By Josh Garver, Territory Manager, United Animal Health

Bacillus direct-fed microbial use on dairies has been a topic of increased buzz. Many products seem similar on the surface, and each farm’s unique challenges may raise questions on whether to feed Bacillus. The answer is, as usual, it depends. No two Bacillus strains have identical capabilities, and some have unique benefits. Their capabilities include enzyme production and immunomodulatory action, but some of the primary benefits are their antimicrobial/antifungal/antiviral properties. Microbial pathogens are always present in the gut and environment but are often opportunistic in nature. This means that a detrimental increase in these pathogens can be precipitated by anything from a new cow entering the herd to a sudden ration change. In particular, high-starch diets increase the risk of pathogen flareups by altering the pH and nutrients present in the gastrointestinal tract.

High-starch diets are often used due to the low cost of corn, keeping ration costs low but increasing the risk of sub-acute or acute ruminal acidosis. Producers are familiar with this challenge and its effect on butterfat, but the risk of a pathogen flareup in the rumen or intestinal tract is equally important.

In the rumen, rapidly fermentable carbohydrates from a high starch diet can decrease rumen pH by driving the excess production of volatile fatty acids (VFAs). When pH decreases, certain beneficial bacteria die off in the less than ideal environment. Though these beneficial bacterial populations can recover quickly, a larger concern arises from the endotoxins released when pathogens die. Endotoxins like lipopolysaccharides (LPS) can initiate strong immune responses from the animal which are energetically taxing, diverting energy away from production or reproduction. Once LPS is released, it can cross the intestinal wall and enter circulation, causing systemic inflammation. Downstream, it can disrupt the intestinal barrier (resulting in increased permeability or leaky gut), opening the door for other pathogenic bacteria.

The second challenge with these diets is the risk of hindgut fermentation. When fermentation in the rumen is incomplete, fermentable carbohydrates spill over into the small intestine, creating an environment where opportunistic bacteria thrive and cause damage to the protective mucosal layer. This damaged environment creates further opportunity for pathogens to encounter the intestinal cell wall, triggering absorption and immune response.

Bacillus may be able to help in this situation. Bacillus strains can directly compete with pathogenic bacteria for binding sites on the gastrointestinal mucosa. This is known as competitive exclusion. Secondly, carefully selected strains can secrete antimicrobial compounds that inhibit specific pathogenic bacteria. According to a national pathogen surveillance conducted by United Animal Health, increased quantities of Clostridium species and E. coli were found to be associated with sick cows across the United States. If feeding Bacillus is right for your herd, it is important to use strains active against both species.

Bacillus is not a necessity, but it can be used as a helpful tool or insurance. From a diet standpoint, decreasing starch is the simplest way to minimize risk. Alternatively, feeding a combination of slow starch with fast starch can assist in spreading out fermentation which allows for better utilization of VFAs and limits pH drop. Additionally, feeding a fiber source to maintain the fiber mat in the rumen will promote rumination and slow down the passage rate, decreasing nutrient spillover. Beware that using NDF as an indicator can be misleading, so make sure you have adequate effective fiber in the diet. Even with these dietary precautions there are still many factors that could make feeding Bacillus profitable, such as herd flow, manure management, and bunk management. If any of these are in question a Bacillus DFM may benefit your herd.