The wide variation in grass growth across the UK this spring means the dietary needs of lactating ewes must be carefully monitored – failure to reach peak milk yield could see lambs weigh 3-4kg lighter at weaning.
The severe grass shortage in some areas is putting ewes with lambs under pressure. Advisers say a close watch must be maintained on precisely how much grass is available – even when grass appears ample at turnout – and urge flockmasters to be particularly vigilant about supplementary feeding in the coming weeks.
Although ewes and lambs may appear to be thriving in the dry conditions, cutting out supplementary feeding too quickly will immediately hit milk production and lamb growth rates will suffer.
John Vipond, SAC sheep specialist, says it’s essential to measure grass growth accurately this spring. “Measure often and measure carefully. Until grass reaches 4cm in height ewes will need supplementary feed. Once it has reached that level they should be OK.”
But new research work at the Macauley Institute has highlighted the need for sheep producers to look closely at the type of supplementary feed being offered to bolster spring grass.
“New spring grass, however little there may be of it in some areas, is high in nitrogen and provides more than the ewe’s rumen can handle.
“To cope with this the diet should contain soya or protected soya – such a sopralin – so that maximum milk yield can be achieved by supplying a source of digestible, undegraded protein (DUP). Maintain the feed rate for longer at about 1kg a day in two feeds for older and thinner ewes.
“In early lactation the ewe is under pressure to produce protein for milk and that means she’s less resistant to parasites. Feeding this type of diet will reduce the ewe’s faecal egg production – and that has the potential to increase lamb growth rates by 25% because of the lack of parasitic challenge,” says Mr Vipond.
And even though there appears to have been ample grass for ewes and lambs at turnout in western areas, farmers are advised to keep a close eye on sward height. If ewes make a sudden impact on grass and the grazing height falls below 4cm, they are potentially under pressure at a critical time in the run-up to peak lactation.
Cumbria sheep vet Matt Colston, of Frame, Swift and Partners, Penrith, says young grass at 4-5cm will provide the 30MJ of energy a day required by a lactating ewe in correct body condition post-lambing and for the first four weeks thereafter.
“But it’s important to keep a close eye on sward height. If it’s old grass there may be enough of it but its feed value won’t meet the ewes’ nutritional needs. If grass gets stalky or ewes get ahead of the re-growth it won’t provide enough for ewes to attain peak milk yield. So monitor all grass carefully and regularly,” says Mr Colston.
And where field conditions are wet excessive poaching will occur around troughs and feeders – a situation that could trigger foot problems in ewes and even lambs. Sheep advisers recommend moving troughs daily to avoid adverse ground conditions developing and to be aware that lameness in wet conditions will worsen more rapidly if not treated.