Starter cultures are preparations of live microorganisms or their resting forms, whose metabolic activity has desired effects in the fermentation substrate, the food.
I think this paper may be useful. It evaluates the effects that live yeast supplementation might have on performance, rumination time, and rumen pH on dairy cows under commercial farm environments, specifically a standard commercial diet, an acidotic challenge, and outside grazing grass.
Thank you very much Dr. Disney. In fact in in previous projects our team isolated some yeast strains from Sudanese fermented milk products (Robe, Garris and Cheeses), the isolated yeast strains have their roles in the fermentation processes