes. The lambs were of five different genetic origins which were equally distributed over the three husbandry systems. The genetic groups included purebreds from the hardy ‘Rhönschaf’ (RHO) and from the ‘German Blackface’ (GBF) mutton breed and the reciprocal crosses of these breeds (GBF ✕ RHO, RHO ✕ GBF). The fifth group were crossbreds between rams of the small-framed French mutton breed ‘Charmoise’ (CHA) and Rhönschaf-ewes (CHA ✕ RHO). The time period between parturition and first standing (‘time to stand’) and the time period from birth to first sucking (‘time to suck’) were considered as vigour traits. Vigour was visually assessed and scored. The rectal temperature was measured 3 h post partum. Live-weight gains were estimated from birth to 25 and 42 days of life. No differences between the different husbandry systems were observed in the measured traits. Outdoor-born lambs showed the same vigour and were able to maintain homeothermy as well as those born indoors. Ewes sought the shelter prior to lambing which might have favoured the early vigour of lambs and thus, their ability to maintain homeothermy. The visually assessed vigour score was in good accordance with the vigour traits time to stand and time to suck. The breed of the ewe had a significant effect on lamb vigour, lambs from hardy RHO ewes showing a better vigour than lambs from GBF ewes. Hybrid vigour estimates of time to stand and time to suck were 0·17 and 0·20, respectively, but were not statistically significant.

Crossbred lambs between GBF and CHA mutton rams and hardy RHO ewes had a good vitality and growth performance. Outdoor wintering with a lambing shelter did not adversely influence survival of newborn lambs or their subsequent growth performance.

Survival implications of the development of behavioural responsiveness and awareness in different groups of mammalian young

This paper focuses on the development of behaviours that are critical for the survival of newborn and juvenile mammals of veterinary and wider biological interest. It provides an updated, integrated and comparative analysis of how postnatal maturation of sensory, motor and perceptual capacities support and constrain behavioural interactions between mammalian young and the mother, any littermates and the environment. Young that are neurologically exceptionally immature, moderately immature and mature at birth are compared, and include, for example, marsupial joeys, rodent pups and ruminant offspring. Mothers in these three groups exhibit distinctive patterns of birthing and postnatal care behaviours. To secure survival of the young, maternal care must compensate for behavioural inadequacies imposed by the limited sensory capacities the young possess at each stage. These sensory capacities develop in a predictable sequence in most mammals such that before birth the sequence progresses to an extent that parallels the degree of neurological maturity reached at birth. The extent of neurological maturity is likewise reflected in how long it takes after birth for the necessary brain circuit connectivity to develop sufficiently to support cortically based cognitive modulation of behaviour. This takes several months, days-to-weeks or minutes-to-hours in young that are, respectively, neurologically exceptionally immature, moderately immature, or mature at birth. Once achieved, cognitive awareness confers a high degree of behavioural flexibility that allows the young to respond more effectively to the unpredictability of their postnatal environments. It is shown that the onset of this cognitively based flexibility in the young of each group coincides with their first exposure to a variable environment that requires such behavioural flexibility.

Lamb survival in Australian flocks: a review

Lamb survival is known to be a key component of reproductive efficiency in sheep flocks. It has been the subject of a large number of studies over the decades and this review provides an update and insights into the latest understanding of the extent and variability of lamb losses across Australia. The pattern of causes of lamb losses, including dystocia, starvation/exposure, mismothering and predation, are examined. Likewise the importance of birthweight in contributing to such losses is discussed as are strategies for improving lamb survival. The strategies examined include improved ewe nutrition, shelter provision and selection for cold resistance and improved maternal behaviour.

The use of GNSS technology to identify lambing behaviour in pregnant grazing Merino ewes

This current study investigated whether pre-lambing behavioural changes could be identified with the use of global navigation satellite system (GNSS) technology. GNSS devices were deployed on 20 pregnant Merino ewes grazing a 1.6 ha paddock and their lambing activity was compared with the metrics derived from the spatial data. The aims were to evaluate the lambing event using the following three separate metrics: (1) mean daily speed (MDS) of ewes 7 days before and to 7 days after lambing, inclusive (n = 12); (2) mean hourly speed (MHS) 12 h before and 12 h after lambing, inclusive (n = 9); and (3) the mean distance the lambing ewe to her peers in the 7 days before and the 7 days after lambing (mean distance to peers (MDP); n = 9), inclusive. There was a significant (P < 0.01) difference between pre- and post-lambing MDS with average ± se MDS pre-lambing being faster than post-lambing (0.051 ± 0.0004 vs 0.047 ± 0.0005 m/s). Pre- and post-lambing MHS differed significantly (P < 0.05), with mean ± s.e. MHS pre-lambing being faster than post-lambing (0.049 ± 0.002 vs 0.038 ± 0.002 m/s). Mean distance to peers indicated that at the time of lambing, ewes were significantly (P < 0.01) further from their peers than at either pre- or post-lambing (83.6 ± 14.59 vs 35.2 ± 2.82 vs 35.6 ± 1.68 m). Despite MDS and MHS metrics indicating significant changes pre- and post-lambing, neither metric was able to identify the time of lambing. The MDP metric could not identify differences pre- and post-lambing but was useful at predicting lambing. The current study found that MDS and MHS metrics have the potential to determine a ‘trigger’ point that could identify parturition and therefore could be used to determine the day of lambing. Therefore, further research is required to determine if a combination of these metrics could identify pre-lambing activity that would enable informed management decisions to be made.

