Eight horses were allotted into pairs consisting of one cecum- and right ventral colon-fistu- lated animal and one cecum-fistulated animal They were fed daily at the same level of intake either a high- fiber (HF) or a high-starch (HS) diet without or with 10 go f aSaccharomyces cerevisiae preparation, in a 4 × 4 Latin square design The HS diet provided a starch overload (ie, 34 g starchkg −1 BWmeal −1 ) while main- taining a high amount of fiber intake (ie, dietary NDF/ starch ratio was 10) A 21-d period of adaptation to the treatments occurred before cecal and colonic contents were withdrawn 4 h after the morning meal to count total anaerobic, cellulolytic, and lactic acid-utilizing bacteria, lactobacilli, and streptococci Lactic acid, vola- tile fatty acids, ammonia concentrations, and pH were measured on cecal and colonic fluid samples collected hourly during the first 12-h postfeeding When the HS diet was fed, the concentration of total anaerobic and lactic acid-utilizing bacteria increased (P < 0001), whereas that of cellulolytic bacteria decreased (P < 005) in the cecum The concentration of lactobacilli and streptococci increased (P < 0001) in the cecal and co- lonic contents These alterations of the microbial pro- files were associated with decreases (P < 0001) of pH, (acetate + butyrate)/propionate ratio and with an in- crease (P < 0001) of lactic acid concentration Supple- menting the S cerevisiae preparation increased (P < 001) the concentration of viable yeast cells, averaging 43 × 10 6 and 45 × 10 4 cfu/mL in the cecal and colonic contents, respectively Yeast supplementation had al- most no effect on microbial counts in the cecum and colon The supplementation of S cerevisiae appeared to modify (P < 005) pH, concentrations of lactic acid and ammonia, molar percentages of acetate and buty- rate with the HS diet and ((acetate + butyrate)/propio- nate) ratio when the HF diet was fed The effects of the S cerevisiae preparation were greater in the cecum than in the colon, which coincided with the abundance of yeast cells When the digestion of starch in the small intestine was saturated, the effect of the addition of a S cerevisiae preparation appeared to limit the extent of undesirable changes in the intestinal ecosystem of the horse

Effect of a preparation of Saccharomyces cerevisiae on microbial profiles and fermentation patterns in the large intestine of horses fed a high fiber or a high starch diet.

https://www.gshepherdanimalhealth.co.uk/image/data/pdf/Bicarb%20Yeast%20Marden_9108_3528.pdf

How Does Live Yeast Differ from Sodium Bicarbonate to Stabilize ruminal pH in High-Yielding Dairy Cows?

Microbial feed additives for ruminants.

The effects of a live yeast strain of Saccharomyces cerevisiae have been investigated on zoospore germination, metabolism, and cellulolytic activity of the anaerobic rumen fungus Neocallimastix frontalis MCH3. The addition of yeast cells to a vitamin-deficient medium stimulated the germination of fungal zoospores, increased cellulose degradation and hydrogen, formate, lactate, and acetate production. Responses depended on the concentration of yeast cells added and on their viability. Yeast supplementation provided vitamins such as thiamine, which is essential for fungal growth and activity. These results demonstrate that yeasts could enhance plant cell wall colonization by N. frontalis. With certain diets, yeasts could therefore be a good tool to optimize the microbial degradation of lignocellulosic materials, but more research is needed to understand their mechanisms of action, so that they can be used with maximum efficiency as feed supplements.

Effects of live Saccharomyces cerevisiae cells on zoospore germination, growth, and cellulolytic activity of the rumen anaerobic fungus, Neocallimastix frontalis MCH3.

Six ruminal cannulated Texel sheep were used to assess the dose response and the effect of live yeasts (Levucell® SC, Saccharomyces cerevisiae CNCM I-1077) on the prevention of induced ruminal latent acidosis. The sheep received, in a replicated 3×3 Latin-square design, an acidotic diet (wheat +lucerne hay, 60:40 (dry matter (DM) basis); starch: 410 g/kg DM) without yeast (control group; L0 treatment), supplemented with 0·2 g/day yeast (4×109 colony-forming units (c.f.u.) per day corresponding to producer recommendations; L1 treatment) or with 2 g/day yeast (4×1010 c.f.u. per day; L10 treatment). The following measurements were carried out: food intake, ruminal pH, ruminal volatile fatty acids (VFA), lactate and ammonia (NH3) concentrations, protozoal and lactate-utilizing bacterial counts, relative proportions of two main bacteria implicated in lactate metabolism (a lactate-producing species, Streptococcus bovis, and a lactate-utilizing species, Megasphaera elsdenii) using specific 16S-rRNA-targeting oligonucleotide probes, activities of lactate dehydrogenase (LDH) and of polysaccharidases involved in plant cell wall (xylanase, carboxymethylcellulase) and starch (amylase) degradation. The acidotic diet (L0) induced a butyric (12 mol per 100 mol total VFA) rather than lactic ( 0·1). Yeast supplementation tended to increase ruminal protozoal population (P<0·1) and intake of animals (P<0·1). The recommended yeast concentration (L1) was sufficient to ensure these effects. The yeast's action may differ according to the nature and function of the micro-organisms involved and the type of fermentative pattern favoured (protozoa/butyrate v. lactate-metabolizing bacteria/lactate and propionate) during ruminal acidosis in sheep.

Dose effect of live yeasts on rumen microbial communities and fermentations during butyric latent acidosis in sheep: new type of interaction

Five mature wethers fitted with rumen fistulas were fed grass hay and a sugarbeet-pulp-based concentrate or maize silage and a cereal-based concentrate (50/50 digestible organic matter basis), or without with 5 g yeast supplement (Saccharomyces cerevisiae, Biosaf) per day in a latin square design. Diets were given for a 28-d adaptation period, followed by a 10-d collection period to determine digestibility and nitrogen retention data. Afterwards, rumen samples were taken on 3 consecutive days and analysed for volatile fatty acids, pH and ammonia. Digestibility and nitrogen balance were not affected by yeast treatment. Supplementation of yeast increased acetate: propionate ratio, butyrate, isoacids, pH and ammonia. The effects were more pronounced for the maize silage diet. These results demonstrate that the effect of yeast culture on rumen fermentation may depend on the nature of the diet. Living yeast cell number in the rumen fluid rapidly declined when dietary yeast was ceased. Furthermore, yeast cells survived the passage through the digestive tract.

/pdf/effect-of-a-viable-yeast-culture-on-digestibility-and-rumen-1glrzkgrkq.pdf

L. Dussert

Papers

Effect of a viable yeast culture on digestibility and rumen fermentation in sheep fed different types of diets.