Neonatal Lamb Mortality Research Articles

Risk factors associated with neonatal mortality in LAMBS: An overview

Risk factors associated with neonatal mortality in LAMBS: An overview

Ewe udder and teat traits as potential selection criteria for improvement of Merino lamb survival and growth

Neonatal lamb mortality is a major economic and welfare issue for Australian sheep producers. The contribution of udder and teat traits of the dam to the survival and subsequent growth of the lamb is relatively unknown. This study aimed to estimate phenotypic and genetic parameters associated with objectively measured and visually scored udder and teat traits in Australian Merino sheep, and to evaluate the impacts of udder and teat traits of the dam on survival and growth of their lambs to weaning. Ewes from the New England Merino Lifetime Productivity flock (n = 1341 ewes) were assessed for udder and teat traits, and phenotypic and genetic parameters for individual traits and relationships among them were estimated using linear mixed models. Odds ratios were calculated to investigate the influence of udder soundness on lamb mortality. Further, the influence of udder traits on variation in lamb weaning weight was explored. Measured udder and teat size traits were estimated to have moderate to high heritabilities (0.32 (0.09) to 0.56 (0.10)), while the heritabilities of visually scored traits were lower (0.09 (0.05) to 0.17 (0.07)). Measured traits were highly correlated genetically with their equivalent visually scored traits. The odds ratio of mortality for lambs born to ewes with unsound versus sound udders was 1.54 (95 %CI 1.1–2.2, P < 0.05). The odds ratio of lamb mortality from starvation compared to all other causes of death for lambs born to ewes with unsound versus sound udders was 4.62 (95 %CI 2.4–8.9, P < 0.001). Dam udder and teat traits collectively contributed 8 % of the variation in lamb weaning weight observed. Results suggest that targeting optimal ewe udder and teat characteristics in sheep breeding programs has the potential to significantly improve lamb survival and growth in extensive production systems.

Neonatal mortality of lambs in production systems in a semi-arid environment: main risk factors

AbstractThe sheep farming has economic and sociocultural importance in semi-arid regions worldwide. Of the total of 1.2 billion sheep in the world, 0.4 are found in semi-arid regions. In this review, we have discussed the main risk factors for neonatal lamb mortality and its association with the prevailing environmental conditions of tropical semi-arid regions. Over the last decades, the average mortality rate of newborn lambs remained relatively constant (~15%) around the world. This rate is reported to be higher (Up to 30%) in small-scale sheep farming systems from developing countries. Overall, the main risk factors of neonatal mortality include low birth weight, dystocia, adverse weather conditions, inadequate milk, or colostrum supply, competition between siblings in multiple births, and poor expression of maternal behaviour. In tropical semi-arid regions, recent findings revealed that newborn lambs from hair coat sheep breeds are less vigorous to perform the first suckling when even exposed to moderate cold conditions (18–20°C). On the other hand, the high radiant heat load in these areas can also challenge the thermoregulation of ewes and newborn lambs, especially if they are kept in areas without protection against direct short-wave solar radiation. Under such circumstances, newborn lambs were reported to be hyperthermic. The heat stress as risk factor for neonatal lamb mortality is a topic that deserves more investigation, particularly in tropical semi-arid areas, where is expected to be drier and hotter as consequence of rapid advances in climate change.

Reaction-norm analysis of neonatal lamb mortality suggests heritability varies with cold-stress: an example in the Elsenburg Merino selection lines

