Ensuring diets are carefully balanced and make full use of forages can improve performance and margins at lambing time according to Rosie Miller, ruminant nutritionist with Trouw Nutrition GB who stressed the importance of getting silage for pregnant sheep analysed.

“Managing ewe nutrition in the run up to lambing is an important step toward a successful lamb crop influencing lambing ease, lamb survival and vigour and milk yield and growth,” she commented.

“Trying to achieve this accurately and cost-effectively is crucial. A representative silage analysis and a clear picture of the nutritional content of the forage will help ensure cost-effective and balanced nutrition.

“The starting point of any ration is good quality forage, with compound feed or straights fed to complement it. If you don’t know how good the forage is it is impossible to select other feeds supplement correctly to satisfy the total requirements of the ewe. And you won’t know this just by opening the bale and visually assessing the forage," she said.

Rosie added forage is an important part of pre-lambing diets at what is a crucial stage for the ewe and the lamb crop and assuming an average analysis as the basis for supplementation decisions could result in ewes being either over-fed or underfed, as not only will energy levels vary but intakes will be affected too.

She said that providing a typical 9.8MJ baled silage, a 70kg ewe in the three weeks pre-lambing would consume 1.2% of bodyweight or 0.84kgDM of silage per day. If a 10.8MJ silage is available the same ewe could consume 1.4% of bodyweight, equivalent to 0.98kgDM of silage per day.

The ewe would have an energy requirement of 15.3MJ per day, but while the ewe on poor silage would derive 7.6MJ from forage, the ewe on the better silage would be getting 10.8MJ from silage which makes a big difference to the level of concentrates required.

Assuming an 11.8MJ concentrate, the ewe on good silage would require 0.43kg freshweight of concentrates to meet her requirements, while the ewe on poor forage would need 0.60kg freshweight of concentrates, an increase of 0.17kg/day.

“Without an analysis of the forage, the level of concentrates to feed will be a guesstimate rather that a calculated amount," said Rosie. "This can have a significant impact on performance. With a greater proportion of lamb losses occurring at and immediately post lambing, getting nutrition right can have a big impact on profitability.”

The consequence of over-feeding ewes will be higher feed costs and a range of potential problems. Overfed or fat ewes face an increased risk of twin lamb disease, dystocia and prolapse. They will also have decreased feed intakes post-lambing which will affect milk production and lamb growth.

Underfeeding means ewes may lose excess body condition and they will be more likely to give birth to lighter lambs. They will have poorer colostrum quality and yields and reduced milk yields all of which will compromise early lamb growth and increase mortality.

“Using our example, if the farmer assumed he was using average quality silage and supplemented accordingly but actually had the better quality forage, ewes would be being over fed by 170g/day. For a 350-ewe flock this is 60kg of concentrates per day that is being fed unnecessarily and increasing the risk of problems with overweight lambs and more difficult lambings.”

Trouw Nutrition GB has created a special analysis report especially for sheep farmers which provides the information they require such as metabolisable protein levels, and is available through the farm’s feed supplier.

She also advises looking carefully at the protein being fed, as the source of protein in supplementary feed can affect ewe performance. Adding proteins like soya bean meal which is high in DUP, can improve milk yields if overall dietary protein is low.

If however, forages are high in protein as has been more commonly the case this year, there will be no response to increasing DUP levels in supplementary feeds and all that will happen is costs will increase.

“A forage analysis will allow you to tailor the type of concentrates as well as the amount fed to meet ewe requirements at the most appropriate cost.”

She also stresses the need to feed sufficient minerals, particularly selenium and iodine. Selenium is essential for lamb health and vigour, passing to the lamb across the placenta in the colostrum and milk. Iodine plays roles in thermo regulation, growth and foetal development.

“Trace elements are included in compound feed and as a rule of thumb a ewe fed more than 0.5kg of compound per day should be meeting her mineral requirements but it is well worth checking the mineral balance of the diet, particularly at lower feed rates,” concluded Rosie.