In Part I of this series, we began a discussion of prebiotic and probiotic products used in feeding cattle. The types and species are numerous and in many cases, not well understood. Let’s pick up here on the discussion of different products and applications.

Fungal products

While yeasts may be considered a fungal product, for the purposes of this discussion, fungal products are differentiated from yeast products. One common fungal product is Aspergillus oryzae (AO), which has been used in a number of applications, largely to improve fiber digestion. Research with AO has been more common in dairy cattle than other classes, and earlier work seemed to suggest that the greatest responses have been in dairy cows early in lactation that are fed higher-energy (higher-grain) rations.

However, more recently, AO research has focused on its potential to assist with improving fiber digestion. Some work has shown that feeding AO to beef cows helped improve digestion and subsequent nutrient availability when feed poorer-quality forages.

Other aspergillus products have also seen use in feeding applications. Aspergillus niger (AN) is often fed and shows similar improvements in nutrient digestion, not just fibers. The effectiveness of AO and AN appear to be their tendency to act as a source of various catabolic enzymes (proteases, lipases, cellulases), all of which assist in improving the rumen fermentation process. Both products have been fed alone or individually.

Enzyme products have also emerged on the dairy feeding scene and in many cases are fungi. In some cases, enzyme products are from bacteria sources as well. Commonly, these are a combination of several organisms. While there is promise here, there is a great deal of research and understanding still needed to recognize how to optimize product use.


Cell wall products


Mannanoligosaccharides (MOS) are commonly extracted from the cell walls of yeast cells (generally Saccharomyces cerevisiae). In the yeast cell wall, MOS are present in complex molecules linked to the protein component of the cell. The structure on the cell surface is very attractive to water and creates variable “brush like” structures that can fit on various attachment locations in the animal’s digestive tract. It also allows for binding to receptors on the surface of bacterial membranes, affecting the bioactivity of these molecules.

The MOS-protein combinations are involved in interactions with the animal’s immune system and as result enhance intestinal immune system activity. They also play a role in animal antioxidant and antimutagenic (cell mutation) defense.

In some cases, this MOS attachment can aid with nutrient absorption. In other situations, it can prevent pathogenic organisms from binding to intestinal membranes where they can cause inflammation and invade the body (competitive inhibition). Finally, MOS can function to enhance the performance of the immune system (improve effect and efficiency).

In food animals, gut health plays an additional role. A healthy gut enables more efficient use of feed, thus improving feed efficiency. One potentially important function for MOS, based on the previous description, is a possible replacement for fed antibiotics.

For years, antibiotic drugs have been added to the diets of food animals at non-therapeutic levels in the absence of disease, in order to enhance the feed conversion ratio, accelerate growth and protect animals’ health, therefore increasing profitability for producers. With the current global push to reduce the use of medically important antibiotics as feed additives for farm animals, there is significant interest in “natural” nutritional concepts. Based on a large body of research, MOS has established itself as one of the more important natural additives in food animal production.

The health status of young calves is one of the most important factors contributing to growth and performance. Diarrhea in young calves is a major issue in the dairy sector. In many cases, an E. coli infection of the intestine is often involved. As MOS can bind E. coli, it can modify and help to improve the composition of the intestinal microflora. This resulted in a reduction in fecal E. coli counts and improvements in fecal scores in calves fed MOS.

These improvements were coupled with an increase in concentrate (dry feed) intake and better performance. In addition to changes in the gut, several workers also noticed improvements in respiratory health, which can also contribute to better performance. Conversely, one trial reported no effects on live weight gain, despite increased feed intake. Higher live weight gain, similar to that gained with the use of antibiotics, has been achieved following supplementation of milk replacer with MOS.

Mature dairy cows fed MOS had better immune protection against rotavirus and were able to pass some of this protection on to their calves. The transfer of immunity from cow to calf is critical in order to protect calves from many different diseases. It can be assumed, therefore, that these positive effects can also be noted in beef cows and calves.


Like MOS, Beta-glucans (BGs) are major structural components of the cell wall of yeast and some cereals such as barley and oats. While BGs are similar to MOS, they are significantly different and function differently in the digestive tract. Whereas MOS is based on the mannose sugar molecule, BGs are combinations of glucose molecules characterized by specific linkages.

BGs are a diverse group of molecules that can vary with respect to molecular mass, solubility, viscosity and three-dimensional configuration. They occur most commonly as cellulose in plants, the bran of cereal grains, the cell wall of baker’s yeast, certain fungi, mushrooms and bacteria.

BGs are notable for their ability to have a positive effect on the immune system. BGs are known as “biological response modifiers” because of their ability to activate the immune system. They are also referred to as immunostimulants. The use of immunostimulants, for enhancement of disease resistance to a wide spectrum of pathogens at times of stress, provides a strategy that can improve suboptimal immune function and thus increase resistance to infectious diseases.


There have been a variety of positive responses to feeding. From a broad perspective with bacteria, yeasts and fungi, we see improvements in fiber digestion, improved pH levels and overall better rumen performance. This results in improved milk production, feed efficiency and component products.

Some of this will depend on the stage of production when fed. In many cases, the greatest benefits appear to come when feeding in pre-fresh and post-fresh diets, when significant physiological changes are occurring as well as diet changes. The prebiotic-probiotic combination appears to be useful in helping animals through stress.

Other benefits appear on the health side of performance. Products such as MOS and BGs appear to have important effects on animal health, including reduced pathogen effect, mycotoxin binding and overall enhancement of immune response. Improvements in somatic cell counts have been noted with the feeding of some products, as well as other overall reductions in infection levels. This still requires further, extensive research to better understand the effect.


Most of these products cost only pennies per day to feed. It is important to consider and test various products on a specific operation to determine the effectiveness of a product or group of products. There is variability in response. In some cases, the use of a given product may result in an additional two to four pounds of milk per day, which shows the most recognizable benefit.

Those products with a claim of improvements in fiber digestion may be an obvious starting point. Others may improve components or health, but this requires time and careful record keeping to define and recognize. Certain products that claim improvements on both performance and health may be particularly useful and cost effective. The problem is that like with many additives, response variability is common.

This article is the second of a two-part series. Read Part I here.

References omitted but are available upon request by sending an email to email an editor.