Context Coping with high levels of cold stress should be beneficial to survival of lambs, given the high mortality rate associated with severe winter storms. The Elsenburg Merino selection experiment involved divergent selection for reproduction. Phenotypic results comparing the positively selected H-Lines and negatively selected L-Lines suggested that cold-stress adaption could have contributed to the favourable genetic trends for survival of H-Line lambs. However, observing the genetic merit of better adapted animals depends on the presence of cold stress at the time of recording. A genotype by environment component (G × E) could, thus, be important when assessing survival/mortality phenotypes. Aim This study proposed the genetic analysis of this possible G × E component and compared the H- and L-Lines in this regard. Methods The sire model allowed the use of progeny phenotypes for neonatal mortality recorded during different levels of cold stress, and the possible G × E could be investigated through the reaction-norm approach. Genetic parameters were evaluated as random regression components by implementing a Gibbs sampling approach. A data set of 5723 individual lamb records was analysed as the progeny of 213 sires. Results A modelled G × E component played an important role in mortality outcomes, with the mean estimate (and 95% confidence interval) for the slope ( σ s b 2 = 0.113 [ 0.0019 – 0.28 ] AN22464_IE1.gif) only marginally smaller than the corresponding estimate for the intercept ( σ s a 2 = 0.124 [ 0.003 – 0.26 ] AN22464_IE2.gif). The reaction-norm model showed a higher heritability (h2 ± posterior standard deviation) for mortality at 3 days of age during high cold-stress (0.22 ± 0.16 at ~1100 KJm−2h−1) than during mild (0.13 ± 0.10 at ~960 KJm−2h−1) conditions, suggesting a greater ability to discriminate between sires at increasing stress levels. Conclusions Failure to account for this G × E component putatively contributes to the low h2 commonly reported for survival traits. The higher h2 at increased levels of cold stress could have played an important part in the higher survival of the H-Line progeny, who were better at coping with cold, wet and windy conditions. Implications Larger studies representing a wider environmental trajectory are recommended. This should be very feasible since cold stress can be derived from commonly available weather-station data.

Using Pen-Side Measurable Blood Parameters to Predict or Identify Dystocic Lambing Events.

Simple SummaryProlonged or non-progressive labour is the greatest risk factor for loss of newborn lambs in Australia and poses significant welfare and economic concerns worldwide. In this study, we set out to investigate whether pen-side technology could be used to predict which ewes would be at risk of prolonged labour. In our pilot trial, we found potentially useful markers. We next developed a sampling protocol by looking at changes in candidate markers over time in normal lambing events. Finally, we searched for blood markers that could distinguish between normal and difficult lambing events, sampling pre-birth (estimated one week before birth), at birth (within 3 h) and post-birth (16–26 h). Possible predictors of lambing difficulty were chloride, haematocrit and haemoglobin, sampled one week before birth; creatinine, sampled at birth; and acid–base related parameters after birth. In conclusion, we found that pen-side analysis of blood markers showed promise in identifying dystocic lambing events. More information is required to decide whether pen-side diagnostics could be useful to identify and predict dystocic lambing in the future.Dystocia is the greatest contributor to neonatal lamb mortality in Australia and poses significant welfare and economic concerns worldwide. In this study, we set out to investigate whether pen-side analysis technology could be employed to detect blood parameters predictive of dystocic labour events in sheep. In a pilot trial, we collected and analysed blood samples in pen-side assays for glucose, lactate, pH, pCO2, pO2, base excess, HCO3, TCO2, sO2, lactate, sodium, potassium, chloride, calcium, urea nitrogen, creatinine, haematocrit, haemoglobin and anion gap. From the pilot data, we identified creatinine, TCO2, chloride and calcium as potentially useful markers. To develop a time course and to establish variability of the selected blood parameters, a time series of samples was collected from 12 ewes, from mid-gestation to 48 h after birth. For the main trial, blood samples were collected at mid- and late gestation for glucose determination and for the full set of blood parameters at three time points before, at and after birth. Possible predictors of lambing difficulty were chloride, haematocrit and haemoglobin, sampled one week before birth; creatinine, sampled at birth; and blood pH and base excess after birth. In conclusion, we found that pen-side analysis of blood markers showed promise in identifying dystocic lambing events.

Spatial behaviour of sheep during the neonatal period: Preliminary study on the influence of shelter

Effective shelter has been demonstrated to reduce neonatal lamb mortality rates during periods of inclement weather. Periods of high wind speed and rainfall have been shown to influence shelter usage; however, it is not yet known how ewe factors such as breed, age and body condition score influence shelter-seeking behaviour. This study, conducted on a working upland farm in the UK, examined impact of artificial shelter on the biological and climatic factors that influence peri-parturient ewe behaviour. Pregnant ewes (n = 147) were randomly allocated between two adjacent fields which were selected for their similarity in size, topography, pasture management, orientation to the prevailing wind and available natural shelter. In one field, three additional artificial shelters were installed to increase the available shelter for ewes, this field was designated the Test field; no additional artificial shelter was provided in the second field which was used as the Control field. Individual ewes were observed every 2 h between 0800 and 1600 for 14 continuous days to monitor their location relative to shelter. Ewe breed (Aberfield and Highlander), age (2–8 years) and body condition score were considered as explanatory variables to explain flock and individual variance in shelter-seeking behaviour and the prevalence of issues which required the intervention of the shepherd, termed ‘shepherding problems’. Any ewe observed with dystocia, a dead or poor vigour lamb or who exhibited mismothering behaviour was recorded as a shepherding problem. The prevalence of these shepherding problems which necessitate human intervention represents arguably the most critical limiting factor for the successful management of commercial sheep flocks in outdoor lambing systems. Overall, ewes in the Test field with access to additional artificial shelter experienced fewer shepherding problems than those in the Control field (P < 0.05). A significant breed effect was also observed, with Highlander ewes more likely to seek shelter than Aberfield ewes (P < 0.001), and experiencing significantly fewer shepherding interventions (P < 0.05). These findings demonstrate the substantial and significant benefits to animal welfare and productivity that can be achieved through the provision of shelter in commercial, upland, outdoor lambing systems in the UK.

