Yeast is an old feed and food ingredient, and as such it needs little introduction. In dairy nutrition, alone, vast quantities of brewer’s yeast (and all modern derivatives) are being used worldwide. In fact, yeast competes with sodium bicarbonate as the most significant or widely used additive in dairy cattle feeds. Of course, yeast products are used in many other farmed species, but not to the extent or consistency by which this additive is being employed in dairy feeds. In fact, one could rightly claim yeast as an indispensable raw material for these feeds, in line with corn silage and soybean meal.
But yeast is never just yeast, at least not anymore. In the past, we had the plain old dried brewer’s yeast – the one associated with beer making – that was essentially a dead yeast product. Today, we still have this ingredient, but also we have it broken up in parts with cell walls having additional beneficial claims and cell contents still trying to find their place in animal nutrition. We also have live yeast products, with slightly different claims and mode of action, but essentially with similar end result – that of promoting rumen health and functions.
Despite the plethora of yeast products, in all of the above mentioned forms, one is hard pressed to find evidence about the efficacy of dried versus live yeast products. As most such products are now heavily branded, the question has become this brand versus that one, without much regard on the underlining principles. So, with modern, improved strains of brewer’s yeast used for producing such a common feed additive, we still lack a clear understanding when we should be using a live versus a dried (dead) yeast product.