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Context: Proven strategies to address lamb mortality include pregnancy scanning and the differential management of single- and twin-bearing ewes. However, current adoption rates of this best-practice management by Australian producers remain low at ~20%. Aims: We explored producer perceptions about lamb mortality and the adoption of pregnancy scanning, and analysed whether producer characteristics, demographics, beliefs or management practices have an influence on perceptions towards pregnancy scanning or lamb survival. Methods: Data were collected through an on-line self-administered survey of lamb producers in New South Wales, Australia. Descriptive and inferential statistics were used to summarise the data and test for interdependence of variables. Key results: The survey results revealed that New South Wales sheep producers have low participation rates in extension programs and low engagement in record-keeping practices. Only 4% of respondents considered current lamb mortality rates acceptable and the majority agreed that lamb mortality poses a threat to Australia's sheep industry. Findings identified numerous significant relationships between producer characteristics, demographics, beliefs, management practices, non-participation in extension programs, and perceptions towards pregnancy scanning, lamb mortality and sheep welfare. Survey participants were more likely to have adopted pregnancy scanning if they had participated in extension programs. Conclusions: Further extension efforts should be focused on producers who have not adopted any record-keeping practices or previously participated in extension programs. Extension should be tailored to different enterprises, owing to the influence of enterprise focus on beliefs, while also considering producer demographics. Implications: A strong case exists for continued investment in future marketing, education, and research, development and extension to increase the capacity of Australia's sheep industry and, in particular, to increase the adoption of pregnancy scanning. Negative consumer perceptions of animal welfare associated with high lamb mortality rates pose a threat to Australia's sheep industry. Strategies to address lamb mortality include pregnancy scanning; however, current adoption rates by Australian producers are low. Key results related to producers' beliefs towards lamb survival revealed that non-participation in extension programs is a significant barrier to the adoption of pregnancy scanning, and a strong case exists for continued investment in future extension tailored to different types of sheep enterprises. [ABSTRACT FROM AUTHOR]

In a previous study we investigated the association between two single nucleotide polymorphism (SNP) genotypes, namely steroid 17-alpha-hydroxylase/17,20 lyase (CYP17) SNP628 and dopamine receptor D2 (DRD2) SNP939, with two temperaments (calm and nervous) in Australian Merino sheep and concluded that the DRD2 SNP939 T/T genotype combined with the CYP17 SNP628 G/G genotype is associated with a calm temperament and could be used as a potential marker for calm sheep, whereas the DRD2 SNP939 C allele combined with the CYP17 SNP628 A/A genotype is associated with a nervous temperament and could be used as a potential marker for nervous sheep. In sheep, the association between temperament and reproductive performance has been determined, but the association of these two SNP genotypes with sheep reproduction has not been investigated. Therefore, using Chinese Sinkiang Merino sheep, the present study investigated the association of the two CYP17 SNP628 and DRD2 SNP939 genotypes with sheep reproductive performance. Sheep with the DRD2 SNP939 T/T genotype combined with the CYP17 SNP628 G/G genotype had a higher ovulation rate, multiple gestation rate, better maternal behaviour and lower lamb mortality. Thus, the results of this study contribute to our knowledge of the association between genotypes and reproduction in sheep, which is beneficial for sheep genetics and breeding. In sheep, the association between temperament associated with two single nucleotide polymorphism (SNP) genotypes and sheep reproduction has not yet been studied. This study investigated the association between steroid 17-alpha-hydroxylase/17,20 lyase (CYP17) SNP628 and dopamine receptor D2 (DRD2) SNP939 genotypes and concluded that sheep with the DRD2 SNP939 T/T genotype combined with the CYP17 SNP628 G/G genotype had better reproductive performance and maternal behaviour. The findings may be beneficial for sheep genetics and breeding. [ABSTRACT FROM AUTHOR]

The genetic parameters for maternal rearing-ability of ewes were investigated by ignoring or defining the rearing ability trait separately by litter-size class (singles versus multiples) using multi-generational data from three, fully pedigreed Merino flocks differing in prolificacy, production level and environment. Genetic correlations (ra) between litter size (LSIZE) and the percentage of lambs surviving (PLSURV) were more negative with an increasing mean flock litter size (ra: -0.21 ± 0.17 to -0.73 ± 0.08), while the corresponding range in phenotypic correlations (rp) was substantially lower (rp: -0.15±0.01 to -0.33±0.01). Rearing-ability traits defined separately by litter-size class were highly correlated (ra: 0.49± 0.19 to 0.64±0.38), but not genetically identical traits in the most prolific flock. Defining rearing-ability traits separately by litter-size class reduced the antagonistic genetic correlations between LSIZE and PLSURV to between -0.39±0.14 and 0.14 ±0.28, through accommodating the change in mean and variance of PLSURV with LSIZE. Similarly, linear transformation (TSURV) of PLSURV within each litter size to a common mean and variance reduced the antagonistic trend in genetic correlations between LSIZE and TSURV to range between -0.05±0.17 and -0.43±0.13. Since genetic correlations are low to moderate between TSURV and LSIZE, it is possible to select for improvements in both the number of lambs born and lamb survival simultaneously. Defining rearing-ability traits separately by litter-size class and the role of transformation will be investigated further for improving the accuracy of genetic evaluation for rearing ability across a range of flocks, breeds and environmental conditions using more extensive industry data. [ABSTRACT FROM AUTHOR]

