Yeast products are widely utilised as feed additives for ruminant animals in many parts of the world. While the number of yeast products that have undergone substantive evaluation in controlled research studies is somewhat limited, there is a widespread belief among dairy and beef producers, and ruminant nutritionists, that yeast products are beneficial by enhancing dry matter (DM) intake and overall animal performance.
Mechanisms have been proposed to explain why yeast products could stimulate DM intake and productivity in growing and lactating cattle. Perhaps the oldest hypothesis is that the yeasts are able to grow, at least for a short period of time, in the rumen thereby directly enhancing fibre digestion and/or producing nutrients that stimulate growth of rumen bacteria, which do the bulk of the fibre digestion.
Since none of the added live organisms can digest structural carbohydrates, their role must involve some cross-feeding of essential factors that might be limiting to the main rumen population. The possibilities are quite broad and include amino acids, peptides, vitamins and enzymes.
It has also been suggested that the yeasts utilise nutrients, such as lactic acid that, if allowed to accumulate in the rumen, could suppress bacterial growth and/or suppress DM intake by driving rumen pH down.
For more of the article, please click here
Article made possible through the contribution of Dox-al.