Practical resources for Merino ewe survival

Findings from an Australian Wool Innovation (AWI) and MLA co-funded project will underpin the development of best practice management resources to help wool growers optimise ewe survival before, during and after lambing.

Known as the periparturient period, this is a vulnerable time for ewes and their lambs.

The project focused on the prevalence and causes of Merino ewe periparturient mortality and trialled practical intervention strategies to determine their impact on ewe survival.

Understanding ewe survival

As Merino ewes make up about two-thirds of Australia’s breeding ewe flock, it’s critical to optimise their health and survival to improve overall productivity and wellbeing. 

A national online survey conducted with 160 Merino producers across WA, SA, Victoria and NSW provided valuable information around rates of ewe mortality across a 12-month breeding cycle. 

Most producer respondents were scanning and managing ewes according to litter size and reported ewe mortality rates during lambing for self-replacing Merino flocks of 1.95% which were below the industry average (2–10%). 

A team of researchers, veterinarians and consultants from Pinion Advisory worked closely with a group of 14 participating Merino producers in key Australian wool-producing regions to test the practical intervention strategies. AWI General Manager – Research, Bridget Peachey, said this will inform the development of resources to help producers boost ewe and lamb survival.

“We know that ewe losses tend to occur mainly during and around lambing, so this project aims to trial and develop cost-effective and practical intervention strategies to increase ewe survival rates,” Bridget said.

“Advice on best practice will be developed and made widely available for adoption by Merino sheep and wool producers.”

Top causes of ewe mortality 

Producer-reported data and veterinary investigations were used to determine the pattern of periparturient mortality across the farms as per the producers’ regular management practices. 

All the producers kept a farm diary to document ewe mortalities over the lambing season, including reporting cause of death if known. Veterinarians visited host farms to conduct autopsies on deceased ewes to determine the cause of death at key stages of the lambing season. 

Across all participating regions, the top three causes of ewe mortality in the study were:

• dystocia (a prolonged or difficult birth)
• hypocalcaemia (low levels of calcium in the blood)
• metritis-related septicaemia (an acute inflammation of the uterus that occurs within 1–10 days after giving birth).

These were either sole or contributing causes of death. The frequency with which different causes were diagnosed varied across the seven participating regions. Regionally-important causes of mortality included pregnancy toxaemia, vaginal prolapse and ruminal acidosis.

Intervention strategies 

Of the 42 Merino businesses that participated in the first phase of the project, 14 businesses trialled an intervention strategy during the 2025 lambing season while being guided by a project veterinarian, who conducted post-mortems of any mortalities. 

Intervention strategies during the project included:

• Calcium supplementation: Given to ewes during the periparturient period.
• Body condition scoring and weight of ewes prior to lambing: Lighter ewes were drafted out to allow differential management through feeding in a containment feeding system.
• Body condition scoring of ewes at joining, scanning and weaning: Ewes were drafted into groups to allow for differential feeding to reach target condition at lambing.
• Vitamin E supplementation: Ewes received supplement in either a containment feeding system or while being grainfed on dry pasture in the lead-up to and during lambing. This was used in conjunction with body condition score monitoring.
• Vitamin ADE supplementation: Ewes received a commercial injectable supplement one month prior to lambing.

The project also quantified the economic impacts of Merino ewe mortality and intervention strategies at farm and industry levels to help drive industry adoption of best practice management.

Veterinarian insights into ewe mortality

Elsa Glanville was one of five core veterinarians guiding participating producers through their involvement in the project. 

Elsa, who is based in the Central Tablelands of NSW, has also been involved in the design, collation and interpretation of results across the project. 

She said seeing producers’ enthusiasm to understand what’s going on in ewes over lambing, the pattern of ewe mortality across their flock and helping design targeted intervention strategies has been a highlight. 

“Marked differences in the pattern of ewe mortality between regions highlight how important cross-regional projects are to informing practical, relevant recommendations,” Elsa said. 

“Some of our Central NSW producers commented that they’re unsure how applicable management recommendations based on research from other regions are to their farms. 

“They were excited about being involved in this project and took great care in documenting observations over lambing.”

Elsa said producer-reported causes of death, as well as veterinarian post-mortems, revealed differences in ewe mortality in her region compared to others, emphasising the importance of incorporating different production regions into the project.

She said another take-home message from this research was the importance of investigating rather than assuming causes of death. 

“Across the project, around 60% of dystocia cases had no external evidence of birthing difficulties. If we hadn’t opened those ewes up, we wouldn’t have made a diagnosis of dystocia. 

“Equally, cases of metabolic disease like hypocalcaemia show little on post-mortem and require lab samples for confirmation.”

Her advice for producers is, where possible, to get a vet or someone trained in conducting post-mortems out to help figure out what’s going on.

“Then you can tailor a response that’s appropriate to the challenge. This is what we’ve done with our intervention strategies, especially on one farm with a specific disease challenge, and it’s been a really rewarding process,” Elsa said.

Setting up flocks for success 

Jillian Kelly was another of the project’s veterinarians who guided producer participants during their on-farm implementation of the various project interventions. She was pleased the project confirmed that if producers use the right management strategies, they will set their flocks up for success.

“It’s great to have northern NSW included in this sort of science. The producers have been really keen to be involved to learn more about what really happens on their farm during lambing,” Jillian said.

“I’m excited that the project has highlighted that good ewe survival is possible under our extensive management conditions and that the main causes of death such as hypocalcaemia and dystocia have practical strategies such as calcium supplementation and body condition scoring that can be undertaken on-farm to manage them.

“This gives us more impetus to drive best practice ewe management for improved outcomes.”