Better odds of lamb survival in sheep at dry arid tropical region of India

Lamb survival till first 28 days of life is critical as it increases the chances of economic gain in flock. Objective of the current study was to assess the incidence of neonatal mortality in lambs born in arid region of India and genetic and non-genetic factors affecting it. The present study was conducted using the data on 4,137 Magra and 4,595 Marwari sheep over 17 years (1999 to 2016). Incidence of neonatal mortality was very low in Magra (1.04%) and Marwari (2.48%) sheep, respectively in semi-intensive management system. Year and seasonal variation was observed for neonatal losses. Males had lower odds of survival as compared to females. Odds of survival were low if the lambs were born to dams of low body weight and in their first parity. It was observed that the lamb survival can be improved if due care of the lambs born with low birth weight (&lt;2 kg) is taken. The heritability estimate was moderate in Magra sheep (0.17), indicating further scope for genetic improvement for lamb survival through selection. However, for Marwari sheep, the total heritability was 0.02, thus limiting the scope for selection. Arid region favoured the lamb survival. Hardiness of the Magra and Marwari sheep, their high lamb survival along with standard production potential is indicative of the good genetics of these sheep along with better management practices adopted at arid regional campus, thus reflecting better sheep welfare practices.

Transcriptome Landscape of Intracellular Brucella ovis Surviving in RAW264.7 Macrophage Immune System

Brucella ovis infection results in genital damage and epididymitis in rams, placental inflammation and rare abortion in ewes, and neonatal mortality in lambs. However, the mechanism underlying B. ovis infection remains unclear. In the present study, we used prokaryotic transcriptome sequencing to identify the differentially expressed genes (DEGs) between wild-type B. ovis and intracellular B. ovis in RAW264.7 macrophages. Gene ontology (GO) term enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed, and quantitative reverse transcriptase PCR (qRT-PCR) was used to validate the top 10 upregulated and downregulated DEGs. The results showed that 212 genes were differentially expressed, including 68 upregulated and 144 downregulated genes, which were mainly enriched in 30 GO terms linked to biological process, cellular component, and molecular function. KEGG analysis showed that the DEGs were enriched in the hypoxia-inducible factor 1 (HIF-1) signaling pathway, mitogen-activated protein kinase (MAPK) signaling pathway, beta-alanine metabolism, and quorum sensing pathway. BME_RS01160, BME_RS04270, BME_RS08185, BME_RS12880, BME_RS25875, predicted_RNA865, and predicted_RNA953 were confirmed with the transcriptome sequencing data. Hence, our findings not only reveal the intracellular parasitism of B. ovis in the macrophage immune system, but also help to understand the mechanism of chronic B. ovis infection.

Watery mouth disease in neonatal lambs: a systematic literature review

Watery mouth disease is considered to be a significant cause of neonatal mortality in lambs. The clinical signs are strongly associated with an endotoxaemia produced as a result of the lysis of Gram-negative bacteria. It has been associated with mass antibiosis to neonatal lambs at birth, a practice which is now untenable. It can be prevented in many cases through the timely administration of good quality colostrum and a hygienic birth environment. However, despite this, much remains unknown about the specific aetiopathogenesis. Alternative strategies for prevention, treatment and control are required, particularly when colostrum quality is poor, or delivery is absent, and where unhygienic conditions predominate.

