Different yeast products such as live yeasts, yeast culture products and hydrolyzed yeasts are widely used in ruminant feeding. Their marketing claims include modulation of rumen fermentation, improved feed efficiency and stimulation of immunity. Although the marketing claims are often similar, the product characteristics and modes of action steering the effects in animals can be very different. Understanding the factors behind the effects of dietary yeast is crucial for their evaluation.

READ also the blog about yeast products for monogastric animals

Specific molecular structures of yeast are important for their effects in ruminants

The modes of actions of yeasts in ruminants have been extensively studied but they are still largely ambiguous. Because biological functions between microbes and animals are generally based on the molecular interactions, the specific molecular structures of yeast are likely to affect their interplay also in the rumen. Size, shape, electrical charges and other physical properties of the yeast molecules may thus steer their effects on rumen microbiota and fermentation.

Yeast hydrolysate Progut® has shown to increase milk yield and to reduce somatic cell count in lactating dairy cows (Gaffney et al. 2014). The beneficial performance effects can be explained by its ability to beneficially stimulate the ruminal fermentation. In numerous rumen simulation studies and in trials with fistulated cows it has increased the microbial density and production of short chain fatty acids and thus increased the amount of protein and energy available for the cow. In the rumen simulation experiment (Kettunen et al., 2016), Progut® stimulated those bacterial groups that were active at the given phase of the simulation. More specifically, during the first 6 hours of the simulation, Progut® favored lactic acid producers whereas at the 12 and 24 hour time points, it enhanced the growth of lactic acid degraders and cellulolytic microbes. This resulted in increased concentrations of propionic and acetic acids in the end of the simulation. In this trial, Progut® addition boosted ruminal fermentation equally with different concentrate amounts (25 % to 75 %) of the diet indicating its ability to improve the performance of cows with different feeding concentrations.

The fact that the density of many microbial groups were increased as a response to Progut® addition may indicate Quorum Sensing signaling systems involvement in the regulation of bacterial density. Microbes can produce and release chemical signal molecules by which they communicate and regulate different physiological activities. The cell-cell communication via chemical signal molecules occurs both within and between bacterial species in response to cell-population density. It may be that rumen bacteria can also recognize increased amount of yeast cell structures and grow in number for better competence. Enhanced degree of yeast hydrolysis increases the amount of soluble molecular structures in the product. This seems to be connected to improved rumen fermentation. In a Rusitec rumen simulation study at the Veterinary University of Hannover Progut® improved rumen fermentation more than the same yeast with lower hydrolyzation (figure 1). The result points out also to the direction of Quorum Sensing.

Due to its optimized hydrolysis process Progut® contains more soluble molecular structures than the competing live yeast and yeast culture products. In the rumen simulation trials in vitro it has shown to enhance rumen fermentation more effectively than the competition. Progut® has enhanced rumen fermentation and milk yield regardless of the feeding concentration. The positive results with the competing yeast products in ruminants have mainly been observed in early lactating cows with high concentrate feeding. This indicates that the modes of action of the products are different.

Figure 1. The degree of yeast hydrolysis affected the production of acetate and propionate in vitro. Rusitec trial at the Veterinary University of Hannover

Suitable molecular patterns of yeast can also trigger beneficial immune responses

Many of the health problems of dairy cows and calves are connected to low immune status. Yeast hydrolysate Progut® contains several immune stimulating compounds (β-glucan, mannoprotein and chitin structures) and has increased water-solubility by hydrolysis for better visibility to immune receptors. It is assumed that part of these molecules are by-passing rumen and affecting the immune cell receptors in the small intestine. Lower somatic cell count in dairy cows (Gaffney et al. 2014) by Progut® addition can be regarded as a sign of enhanced immunity. In a dairy cow trial at the University of Helsinki Progut® speeded up the recovery of cows’ immune status after calving stress (unpublished). Its supplementation in the starter feed significantly increased the antigen specific IgA production in vaccine-challenged calves and improved also the health and diarrhea scores of the animals (Kim et al. 2011).

Benefits of Progut® for lactating dairy cows and calves

In the dairy cow trials Progut® has increased the milk yield on average by 1,8 kg/cow/day and improved feed efficiency by 5-7 %. The responses have been similar in different lactation phases regardless of the amount of concentrates in the feeding. It has also fastened the recovery of cows’ immunity from calving stress and reduced somatic cell count in the milk. As a yeast hydrolysate Progut® is stable in feed processing and storing. Addition of Progut® in calf starter feeds has fastened their immune development and supported their health status. In calf trials it has also increased concentrate and roughage intakes and growth which can be seen as an indication of faster rumen development.

SUMMARY: The functions of yeast hydrolysates in ruminants depend on their molecular structures

The main functions of yeast hydrolysates in ruminants, enhancement of ruminal fermentation and immune stimulation, are most likely based on their molecular structures. These three-dimensional structures are specific enough for the working interactions with their target receptors.

Hankkija’s whole yeast hydrolysate Progut® is produced by a specific hydrolysis process, is rich in the bioactive molecular structures and has been shown to be an efficient rumen fermentation and immune enhancer, thus improving the performance and well-being of dairy cows and calves.