Tom Clune

Context
Scanning for fetal count enables producers to alter pre-lambing management of ewes according to litter size, for improving lamb and ewe survival outcomes. However, accurate scanning in industry flocks is important to achieve this goal.

Aims
This study aims to characterise accuracy of scanning in current field data and relate this to lambs recorded at both the ewe and flock levels.

Methods
Four experimental flock data sets and two large industry data sets derived from Sheep Genetics were used to demonstrate the repeatability of scanning and investigate how data quality influences the assessment of accuracy of scanning to predict lambing outcomes.

Key results
Scanning for pregnancy determination and fetal count is highly repeatable for experienced scanners, but at higher litter size (> 2 lambs) error rates in fetal count increase. The accuracy of distinguishing singles from multiples can be higher than for fetal counts. However, accuracy in predicting lambs born from scanning results is more strongly influenced by poor quality of recording lambing outcomes against individual ewes than to scanning errors. Scanning for fetal count does not have as high accuracy for predicting lambs reared due to lamb losses, which are also influenced by litter size.

Conclusions
Technical improvements and slower scanning speed might be required to increase accuracy of fetal counts at high litter size, but the overall impact is relatively low at current mean litter sizes, in flocks where triplet litters are relatively scarce.

Implications
Scanning accuracy is facilitated by using experienced scan practitioners requested to distinguish fetal counts, with appropriate pre-scanning preparation, and with all ewes scanned within correct ranges for fetal age at the time of scanning.

Microplastics (MP) are ubiquitous in the environment, and have been detected in the tissues of several species. Limited studies quantify the presence of MP in food producing species, including sheep. Here, MP were screened in tissue samples from Australian sheep using low-cost methodologies, with the aim of enabling their subsequent chemical characterization and quantification. Samples of several organs from six sheep were prepared using (i) a standard digestion and filtration protocol, and (ii) a novel impression smear method. Both methods involved staining with Nile Red (10µg/ml) and observation by fluorescence microscopy. Suspected MP were detected in 32.3% (10/31) of digestion samples, 51.6% (16/31) of smear samples and 50.0% (8/16) of controls. Such results will direct further research aimed at contributing to food safety and public health policies focused on animal and human health.

Managing breeding ewe mortality is a priority for the Australian sheep industry. The periparturient period carries the highest risk of mortality, but the incidence and causes in Merino ewes are not well characterised. Here, we outline the reported incidence of annual and periparturient mortality for Australian Merino ewes, causes and risk factors for ewe mortality and current recommendations for managing periparturient ewes and gaps in the literature. The mean incidence of periparturient mortality reported in Merino ewes ranges from 0.3% to 11.4%. However, there are challenges with reporting mortality figures in extensive production systems due to the nature of record keeping and farm characteristics. Studies reporting causes of periparturient mortality indicate that these are typically multifactorial, with metabolic disease and dystocia likely to be important. Identifying potential mitigation strategies has the potential to improve productivity, profitability and welfare on Australian farms.

This chapter addresses the nutritional, husbandry and disease processes which affect ewes and their foetuses in the time from early pregnancy to parturition and through early lactation. Nutrition of the ewe through pregnancy has a major effect on her health, her ability to deliver robust and healthy lambs and her ability to bond with, protect and nourish her lambs in the neonatal period. It also has major effects on the survival rate of the lambs in the neonatal period. Some of the most common clinical diseases which affect ewes during pregnancy are pregnancy toxaemia and hypocalcaemia, and these conditions are most effectively prevented by flock management strategies. There are numerous infectious agents which can cause abortion in ewes. Many of these agents can also cause stillbirths and the birth of lambs of low birthweight and poor viability. The normal behaviours of ewes and lambs at parturition are described. Factors which interfere with the development of a strong bond between ewes and lambs, and factors which reduce the intake of sufficient nutrients by lambs soon after birth, have a major effect on the probability of lamb survival in the first few days of life. Perinatal mortality in lambs is one of the most important causes of economic loss to the Australian sheep industry. Veterinary investigations of perinatal mortality can identify the steps that need to be taken to reduce perinatal mortality on sheep farms. Adequate nutrition of the lactating ewe is essential to achieve satisfactory health and growth in their lambs. The most important disease condition of the lactating ewe is mastitis.