The Relationship between Neonatal Lamb Mortality and Toxoplasmosis

In this study, it was aimed to reveal the relationship between neonatal lamb mortality and toxoplasmosis. The study was carried out in a sheep farm that declared the death of lambs. Brood ewes (N= 50) were included into the study and they were divided into 2 groups. The first group consisted of 25 sheep whose lambs had died, and the second group consisted of 25 sheep whose lambs were alive. Blood samples were collected from the two groups and the blood sera were obtained. The sera were examined with the Sabin-Feldman Dye Test for the antibodies against Toxoplasma gondii (T. gondii). Of the 50 blood sera examined, 29 (58%) were positive for T. gondii, 20 (80%) of which were from the sheep whose lambs had died. On the other hand, only 9 (36%) of 25 blood sera from the sheep with healthy lambs were found to be positive. The frequency of T. gondii infestation was statistically evaluated by chi-square test and the difference between the two groups was found to be significant. (p

Seroprevalence and risk factors of Brucella ovis in domestic sheep in Wyoming, USA

BackgroundBrucella ovis causes a sexually transmitted, infectious disease of domestic sheep characterized by genital lesions and epididymitis in rams, placentitis and rare abortions in ewes, and neonatal mortality in lambs. This study was designed to 1) estimate animal and flock seroprevalence of B. ovis in sheep across Wyoming, USA, and 2) describe epidemiologic risk factors associated with seropositive sheep and flocks. For the animal seroprevalence estimate, 2423 blood samples were collected from sheep on 18 producer-selected operations and a questionnaire about possible risk factors was distributed. For the flock seroprevalence estimate, blood samples from 82 operations were obtained, including samples from the previous 18 operations and 64 additional operations that sent samples to the Wyoming State Veterinary Laboratory for diagnostic testing. Categorical risk factors were created based on questionnaires and submission forms. Sera was analyzed using the B. ovis enzyme-linked immunosorbent assay.ResultsEstimated true animal and flock seroprevalence were 0.53% (95% CI: 0.21–1.01%; 22/2,423) and 22.5% (95% CI: 14–32%; 18/82), respectively. Using Fisher’s exact and Mid-p exact tests to compare apparent seroprevalence with respect to possible risk factors, increased age and breed type were risk factors associated with seropositive sheep, while region and large flock size were risk factors associated with seropositive flocks.ConclusionsResults from this study suggest few sheep have been exposed to B. ovis, but many flocks contain at least one seropositive animal. Each region in Wyoming contained at least one seropositive animal and flock, emphasizing the importance of disease-free documentation before purchasing new sheep. Aged sheep (≥ 6 years of age) had the highest seroprevalence among age groups; hence, we propose the separation of young rams from older rams to help reduce disease spread outside the breeding season. Wool breeds (Rambouillet and Merino) may be less susceptible to B. ovis infection given they had the lowest animal seroprevalence of the breed types, and large flocks (> 100 breeding rams) had the highest seroprevalence of the flock size categories, likely due to more intensive management strategies that can contribute to the introduction and persistence of B. ovis infection in sheep and flocks.

An approach to neonatal lamb post-mortem examinations

Neonatal lamb mortality is a significant threat to welfare and production in commercial sheep flocks and is defined as the death of lambs during the first week of life with the predominant risk period being the first 48 hours. Lamb mortality between scanning and sale ranges from 10 to 25%, with examples of losses between 0 to 48 hours old ranging from 5.9% to 12.5%. Lamb post-mortem examinations are a tool which can facilitate achieving further understanding of the scale and cause of losses for flocks. We discuss an approach to postmortem examinations on neonatal lambs, the common differentials affecting lambs between 0 and 48 hours old, and discuss the role of farmers in surveillance.

Risk factor analysis for neonatal lamb mortality in Malpura sheep

The magnitude of risk for neonatal mortality (NM) due to non-genetic factors was assessed using data on 5,722 Malpura lambs born during 1991–2016 at ICAR-Central Sheep and Wool Research Institute, Avikanagar, Rajasthan. The association of non-genetic factors influencing lamb mortality was obtained by odds ratio (OR). The overall annual NM was 4.07% with around 3 times higher in hebdomadal (3.15%) than post-hebdomadal (0.93%) phase. In comparison to lambs with &gt;3.50 kg birth weight, the OR varied from 2.03 (birth weight 3.01–3.50 kg) to 19.29 (birth weight &lt;2.00 kg). Neonatal mortality was significantly higher (6.51%) in lambs born to younger ewes (up to 2 yr). The parity of dam had significant effect on NM with maximum mortality in lambs born to ewes in 1st (5.59%) parity. Dam’s weight at lambing revealed significantly maximum (32.35%) mortality in lambs born to ewes with &lt;20.0 kg body weight. In comparison to ewes with 30–35 kg body weight at lambing, the OR for NM was maximum (17.28) in lambs born to ewes with &lt;20.0 kg body weight at lambing. The causes of neonatal lamb mortality exhibited predominance of septicaemia/ toxaemia with 25.75% contribution in total deaths followed by neonatal inanition (21.89%), pneumonia (12.02) and enteritis (8.58%). The study revealed that NM during early phase of life was primarily influenced by both lamb and ewe factors. Strategies should be adopted for proper nutritional care of primiparous and weak ewes during gestation, intensive monitoring of lamb and ewes during the neonatal period with ensured colostrum or milk replacer feeding and suitable housing facility to minimize the neonatal losses.

