Probiotics have been gaining attention in all segments of animal agriculture in the last several years. Although this has been influenced by several factors, the biggest overall driver has been the goal of reducing antibiotic usage due to government regulations and consumer demand.
The use of probiotics is not new, as the popularity of Lactobacillus acidophilus therapy in humans reached its peak in the 1930s.
This faded due to the advent of antibiotics following World War II. However, since the 1950s, there has been a slow increase in the use of bacterial probiotics in both humans and animals as researchers learn more about their benefits.
A probiotic is defined as “live micro-organisms which, when consumed in adequate amounts, confer a health effect on the host.” There are two general classes of probiotics: fungi and bacteria.
Fungal probiotics are primarily live yeast. They work within the rumen to improve fermentation, scavenge oxygen, stabilize rumen pH, improve fiber digestion and increase microbial growth. Bacterial probiotics have three primary modes of action.
The first is through competitive attachment, which prevents pathogens from binding to the gut wall. The second mode of action is an antibacterial-like effect in which they can help reduce pathogens in the intestine. The final mode of action is the modulation of immune response, improving the host’s response to disease. So what does this actually mean to your bottom dollar?
When we think of the gastrointestinal tract (GIT), we realize it is a complex system that provides many roles in the animal’s life. It is where feed is digested and nutrients are absorbed. It is also home to approximately 75 percent of the immune system.
Epithelial junctions between cells, a mucous layer, immunoglobulins and antimicrobial peptides all make up the intestinal defense system. When this barrier is disrupted, pathogens can damage the lining of the intestine and induce inflammation.
Probiotics can impact this defense system by regulating and modulating different inflammatory processes. These probiotic bacteria use several different methods to support barrier formation and prevent competitive attachment of pathogens. Probiotics can regulate genes responsible for the tight junctions between epithelial cells within the GIT.
They can also begin repairs to the tight junctions if they are damaged, decreasing the time needed for the host to make the repairs. Probiotics also increase the amount of mucous secretion in the GIT. Some probiotics are known to alter the composition of the mucus, preventing pathogen binding.
Many probiotics can produce antimicrobial peptides that target pathogenic organisms. Specialized probiotics induce the release of defensins from the epithelial cells. Defensins are small peptides or proteins active against bacteria, fungi and viruses. Although most of the research on probiotics has been conducted in a laboratory setting, how they function within an animal is still being researched.
The impact probiotics have on the immune system is very intriguing. Some strains of probiotics can stimulate the innate immune response so host cells recognize pathogens more quickly. This helps reduce the amount of tissue damage, including inflammation. The damaged tissue decreases the ability of the GIT to absorb nutrients and increases the risk of additional pathogen damage.
A calf is born with a blank slate when we consider the GIT micro-organisms. Micro-organisms begin populating both the rumen and lower GIT soon after birth. Using bacterial probiotics can help establish a normal gut microbiota.
If a calf has a healthy GIT, we usually see a reduction in diarrhea. As lactobacillus levels decrease in the GIT, more diarrhea is likely to occur. Increasing the beneficial micro-organisms in both the rumen and hindgut is crucial for transitioning calves from milk to solid feed.
A recent study showed feeding a combination of lactobacillus and propionibacterium resulted in more developed rumen papillae and healthier small-intestinal epithelium after weaning. When the small-intestine epithelium is healthy, we can see an increase in the immune function of the animal.
This will result in improved nutrient absorption. In a healthy small intestine, the epithelium provides an area where the cells responsible for the immune system reside. When the epithelium is inflamed the areas where these cells reside is reduced, allowing them to be caught up in the flow of digesta and expelled from the GIT.
In cows, probiotics are still considered an unfamiliar and novel technology, but they are gaining traction with recent regulations and consumer demands. Approximately 20 percent of the cows in the U.S. are fed some form of a probiotic. Larger herds tend to be more receptive to these alternative technologies.
When nutritionists were asked why they recommend probiotics, three main answers were given: increased efficiency of milk production, better starch and fiber digestion, and improved herd health. When the same question was asked of dairymen, the overall responses focused on cow health and the digestive benefits of probiotics. Not a single response was due to more milk.
In research, we typically see a 2 to 3 percent improvement in the efficiency of milk production when using a combination of lactobacillus and propionibacterium. From field and university studies, we see an improvement in starch and fiber digestibility.
The effects on health are difficult to access in a university setting. Cows are typically very well managed, and labor is not in short supply. A couple of field observations with larger dairies have shown a substantial improvement in health with over 40 percent reduction in adverse health events with probiotic feeding. If we can keep a cow healthy, it will utilize feed more efficiently, produce more milk and improve your milk check.
Overall, probiotics have shown the ability to improve health in calves and improve milk production efficiency in cows. As we learn more about these organisms, we see more opportunity for benefiting the producer. 
Jim Turner is a technical services manager at Chr. Hansen.
