Greater precision in feeding ewes can bring big benefits, with a close focus in late pregnancy having a major bearing on lamb numbers, lamb viability and potential returns per ewe.

According to Laura Drury, ruminant technical advisor with Trouw Nutrition GB there are two crucial objectives of feeding late pregnancy with the first being to manage and maintain ewe condition, achieving target lambing BCS of 3.0-3.5 for lowland ewes and 2.5 for hill ewes. Target lambing BCS should be achieved before the late pregnancy period, so body condition score change must he achieved during mid-pregnancy.

“You need to avoid weight loss in thin ewes, below BCS 2.0, while encouraging weight loss in overfat ewes (>4.0 BCS). Overfat ewes will have a lower DMI during late pregnancy, leading to increased fat mobilization and a higher susceptibility to twin lamb disease.

As ewes enter late pregnancy, Ms Drury says the focus has to also include the development of the lamb both in utero and immediately after birth Around 75% of lamb growth will occur in the last six weeks of pregnancy when ewes also have to start to produce milk and colostrum.

“Colostrum production is crucial for lamb survival. As many as 49% of lamb losses occur in the 48 hours immediately after birth with a significant proportion due to insufficient or poor-quality colostrum. Lambs require 200ml of colostrum per kg of bodyweight in the first 24 hours of life so it is vital the ewe is fed adequately to produce a sufficient, good quality supply.”

If ewes are underfed the risk of smaller, weaker lambs with poorer growth rates is higher, and made worse by a delayed onset of lactation and lower colostrum and milk yields. They are also at an increased risk of twin lamb disease. Conversely if overfed, ewes are at an increased risk of producing large lambs, dystocia and prolapses while lambing difficulties can compromise early lactation production.

“Achieving precision in late pregnancy nutrition is a major challenge as the ewes’ energy requirements increase by 60% from seven weeks before lambing to the week immediately prior to lambing. At the same time, dry matter intakes will be only 2-2.5% of bodyweight, or 1.6kg for a 70kg ewe,

“One week pre-lambing she will need 18.3MJ/day so the ration requires an energy density of 11.5MJ/kgDM and must be well-balanced.”

Ms Drury stressed the importance of getting forages analysed as they form the basis of the diet and other feeds may be required to supplement them. Without a forage analysis, developing accurate rations and ensuring ewe nutritional requirements are optimised is close to guesswork, risking poor performance and increased costs.

The diet needs to be the correct balance of rumen fermentable energy, from cereals such as barley and oats, and rumen degradable protein (RDP), from for example forages. An imbalance can reduce starch utilization which can compromise colostrum production.

“Choose compounds carefully. Look for quality ingredients like soya which has twice the bypass protein content of other protein sources like rapeseed meal. Oats have a lower energy content than barley but are more rumen friendly while molasses and sugar beet provide a good source of sugars and are palatable.

“Minerals are also vital. Supplementing with vitamin E, selenium and cobalt has been shown to improve lamb survival. Increased selenium levels in colostrum and milk supports newborn immunity, reducing the risk of hypothermia, and supporting ewe immunity. Inclusion of a good quality selenium yeast which is significantly more bioavailable than inorganic selenium, will be of particular benefit during pre-lambing,” she said.

Ms Drury added feed management in late pregnancy is vital for a successful lambing season. She advised feeding a maximum of 0.5kg concentrates per feed to reduce the risk of acidosis and to feed concentrates at the same time every day. Also ensure forage is always available.

“Also provide adequate trough space to minimize barging which can cause stress. Competition at the trough may also lead to problems with twin lamb disease in shy feeders, and acidosis and prolapse in more dominant ewes. Keep troughs clean, removing any unpalatable or contaminated feed. Make sure there is plenty of unobstructed access to clean, fresh water.

She said the best forage should be fed to ewes closer to lambing and those carrying more lambs. If feeding rolls, consider floor feeding as ewes will graze rolls from bedding which will slow down intakes and further reduce the acidosis risk.

“Planning now to ensure ewes are correctly fed late pregnancy could have significant benefits for the size of the lamb crop sold and flock margins.”