Maximising returns from store lamb production: diet advice and the role of Actisaf live yeast

Assuming farmers have assessed resources, prepared a budget and are going to finish home grown or bought-in lambs, there are a number of key nutrition and management factors to get right to ensure success.

Optimal returns will be achieved by having:

  1. Balanced costs of production (e.g. feed costs, lamb purchase cost, veterinary)
  2. High levels of performance (e.g. high levels of liveweight gain, low levels of mortality)
  3. Time of year and prices when marketing finished lambs
  4. Marketing lambs in spec, clean, dry and not bruised

Step 1: Calculating Feed Supply: 

  • With the current shortage in available forage, it is more important than ever to determine how much forage is currently on farms.
  • Measure silage clamps and count the number of hay and silage bales in the yard and see how much good quality straw you can access.
  • Determine the quality of the forage on farm by getting it analysed; the analysis results will form the basis of any feeding decisions. It will be a sound investment, especially in difficult times.
  • Where forage crops have been grown, the following document produced by AHDB Beef and Lamb is a useful resource in calculating yields: Using Brassicas for Better Returns
  • Feed advisors can play a vital role in assisting farmers with measuring silage pits, estimating forage quantity/quality, and preparing autumn and winter feeding plans.

Step 2: Calculating Feed Demand: 

  • Lambs generally consume 4% of their body weight per day so do not underestimate that overwintering lambs on pasture can have a negative effect on spring grass availability and competition for resources with other stock (e.g. ewes).

Where forage is short, moving heavier lambs onto an ad lib finishing diet will be essential. Assuming a 38kg lamb eating 4% of BW, this would be a saving of 1.3kg/DM per lamb, assuming 200g of forage DM is supplemented.

Over 200 lambs, this equates to 260kg DM/day or 1.3 round bales of silage a day (650kg FW and 30% DM)

Dividing lambs by finishing weight into short keep (35kg+), medium keep (30-35kg) and long keep (<30kg) is essential when deciding on the most appropriate diet and finishing system as these lambs will have different requirements in order to maximise the use of available forage.

For example, lighter lambs needing further frame growth require a higher protein diet, whereas heavier animals require a more energy dense diet to achieve a final level of finish and do not need much forage to achieve this.

Short Keep lambs (35kg or more):

This group can often be finished off on grass alone, but only when grass quality is excellent and with supplementary concentrate to make up for the grass’s declining energy levels until the end of October.

However when grass supply is low, finishing lambs can easily be transitioned onto an ad-lib concentrate diet with forage supplemented at low levels to maintain rumen function. This approach will be explained later.

Where forage is scarce, these lambs can perform well on a well balanced concentrate formulated for ad-lib feeding with 200-300g of straw or hay when fully built up as long as feed management is excellent. 

Medium and longer keep lambs:

These lambs will often need to grow additional frame before adding the final finish. Because of this, they may need supplemental protein, especially if forage has a low protein level. When grass is plentiful, grazing is often a cheap way of adding frame growth until the end of October, after which grass will be contributing very little to lamb growth rates and as such alternative diets will be needed.

Ad-lib concentrate diets for these lambs are difficult to get right because a typical high energy diet will often cause them to go fat before they have grown sufficient carcass to reach market specification.

Leafy brassicas can be particularly useful forages for these animals to grow frame due to their higher protein content, as can root brassicas supplemented with additional protein.

Each crop comes with its own set of considerations. For leafy brassicas (e.g. kale, rape, hybrids) additional energy may need to be brought in to ensure optimal live weight gains, whereas root crops may require additional protein for growing lambs. A grass runback should be provided for all crops and a supply of forage or roughage should always be available ad-lib. Ideally these crops should not make up more than 70% of the total diet and in many instances no more than 50%.


Table 1: Supplementary Crop Quality


Dry Matter %

ME (MJ/kgDM)


Forage Rape             




Stubble Turnips












Source: Forage Choice, Crops and Rotations Report 2010 Kingshay


What weight gain can we realistically expect from grass through the season?

