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Nutritional building blocks to a successful lamb crop

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Nutritional Building Blocks to a Successful Lamb Crop

Nature dictates that more than 70% of lamb foetal growth occurs in the final six weeks of pregnancy. This period is quickly followed by a rapid growth period needed to hit key markets with well grown lambs.

As a result, the period leading up to lambing, and then through to weaning is critical in the ewe and lamb feeding calendar, explains David Thornton, Rumenco’s technical manager.

“Maximising forage intake and utilisation will form the basis of feed plans on farm during the period both pre- and post-lambing. It is, therefore, critical that forage sampling and analysis is undertaken to ensure nutrient requirements of all stock are fully met, and cost-effectively. 

“A basic forage analysis report will outline at least, the dry matter content, protein, energy and intake potential of a forage and, therefore, allow the remaining animal requirements to be constructed around the basal forage contribution,” he says.

Where silage forms the forage base of the diet then ensuring it is sampled and analysed is critical in order to understand the potential to maximise its intake and how to accurately balance any potential shortfall in nutrient supply, adds Mr Thornton.

“Target forage dry matter intakes of 1.6% of ewe bodyweight should be aimed for at six weeks pre-lambing, reducing to 1.4% from three weeks pre-lambing to lambing.  This requires good quality, well-made silage or well managed pasture to be offered in such a way that doesn’t restrict consumption.

“The energy and protein content of forage will play a significant role when trying to achieve high forage intakes, offering the possibility of delaying concentrate inputs until quite close up to lambing, or not feeding traditional concentrates at all, but considering a free access supplement,” he explains. 

“Knowing the protein content of your forage will also influence the type of supplement required to ensure ewe requirements are fully met.  Grass based forages supply mainly rumen degradable protein (ERDP) processed by rumen microbes to become microbial protein.

“Where the forage protein content is 11% or above there is typically adequate ERDP to satisfy rumen microbial needs meaning only a dietary contribution of digestible undegraded protein (DUP), commonly known as bypass protein, is required.  This will typically be achieved through the feeding of soya as part of the supplementation and helps support colostrum and milk production and to heighten ewe immune response.”

But, where ewe diets are not based on grass-based forages and are based on crops such as maize and whole-crop silages, then the protein level of the forage will typically be about 7-9% meaning additional rumen degradable protein will be required.  “This will ensure rumen microbes have the required protein to function meaning supplements should have a higher protein content (18-20%) and ideally contain distillers or rapemeal, both rich in rumen degradable protein.

“Forage is also better used where animals are offered supplementation on a little-and-often basis to reduce the risk of metabolic upsets associated with traditional high concentrate feed rates and their subsequent negative impact on rumen pH,” says Mr Thornton.

Supplementing via blocks or buckets fits this scenario perfectly. As well as offering savings in overall feed, time and labour for farmers, free access supplements reduce stress on ewes at feeding time plus allow improved grazing utilisation through positioning of supplements across the grazing area.

“Recognising the difference between supplements should be the starting point in selecting the most appropriate for your scenario – some supplements supply only minerals and vitamins while others, including concentrates, supply varying degrees of energy and protein plus minerals and vitamins.

Rumenco Lifeline buckets, when consumed at the target 150g/ewe/day, can supply about 10% of ewe daily energy requirements alongside high quality bypass protein, yeast fermentation extracts plus minerals and vitamins to support ewe and unborn lamb health and immunity.  

Fed alongside ad-lib 10.5MJ ME/kg DM forage these blocks can supply the requirements of a twin-bearing 75kg ewe until 3-4 weeks before lambing.  At three weeks pre-lambing 0.45kg a day of concentrate will be required. For thin twins, yearling twins and triplets this will need to be about 0.75kg/day, to make good the typical 4-5 megajoule a day deficit in energy requirement, albeit at a reduced level compared to not offering these buckets, he says.

Ensuring lambing is as smooth and successful as possible for both ewe and lamb is crucial to achieving the best lamb crop results possible.  However, targeted feeding pre-lambing, ensuring ewes are fit, not fat and they have plentiful high-quality colostrum is only one part of the jigsaw.

Feeding ewes and lambs post-lambing after turnout isn’t easy. The nutritional contribution from grass is difficult to estimate apart from a visual assessment of how the lambs are doing.

“Grass is abundant in rumen degradable protein (ERDP), whereas both ewes and lambs have a requirement for bypass protein (DUP) to support milk production and lean muscle growth respectively.  Complementing the protein found in fresh grass with additional bypass protein has been shown to deliver significant benefits to lambs from an early age. 

“Improved milk supply from the ewe leads to higher growth rates and also supplying the young lamb with protein it is able to use from a very young age, even before its rumen has fully developed, encourages lean muscle growth and hence weight gain.   

“One way to optimise both ewe milk yield and, as a result, early lamb growth is to offer  Rumevite Graze DUP.  Targeted to feed post-lambing at turnout to grass, as a block product it also has the added benefits of ensuring feeding is easier, less time consuming and less stressful.  It can readily replace concentrate feeding when there is at least 4cm grass sward plus reduces the opportunity of mis-mothering often associated with trough or ground feeding at grass in the early stages of life.

“Independent studies carried out over the past two lambing seasons have clearly shown the benefits of this high DUP supplement at grass in maximising weight gain and lamb performance,” adds Mr Thornton.

In the first study, twin lambs from the block fed group were each nearly 2.3kg heavier than controls at 12 weeks of age, probably due to increased milk supply from their mothers.  The second study, on a different farm, was also carried out using twins and included a group of ewes fed Lifeline pre-lambing.  These lambs were 0.8kg heavier at weaning and grew at almost 20g more a day from birth, but the combined effects of feeding both blocks saw a significant response with twin lambs 4.2kg heavier at 12 weeks.

Targeting the highest possible returns with each lamb crop begins with fully using low-cost forages both before and after lambing.  Reviewing traditional feeding systems to ensure you are offering the correct supplement should form part of planning for this years’ lamb crop, he explains.

“Feed choice should complement forage, not replace it, with the aim that ewes lamb in fit, not fat condition with adequate, high quality colostrum and continue to produce adequate milk for their lambs after turnout. 

“Targeted supplementation will enable farmers to maximise spring grass utilisation while achieving the target growth rates to hit the most profitable markets, making sure the correct nutritional building blocks are used will pay dividends in the long-term,” says Mr Thornton.


Study One:


Weaning weight (kg)

Faecal egg count

Feed block consumption (g/day)

Graze DUP Feed Blocks









+ 2.29

(s.e.d 0.503 kg)



Statistical significance





Study two:




Lifeline + GDUP

Ewes at start




Lambs at scanning




Ewes at end




Lambs marking (%)




Lamb birthweight (kg)




Lamb wt at 6 weeks (kg)




Lamb ADG from birth (g)




Lamb wt at (12wk) weaning (kg)




Lamb ADG from birth (g)



333 (+18% faster than controls)

Block intakes g/ewe/day



120 + 101