Respiratory disease is one of the main diseases of sheep in many regions globally. Respiratory syncytial virus (RSV) causes severe disease in humans and in calves, but little is known about the role of RSV in sheep. We studied the prevalence of ovine RSV in sheep processed at 5 abattoirs in southern Australia. Bronchial swab samples were collected from 182 consignments of lambs up to 12 months of age and 71 consignments of adult sheep; these were tested for the presence of the virus using a qPCR based on the F gene sequence. Six of the 253 abattoir consignments (2.4%) tested positive for ovine RSV. Four of the positive consignments were lambs and 2 were adult sheep. To our knowledge, this is the first report of the ovine strain of RSV in sheep with pneumonia from Australia. Further research is needed to clarify the role of RSV in pneumonia in sheep.

Chlamydia pecorum is a veterinary pathogen associated with abortions and perinatal mortality in sheep. Recent studies investigating foetal and perinatal lamb mortality in sheep from Australia and New Zealand identified C. pecorum clonal sequence type (ST)23 strains in aborted and stillborn lambs. Presently, there is limited genotypic information on C. pecorum strains associated with reproductive disease, although whole genome sequencing (WGS) of one abortigenic ST23 C. pecorum strain identified unique features, including a deletion in the CDS1 locus of the chlamydial plasmid. We applied WGS on two ST23 strains detected in aborted and stillborn lambs from Australia and used phylogenetic and comparative analyses to compare these to the other available C. pecorum genomes. To re-evaluate the genetic diversity of contemporary strains, we applied C. pecorum genotyping, and chlamydial plasmid sequencing to a range of C. pecorum positive samples and isolates from ewes, aborted foetuses and stillborn lambs, cattle and a goat from diverse geographical regions across Australia and New Zealand.The two new C. pecorum genomes are nearly identical to the genome of the Australian abortigenic strain including the unique deletion in the chlamydial plasmid. Genotyping revealed that these novel C. pecorum ST23 strains are widespread and associated with sheep abortions on Australian and New Zealand farms. In addition, a goat C. pecorum strain (denoted ST 304) from New Zealand was also characterised. This study expands the C. pecorum genome catalogue and describes a comprehensive molecular characterisation of the novel livestock ST23 strains associated with foetal and lamb mortality.
•C. pecorum was a sole agent readily detected in foetal loss and perinatal lamb mortality cases.•We provide two new genomes of the unique abortigenic clonal ST23 C. pecorum strains.•Expanded genotyping revealed that these ST23 strains are widespread.•These novel ST23 are associated with sheep abortions on Australian and New Zealand farms.•Novel genetically diverse livestock strains were also characterised.

This case-control study investigated associations between Campylobacter fetus or Campylobacter jejuni titre and reproductive outcomes in 22 flocks of Merino and non-Merino maiden ewes aged 1–2 years old. Campylobacter titres were also determined for multiparous ewes aged 3 years or older on the same farms. C. fetus ‘positivity’ (titre ≥1:80) was detected for 12% (57/462; 95% confidence interval [95% CI] 9.6 to 15.6) of maiden ewes and 31% (65/210; 95% CI 25.0 to 37.4) of mature ewes. The odds for failing to rear a lamb in C. fetus-‘exposed’ maiden ewes (titre ≥1:10) was 2.01 times that of seronegative ewes (95% CI 1.09 to 3.77; P = 0.027), but there was no association between C. fetus-‘positivity’ (titre ≥1:80) and failure to rise (OR 1.69; 95% CI 0.77 to 3.76; P = 0.191). C. fetus abortions were confirmed with microbial culture in one maiden ewe flock. In this flock, C. fetus titres fluctuated and often waned by lamb marking, highlighting the value of necropsies during abortion investigations. C. jejuni-‘positivity’ (titre ≥1:80) was detected for 44% (204/462; 95% CI 39.7 to 48.7) maiden ewes, but odds of failing to rear were decreased for C. jejuni-‘positive’ ewes (OR 0.52; 95% CI 0.32 to 0.83; P = 0.007). The association between Campylobacter serology and the reproductive outcome was inconsistent in these flocks. Serology should be considered in the context of other risk factors and used in conjunction with other strategies to investigate the impact of Campylobacter exposure on ewe reproductive performance such as monitoring for abortions and lamb necropsies to determine aetiological diagnosis, and vaccination trials.