As the season progresses it is unrealistic to expect high levels of performance from grazed grass alone.  Lambs need to be supplemented with concentrates, excellent quality silage (11ME +) or root/forage crops in order to maintain performance.


Table 2: Typical performance of lambs on a grass diet

Time of year

ADG (g/day)

Kg gain/week










Adapted from Diskin et al., 2017


Table 3: Typical performance of lowland terminal sired lambs on good quality grass

Time of year

ADG (g/day)

Kg gain/week










Adapted from Diskin et al., 2017


This year in particular, it is essential to prioritise available grass supplies to animals with a lower requirement (e.g. ewes) and to ensure there is adequate grass supplies available for next spring. Making high levels of grass in the diet of lambs unlikely to be suitable this year.


Calculating diet requirements:

Lambs require nutrients firstly to maintain themselves (e.g. immune system, digestion, maintenance of body temperature etc.) and secondly for growth.

Therefore it is essential to maximise the nutrients provided above maintenance requirements to ensure optimal use of resources.

High levels of liveweight gain require excellent quality forages. When forage is in short supply or quality is not adequate, concentrate feeding may be required to supplement forages. Getting forages analysed is essential when deciding if supplementary feed is required and the analysis results should be the starting point for any feeding plan.


Maximise Intake:

Calculating diets is a balance between providing the required nutrients in the most cost effective manner.

Achieving high levels of dry matter intakes is essential in order to ensure lambs can consume enough nutrients to cover their maintenance and consume enough food to put on weight.

Trough space is particularly important to ensuring sufficient feed and water intakes. There should be 30-40cm of feed trough space and 1cm of water trough space per lamb.  

The table below demonstrates the effect of increasing liveweight on maintenance requirement and the resulting requirement to increase the diet’s energy density for heavier lambs to achieve a final level of finish. As well as increasing the energy density, it is essential to maximise intakes in order to get these lambs to achieve target growth rates of >200g/lamb/day.


Table 4: Effects of increasing liveweight

Lamb Weight


assuming good quality forages

and 4% of BW

Maintenance Requirements

Energy Requirement

  to gain 140g/day (low ADG)

ME/KgDM required 

(energy density )

30 kg                               


6.0 MJ/day



35 kg


6.5 MJ/day



40 kg


7.0 MJ/day



45 kg


7.5 MJ/day



48 kg


7.8 MJ/day



(assuming 43 MJ ME/kg LWG and 140g/lamb/day)


Rumen Function:

The rumen is the engine room of the lamb and it has a number of key requirements to keep it running efficiently. Acidosis and poor rumen function are often seen in:

  • Lambs that are not adapted to grain-based diets
  • Diets with a low structural fibre content such as some forage crops
  • Animals fed finely ground or rapidly fermentable feed ingredients
  • Animals that gorge following a period of feed restriction
  • During diet transitions

Diet Transitions:

  • The most important pinch point for lambs is with diet transitions and getting lambs adapted onto finishing rations quickly, which generally takes 14-21 days.
  • Diet changes that occur too quickly can often result in poor rumen function, acidosis and often death.
  • Careful diet transitions are also essential as Clostridial diseases such as pulpy kidney (Clostridium Perferinges Type D) are most commonly seen during transitions onto a new diet, especially onto highly digestible diets as the bacterium, naturally present in the intestines, rapidly increase toxin production.
  • It is generally recommended to start with 300g/hd/d of concentrate and increase by 100g every three days until lambs achieve the desired feed rate. If lambs show signs of digestive upset or poor thrive, stop increasing feed rates until good condition is restored.
  • Start with 20kg/100 lambs on day one and move to 25kg by day three, 30kg by day six etc. until you reached the desired level of feeding.
  • Lambs that have been creep fed will adapt much quicker.
  • Many hill bred lambs will often reject feed (“shy feeders”). Ideally these animals should be identified and grouped together for monitoring.

Feed Management:

  • Make diet changes slowly.
  • Do not let lambs run out of feed for a significant period of time as this can lead to gorging.
  • Remove rejected feed regularly to allow room for fresh feed. Lambs will often reject unpalatable feed and may gorge when new feed is offered, causing issues with acidosis etc.
  •  Fresh, plentiful water should be free available at all times.