Perinatal lamb mortality is a major challenge for sheep producers worldwide. Lamb losses from ultrasound pregnancy scanning to lamb marking were assessed in 125 mobs of ewes sourced predominantly from sheep flocks in southern New South Wales. In total, 103 086 lambs were marked from100 165 ewes present at joining. Despite the majority of producers undertaking best-practice ewe management, including ultrasound scanning for pregnancy and preferential feeding of multiple bearing ewes, losses were similar to those reported previously (11% and 29% for singles and twins respectively). Non-Merino ewes had significantly lower losses than did Merino ewes, irrespective of ram type (13% versus 21%, P < 0.001). There was a tendency for mob size in twin-bearing ewes to influence survival, with a lower mob size (<200) having lower losses (29% versus 33%, P = 0.07). These results are discussed in the context of existing extension advice about ewe management and perinatal lamb mortality. [ABSTRACT FROM AUTHOR]

Lamb survival is an issue of high relevance to the Australian sheep industry, as lamb-survival rates have direct bearing on overall reproductive performance of the sheep, and also constitute a main concern from an animal welfare perspective (Mellor and Stafford 2004). Both genetic and management factors play an important role in this complex issue (Hinch and Brien 2014). Ewe nutrition is of particular relevance as the intrauterine growth conditions prepare the lamb for the crucial transition to life outside the uterus. Effects of body condition of the ewe during various stages of the pregnancy have been investigated in detail, yet much less is known about the critical role of micronutrient provision to the ewe. Although several risk factors for selenium (Se) and iodine (I) subclinical deficiencies exist for sheep on pasture in Australia, determining micronutrient status in sheep or pasture is not straightforward. Several studies have separately found effects of Se and I supplementation on lamb survival. Studies investigating the interaction of Se and I supplementation have been few but results have demonstrated an interaction between Se and I. With increased twinning rates as a result of increased selection of numbers of lambs weaned, nutritional demands during pregnancy across flocks are increasing, and effects of micronutrients on lamb health and survival have greater impact. New opportunities in nutritional research are encouraging new studies into the effects of Se and I supplementation on lamb survival. [ABSTRACT FROM AUTHOR]

