Diet Formulation for Sheep
This time of year signals the start of one of the most important phases in the sheep production cycle. One of the biggest potential causes of poor flock performance at lambing and during early lactation is management of ewe nutrition during late pregnancy, as Frank Campion Teagasc Researcher advises
Nutrition during late pregnancy
Nutrition during late pregnancy has been shown to influence ewe body reserve mobilisation, ewe colostrum production, lamb birth weight, lamb vigour and ultimately lamb survival. Where any of the aforementioned are negatively affected, the performance of the flock at lambing will be below its potential. Late pregnancy is typically defined as the last 6-8 weeks pre-lambing during which time approximately 80% of foetal growth takes place. Dietary formulation during this time is challenging as the rapid growth of the foetus reduces feed intake potential leading to the necessity to use concentrate supplementation.
During this time energy is typically the most limiting factor in the ewe’s diet with the ewes energy requirements increasing rapidly as presented in Table 1. which shows the energy requirement for the ewe and the growing foetus from 6 weeks pre-lambing. As lambing approaches energy requirements increase as shown, hence why concentrate feeding levels are stepped up as lambing approaches, usually at fortnightly intervals.
Protein requirements also change, particularly during the final 3 weeks of pregnancy when there is a requirement to ensure the ewe is receiving a source of rumen undegradable protein for mammary gland development and colostrum production. The level of concentrate supplementation required is dictated by the quality of forage available to the ewes with higher quality forage leading to a reduced concentrate requirement. Hence it is vital when formulating diets for sheep to have the forage quality tested first so that the correct levels of concentrates are offered. When deciding what concentrate to offer there a few guidelines that should be followed. The ration needs to have a high energy value with a UFL of 1.1 /kg DM or a ME of 12.5 MJ/ME/kg DM desired. The ration should also have a crude protein value of 18-20% also and contain a suitable pre lambing mineral.
When considering the energy of the ration offered it is important to look at ingredients list on the ration bag. The top three listed ingredients will usually make up the majority of the ration and within that there should be soya bean meal and two high quality energy ingredients such as cereal grains like barley or maize. Beet pulp is also a relatively high energy ingredient that can be included in rations. However, filler ingredients that are low quality, such as wheat feed and palm kernel should be avoided. It is also important to ensure that the ration has at least 20% soya bean meal included.
Soya bean meal is an excellent source of rumen undegradable protein and has been shown in the past to improve subsequent lamb performance over other protein sources.
When feeding concentrates to ewes pre-lambing it is vital that ewes are introduced to concentrates slowly and when feeding levels are being increased it is done gradually. It is also essential that when concentrate feeding levels exceed 600g/head/day that the feed is split into two feeds at least 8 hours apart to avoid digestive upsets such as ruminal acidosis. Ewes also require access to a supply of fresh clean water.