RWN Yeast Supplements

Live Yeast Supplements for Cows

Why do we need to Feed Yeast to Cows?

Live yeast supplements improve feed conversion efficiency in the cowYeast Supplements - have always been difficult products to assess, since the effects of yeast are by no means instantaneous, but over the years trial after trial has shown yeast to be about the most consistently reliable and cost effective performance enhancing feed ingredient available. The effect of a live yeast is to improve feed conversion efficiency by between 5% and 15%. The result is 1 - 2 litres more milk per cow, usually accompanied with other benefits in terms of milk quality, improved fertility, body condition and overall herd health.

How does Yeast Work?

The mode of action of live yeast which involves scavenging oxygen from the rumen and removing lactic acid has been thoroughly researched and is now well understood. Oxygen is highly toxic to rumen microbes. Live yeast supplements rapidly eliminate oxygen from the rumen and increasing microbial activity. Yeast changes the microbial population in the rumen stimulating the proliferation and activity of both fibre digesting bacteria and lactic acid utilising bacteria. The effect of yeast is to raise rumen pH reducing acidosis, and to increase the rate of digestion of the diet, particularly of fibre. Yeast increases redox potential resulting in greater rumen activity and a higher level of digestibility of the overall diet. As a result of faster and more complete digestion of the diet, total dry matter intake increases by up to 1kg - 2kg per cow. In addition increased rumen bacterial activity creates up to 15% more microbial protein which has a superior feed value to fishmeal. Utilisation of additional degradable protein also results in reduced blood urea nitrogen (BUN) levels.

Biocell Live Yeast supplements containing Actisaf SC47, improve feed efficiency and reduce acidosis risk by helping to keeping rumen pH closer to optimum levels for efficient digestion between 6 ph and 7 pH

Feeding Yeast to Dairy Cows

Yeast improves herd health and is one of the most cost effective feeds availableThe standard recommendation is to introduce yeast to the cows diet at least 3 weeks before calving to get the beneficial effects of yeast when they are most needed, during transition and during early lactation. Then to continue feeding throughout the lactation.

It takes 2 to 3 weeks for the rumen microflora to adjust fully to the introduction of live yeast. The effects of the improved digestion are gradual but what we generally see in practice is cows that started the lactation on yeast will peak 2 - 3 litres higher. Mid-lactation cows have more persistent yields and over a lactation cows invariably produce several hundred litres more milk. Responses to improved energy metabolism are not instant. Be patient and in time you will see that healthier cows produce more milk.

If you decide to feed yeast we recommend that you try it for a full lactation in order to see the benefits, and yes, most of our clients do continue feeding yeast at grass, where it is equally beneficial. Yeast is very cost effective to feed so it makes sense to include it in all ruminant diets as standard.

Feedback from the vast majority of dairy farmers who have used yeast for a season, when asked, say that "the thing we have noticed most is that our cows have been much healthier, cleaner, more settled and with fewer problems".

Yeast Dairy Farm Trial Results

Many trials have clearly demonstrated the benefits of feeding yeast. One of the best trials to demonstrate the long term benefits of yeast supplements was done by a team of vets at Velcourt Farms in Dorset in 2004 using Yea-Sacc. This trial was fully independent and paid for by the farmer. The trial was on a high yielding 200 cow, full TMR fed herd, housed all year, on an even calving pattern, was in a steady state with no changes to the diet or to the forages throughout the trial. Yeast was fed for 5 months at normal rate, cows were recorded automatically. Dry matter intakes were recorded daily by weighing the feed that the cows didn't consume each day. Rumen pH was recorded by sampling rumen fluid.

Live Yeast supplements such as Yea-Sacc have been shown to increase rumen pH resulting in more efficient digestion and higher milk yields

At the start of the trial rumen pH was low at 5.83 verging on sub-acute rumen acidosis or SARA. Rumen pH increased steadily over 5 months after the introduction of yeast, to 6.51. This evidence supports our own field observations. At 6.5 which is optimum pH, we would expect to see very settled, clean, healthy cows, cudding well with optimum rumen function and very efficient digestion, which is exactly what we see regularly on commercial farms who feed yeast.

Live Yeast has also been shown to increase total dry matter intake (DMI). The effect of yeast improves over several months

Dry matter intakes improved steadily throughout the 5 month trial. Despite DMI being at 26.1 kg at the start of the trial DMI still improved by another 1 - 2 kg per cow. This is typical of what many commercial dairy farmers commonly report, cows perform better and better, with fewer health problems the longer they are on yeast.

Yeast Trial - Yeasacc - Milk Yields in high yielding dairy cows continued to rise over several months

Again on these trials milk yield gradually improves by over 2 litres per cow. The milk yield increases as more cows calve onto yeast with higher peak yields than those drying off from the previous lactation. What this trial shows very clearly, is that feeding cows is a long term process, where the full benefits of what we do today may not be seen for at least another year. It is quite clear that feeding yeast brings long term benefits.

