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Not all yeasts in dairy rations perform the same

Gerd Bobe Published on 30 June 2014

Cows eating at a dairy

Saccharomyces cerevisiae fermentation products, more commonly but less accurately referred to as yeast fermentation products (Saccharomyces cerevisiae is one species of yeast which is commonly used for baking, brewing and wine-making), are one of the most commonly used feed additives currently on the market for dairy rations.



Feed additives are feed ingredients that have a non-nutritive value. That means feed additives are not essential for animal well-being; however, feed additives can improve feed utilization, feed intake, animal health, milk production, milk quality or a combination of them, thereby improving the profitability of dairies.

Live products
There is often confusion about the differences and similarities of Saccharomyces cerevisiae fermentation products and live Saccharomyces cerevisiae products, as both are often grouped together in reviews as yeast products and yeast.

Saccharomyces cerevisiae fermentation products are different in function, responses and results to live Saccharomyces cerevisiae products. Live Saccharomyces cerevisiae products contain live Saccharomyces cerevisiae , which can modify ruminal fermentation after colonization in the rumen.

The potential effects include scavenging of oxygen, utilization of lactate, release of growth factors and competitive exclusion of pathogens. So the responses to live Saccharomyces cerevisiae products depend on if and how well the live Saccharomyces cerevisiae can colonize in the rumen.

Another challenge with live Saccharomyces cerevisiae products is their stability, as storage length and conditions and the premix composition can alter Saccharomyces cerevisiae viability, as demonstrated by Dr. Bradford at Kansas State University. As a consequence, the response to the same live Saccharomyces cerevisiae product may vary considerably.


Dried fermentation products
In contrast, Saccharomyces cerevisiae fermentation products are dried end products of Saccharomyces cerevisiae fermentation grown on culture media under standardized conditions. Saccharomyces cerevisiae fermentation products are a mixture of hundreds of compounds.

These compounds provide nutrients to beneficial rumen microbes and thereby promote feed utilization, feed intake and prevent pH fluctuation.

In addition, Saccharomyces cerevisiae fermentation products are rich in B vitamins, amino acids, peptides, nucleotides, yeast cell wall products, phenolic compounds and phytosterols that alone or in combination can act as antioxidants, appetite stimulants, growth promoters, inhibitors of pathogen colonization or growth and immunonutrients.

Saccharomyces cerevisiae fermentation products, however, are also not created equal. Product quality and consistency depends on the type and standardization of culture media, growing conditions and drying conditions.

Therefore, it is important to focus on the results of specific Saccharomyces cerevisiae fermentation products and how consistently they work across several studies when considering which Saccharomyces cerevisiae fermentation product to use.

Some brands of Saccharomyces cerevisiae fermentation products have consistently been shown to improve dry matter intake, milk production and feed utilization in dairy cows throughout lactation. These effects may not always be statistically significant; however, they are consistent in direction, and when combined, show the benefits of feeding the product.


Quantifying the benefits of yeast
In two recent studies from our group, we evaluated the effects of feeding various dosages (0, 2, 4 or 8 ounces per cow and day) of a Saccharomyces cerevisiae fermentation product during the transition period on milk production, feed intake behavior and metabolic, nutrient, macromineral and immune status.

Feeding a Saccharomyces cerevisiae fermentation product improved dosage-independent nutrient status (higher serum glucose and urea nitrogen concentrations), macromineral status (higher serum calcium and phosphorus concentrations; fewer cows with low blood calcium concentrations during the first 48 hours after calving) and immune status of dairy cows during the first days after calving, resulting in higher milk production and lower somatic cell counts.

The question arises: How much of Saccharomyces cerevisiae fermentation products should be fed? In our studies, we compared no supplementation (0 ounces per day), feeding the recommended dosage (2 ounces per day) or feeding higher dosages (4 or 8 ounces per day) as top dressing to the TMR.

We did not detect statistically significant differences in responses when cows were supplemented with 2 ounces or more. This does not mean that 2 ounces per cow per day is the optimal dosage. In one of our studies, the increase in milk production from 2 to 4 ounces of feed additive was 2.4 pounds per day, which was not statistically significant.

Thus, feeding higher-than-recommended dosages may result in higher milk production; however, the incremental increases in production and returns diminish.

In the same study, milk production increased dramatically by 10.1 pounds per day from 0 to 2 ounces of feed additive. Thus, feeding lower-than-recommended dosages may dramatically reduce the benefits from feeding the supplement. How could this play out on a dairy?

Cows that do not consume their formulated intake (for example, cows around calving, cows that are sick – high somatic cell count, low blood calcium concentrations) or cows that are environmentally challenged (e.g., heat stress) will receive less than the calculated dosage of the supplement.

For example, if the diet is formulated to contain the recommended amount of 2 ounces per cow per day, cows that consume less than the formulated intake will consume less than the recommended dosage of the feed additive.

The results are potentially lower returns. In our study, we fed cows the feed additive individually as top dressing and monitored their supplement intake to ensure cows received the prescribed amount of the feed additive.

Another point to consider is that higher dosages may provide critical health benefits for cows during times when there are more challenges, such as around calving when there is a dramatic increase in nutrient demand for milk production, feed change, depressed immune function, low blood calcium concentrations, low feed intake and high risk of infectious and metabolic diseases.

Therefore, the optimal dosage may differ among cows depending on genetic potential, health status and production system or level as well as which physiological function is targeted (e.g., feed intake, immune function, feed utilization and metabolic status). As one can see, the question regarding the optimal dosage of Saccharomyces cerevisiae fermentation products needs to be evaluated from more than one angle.

In summary, adding S accharomyces cerevisiae fermentation product to dairy rations may improve feed intake and utilization in dairy cows, resulting in higher milk production and profitability. Further studies are needed to fully understand the optimal dosage for supplementation. PD

Dairy cows in the study were fed fermentation products as a top dressing (contained in the bowls) and were monitored to assure the additives were consumed. Photo courtesy of Gerd Bobe.

gerd bobe

Gerd Bobe
Assistant Professor in Ruminant Nutrition
Oregon State University