Lamb mortality represents reproductive wastage and an animal welfare concern. While lambs are thought to be at a thermogenic advantage following birth in comparison to other species, death from exposure can still be a major contributor to lamb mortality, largely because of the inclement conditions often prevailing at lambing. For this reason, thermogenesis has been studied extensively in neonatal lambs. Heat is produced in the neonatal lamb by shivering and nonshivering thermogenesis. The latter is heat generated by metabolism of brown adipose tissue (BAT) found largely in the thorax and peri-renal areas of the newborn lamb. Brown adipose tissue differs from normal adipose tissue in that it contains densely packed mitochondria, a high cytochrome c content and a vast vascular network. Heat is generated in BAT by uncoupling of the proton conductance mechanism from ATP production, resulting in heat production instead of stored energy. The ability of lambs to resist cooling differs among individuals and this is likely to be due to both genetic and phenotypic factors. The heritability of cold resistance is moderate-to-high and polymorphic gene markers associated with energy homeostasis and cold-related mortality have been identified. Additionally, several aspects of the phenotype of the lamb have been associated with cold resistance. Most relate to properties of the coat, skin and bodyweight, the latter being particularly important, presumably through effects on surface area to volume ratios and subsequent heat loss. The ability of the neonate to achieve the transition from intra- to extra-uterine life has been termed physiological maturity and is associated with the ability to activate appropriate neuro-endocrinological and behavioural changes that are consistent with homeostasis of energy metabolism. Ways to alter physiological maturity of the lamb, such as nutrition, pharmacology and genetic selection, have been identified, and while these show promising results with regards to thermoregulation, a key limitation of their application has been the lack of a repeatable, representative model of neonatal cold stress. An estimation of the non-shivering component potential of a lamb's ability to thermoregulate can be derived from norepinephrine challenges, but more useful models of real-world cold stress are climate chambers or controlled water bath tests. Further use of repeatable test models such as these with appropriate neuroendocrine and metabolic metrics will identify key components and markers of physiological maturity associated with lamb thermogenesis and survival. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Achieving higher lamb weaning percentages by reducing lamb mortality can improve the profitability of sheep enterprises. In this paper we estimated the financial benefits from providing shelter to reduce the mortality of twin lambs in self-replacing Merino or dual-purpose Merino flock enterprises in south-west Victoria. A whole-farm bio-economic model (MIDAS) was initially used to estimate the increase in profit from reducing mortality of twin lambs and a second analysis included the costs of using perennial grass hedges to provide the shelter during lambing. The economic value of providing shelter was tested at three rates of twinning (10, 30 and 50%), three rates of mortality without shelter (70, 50 and 30%) and two levels of reduction in lamb mortality by providing shelter (25 and 50% reduction). A sensitivity analysis to wool and lamb prices, costs of establishing the grass hedges and stocking rates in the shelter area were also tested. Overall, more than 2500 scenarios were tested. Across the range of twinning rates and levels of twin mortality tested, at standard wool and meat prices, providing shelter to the dual-purpose Merino ewe flock was always profitable ($0.05 to 11.35/ewe) and the profits from providing shelter to the self-replacing Merino ewe flock were generally lower ($0.15 to $6.35/ewe). The impacts of changing wool and lamb prices depended on enterprise type, whereas the costs of establishment of the hedges or stocking rate of ewes in the hedge area during lambing had little impact on profitability. The main factor that determined the economic return from shelter was the reduction in mortality provided by the shelter but the proportion of twin-bearing ewes in the flock and the base rate of lamb mortality without shelter was also important. Overall, based on the assumptions used, we conclude that the profitability of many sheep enterprises lambing during frequent high chill weather conditions in temperate areas of south-eastern Australia could be improved by providing low cost shelter for twin-bearing Merino ewes lambing from July to September. Achieving higher lamb weaning percentages by reducing lamb mortality can improve the profitability of sheep enterprises. We estimated the financial benefits from providing shelter to reduce the mortality of twin lambs on two modelled sheep enterprises in south-west Victoria. The reduction in mortality that could be achieved was a key factor determining benefits and the profitability of sheep enterprises lambing during high chill weather conditions could be improved by providing low cost shelter. [ABSTRACT FROM AUTHOR]

Vitamin E concentrations in dried pastures, stubble and most grains are below the recommended requirement of 10-25 mg/kg dry matter (DM). Sheep grazing in an environment when dry pastures and cereal crop stubbles are their primary source of nutrients for a few months have a high risk of developing vitamin E deficiency. If the low vitamin E status coincides with late gestation, the neonate is likely to have a deficiency of vitamin E. Some of the consequences of this are well known, with nutritional myopathy (with high mortality) a risk in young growing sheep unless vitamin E supplements are provided. Vitamin E plays an important role in the management of oxidative stress. Sperm are subject to oxidative damage due to high metabolic rate and high concentration of polyunsaturated fatty acids in their membranes. Oxidative stress may also compromise follicular development and ovarian activity. Vitamin E is also involved with improvement in immune response. For these reasons, vitamin E status is important for reproductive efficiency in both males and females and in the survival of lambs and weaners. In addition, vitamin E deficiency is potentially exacerbated by a lack of other nutrients involved in the management of oxidative stress and immune function, such as selenium (Se) and sulfur amino acids. A Se concentration of 0.1 mg/kg DM in feedstuffs is required to maintain immune competency in sheep. In considering possible consequences for reproduction, further investigation is justified into: (i) effects of low vitamin E, in combination with low levels of other natural antioxidants, on the quality and quantity of sperm produced before and during mating; (ii) follicle development, fertilisation and embryonic mortality in Se-supplemented ewes; (iii) assessment of supplementing formulated antioxidants to rams and ewes during the mating season; (iv) managing oxidative stress in the newborn - consequences of large doses of vitamin E to ewes before parturition to boost lamb reserves; (v) potential benefits to lamb survival through boosting maternal innate immunity; (vi) choices for boosting antioxidant and immune function in ewes and lambs through 'immune pack' nutrient options that may target nutrients lacking in dry grass pastures; (vii) the potential role of heat stress in modifying the requirements for, and responses to, vitamin E in extensive grazing systems. Nutrient and environment related oxidative stress can impact rams and ewes during the reproductive period, resulting in low reproductivity and high lamb mortality. Managing oxidative stress of the newborn by giving ewes large dose of dietary antioxidants, like vitamin E and selenium, could boost immune competency of ewes and lambs to improve lamb survival. A number of related issues remain to be resolved for Australian environments. [ABSTRACT FROM AUTHOR]