Yeast trials have shown increased growth rates and feed efficiency in heifers, beef and growing livestock of 10% - 15%Yeast supplements are often viewed as being an expensive and unnecessary add on by both dairy farmers and also by inexperienced or non-nutritionally consultants. In our view this is incorrect. Whilst there is wide variation in the efficacy of different yeast strains, the levels of activity as well as the levels and quality of yeast supplied in different yeast supplements, most yeast strains available in the UK, are EU approved and as such have gone through rigorous trials to prove their effectiveness.

Yeast supplements do work. They bring both improved performance, herd health benefits and are very cost effective. In fact because of their positive effect on feed efficiency we view yeast as being one of the cheapest feed options available. Yeast supplementation should not be viewed as something which is only applicable to high genetic merit herds at peak production where cows are suffering from acidosis. Yeast supplementation is beneficial and cost effective in most livestock, youngstock and dairy diets.

Yeast supplements based on micro-encapsulated Actisaf SC47 yeast have repeatedly been shown to be particularly effective in trials both in the UK and overseas.

Actisaf live yeast benefits milk yields, butterfat, milk protein, herd health and feed efficiency.Trials from feeding Actisaf yeast to dairy cows in Denmark clearly demonstrate improvements in Milk Yields, ButterFat, Milk Protein and Herd Health from feeding yeast. The 255 litre yield response over the 3 months period here equates to at UK prices more than £80 worth of extra milk for a cost of less than £8 / cow and this is before the herd health and other benefits.

Generally anything above 0.33 litres milk yield response will yield a financial return. Here the response was in excess of 2 litres per cow per day.

A recent trial in a high yielding UK herd showed the benefit of supplementing dairy cows with Biocell pure live yeast. Cows milked on robots, were divided into two groups (control and Biocell groups) for a 90 day period. Cows in each group were in early lactation and were balanced for parity, days in milk, milk production level and milk composition. The graph below clearly shows improved performance from cows supplemented with Actisaf yeast.

Yeast Trial - Yeasacc - Milk Yields in high yielding dairy cows continued to rise over several months

Assuming an average yield response of around 1.5 litres of milk per cow plus other benefits, with a cost for yeast of only 7p / cow / day we can be confident of at least a 4:1 return on the cost of the yeast even when milk prices are low.

Live yeast supplements should not be seen as an expensive add on, but rather as one of the cheapest, best value feeds available. Yeast improves efficiency of digestion in the rumen, and has the ability to both lift output and to reduce overall feed costs per litre by allowing the cow to get more out of it's existing diet.

Making best use of the wide range of feeds available is an area where our nutritional expertise is of particular benefit to our customers

Live Yeast and Fibre Digestion

We have routinely advised feeding live yeast product as standard in high yielding dairy diets. One of the reasons for this recommendation is that feeding a live yeast supplement improves feed efficiency and fibre digestion. In short you get more out of every mouthful of feed that the cow eats. This is illustrated well by worked carried out by Ensat, J Dairy Science 2008.


Live Yeast SC47
pH minimum
Redox Potential
DM Digestibility
NDF Digestibility
ADF Digestibility

Redox potential is an indication of microbial activity within the rumen. The live yeast increased microbial activity as well as markedly increasing the digestibility of dry matter, neutral detergent fibre and acid detergent fibre. Lactic acid levels in the rumen were also reduced. Interestingly whilst 150 gms sodium bicarbonate raised rumen pH to 5.94, it had no effect on lactic acid or DM digestibility and was much less effective than yeast at improving Redox Potential or fibre digestibility. This work was carried out with the SC47 yeast strain used in Biocell farm mix and should not be applied to other strains which may not have this effect.

Yeast Feed Efficiency and Carbon Footprint

The University of Nottingham’s Centre for Dairy Science Innovation (CDSI) recently studied the effect of feeding Actisaf to their high performing 12500 litre dairy herd.

Biocell Farm Mix contains Actisaf / Actisaf returns up to 8 times your investment through improved milk yields.They found that Actisaf increased milk yield by 2.8 kg/day with no associated lift in dry matter intake thereby significantly improving feed conversion efficiency by an average of 5.5%. This improvement in performance had no negative effects on body condition, health, methane emissions or fertility.

Actisaf has been shown to return up to 8 times your investment through improved milk yields as well as improving feed efficiency and reducing the carbon footprint for each litre of milk produced.

Feed efficiency and carbon footprint both improved by 5.5% with Actisaf

Actisaf is the only live yeast scientifically proven to reduce lactic acid levels in the rumen (which accumulate and cause acidosis). Published research in the Journal of Dairy Science has shown Actisaf to lower lactic acid levels to a greater extent than sodium bicarbonate. It also increase fibre digestion in the rumen, unlocking more energy from silages and increasing herd performance.

