CitriStim is a proprietary feed ingredient manufactured by ADM using a controlled fermentation process. Research conducted by ADM over the last few years has shown CitriStim is effective in improving performance of beef cattle. CitriStim, a Candida yeast product, is a source of mannan oligosaccharides (MOS) and beta glucans. Researchers have demonstrated MOS can have a beneficial impact on animal growth and health by binding pathogenic gut bacteria. In a review of literature on yeast product usage in livestock, Pettigrew (2000) and Hooge (2003) concluded that yeast products are efficacious and cost effective.

Suggested Mode of Action
Yeast Cell Walls
The intracellular components of the yeast cell are known as yeast extract. The yeast cell wall is the portion remaining after the inner contents of the yeast cell have been removed. The yeast cell wall contains oligosaccharides, which are complex carbohydrates. Yeast cell wall products consist of two major active components:

• Mannan oligosaccharides

• Beta glucans

Mannan Oligosaccharides
The mannan oligosaccharides (MOS) component of the cell wall are considered a type of carbohydrate that may account for benefits observed when livestock are fed yeast products. Thousands of tons of yeast products are added to commercial animal diets annually. For more than 25 years, it has been known that certain carbohydrates, specifically mannose and its analogues, can influence the ability of certain microbes to colonize the gut.

Studies by Salit and Gotschlich (1977) demonstrated that D-mannose, yeast mannan, and alpha-methyl-D-mannoside have the ability to interfere with E. coli binding, while other common carbohydrates had little effect. From this work, the most important point to consider is that yeast mannan is a good inhibitor of E. coli binding. This means yeast mannan can be beneficial because it prevents E. coli from binding to the gut wall and causing damage.

Research Results
In Vitro Cell Culture
Laboratory analyses were conducted to determine whether CitriStim was effective at binding E. coli. As discussed previously, one proposed mode of action of yeast MOS is the ability to bind bacterial pathogens in the gastrointestinal tract and block pathogen colonization. CitriStim and several yeast products were sent to an independent laboratory to test their ability to bind E. coli. The assay measured E. coli remaining in the cell culture solution after E. coli Strain MT21 was cultured with yeast products. E. coli that were bound to yeast were not measured in solution, so the lower the bar value in Figure 1, the better the E. coli binding capacity. Results indicted that CitriStim had similar binding capacity to two yeast products (YP2 and YP3) and better binding capacity than three yeast products (YP1, YP4, and YP5). The data suggest that CitriStim is effective in binding pathogens that may be found in the gastrointestinal tract.

Receiving Cattle Studies
Two receiving cattle studies conducted by ADM Alliance Nutrition have shown the benefit of supplementing CitriStim (Table 1). In study 1, 80 head weighing an average of 462 lb were fed diets with and without CitriStim during the receiving phase. Dry mater intake and average daily gain were improved 5.3% and 18.8%, respectively. Feed efficiency was improved 13.4%. In the second study, 40 head weighing an average of 612 lb were fed diets with and without CitriStim during the receiving phase. Dry matter intake improved 8.7% and average daily gain improved 11.7%. Feed efficiency improved 5.6% by feeding CitriStim.