Diagnose Your Ewe Deaths

Wednesday, July 22, 2020

By Tiffany Bennett, Livestock Consultant

Current seasonal conditions across South Australia have posed challenges in maintaining ewe health and optimising ewe nutrition. The result has been an increase in reports of ewe deaths across the state, particularly during late pregnancy and lambing. In many cases the cause of death is not obvious, nor clear – and possibly multifactorial. 

Recording ewe deaths is important to identify issues and provide the real cost to the sheep enterprise. Ewe death rate should be calculated at marking, as a percentage of the ewes joined. As with marking and weaning data, ewe death data compiled over the years can help identify potential issues.

Subsidised veterinary investigations into ewe deaths may be available through the Primary Industries and Regions SA’s Disease Surveillance program. Please contact your private veterinary practitioner or PIRSA Animal Health Officers for further information

There are many reasons why ewes may die, particularly in late pregnancy and early lactation. However, the most common causes are pregnancy toxaemia from inadequate energy intake, and hypocalcaemia as a result of low blood calcium. Given the tough seasonal conditions which have involved hay shortages, prolonged and high levels of grain feeding, poor quality hay, lack of access to grazing, grazing cereals for early feed, along with management factors, there are many factors potentially contributing to ewe deaths. 

Producers should not accept and assume that a few deaths here and there, without diagnosis or explanation, is normal. 

Some of the common causes of ewe deaths are described below, but this list is not exhaustive.

Pregnancy Toxaemia occurs in late pregnant ewes most commonly in the last six weeks when the ewe has her greatest energy requirement, as a result of lamb growth. This can occur in fat ewes that do not have adequate energy intake in the last six weeks of pregnancy. British breeds are more susceptible, as well as ewes that are bearing multiple lambs. Pregnancy toxaemia and hypocalcaemia are often confused with one another.

Hypocalcaemia is a result of low blood calcium and is complicated by low blood magnesium and high phosphorus.  While many producers sow cereal crops for early feed they can pose some problems, including marginal magnesium and calcium levels, high potassium and low sodium levels (particularly in wheat and triticale). High potassium and low sodium further reduce magnesium absorption from the rumen resulting in magnesium deficiency. Low calcium may induce hypocalcaemia. 

It is important to provide a mineral supplement consisting of magnesium oxide, lime and salt in a 2:2:1 ratio. A small amount of added grain may assist initial acceptance of the supplement.

Seasonal conditions have resulted in prolonged and high levels of cereal grains being fed. Cereal grains are low in calcium and high in phosphorus, and unless a calcium supplement is provided, sheep will draw on their calcium bone reserves. These reserves become depleted and hypocalcaemia occurs. This can happen over a period of weeks or months depending on the requirement of the ewe but particularly in late pregnancy or with the onset of lactation.

 Acidosis, often referred to as grain poisoning, may contribute to ewe deaths. The situation has been compounded this season with producers ‘rationing’ hay (given the state wide shortage) but still needing to feed high levels of grain. There are a number of other management issues contributing to the onset of acidosis, including: 

  • sudden introduction of grain
  • high levels of grain with inadequate fibre and not buffering
  • infrequent feeding or slug feeding high levels of grain
  • changing grain type, or 
  • inadequate feeder, trough or trail space that allows some ewes to gorge, while other ewes miss their allocation.

Consumption of toxic weeds can predispose ewes to issues.

Ewe mortality during late pregnancy and lambing is strongly correlated with condition score, with ewes less than condition score 2.5 at greatest risk. Ewes in lower condition score may also be more susceptible to worms. Overfat ewes are also at risk with ewes greater than condition score 4. Ewes that are experiencing stress are predisposed to succumbing to infectious diseases and internal parasites.

A ewe death rate of greater than 4% should be investigated. With the industry average of 7-8%, there are many producers overlooking ewe death rate and compromising profit. With the current value of ewes and their lambs, avoiding losses is paramount.

In many instances producers may simply find ewes dead or dying/down. It can be very difficult to determine the cause and therefore it is important to get a diagnosis of why ewes are dying. 

A diagnosis will allow the correct treatment and implementation of strategies to prevent further issues. 

If producers have concerns about ewe deaths on their property, they should contact their local private veterinarian or a Biosecurity SA Veterinary or Animal Health Officer. 

Subsidies are available for disease investigations performed by a private veterinarian.

If you suspect an emergency disease, immediately call the Emergency Animal Disease Hotline number of 1800 675 888.