Survival of twin lambs is increased with shrub belts

Abstract Perinatal lamb mortality is a major source of reproductive loss, particularly for twins. A study was conducted to determine whether provision of shelter in the form of shrub belts (a ‘maternity ward’) could increase survival of twin lambs compared with hedgerows, and whether hedgerows improve survival of single lambs compared with unsheltered paddocks. Measurements were recorded for Merino × Poll Dorset cross twin lambs born in hedgerows (phalaris or hessian) or shrub belts and single lambs born in hedgerows or unsheltered paddocks over the years 2007–2009. Records for 382 single and 726 twin lambs were used. The survival of single lambs was not increased (P = 0.06) by hedgerow shelter. The survival of twin lambs in shrubs was 10% higher (P < 0.05) than that in hessian hedgerow shelter in 2008–2009 (0.77 cf. 0.70), associated with a reduction in deaths from starvation and/or mismothering and/or exposure. The hessian shelter was associated with an increased (P < 0.05) growth rate to weaning of single lambs, but the growth rates of twin lambs were lower (P < 0.05) in shrub than in hessian shelter. In 2010, a second study of 178 twin Merino × Poll Dorset cross lambs found that survival of lambs born alive was not improved by shrubs compared with unsheltered paddocks (0.80 versus 0.77; P > 0.05). It is concluded that shrub belts which forced twin-bearing ewes to lamb in a sheltered environment reduced perinatal mortality in one of three datasets, but was not repeated. The shrubs take time to establish, and the benefit will be small if weather is mild during lambing.

Relationship between lamb vigour and ewe behaviour at parturition

Maternal behaviour and lamb vigour are both considered major variables affecting lamb survival, but there are few data to describe their relative importance. To investigate the relationship between lamb vigour and maternal behaviour this study compared the behaviour of pure Scottish Blackface lambs with Mule (Bluefaced Leicester ♀. × Scottish Blackface ♂) lambs, all born indoors. Anecdotal accounts suggested a significant reduction in lamb vigour in Mule lambs, a matter also of significant practical importance given the current incease in Mule numbers. Observations on the grooming behaviour of 32 single or twin-bearing ewes, and on the general activity and udder-seeking behaviour of their lambs were made at parturition. In this study, neither ewe grooming behaviour nor general lamb activity were directly related to lamb sucking success. It was shown that, although Mule lambs had high birth weights and stood as quickly as Blackface lambs, they showed significantly fewer sucking attempts (P < 0·01) and took longer to suck successfully (28 min for Blackface v. 55 min for Mules). The inability of Mule lambs to suck successfully was due to their failure to show proper udder-directed behaviour. These results indicate the importance of considering the behaviour of both ewes and lambs as it would seem that it is not ‘poor’ maternal behaviour but inappropriate lamb behaviour that is a limiting factor in lamb survival in the Mule breed.

From birth to colostrum: early steps leading to lamb survival

New-born lambs have limited energy reserves and need a rapid access to colostrum to maintain homeothermy and survive. In addition to energy, colostrum provides immunoglobulins which ensure passive systemic immunity. Therefore, getting early access to the udder is essential for the neonate. The results from the literature reviewed here highlight the importance of the birth site as the location where the mutual bonding between the mother and her young takes place. Attraction to birth fluids by the periparturient ewe leads to intense licking of the lamb. Grooming not only dries, cleans and stimulates the newborn it also facilitates bonding through learning of its individual odour. Ewes having twins should ideally stay on the birth site for at least six hours in order to establish a strong bond with both lambs and favour lambs survival. However, primiparous ewes or ewes having high levels of emotivity are more likely to exhibit poor maternal behaviour. In addition, difficult parturition and weather conditions have an indirect effect on the behaviour of the mother and are other major causes of lamb death. On the lamb's side, rapid access to the udder and early suckling are extremely important. Delayed lactation or insufficient colostrum yield may be fatal especially since suckling has strong rewarding properties in the establishment of a preference for the mother, which in turn increases lamb survival. Insufficient access to the udder in mothers leaving the birth site too soon after parturition, especially in twin-bearing ewes, could also partly account for the high incidence of loss of mother-young contact and subsequent death in such lambs. Strategies to improve neonatal survival should be aimed at maximising lamb vigour, colostrum production, and mutual mother-young bonding through adequate feeding in late pregnancy and selection on behaviour.