Risk factor analysis for neonatal lamb mortality at an organized farm of arid Rajasthan

Risk factor analysis for neonatal lamb mortality at an organized farm of arid Rajasthan

Genetic parameters for neonatal mortality in lambs at semi-arid region of Rajasthan India

Lamb survival is essential for successful rearing of lambs for sale and replacement of breeding stock given a profitable sheep enterprise. The present study was conducted using the data on 4694 Avikalin, 5015 Chokla and 5718 Malpura sheep recorded from 1991 to 2016 for studying the neonatal mortality in lambs. The effect of influential factors on neonatal mortality of lambs was ascertained and the genetic parameters for lamb survival till first 28 days of life using Gibbs sampling were estimated. Incidence of neonatal mortality was 4.29%, 5.17% and 4.07% in Avikalin, Chokla and Malpura sheep, respectively. Logistic regression analysis revealed significant impact of year of birth and lamb's birth weight on neonatal mortality for all the breeds. Year (1997, 2011–12) negatively affected the survival due to sudden shift in policy decision. Dams with low body weight and in their first parity were also found to affect the lamb survival negatively. Due care of the lambs born with low birth weight (< 2.00 kg) and for primi-parous dams with low weight (< 20.00 kg) can improve the chances of lamb survival. Genetic analysis revealed that the direct heritability for Avikalin sheep was 0.17 ± 0.02, indicating scope for genetic improvement through selection. However, for Chokla and Malpura sheep the direct heritability were 0.05 ± 0.00 and 0.06 ± 0.01, respectively. Maternal permanent environmental effect was important in Avikalin and Chokla sheep with maternal heritability estimates of 0.10 and 0.11, respectively. However, for Malpura sheep, with little genetic variance, only direct genetic effect was important. Apart from care and management, accounting for both direct and maternal effects in breeding program can improve the lamb survival.

Wind chill index and neonatal lamb mortality at an organized farm in semi-arid Rajasthan

Using climatic data from 1991 to 2016 recorded at Avikanagar, wind chill index (WCI) was calculated for each day during winter (December–February) coinciding with major lambing season. The WCI (kcal/m2/h) was categorized as no chill (<300.0), low (<300.1–350.0), moderate (350.1–400.0), high (400.1–450.0) and extreme (>450.1) and the neonatal lambs death (857) in a total of 2257 days (December–February of each year) were considered to observe the effect of WCI. The overall annual neonatal lamb mortality was 5.85%. Over the years daily WCI revealed a significant increase in number of extreme chill days (WCI > 400.1 kcal/m2/h) since December 2003. The overall proportion of neonatal death ranged from 2.10% (WCI < 300 kcal/m2/h) to 69.34% ((WCI > 400.1 kcal/m2/h). The climatic data showed that out of total days, majority of days (64.99%) covered were of high to extreme chill in nature (WCI > 400.1 kcal/m2/h). The daily rate of neonatal mortality found to possess a positive and linear relation with WCI and ranged from 0.25 lamb death/day (WCI < 300 kcal/m2/h) to 0.46 lamb death/day (WCI > 450.1 kcal/m2/h). The entities responsible for exposure-inanition syndrome (EIS, debility, exposure, inanition) had positive relation with WCI. The contribution of EIS in overall neonatal mortality ranged from 29.08 (WCI 300.1–350.0 kcal/m2/h) to 42.00% (WCI > 450.1 kcal/m2/h). The analysis suggested requirement of proper shelter management for neonatal lambs during extreme climate.

Can farmers reliably perform neonatal lamb post mortems and what are the perceived obstacles to influencing lamb mortality?

