Prepare early to save ewes

Planning ahead and keeping an eye on ewe nutrition are the most effective strategies for preventing Pregnancy Toxaemia in twin-bearing ewes, and occasionally large single bearers.

According to NSW Department of Primary Industries Sheep Development Officer, Geoff Casburn, it may be too late for some producers with lambing already underway or complete, however, lessons can be learnt from this year to minimise future losses.

While inadequate pasture is a major cause of the disease in tight years, Geoff believes the main cause this year, will be overfat ewes and ewes suffering from foot abscess.

“The main focus should be on prevention by ensuring twin bearing ewes are being fed adequately and handled with care,” he said.

“Treatment is seldom successful so the disease often results in the animal dying.”

What is it?

Geoff said Pregnancy Toxaemia, also known as lambing sickness or twin lamb disease, is caused by low levels of glucose in the blood.

“It commonly occurs during the last month of pregnancy when there is a high demand for glucose from the rapidly growing foetuses,” he said.

“The level of glucose in the blood is directly related to amount and quality of the feed being digested and, at times, the requirement for glucose cannot be met from the diet alone and needs to be sourced from the ewe’s own reserves.”

Geoff said, during this process, fat is used as a major maternal energy source and ketones are produced as a consequence.

“The more fat used by the mum, the more ketones produced - ketones are used as an energy source by muscle in times of severe nutrient deficiency,” he said.

“Over a prolonged period of severe undernutrition, the level of ketones produced becomes toxic and this leads to a further fall in feed intake and, eventually, clinical signs of Pregnancy Toxaemia.”

Symptoms

The first signs of the disease are ewes walking around with their heads held high, not feeding and separated from the mob.

They may walk into fences or stand with their head near the ground.

If they lie down they are unlikely to rise unless assisted. 

Geoff warned that Hypocalcaemia is often mistaken for the disease, however, Hypocalcaemia is easily treated with an injection of calcium boro-gluconate resulting in rapid recovery.

“This is the first step in diagnosis of the disease, as ewes that don’t recover quickly are likely to have Pregnancy Toxaemia,” he said.

“In this case they may benefit from continual treatment with a glycerol drench.” 

Geoff recommended producers seek veterinary advice.

Causes

There are three general scenarios that lead to Pregnancy Toxaemia:

1. stress and fasting
2. over-fat ewes
3. inadequate pasture

Pregnancy Toxaemia can be triggered by stress resulting from unfamiliar locations, transport, cold wet weather, internal parasites and foot abscess or by fasting due to extended periods of handling (eg shearing).

Geoff said, on their own, these practices generally don’t result in Pregnancy Toxaemia, as their impact on fat utilisation is often within acceptable limits.

However, when these circumstances coincide with prolonged under-nutrition, it can be enough to ‘tip the balance’,

Geoff said Pregnancy Toxaemia also occurs when twin-bearing ewes are ‘fat as mud’.

“The reason for this is ‘fat’ ewes eat significantly less than ‘thin’ ewes in late pregnancy,” he said.

“Pasture intake decreases as fat score increases, to the point where a fat score 5 ewe at day 130 of pregnancy, grazing good pasture can lose around 170g/day.

“At this level of weight loss, the ewe needs to be handled carefully to prevent undue stresses.”

Prevention

Geoff said over-fat twin-bearing ewes, within four weeks of lambing, are likely to need supplementation of high energy-dense feeds such as cereal grain or lupins to help overcome the energy deficits resulting from lower feed intake.

“If pasture conditions are likely to promote foot abscess, select paddocks for twin-bearing ewes containing dry areas to allow feet to dry out, such as contour banks, dam walls or roads,” he said.

For next year, the best way to prevent Pregnancy Toxaemia is to prevent ewes from getting too fat in the first place.

The warning signs are ewes in fat score 3.5 or greater at joining and good soil moisture to drive pasture growth.

It is often too late to wait until scanning to identify twin-bearing ewes and take action to reduce their fat score if needed.

The damage has been done, as in most cases ewes are unable to lose the required weight without negatively impacting on the growing foetus.

It is better to reduce weight gain in all fat ewes leading up to scanning rather than induce weight loss in twins from scanning onwards.

Contact: NSW Department of Primary Industries Sheep Development Officer Geoff Casburn T: 02 6938 1630 E: geoff.casburn@dpi.nsw.gov.au

More information:

NSW Department of Primary Industries Prime Fact on Pregnancy Toxaemia.