Feeding Live Yeast with Ostrea Rumen Buffer can be highly beneficial in reducing acidosis risk, optimising rumen pH and improving feed efficiency. Reduction in body condition loss at grass will also improve performance during the coming winter.Yeast in Grazing Diets

Acidosis is very common at grass. A high proportion of cows are affected by acidosis and sub-optimal rumen pH throughout the grazing season. Good quality grazing is high in fast fermentable energy and low in fibre. At up to 12.5 MJ/kg DM, grazing can affect rumen pH in the same way as a high concentrate diet.

Consider why cows turned out in good body condition in the spring, lose body condition throughout the grazing season despite grazed grass being much higher in energy than the more mature conserved silages fed during the winter.

Look at your cows as they come in for afternoon milking with the sun low in the sky in late summer early autumn. Do the ribs show? They didn't when you turned out in the spring.

Cows at grass with a stable rumen pH, lose less body condition and give more milk

Feeding Live Yeast together with an effective Rumen Buffer at grass generally results in a more stable rumen pH, more milk, more butter fat and more proteinWhen rumen pH is below optimum digestive efficiency fall off. Cows get less out of the diet. A percentage of the diet is wasted whether it is grass or concentrates. Cows have loose dung and scour. Herd health and fertility suffer. It is not uncommon to lose a unit of body condition over the summer.

Cows that have lost a lot of body condition at grass take a long time to get going and a lot of extra concentrates over the 2 to 3 months after housing.

A study at University College Dublin 2006 on commercial farms illustrates the extent of the problem of acidosis on grazing systems. For more information download Fresh Grazing Brings Acidosis Risk.

Where practical we recommend feeding both Biocell farm mix, live yeast supplement and Ostrea Rumen Buffer as a matter of course throughout the grazing season as a means of improving feed efficiency and output.

Yeast in Calf, Growing Livestock and Transition Diets

Yeast supplements are cost effective to use in all lactating dairy, dry cow, transition, calf, lamb, beef and heifer rearing diets Live yeast supplements also give very good responses in calf, lamb, beef and heifer rearing diets. Typically we see a 10% - 15% improvement in both growth rates and feed conversion efficiency. Yeast should be fed through the transition diet. This gives time for the rumen to adjust so that new calvers hit the ground running. Yeast is an absolute must for the close-up dry cows.

Our Range of Live Yeast Supplements

We have routinely advised feeding live yeast products for a number of years using tried and tested E.U. approved products which give consistent and predictable results. Yeast needs to be live and fully viable for the full effect. Not all yeasts are the same and not all products that do contain the same strain of yeast, apply the full recommended amount. Our advice is to stick with tried and tested market leaders. Remember live yeast is a "live" product and needs to be treated accordingly in order to retain it's full viability.

Biocell Farm Mix - contains Actisaf SC47 the worlds leading live yeast. Actisaf differs from other live yeasts in that it is micro-encapsulated to improve viability for use under commercial farm conditions. Independent University research trials have also demonstrated higher levels of activity of Actisaf SC47 compared with other commercially available strains of yeast. Actisaf is produced by the Phileo Lessafre the World largest yeast company and SC47 is one of the most researched yeast strains worldwide.

Biocell Actisaf / Biosaf SC47 Micro-encapsulated live yeastThe levels of yeast used in Biocell are higher than in many other commercially available products so it is not surprising that Biocell gives us such consistent improvements in intakes and performance in dairy, calf and heifer rearing systems. We have many satisfied customers. Biocell should be fed as routine in all high yielding dairy herds, summer and winter. Start with the close-up dry cows 3 weeks before calving and feed right through lactation.

The University of Nottingham’s Actisaf study along with a large library of other peer reviewed trial work is proof that feeding Actisaf results in a wide range of benefits.

Actisaf has been shown to return up to 8 times your investment
through improved performance

Actisaf Dutch trials confirm incresed milk output resulting from improved feed efficiency. See details of these Actisaf trials.

Additional details can be found in this video and white paper, ‘Mighty Microbes: How the rumen microbiome can help dairy reach Net Zero’.

We have had tremendous results on a large number of farms with this product

Biocell Actisaf Yeast really does work

Biocell Yeast Farmpack contains Actisaf SC47 micro-encapsulated live yeast (previously known as Biosaf SC47)

Live yeast improves feed efficiency as well as animal performance. Yeast allows the cow to get more out of its existing diet and actually saves you money.

Yeast really does work. If you haven't used yeast, try some.


Making best use of the wide range of feeds available is an area where our nutritional expertise is of particular benefit to our customers

For more information or for an in depth consultation contact Richard Webster.

Independent Suppliers of Quality Feeds and Associated Products
for the High Yielding Dairy Cow

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