Neonatal lamb mortality constitutes a significant economic cost and is an important welfare challenge. Despite compelling evidence for reduction strategies and cost benefits associated with them, there has been no documented reduction in mortalitysince the 1970’s. We aimed to evaluate whether a knowledge exchange solution could be used to define farm specific loss risks accurately. This was done by training farmers how to examine neonatal lambs post-mortem to record and interpret common causes of mortality by following a basic framework. We used participatory rural appraisal to assess some of the existing challenges to reducing lamb mortality. When considering outcomes for specific post mortem questions, there was 87.5% agreement between veterinary and farmer answers and 82.3% of farmer diagnoses (n=96) agreed with the veterinary conclusions. When merged with farmer performed post-mortems, farm specific mortality pie-charts were developed to highlight the variation between flocks and the necessity for flock specific advice. Common challenges to reducing lamb loss included level of labour, skill set of labour, communication within teams and whether farmers generally considered post-mortems to be a valuable tool. We consider that farmer post-mortems of lambs could be a tool for the veterinary-farmer team, facilitating the communication of farm specific advice and empowering farmers to effect positive change.

Early neonatal lamb mortality: postmortem findings

An investigation of stillbirth and early neonatal lamb mortality was conducted in sheep flocks in Norway. Knowledge of actual causes of death are important to aid the interpretation of results obtained during studies assessing the risk factors for lamb mortality, and when tailoring preventive measures at the flock, ewe and individual lamb level. This paper reports on the postmortem findings in 270 liveborn lambs that died during the first 5 days after birth. The lambs were from 17 flocks in six counties. A total of 27% died within 3 h after birth, 41% within 24 h and 80% within 2 days. Most lambs (62%) were from triplet or higher order litters. In 81% of twin and larger litters, only one lamb died. The most frequently identified cause of neonatal death was infectious disease (n=97, 36%); 48% (n=47) of these died from septicaemia, 25% (n=24) from pneumonia, 22% (n=21) from gastrointestinal infections and 5% (n=5) from other infections. Escherichia coli accounted for 65% of the septicaemic cases, and were the most common causal agent obtained from all cases of infection (41%). In total, 14% of neonatal deaths resulted from infection by this bacterium. Traumatic lesions were the primary cause of death in 20% (n=53) of the lambs. A total of 46% of these died within 3 h after birth and 66% within 24 h. Severe congenital malformations were found in 10% (n=27) of the lambs, whereas starvation with no concurrent lesions was the cause of death in 6% (n=17). In 16% (n=43) of the lambs, no specific cause of death was identified, lambs from triplet and higher order litters being overrepresented among these cases. In this study, the main causes of neonatal lamb mortality were infection and traumatic lesions. Most neonatal deaths occurred shortly after birth, suggesting that events related to lambing and the immediate post-lambing period are critical for lamb survival.

Preliminary survey of lamb losses (black loss) in Highland sheep flocks

THE sustainability of British sheep farming is dependent on the sale of lambs to provide income. The percentage of lambs reared is affected by losses at different stages in the...

Neonatal lamb mortality: factors associated with the death of Australian lambs

The objective of the present study was to examine the factors associated with the death of neonatal lambs. Postmortem autopsy data were collected from 3198 newborn lambs in the Sheep CRCs Information Nucleus Flock situated in various environments throughout southern Australia. The proportion dying by category from highest to lowest was starvation–mismothering (25%), stillbirth (21%), birth injury (18%), dystocia (9%), death in utero–prematurity (10%), predation (7%), cold exposure (5%), undiagnosed (4%), infection (1%) or misadventure (1%). Factors best explaining the probability of lambs falling into a death category included both birth type and birthweight for dystocia, stillbirth, starvation–mismothering and death in utero–prematurity. The probability of a lamb falling into any category was predicted at the mean birthweight, within birth type. Single-born lambs were more likely to die from dystocia and stillbirth, while twin lambs were more likely to die from birth injury, starvation–mismothering or from undiagnosed causes. Triplet lambs were more likely to die from starvation–mismothering or death in utero–prematurity. Sire type (Merino, maternal or terminal) did not affect the proportions of lambs within any category. The proportions lost to each cause of death were largely consistent among locations, despite the rate of death varying. Dystocia, stillbirth and birth injury, as evidenced by the presence of oedema around the head and neck or by lesions of the central nervous system, accounted for 48% of autopsied lambs. We conclude that for improvements to occur in the rates of lamb survival, the Australian sheep industry must focus on minimising losses due to dystocia, stillbirth, birth injury and starvation.