Effects of supplementing saccharomyces cerevisiae yeast probiotics on rumen fermentation parameters of high concentrated total mixed rations in vitro

Saccharomyces cerevisiae is one of the most commn probiotics used in ruminant nutrition. Saccharomyces cerevisiae increase gas production through specific biochemical mechanisms. Some of these mechanisms, based on the yeast's ability to excrete excess oxygen from the rumen, create a better space for ruminal anaerobic bacteria. The yeast Saccharomyces cerevisiae can provide a place for metabolic exchange and a suitable environment for the growth and activity of beneficial microorganisms around the substrates. On the other hand, increased gas production by adding yeast may be due to increased propionate fatty acid production due to improved ruminal fermentation. Because carbon dioxide is produced by some rumen bacteria through the succinate-propionate pathway when propionate is produced. Because the fermentation of dietary carbohydrates into volatile fatty acids produces gases in the rumen that are mainly hydrogen, carbon dioxide, and methane, the addition of yeast not only has the potential to improve gas production. , But can cause qualitative changes in the gases produced and reduce the negative impact on the environment. Addition of yeast in concentrated diets increased the population of fiber decomposing microorganisms compared to the control group without adding yeast. Yeast also directly stimulates ruminal fungi, which may improve fiber digestion. Gas production forms the basis of any substrate, mainly dependent on the availability of nutrients for ruminal microorganisms It is quite clear that the increase in gas production was due to the increase in crude protein content. It is well known that Saccharomyces cerevisiae has the ability to reduce the production of ammonia in the rumen. By reducing protein degradation and overall nitrogen excretion by the animal, which helps reduce ammonia emissions from cattle manure. The direct result of this action is an increase in protein bypass in the rumen, which is absorbed and metabolized as a real protein in the gastrointestinal tract and small intestine. Reducing the latency phase by increasing the protein content (for example, a diet with higher crude protein) indicates the rapid activity of Saccharomyces cerevisiae on the fermentation process. In addition, Saccharomyces cerevisiae contains small peptides and other nutrients that are needed by the dominant ruminal cellulite bacteria to initiate growth. The activity of Saccharomyces cerevisiae depends on many factors, including the availability of nutrients to rumen microorganisms, which stimulates the fermentation process. the aim of this study was to investigate the effects of yeast supplementation on fermentation parameters in total mixed rations in vitro.

Accordingly, the effect of 4 levels of yeast supplementation involved, zero, 4, 8 and 12 mg/g of yeast in two TMR diets containing 60 and 70% of concentrates, on the kinetics and parameters of gas production, rumen fermentation parameters including pH, ammonia nitrogen, concentration and profiles of volatile fatty acids, and true digestibility of dry matter and neutral detergent fibers were evaluated. In addition, the effect of yeast supplementation on the population of protozoa, anaerobic fungi and cellulolytic microorganisms were evaluated using molecular techniques. In this experiment, three adult Holstein steers equipped with ruminal fistulas were used to prepare ruminal fluid. For the polymerase chain reaction, after sequencing the primers, DNA extracted was amplified using PCR to check their specificity. DNA amplification was examined by system (R-T PCR) with three replications for each pair of primers.

Addition of different levels of Saccharomyces cerevisiae supplementation caused a significant increase (P <0.05) in the amount of gas produced by increasing the incubation time of experimental diets. The results show that there is a statistically significant difference (P <0.05) between different levels of supplementation, so that from 24 hours after incubation onwards, the highest amount of gas produced in the experimental diets was at the level of 12 mg/g supplement was observed. Addition of different levels of Saccharomyces cerevisiae supplementation caused a significant increase (P <0.05) in the total amount of VFA produced in the rumen with increasing levels of supplementation in experimental diets. The results show that there is a statistically significant difference (P <0.05) between different levels of supplementation, so that the highest amount of total VFA produced in both diets was observed at the level of 12 mg/g supplement. The effect of adding different levels of Saccharomyces cerevisiae supplementation on ruminal parameters caused a significant increase (P <0.05) in ruminal pH and a decrease in ruminal ammonia production by increasing the level of supplementation in experimental diets. The results show that there is a statistically significant difference between different levels of supplementation, so that the greatest increase in ruminal pH and decrease in ammonia production in experimental diets at the level of 12 mg/g. The effect of diet type was also significantly different (P <0.05). The highest increase in ruminal pH and decrease in ammonia production was observed in diets containing 60% concentrate. The results of this study showed that the yeast supplementation in high fermentative TMR diets, increased (P<0.05) the rumen environmental stability, increased (P<0.05) the fermentability of dietary insoluble fraction, reduced (P<0.05) the gas production rate and reduced (P<0.05) the lag phase. degradation of nutrients without affecting the digestibility of insoluble fibers in neutral detergents and the digestibility of insoluble fibers in acidic detergents with diets containing higher crude protein, even with the addition of Saccharomyces cerevisiae, dry matter digestibility showed improved.

Yeast supplementation improved fiber digestibility and reduced lactate accumulation and LPS concentration by stabilizing the an-aerobic environment in the rumen and stimulating the growth and activity of fiber-degrading microorganisms.