Effect of yeast culture on in vitro fermentation of a high-concentrate or high-fiber diet using equine fecal inoculum in a Daisy II incubator.

The research article investigates the effect of a yeast culture preparation on diet digestion and fermentation patterns in horses. It also evaluates the use of a closed-system fermentation apparatus, called a Daisy II incubator.

Objective and Methodology

• The primary goal of this study was to assess the effects of yeast culture (YC) preparation on microbial populations, digestion of diet, and the pattern of fermentation in horses’ digestive system using a forced in vitro fermentation apparatus. This equipment, named as Daisy II incubator, provides a controlled environment for the experiment.
• This investigation was carried out in two experimental stages, each involving four mature horses with a specific diet and process of fecal inoculum collection. In the first experiment, the horses were given a diet of 50:50 mix ratio of pelleted concentrate and alfalfa cubes. The second experiment had the horses consuming a high-concentrate (HC) or high-fiber (HF) diet respectively.

Experiment Process

• The first experiment estimated amounts of dry matter (DM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) digested by analyzing samples after 48 hours in the Daisy II incubator.
• In the other, diets were placed in four different vessels along with their respective fecal inoculums. Two of these vessels were added with yeast culture (YC), while the rest served as controls. These were also incubated for 48 hours, and samples collected at 24 and 48 hours respectively.

Results and Conclusion

• The results showed greater digestibility for DM, NDF, and ADF with a sample size of 0.25-g compared to a 0.50-g sample size, implying that smaller sample size may provide a more precise estimate of DM digestibility with less variation.
• The use of YC exerted varying effects on the HC and HF diets: it led to a decrease in ammonia concentrations with the HF diet while generating increased acetate production in the HC diet.
• There were, however, no significant effects observed on pH, lactate, the noted microbial populations, and nutritional aspects—DM, NDF, ADF digestibility—of the diet.
• The research concludes that the Daisy II incubator provides valid estimates of the total digestibility of dietary dry matter in the horse. This outcome further demonstrates that this process could effectively approximate the digestibility of diets varying in concentrate to forage ratios.