The objective of pre-lambing nutrition is to maintain optimum body condition so that ewes have strong, even-sized lambs and adequate colostrum at lambing, CAFRE beef and sheep technologist Eileen McCloskey said last week.

Speaking at a knowledge transfer event in Ballymena, McCloskey maintained that correct pre-lambing nutrition also prevents metabolic disorders, such as twin lamb disease, and minimises unnecessary costs through overfeeding.

Farmers should have ewes batched for feeding according to scanned lamb crop and body condition, with the ideal body condition score being 3.5 for lowland ewes and 3.0 for hill-bred ewes at lambing.

During her presentation, McCloskey presented figures for Blackface twin lamb-bearing ewes, which showed that an underfed ewe produced a total lamb weight of 6.43kg, compared with 7.9kg for a correctly fed ewe.

The underfed ewe also produced 160ml of colostrum in the first hour and 990ml in the first 18 hours, whereas the correctly fed ewe produced 715ml and 1,805ml, respectively.

“Lamb size can often be a good indication of nutrition. Bigger is not always better as it gets to a point where lambs that are too big lead to problems at lambing,” she added.

Energy requirement

Most pre-lambing feed programmes involve feeding concentrates in the last six weeks before lambing to meet energy requirements.

McCloskey said that sheep farmers should look for a ewe ration with ME 11 to 13MJ/kg DM and crude protein 17% to 18%. “Energy levels of rations are important, but most concentrates will not have it on the label, so make sure and ask your supplier what you are paying for,” she said.

On feed labels, ingredients are listed in order of inclusion, so the top-quality ingredients should be at the start.

Barley, maize and wheat are good-quality sources of energy in rations. The best quality protein sources include soya bean, rapeseed, maize gluten, distillers, peas and beans.

Although an expensive ingredient, McCloskey pointed out that soya bean can have an ME of 11.6MJ/kg and crude protein levels of 48%, which is readily available to ewes. Rapeseed might have an ME of 10.8 MJ/kg and crude protein of 38%, but is not as palatable so should make up less than 20% of the ration.

Lower quality protein sources that should be further down ingredient lists include palm kernel, oat feed, wheat feed and sunflower meal.

Forage

Feeding good-quality silage reduces costs, with McCloskey calculating a £2.90 per ewe difference in concentrate costs (concentrates at £210/tonne) when feeding excellent quality (11.7MJ/kg) compared with poor quality (9.6MJ/kg) silage for a six-week period before lambing.

She highlighted that if good quality grass is available, ewes in late pregnancy can be managed without the need for concentrates.

“This can potentially run into problems with too much feed, so don’t underestimate the feed efficiency of grass. Target sward heights of 4cm to 5cm at stocking rates of five ewes per acre for twin-bearing ewes and slightly higher stocking rates for single ewes,” she said.

Causes and consequences of ewe abortion

An abortion-causing problem in sheep can contribute to other reproductive losses within the flock such as still births, poor viability in lambs, high barren rates and increased ewe mortality.

Agri Food and Biosciences Institute (AFBI) vet Jason Barley explained in Ballymena last week that an abortion problem can also be part of a wider issue.

He said that around 40% of aborted materials from sheep submitted to diagnostic laboratories have no abortion causing microbes found.

“This means a lot of abortions are to do with nutritional or metabolic disorders. Ewes abort to prevent toxaemia (twin lamb disease) or hypocalcemia (calcium deficiency). It is their default position to get rid of the lambs,” Barley said.

Other non-infectious causes of abortion include stress caused by over handling sheep pre-lambing and health issues such as fluke or worm burdens in ewes.

The two main infectious causes of abortions in sheep are Toxoplasma gondii (toxoplasmosis) and Chlamydophilia abortus (enzootic abortion).

Toxoplasmosis is caused by oocysts passed by cats on to sheep through infected grass or feed. There is a natural reservoir of toxoplasmosis in rodents, however, older cats will become immune and stop shedding oocysts.

Enzootic abortion is very infectious among ewes and can be passed on easily through aborted material. This can cause other pregnant ewes to abort in the current season or the following year.

Disease prevention

Vaccination is an important means of preventing toxoplasmosis and enzootic abortion and should be administered to ewes at least three weeks before tupping. Replacement ewes should be done before their first tupping. Vaccines typically provide cover for around three years.

In the event of an abortion outbreak, Barley said it is essential to remove aborted ewes, as well as their lambs and placenta, and maintain a high level of hygiene in sheds. If no infectious cause is found in a lab, then a closer look at the overall health of the flock is required.

Barley said that lambs should not be fostered on to aborted ewes and he advised culling ewes found with infectious agents. He also recommended using a long-acting antibiotic on ewes during an enzootic abortion storm. During a toxoplasmosis outbreak, an option is to mix decoquinate (Deccox) in feed, although this may make it less palatable.

The year after an enzootic abortion storm, Barley advised vaccinating ewes before tupping and potentially also treating with a long-acting antibiotic six weeks before lambing.