Written by: Guest | June 24, 2022
By: Gracie Wagner, AFIA communications intern
Using funding from the U.S. Department of Agriculture’s Market Access Program, the American Feed Industry Association’s international trade team works diligently to educate foreign buyers on the value of using American-made feed, feed ingredient and pet food products. One of the team’s biggest areas of focus is on China.
China boasts the largest feed market in the world; this demand is generated because it is one of the world’s leading producers of animal protein. Supported by increased population growth, urbanization and income growth, China’s forecasted meat demand continues to be promising, which directly relates to overall animal feed consumption. China’s population is projected to peak at 1.45 billion by 2030.
The AFIA trade team is developing and translating articles into Mandarin to promote the understanding of U.S. feed products. The first article is from one of our members, Cathy Bandyk, Ph.D., title of ABVista, on the value of yeasts. The article discusses topics like the effects of live yeast on rumen function, live yeast applications and choosing the right live yeast product.
Author: Dr. Cathy Bandyk Source: American Feed Industry Association (AFIA) Published: 2022-06-10
We've all experienced situations where small changes can have a big impact, and the list goes on and on. For example, when a wrong number is entered in a complex series of calculations, and the final result is completely turned upside down; an entire project is ruined by using an oversized drill; or a recipe is missing while serving a guest One key ingredient was forced to change the menu that night.
Fortunately, we often have the opportunity to fine-tune the results in a positive direction. For example, by learning from our own or others' experiences, only relatively small adjustments can be made to significantly improve the efficiency of what we do, or to increase the ultimate benefit.
This is especially true when some biological system or process is involved. Fermentation is a great example, and all winemakers know it: any small change (like ingredient composition, yeast strain, or brewing conditions) can change the fermentation of a batch, just for better or worse— Even a slight microbial contamination could completely destroy the fermentation batch.
The same goes for fermentation in the rumen of ruminants. Nutritionists and researchers have been working to understand how overall formulation composition, individual ingredients, specific additives, and environmental factors affect the composition and number of microbes in the rumen, the rate of ruminal fermentation, and metabolic pathways, respectively. This, in turn, can guide production and help us develop products and management practices that optimize rumen function, thereby increasing feed intake, feed efficiency, and improving animal health.
A beef cow has a rumen volume of 25 gallons (about 95 liters) or more. To be honest, I am sometimes confused as to why only a few grams can affect the function of the rumen. But years of research and experience have taught us that there are several types of feed additives that do, including ionophores, certain biological extracts, enzymes and yeast.
The value of live yeast, especially Saccharomyces cerevisiae, in cattle diet formulations is well recognized, and peer-reviewed research on this goes back decades. The results of the study show that the efficacy of these products in cattle is mainly reflected in improving the utilization of roughage, increasing growth rate and feed efficiency, and improving overall health and immunity.
Multiple mechanisms of action of live yeast have also been discovered, including effects on rumen microbial composition (which in turn affects volatile fatty acid VFA quantity, concentration, ratio, and rumen pH), rumen redox potential, total dry matter intake amount and the ability of the pathogen to bind to the toxin.
Much research on cattle has focused on adjusting pH, mitigating acidosis, improving animal health, and improving carcass quality; increasing the availability of dietary fiber components; and increasing overall dry matter intake, body weight gain, and feed efficiency. Feeding live yeast has a positive effect in the above areas, although the results are not always consistent or predictable.
Compared with other types of cattle, there are more related studies on lactating cattle, and the use of yeast and yeast additives in dairy animals is also quite extensive. However, there are also studies confirming the efficacy of yeast in growing beef cattle and dairy heifers. For example, yeast can improve the number and activity of cellulolytic bacteria, which is obviously beneficial for ruminants that eat a lot of roughage. There are also some studies showing that yeast can reduce methane emissions. In addition, yeast can reduce the activity of lactic acid-producing bacteria and enhance the activity of lactic acid-utilizing bacteria, which is of great benefit to alleviating rumen acidosis in cattle.
A typical gradient experiment was performed on beef cattle at Texas A&M University (Crossland et al., 2018). The results showed that herds fed live yeast had higher mean rumen pH and showed less pH drop after increased grain concentrate feeding, and rumen pH below 5.6 (a sign of subacute acidosis). generally accepted thresholds) for a shorter total time.
A beef calf trial in Canada (Vyas et al., 2014) also found that herds fed live yeast had higher mean and minimum rumen pH and improved multiple indirect indicators related to acidosis. A reduction in symptoms of acidosis should be associated with resolution of liver abscesses, and at least one recent trial (Ran, 2018) confirmed a reduction in the incidence of severe liver abscesses when live yeast was fed.
Dry matter intake is critical for growing animals. In a comparative trial on different types of live yeast and yeast cultures (Finck et al., 2010), all yeast treatments increased feed intake over a 56-day trial period. This result is consistent across multiple published papers.
Digestibility tests can reveal how much nutrients and energy are actually available to the animal in the feed. Various studies in beef cattle have shown that yeast increases the digestibility of full-value diets and their fiber and crude protein content.
Other positive effects of feeding yeast include a reduction in respiratory disease incidence in cattle from 24% to less than 14%, a 1% reduction in carcass acid loss, improved carcass grade, and a reduction in E. coli counts. Future studies will help determine the reproducibility of these results and hopefully improve our ability to predict specific efficacy in different settings.
Of course, as with any feed additive or management tool, the effect of application in a particular situation depends first and foremost on whether there is room for improvement in an area of concern, and also on whether there are unrelated first limiting factors (diet, stress, genetics, management), as these factors can mask potential outcomes of experimental treatments. Differences in test results in published studies are also often due to differences in production process, dosage of additives, yeast strains and the appropriateness of some laboratory culture methods.
A major difference between "yeast" products on the market is whether they provide live yeast to the rumen. Otherwise, they may be composed of dead yeast cells and the medium in which they grow ("yeast culture"), or some specific yeast cell debris such as mannooligosaccharides or beta-glucose.
Some studies suggest that yeast cultures can offer many of the same benefits as live yeast. However, since they are no longer living microorganisms, it is difficult to consume oxygen in the rumen like live yeast. This is important because most rumen microorganisms (especially those involved in fibrinolysis) are strictly anaerobes and cannot survive in the presence of oxygen. There are also published studies showing that the redox capacity of rumen contents is significantly reduced after feeding yeast, validating the ability of live yeast to reduce oxidative stress in this environment.
Another difference between different types of yeast products involves their ability to bind pathogens and toxins. This ability depends to some extent on the properties of the yeast strain and the adsorbed material. A recent collaborative study (Posadas, 2017) demonstrated the ability of yeast to bind to a range of pathogens using scanning electron microscopy imaging and filtration assays. The two live yeast products adsorbed 41% and 34% of the tested bacteria, respectively, while the three yeast lysate mixtures had adsorption rates of 20%-23%. In a separate evaluation, live yeast showed superior adsorption capacity for test strains of E. coli, Salmonella, and Listeria when compared to non-live yeast products.
In a nutshell, yeast additives, although added in small amounts, have a huge effect.