Maternal responsiveness and maternal selectivity in domestic sheep and goats: The two facets of maternal attachment

Sheep and goats rapidly establish an exclusive relationship with their neonate following contact with it during a sensitive period of maternal responsiveness induced by the physiological events occurring at parturition. The data concerning the sensory, physiological, and neurobiological factors involved in the activation of both maternal responsiveness and the establishment of selective nursing indicates that these processes are activated simultaneously by the combined action of two main factors, the prepartum rise in circulating estrogen and the vaginocervical stimulation (VCS) caused by fetus expulsion. On the one hand, these two factors act on a neural network including the main olfactory system (MOB), the medial preoptic area (MPOA), and the paraventricular nucleus of the hypothalamus (PVN) to induce maternal responsiveness towards any neonate. The intracerebral release of oxytocin (OT) from the PVN, and the triggering of olfactory attraction for amniotic fluid (AF) are key elements in this process. On the other hand, VCS at birth also sets the MOB ready to memorize the individual odor of the neonate, through the release of peptides and neurotransmitters (noradrenaline and acetylcholine). In addition to the MOB, the network involved in recognition mainly includes the medial and cortical amygdala. Across consolidation processes, reorganization occurs in the network engaged in lamb recognition. Whether this memorization may be potentiated by other sensory cues is not known. The identification of the chemosensory compounds involved in the attraction for AF and in the recognition of the neonate is important for understanding the mechanisms of maternal attachment.

Mapping the Neural Substrates Involved in Maternal Responsiveness and Lamb Olfactory Memory in Parturient Ewes Using Fos Imaging

In sheep, recognition of the familiar lamb by the mother depends on the learning of its olfactory signature after parturition. The authors quantified Fos changes in order to identify brain regions activated during lamb odor memory formation. Brain activation was compared with those measured in anosmic ewes displaying maternal behavior but not individual lamb recognition. In intact ewes, parturition induced significant increase in Fos expression in olfactory cortical regions and in cortical amygdala, whereas in anosmic mothers, Fos expression was very low. In contrast, no difference was observed between intact and anosmic ewes in hypothalamic areas and medial amygdala, suggesting a differentiation between the neural network controlling maternal responsiveness and that involved in olfactory lamb memory.

The Welfare Implications of Shepherding During Lambing in Extensive New Zealand Farming Systems

A review of the literature was undertaken to consider the possible effects of human intervention (shepherding) at around the time of parturition in extensively farmed sheep. There is little clear empirical evidence to suggest that shepherding ensures either easy births or the integrity of ewe–lamb contact — factors closely linked to the welfare of the animals at this time. There is similarly no clear support for shepherding being harmful. However, the following suggestions are made: first, human presence can inhibit or delay parturition; second, extended parturition can increase the risk of, or is associated with, dystocia; and third, disturbance at birth can compromise ewe-lamb bonding and consequently lamb survival. Furthermore, sheep populations that have undergone rigorous selection for ease of lambing and minimal shepherding in extensive environments have well-documented physical and behavioural traits underlying their predisposition for enhanced lamb survival. Although our cultural legacy may impose a duty to intensively monitor animals at lambing, it is concluded that, at least in some situations, shepherding may not be entirely beneficial. The commonly held view of the necessity for some human intervention in extensive livestock systems is perhaps overly paternalistic, and requires a more comprehensive appraisal.

Physiological correlates of maternal-offspring behaviour in sheep: a factor analysis

The onset of maternal behaviour in sheep is controlled by levels of oestrogen and progesterone in gestation and the release of oxytocin during delivery. Factor analysis was used to investigate the relationships between maternal behaviour, offspring behaviour, and maternal ovarian hormone levels during gestation in sheep. Ewes gave birth to lambs following embryo transfer between two breeds (Suffolk and Scottish Blackface), which differ in their expression of maternal behaviour. Plasma oestradiol-17beta concentration was significantly higher in Blackface ewes in the last 6 weeks of pregnancy, whereas plasma progesterone was higher in Suffolk ewes in early and mid gestation. Factor analysis revealed three factors that accounted for 50% of the total variation between variables. Factor 1 described lamb activity and had positive loadings for lamb behavioural latencies immediately postpartum, and negative loadings for sucking frequency. Factor 2 described some aspects of ewe maternal behaviour, and had positive loadings for ewe-lamb separation and lamb vocalisation, and negative loadings for ewe grooming behaviour and plasma oestradiol concentration. Factor 3 described ewe and lamb-sucking interactions, and had positive loadings for ewe moving as the lamb made sucking attempts, and negative loadings for ewe and lamb vocalisation. Factor 1 scores were significantly affected by lamb breed: Suffolk lambs received positive scores, indicating a longer latency to right and stand, whereas Blackface lambs had negative scores. Maternal progesterone concentration was significantly correlated with Factor 1 scores. Factor 2 and 3 scores were significantly affected by ewe breed. This study has shown that there are two behavioural axes to maternal behaviour in sheep, and that maternal oestradiol concentration is related to affiliative behaviours (e.g., grooming) but only weakly to ewe responsiveness to lamb-sucking attempts.