WHILE preparing for lambing, it is important to plan the nutrition of ewes up to weaning.
Dr Liz Genever, AHDB Beef and Lamb senior scientist says: “There is a massive focus on feeding levels during late pregnancy, but a similar level of focus needs to apply to lactation. Nutrient demands to support milk production increase rapidly after lambing. An 80kg ewe rearing twins will increase her daily energy and protein requirements by 60 per cent and 44 per cent, respectively”
In early lactation, a ewe’s voluntary feed intake only increases by about 10 per cent compared to late pregnancy.
Dr Genever says: “This means in early lactation a ewe will rely on body reserves to produce sufficient milk. A ewe can manage and recover from short periods of nutritional restriction (about seven to 14 days), but longer periods will have a permanent impact on milk production so it is important to make sure feed meets the requirements as intake increases and a ewe reaches peak lactation.”
Ewes suckling twins produce 30-50 per cent more milk than ewes with a single lamb given the same level of nutrition. The increased milk production in ewes suckling twins is related to the demand for milk. Ewes rearing twins have a higher peak yield and this is reached more quickly, two to three weeks post-lambing compared to three to five weeks for ewes rearing single lambs.
Dr Genever says: “Ewes in good condition will maintain milk yield, but lose more body fat compared to thin ewes. Research has shown, where ewes have good body condition scores [more than 3] at lambing, lamb growth is significantly and positively correlated to a loss in a ewe’s BCS up to weaning. Conversely, when ewes are leaner [with a BCS less than 3], with an increased and satisfied appetite, lamb growth is positively correlated to a gain in body condition score. This is a function of the availability of feed. Thin ewes with restricted access to feed will stay thin and have lighter lambs. This has important implications for how resources are allocated across a flock.”
The impact of body condition is therefore variable, depending on BCS at lambing, and it underlines why it is important to maintain ewe condition at target levels (Table 1) during pregnancy and up to lambing.
The sheep key performance indicator (KPI) project, funded by AHDB Beef and Lamb, has shown the importance of monitoring ewes’ BCS at about eight weeks post-lambing, as this is likely to be when their condition score is lowest. This information can then be used to decide when to wean, with ewes with a low BCS weaned earlier.
|EWE TYPE||LOWLAND EWE (60 - 80 KG)||HILL EWE (40 - 60 KG)|
|Target BCS at lambing||3.0 – 3.5||2.5|
|Target BCS at weaning||2.0 – 2.5||2|
|Bodyweight lost (KG)||6 – 8||2 - 3|
|Energy released (1MJ/50g weight loss)||120 – 160||40 - 60|
Dr Genver says: “In practice, most ewes rely heavily on grazed grass during lactation. To keep costs as low as possible it is important to get the most out of grass and forage, but ensure supplementary feeding is offered when required. A sward height of 4.5-8cm will provide maximum dry matter intake.
“When turning out in early spring, sward height may be less than 4cm, so supplementation will be needed until grass growth catches up. If sward height is less than 3cm, extra forage will need to be provided.”
After assessing sward height, stocking density would usually be altered to match available grass, but this is not practical for ewes with young lambs, so supplementation in early lactation is the best option to bridge any gap in nutrient requirements.
Dr Genever says: “If possible, group young or thin ewes together for preferential feeding. If ewes have been housed before turnout, remember to ensure a transition between their previous diet and their diet post-turnout as it will take a few days for their rumen to adjust.”
|Turnout to May||8 – 10cm||4 - 5||4|
|May to weaning||8 – 10||4 - 6||4 - 6|
Grass staggers (hypomagnesaemia) is a potential risk in lactation and a supply of magnesium needs to be provided. High levels of potash need to be monitored as this will increase the risk of grass staggers.
Underfeeding protein and energy in lactation increases mastitis risk. Well-nourished ewes are better able to fight infection. Underfeeding could be a trigger factor, causing bacteria normally resident in the mammary gland to become pathogenic. Hungry lambs may also lead to possible trauma of the teats and udder through over-eager suckling, which can then lead to acute mastitis.
AHDB has been working on updating its ITALS Feeding the Ewe manual to take account of new research since the last version was produced in 1998 and a new version will be available soon.
More information on planning grazing can be found in the Better Returns Programme (BRP) manual ITALS Planning Grazing Strategies for Better Returns. Information on mastitis in sheep can be found in the BRP+ manual Understanding Mastitis in Sheep. All available on beefandlamb.ahdb.org.uk/returns