Are All Yeasts the Same?
Authors: AB Vista’s Dr. Michelle Stewart, Field Veterinarian and Technical Manager;Spenser Becker, PhD, Swine Technical Manager; Laura Merriman, PhD, Swine Technical Manager
Yeast and yeast co-products have garnered considerable attention in the animal feed industry, primarily due to their wide range of benefits on animal health and performance. These benefits include (either directly or indirectly) competitive exclusion, immune modulation, enhanced nutrient utilization, and overall improved gut health. Various yeast-based products are available on the market today but are manufactured or processed differently to exert different health benefits. Understanding these differences is crucial for selecting the appropriate product to meet specific needs.
The benefits of yeast product supplementation can largely be credited to their protein, mannan-oligosaccharide (MOS), beta-glucan (BG), and nucleic acid content.
- Mannans are long-chain polysaccharides undigested by endogenous enzymes. They are considered prebiotics that serve as an energy source in the small intestine by stimulating beneficial bacteria fermentation. Mannans are also largely credited with the ability to bind pathogens within the gastrointestinal tract, alleviating their negative impact on the host.
- Beta-glucans are responsible for stimulating and priming the immune system for future assaults.
- Nucleic acids are part of RNA and DNA. They are critically important for building and repairing tissues.
While these components are broadly included in various yeast feed ingredients, they are not equally effective among different yeast products. This is largely based on their concentration and exposure within the intestinal tract. Other factors can include the species, strain, and cell count of the products. The broad categories of yeasts will now be explored from the least processed to the most refined (Figure 1).
Live yeast products consist of living microorganisms that can function as probiotics when added to animal feed. Live yeasts exert probiotic benefits by helping maintain or improve gut health by stabilizing the gut microflora, increasing the presence of beneficial bacteria, and enhancing overall nutrient utilization. Live yeast has the unique ability to scavenge excess oxygen produced by the animal during high-stress events. Elevated oxygen levels in the intestinal tract can be detrimental to the anaerobic fiber-degrading bacteria; therefore, reducing oxygen improves bacterial fermentation and short-chain fatty acid production. However, the yeast must remain alive through the feeding process and throughout the animal’s gastrointestinal tract.
In contrast, whole dead yeast is inactive, resulting from intentional killing or other processes like drying. It’s often a food, beverage, or ethanol manufacturing by-product. Despite not providing probiotic benefits, whole dead yeast is rich in protein and offers nutritional advantages to the animal. While some dead yeast products are sold as protein sources, others are credited with health benefits due to components like nucleic acids, mannoproteins, and beta-glucans.
Hydrolyzed yeast is produced by breaking down whole yeast cells through processes like autolysis, enzymatic hydrolysis, or acid hydrolysis. Autolysis uses the yeast’s own enzymes to digest itself, while enzymatic or acid hydrolysis involves external agents. The production of autolyzed yeast is inconsistent; therefore, hydrolyzed yeasts are preferred in animal feeds as they yield a more standardized final product. The hydrolysis step aims to break down the yeast components, increasing the exposure and solubility of the MOS and BG. Solubility can be correlated with binding ability; thus, higher solubility may be preferred (Figure 2).
Rupturing of yeast cells during hydrolysis results in a mixture of soluble yeast extract, rich in nucleic acids, and an insoluble yeast cell wall fractions. This mixture is known as the hydrolysate, offering nutritional and functional benefits to the animal. Yeast cell wall products are created by separating the cell wall components from the soluble extract components. In doing this, a product with a greater concentration of MOS and BG is achieved, as they are found within the cell wall. These products are often fed specifically for binding and immunity benefits.
In conclusion, the inclusion of various forms of yeast products in animal feed offers a spectrum of benefits, ranging from gut health and immune support to enhanced nutrient digestibility. However, not all yeast products are created equal. The choice of yeast product should be tailored to the specific needs of the animal, ensuring optimal health and performance outcomes. Understanding the unique properties and benefits of each yeast form is key to making informed decisions and maximizing the potential of these valuable feed additives.
If you’d like more information please contact NAM@ABVista.com or visit abvista.com.