Water: The Forgotten Nutrient

Lambs require up to eight litres of water a day, and all animals should be given plenty of access to fresh clean water. Ideally there should be 1cm of trough space available per lamb, as reduced water intake will reduce feed intake, reduce efficiency of digestion and put lambs at an increased risk of falling ill.


Draft Regularly:

Work from Teagasc has shown that the variation in the liveweight performance of lambs on an all-concentrate diet is significant, which is reported to be directly related to lambs’ concentrate feed intake. Lambs with high intakes of 1.8-2.0kg per day will perform at close to 450-500g per day, while lambs eating less than 0.5kg per day will often perform closer to 100g per day. This highlights the need to sort lambs regularly due to the variation in individual lamb performance, as well as promoting high intakes through the control of variables, like trough space, water, foot health, and parasite control.


Table 5: Performance of light and medium weight Scottish Blackface and Texel cross Scottish Blackface when finished on an ad lib all-concentrate diet.



Scottish Blackface        

Texel x Scottish Blackface





Starting weight (kg)





Daily intake (kg)





ADG (g/day)










Slaughter weight (kg)





Carcass weight (kg)





Carcass Conformation: % ‘U’ % ‘R’ % ‘O’

0% 80% 20%

20% 80% 0%






% Carcass > 15 kg (French)





Adapted from Diskin et al., 2017


Diet Specification:


  1. Introductory Concentrate Mix for finishing lambs (growing lambs requiring frame growth):
  • 16% CP as fed
  • ME 11.5-12.9 MJ ME/kg DM
  • <35% cereals from balanced sources (e.g. maize, barley, oats)
  • Quality Protein sources (e.g. Soya)
  • Balanced digestible fibre sources (e.g. sugar beet, soya hulls)
  • 0.5% ammonium chloride to reduce the risk of urinary calculi or kidney stones, particularly for male lambs.
  • Balanced minerals and vitamins formulated to lambs requirements 
  1. Mix for finishing lambs established on an ad-lib concentrate diet
  • 13-15% CP as fed
  • ME 12-12.9+ MJ ME/kg DM
  • <60% cereals from balanced sources (e.g. maize, barley or oats)
  • Balanced digestible fibre sources (e.g. sugar beet, soya hulls)
  • 0.5% ammonium chloride to reduce the risk of urinary calculi or kidney stones, particularly for male lambs
  • Balanced minerals and vitamins formulated to lambs requirements

Symptoms of poor rumen function/Acidosis:

  • Loose dung/diarrhoea
  • Depressed appearance (head down)
  • Bloating of the left side of the abdomen
  • Not standing to feed
  • Staggering or tender gait and 'sawhorse' stance.
  • Death

 Feeding Actisaf live yeast to lambs

  • Has been proven to aid in diet transitions by helping microbes to adapt to new diets
  • Increase VFA (energy) production, particularly propionate, a key driver of live weight gain and feed utilisation.
  • Reduces the build-up of lactic acid, which causes acidosis.
  • Stimulates the growth of rumen microbes that digest fibre and starch – increasing feed intakes and helping efficient digestion and unlocking more from your forages.
  • Improved feed conversion efficiency, so lambs are putting on more weight for every kg of feed.
  • Trial results have shown that Actisaf improves average daily gain by 10%, feed conversion rate by 11%, and increased carcass weight by 8%.

Below is a list of common nutritional and non-nutritional ailments to consider, as well as key areas of management that can cause/prevent them, when preparing a flock health plan with your farm vet and nutritional advisor:

  1. Acidosis – Diet consistency/transition, step up slowly, balanced diet, Actisaf etc.
  2. CCN – transition slowly, step up slowly, provide balanced diet, avoid ferns, high sulphate levels etc.
  3. Urinary Calculi/kidney stones – encourage high levels of water intake, feed ammonium chloride at 0.5% concentrates
  4. Coccidiosis
  5. Clostridial diseases, in particular, pulpy kidney (Enterotoxemia) - diet transitions
  6. Listeriosis
  7. Fluke & Worms
  8. Lameness
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