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Feeding yeast is a good investment

These single-cell organisms can hit on many cylinders to help optimize milk performance

For many years, I have formulated dairy diets with yeast for both dry and lactating dairy cows. It has been my professional intention to promote good dairy nutrition, or solve a particular problem that limits good dairy performance. On occasion, I have seen direct benefits within a couple of days by adding yeast, while other times there were no apparent changes to milk and milkfat yield or to animal health. While it may not benefit in every situation, I think for the most part feeding yeast to dairy cows has value and thus a good investment.

I’m not alone on my endorsement of feeding yeast to dairy cows. Several years of research backs up my own experience feeding yeast to either dry or lactating dairy cows in field trials. It improves digestion and fermentation of dairy feedstuffs, enhances immune function and marks positive metabolic changes such as lowering body temperatures of dairy cows during heat stress. Dairy producers can often see the practical benefits of yeast, particularly in the lactating dairy barn — improved feed intakes, greater feed efficiency, better feed flexibility and healthier-looking manure, all which encompass optimum milk performance.

Yeasts are single-cell organisms that must be fed to dairy cows continuously to produce their many benefits. They are also part of a larger category of fungal direct-fed microbials (DFM) that are know to survive in the rumen and work amongst the natural microbial population of bacteria.

Types of yeast

One mainstream fungal DFM fed to all classes of dairy cattle is the yeast called saccharomyces cerevisiae (SC). It is produced in large commercial quantities by fermenting vats of nutrient-enriched medium, cereal grains and baker’s yeast.

SC is a “live yeast,” which has been shown to stimulate the growth and activity of all types of natural rumen bacteria in dairy cows.

Some dairy nutritionists suggest that such activities are not the work of actual live yeast, but the end-products or metabolites that they produce and are used as nutrients by the natural rumen microbes in the cow. For example, similar fungal yeasts to SC, such as Aspergillus Oryzae or Aspergillus Niger make no claims of live microbes or viability, but have been shown to increase fibre digestion when fed early-lactating dairy cows as well as reduce heat stress in dairy cows during hot summer months.

There is a wide variety of commercial products that contain “live or non-viable” yeast probiotics or a combination of either yeast with extracts or fermentation substrates. These products are available in many different forms such as granular powders, pastes, boluses, gels and capsules. Depending on the form, yeast can be mixed into all classes of dairy cattle feeds, such as total mixed rations (TMRs), grain rations, top-dressed or given orally to the animal. Some DFM can even be mixed into the drinking water or milk replacer (for baby dairy calves). The amount of yeasts fed depends on the product, but often ranges from a couple of grams to 50 grams per head per day.

Formulate ration with yeast

In the last decade, I have been formulating a commercial yeast-derived product with added DFM-bacteria and feed enzymes into both dry and lactating dairy diets. I often recommend it to be used at 20 grams per head per day. For example, about seven years ago, I start adding it to a dairy diet of a 100-cow operation in Manitoba, in which the dairy cows had suffered serious heat stress during many previous summers. Since the yeast was added, rather than dropping a precipitous 0.6 per cent in milkfat, when hot weather strikes, these yeast-fed cows maintain a constant milk and milkfat yield.

This dairy producer was so pleased with his cows’ heat-stress results that he requested it be added to lactation diets all-year-around. More than once he told me one of the biggest non-summer benefits for feeding yeast to his lactating dairy cows is when he switches from one corn silage bag to another. He finds there is no dry matter intake problems, unlike before he began using yeast. Manure is now more of desired the “porridge-like” consistency, regardless of time of year. Initially, he thought the 25 cents per head per day was costly, but given these visible benefits, he now sees adding yeast as a good dairy investment.

Given this favourable case study, using yeast in dairy nutrition is really an extension to what Mother Nature has already given dairy cows.

About the author


Peter Vitti is an independent livestock nutritionist and consultant based in Winnipeg. To reach him call 204-254-7497 or by email at [email protected]


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