The role of infectious diseases including coxiellosis in causing poorer reproductive performance of primiparous ewes are not well studied. The aims of this study were to determine if natural exposure to Coxiella burnetii is widespread in breeding ewes and whether seropositivity is associated with poor reproductive performance of primiparous ewes. Seropositivity to Coxiella burnetii was 0.08% (CI95% 0.01, 0.36) in primiparous ewes and 0.36% (CI95% 0.07, 1.14) in mature ewes. Coxiella burnetii was not detected in aborted or stillborn lambs using qPCR. These findings suggest C. burnetii infection was unlikely to be an important contributor to abortion and perinatal mortalities observed for primiparous ewe flocks, and exposure to C. burnetii was not widespread in ewes on farms located over wide geographical region of southern Australia. Whilst ewes on these farms were not an important reservoir for C. burnetii, sporadic zoonotic transmission from sheep is reported and has public health implications.

Background Toxoplasma gondii causes reproductive losses in sheep worldwide, including Australia. The reproductive performance of primiparous ewes is typically lower than for mature, multiparous ewes, and younger ewes are more likely to be immunologically naïve and therefore more susceptible to reproductive disease if T. gondii infection occurs during pregnancy. The aim of this study was to assess the impact of infection with T. gondii on the reproductive performance of primiparous ewes in southern Australia using a prospective cohort study. This will inform the need for targeted control strategies for T. gondii in Australian sheep. Results Toxoplasma gondii seropositivity using indirect ELISA was detected at 16/28 farms located across southern Australia. Apparent seropositivity to T. gondii was lower in primiparous ewes (1.1, 95% confidence interval (CI) 0.6, 1.8) compared to mature, multiparous ewes (8.1, 95% CI 6.0, 10.5; P < 0.001). Toxoplasma gondii seroconversion during the gestation and lambing period was confirmed for 11/1097 (1.0, 95% CI 0.5, 1.7) of pregnant primiparous ewes that failed to raise a lamb, and 1/161 (0.6, 95% CI 0.1, 2.9) primiparous ewes with confirmed mid-pregnancy abortion. Conclusions Low frequency of detection of T. gondii seroconversion during gestation and low frequency of seropositivity to T. gondii suggests that toxoplasmosis was not an important contributor to reproductive losses in primiparous ewes on farms located over a wide geographical area in southern Australia.

Lamb survival is an important welfare and productivity issue for sheep industries worldwide. Lower lamb survival has been reported for primiparous ewes, but the causes of this are not well studied. The aim of this study was to determine causes of perinatal deaths for lambs born to primiparous ewes in Western Australia, and identify if infectious diseases are implicated. Lamb mortality from birth to marking were determined for 11 primiparous ewe flocks on 10 farms in Western Australia. Lamb mortality from birth to marking averaged 14% for single-born and 26% for multiple-born lambs. Lamb necropsies (n = 298) identified starvation–mismosthering–exposure (34%), dystocia (24%) and stillbirth (15%) as the most common causes of perinatal lamb death. There was no evidence of exotic abortigenic pathogens in aborted and stillborn lambs (n = 35). Chlamydia pecorum was detected by qPCR in 15/35 aborted and stillborn lambs on 5/6 farms. Preliminary molecular characterisation of C. pecorum detected in samples from aborted and stillborn lambs (n = 8) using both Multilocus Sequence Typing and ompA genotyping indicated all strains were genetically identical to previously described pathogenic livestock strains, denoted ST23, and dissimilar to gastrointestinal strains. High frequency of detection of a pathogenic C. pecorum strains ST23 associated with ovine abortion and stillbirth on multiple farms located across a wide geographic area has not been previously reported. Chlamydia pecorum may contribute to reproductive wastage for primiparous sheep in Western Australia. Further investigation to understand C. pecorum epidemiology and impact on sheep reproduction is warranted.