Live yeast, usually a strain of Saccharomyces cerevisiae, is a type of feed additive that is commonly added to dairy cow diets to improve digestive performance, particularly in the rumen. These yeasts help enhance the environment in the rumen by removing oxygen, which in turn promotes the growth of beneficial anaerobic bacteria. As a result, cows are able to digest their feed more efficiently, especially fibrous components, leading to better nutrient absorption and energy availability (Chaucheyras-Durand & Fonty, 2001).

Based on scientific studies and farm experiences, using live yeast can:

    •    Increase milk yield
    •    Improve milk quality (more fat, protein, and lactose)
    •    Promote rumen health and prevent digestive diseases like acidosis.

1. Impact on Milk Production

a. Increased Daily Milk Yield

Studies have shown that cows receiving live yeast supplementation can produce, on average, 1.5 liters more milk per day (Desnoyers et al., 2009).

b. Improved Milk Composition

Supplementation with live yeast has been linked to higher milk fat and protein content, without reducing lactose levels (Bach et al., 2007).

c. Better Feed Efficiency

Cows that consume the same amount of feed but receive live yeast produce more milk, which indicates improved feed conversion. Studies estimate that live yeast supplementation can improve feed efficiency by 3.7% to 7.6%, and in some reports, even up to 4% to 8% (Perdomo et al., 2020; Hutjens, 2007).

d. Positive Effect Under Heat Stress

During hot days when cows tend to eat less and produce less milk, live yeast helps restore normal production and feed intake (Perdomo et al., 2020).

2. Impact on Rumen Health

a. Control of Rumen Acidosis

Live yeast helps maintain a stable pH in the rumen, preventing sharp drops in acidity and thus avoiding subacute ruminal acidosis (Guedes et al., 2007; Bach et al., 2007).

b. Stimulation of Beneficial Bacteria

Yeast increases the number of beneficial rumen bacteria, such as Ruminococcus, which are essential for fiber digestion and energy extraction from feed (Chaucheyras-Durand et al., 2012).

c. Increased Production of Volatile Fatty Acids (VFA)

VFAs are one of the main energy sources for cows. Live yeast enhances VFA production in the rumen, resulting in more energy available to the animal even with less feed intake (Chaucheyras-Durand et al., 2008).

d. Reduced Inflammation

Cows fed live yeast tend to have lower levels of inflammatory markers in their blood, indicating better overall health (Perdomo et al., 2020).

Conclusion

Supplementing dairy cow diets with live yeast:
    •    Increases milk yield
    •    Improves milk quality
    •    Prevents ruminal acidosis and supports rumen microbial balance
    •    Enhances feed efficiency
    •    Ultimately leads to better economic outcomes for the farmer