Nutrition of the Ewe - Weaning to Lambing
2 January 2018
As we truly enter into the winter months, sheep farmers among us will naturally begin to prepare for lambing season. Some farm systems may have already started lambing and others will certainly be getting the ewes ready for the New Year. Regardless of when you lamb your sheep, correct ewe nutrition throughout the year is critical for quality production.
Underfeeding and overfeeding both have negative impacts on productivity, so ensuring that you calculate ewe requirements at certain times during the shepherd’s year is very important. The first step to this is knowing whether your sheep are fat, fit or thin at specific stages of the production cycle. This can be done using the five-point body condition scoring system described by AHDB (https://beefandlamb.ahdb.org.uk/wp-content/uploads/2013/06/brp_l_Sheep_BCS_190713.pdf). Body condition score (BCS) your ewes at weaning, tupping, mid-pregnancy (usually scanning) and lambing. This allows you to assess which ewes require what in terms of nutritional demand. As a rule, one BCS in a ewe equates to about 10% of live weight; so for a 70kg ewe to gain one BCS, she needs to put on 7kg of weight. It can take up to 8 weeks for a ewe to gain this much weight on good grazing as her daily energy requirement will be around 15.4 Megajoules(MJ) equating to around 1.54kg of grass in dry matter (assuming the grass has an ME of 10MJ/kgDM). Ensuring ewes have enough muscle mass and fat cover for the system at particular times of year leads to improved fertility, increased lamb performance and reduced incidence of metabolic disease. So, perhaps worth that little bit of time and effort handling ewes and monitoring BCS!
It has been proven that having a BCS <2 at tupping has a negative impact on ovulation rate. Current science suggests that purposefully “flushing” ewes is economically inefficient, as any ewe in the correct body condition will not benefit from the increase nutritional level flushing offers. However, it can be beneficial for thin ewes to help boost ovulation; useful to know if you end up with some thin animals and not enough grazing or time to fatten them up. Far better, is to prepare ahead; BCS animals at weaning and plan grazing accordingly to ensure animals are correctly prepared for tupping.
In early pregnancy, ewes require little more than maintenance levels of energy which equates to around 12% of bodyweight. There should be no abrupt changes in feed type at this time and minimal stress. By mid-pregnancy, ewes require just above their maintenance level ideally keeping condition scores at around 3-3.5 for lowland breeds. Scoring and ensuring correct nutrition at this time is important as placental development is very highly related to the BCS of the ewe. It is important not to overfeed at this stage, as fat ewes will be more prone to metabolic diseases at lambing, so splitting ewes into groups following scanning may be a useful management tool.
Feeding ewes in late pregnancy is the big challenge. The ewe’s demand for energy and protein increases to meet the rapid growth of the foetus as well as to support udder development. At the same time, rumen capacity decreases as the foetus takes up more space. Scanned flocks can start to split ewes to optimise their condition and to improve cost efficiency.
This example compares two ewes and two situations in a flock. The ewes are 3 weeks prior to lambing and both weigh 70kg. Ewe 1 is bearing twins, Ewe 2 a single. Both ewes will eat approximately 1.4kg of dry matter per day. The difference in requirements are shown in the table below, which compares the two ewes as well as two different forage types. Note all feed values are given in fresh weight.
The nutrition of ewes in late pregnancy directly affects the birthweight of lambs, colostrum and milk production. Even if at no other time, this is the really critical period to calculate ewe rations. Ensuring that forage intake is maximised and correct amounts of concentrates are used, not only makes feeding financially efficient, it ensures that metabolic issues are minimised and lambing production is maximised.