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Active Dried Yeast

Also known as: Active dried yeast, ADY, baker’s yeast, Saccharomyces cerevisiae

Overview

Active dried yeast (ADY) is a preparation of *Saccharomyces cerevisiae* yeast cells that are dried but retain viability. It is primarily utilized as a probiotic supplement in animal nutrition, particularly for ruminants, to enhance rumen function, promote growth, and bolster immunity. The yeast cells are carefully dried to preserve their live state, allowing for their effective incorporation into animal feed. The main applications of ADY are in livestock, where it is used to improve ruminal fermentation, optimize nutrient utilization, strengthen the immune response, and enhance overall growth performance. Research on ADY is moderately developed, with numerous controlled trials conducted in ruminants, demonstrating its efficacy. However, human clinical data regarding its direct supplementation are limited. The quality of evidence for animal studies is generally good, with available randomized controlled trials (RCTs) and some meta-analyses supporting its benefits.

Benefits

Active dried yeast offers several evidence-based benefits, primarily in ruminant nutrition. Its primary effects include improved ruminal fermentation, characterized by enhanced microbial activity and better digestion of fiber and other nutrients. It also leads to increased dry matter intake (DMI) and average daily gain (ADG) in young ruminants, such as goats and calves. Furthermore, ADY enhances the immune response, including improvements in blood metabolites related to immunity. Secondary benefits encompass the stabilization of rumen pH and a reduction in harmful bacteria like *Escherichia coli* and *Salmonella* by maintaining optimal anaerobic conditions in the rumen. It can also increase serum glucose concentration, indicating improved energy metabolism. Young ruminants, such as dairy goats and beef calves, particularly show significant growth and immune improvements with ADY supplementation. For instance, a study involving 60 young goats demonstrated that continuous ADY supplementation (3 g/day) significantly increased dry matter intake and improved rumen fermentation parameters over 67 days. In weaned beef calves, ADY improved growth performance and immune markers, supporting its potential as an antibiotic alternative. Benefits are typically observed within weeks of consistent supplementation, often within 30-60 days in animal trials.

How it works

Active dried yeast primarily functions by consuming oxygen within the rumen, thereby preserving the anaerobic conditions that are highly favorable for beneficial microbial populations. This action promotes the growth of lactate-utilizing bacteria, which efficiently convert lactate into propionate, a crucial energy source for the animal. Additionally, ADY inhibits pathogenic bacteria through competitive exclusion and by modifying the ruminal environment to be less hospitable for harmful species. Its molecular targets include various rumen microbial populations and metabolic pathways directly involved in fermentation and immune modulation. ADY is administered orally via feed, and its efficacy is critically dependent on the viability and colony-forming units (cfu) of the yeast cells.

Side effects

Active dried yeast is generally considered safe for use in animals, with no significant adverse effects reported in controlled studies. Side effects are rare and not well-documented in the literature concerning ruminants; there are no common or serious adverse events reported for its typical use in livestock. No known drug interactions have been identified in the context of animal feed. Furthermore, there are no reported contraindications for its standard application in livestock. It is important to note that while ADY is generally recognized as safe (GRAS) in food applications, human safety data for its direct supplementation are limited, as it has not been specifically studied as a human supplement. Therefore, while safe for its intended animal use, caution should be exercised regarding its application in humans due to the lack of specific research.

Dosage

Effective doses of active dried yeast in ruminants typically range from 3 to 4.5 grams per animal per day. This dosage usually contains approximately 5 × 10^9 colony-forming units (cfu) per gram of *Saccharomyces cerevisiae*. Continuous supplementation has been shown to be more effective than intermittent dosing for sustained benefits. The timing of supplementation is generally aligned with regular feeding schedules, and no specific cofactors are required for its efficacy. It is crucial that the formulation of ADY maintains the viability of the yeast cells, as their live state and colony-forming units are critical for achieving the desired probiotic effects in the animal's digestive system. Upper limits and safety thresholds are not explicitly defined beyond the effective ranges, given its high safety profile in animal studies.

FAQs

Is ADY safe for all ruminants?

Yes, studies consistently demonstrate the safety and beneficial effects of ADY in various ruminants, including goats, calves, and cattle, without reported adverse effects.

Can ADY replace antibiotics?

Evidence suggests that ADY can serve as an effective alternative to in-feed antibiotics by improving gut health and enhancing the immune response in animals, reducing the need for antibiotics.

How soon do benefits appear?

Benefits from ADY supplementation typically become noticeable within 4 to 8 weeks of consistent administration, as the rumen microbial environment adjusts and improves.

Is continuous supplementation necessary?

Yes, research indicates that continuous daily dosing of ADY yields better and more sustained outcomes compared to intermittent supplementation, maximizing its probiotic effects.

Research Sources

https://pmc.ncbi.nlm.nih.gov/articles/PMC10165222/ – This randomized controlled trial investigated the effects of continuous versus intermittent active dried yeast supplementation in young female Guanzhong dairy goats over 67 days. The study found that continuous supplementation of 3 g/day significantly increased dry matter intake and improved key rumen fermentation parameters and immune markers. The findings suggest that continuous ADY supplementation is more effective for enhancing growth and health in young ruminants, though results may vary with different proprietary strains.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8577086/ – This controlled trial evaluated the impact of active dried yeast on growth performance, rumen fermentation, and immunity in weaned beef calves. The study concluded that ADY improved average daily gain, increased serum glucose levels, and enhanced immune response markers in the calves. These results support the role of ADY as a viable alternative to in-feed antibiotics for promoting health and growth in calf nutrition.