- and why we shouldn't feed it anymore
Brewers Yeast has recently been at the mercy of new research and published studies, with the data showing the ‘yeast’ involved isn’t equine gut-microbe appropriate, as in it’s the wrong type of microbe, aka an imposter.
If it’s any consolation I'm still pouting a bit on this because until recently I was a huge BY fan, but the science is unquestionable so BY is out in my book.
Basically, what the science is saying is that, as per so many other dietary items we feed our horses - including our neon-green leaf-blade growing grass - it feeds the pro-inflammatory lactic-acid (LA) bacteria in the hindgut, who produce lactic-acid as their waste product which can neither be utilised by the horse, plus it creates hindgut acidosis in an environment which should always be at neutral pH.
So, despite my pout over losing BY, we can't ignore the fact that LA in turn lowers the gut pH, creating an acidic hindgut environment which leads to dysbiosis of the biome - a factor we need to avoid at all costs as hindgut acidosis is so prevalent these days.
Here's what apparently happens. The BY settles in the large intestine where it’s hot, humid, and airless, and it does the very job it was designed to do in the brewing industry – it converts sugar (from the plant starches) and water, to … alcohol! Seriously! This is a waste product of the hindgut’s normal energy metabolism when it digests sugar or starch.
This alcohol is absorbed through the gut membrane into the body and, understandably, relaxes the horse, hence why it’s well known that a horse is more relaxed when they’re fed BY, which I completely get because let's face it, I’m a lot more relaxed after a couple of beers. 😉
And would you believe it, there’s actual current research into this in humans as we speak, with a whole series of studies and case reports on ‘Autobrewery's Syndrome’ (https://europepmc.org/article/nbk/nbk513346). The doctors that originally researched this in patients were laughed at, but today this is now considered to be an extremely under-diagnosed phenomenon. I’m just waiting for the published paper on ′'Blood alcohol levels in the horse after feeding'. Imagine that …
I know this sounds like an April Fool's joke but I'm seriously serious. Pulling this all together, BY has generally been fed as a prebiotic yeast, but it’s now confirmed as an inappropriate microbe of the biome structure in the horse’s gut system. In other words, we’ve added an unrecognised ‘invader’ into the biome when it should always be about re-establishing the species-appropriate cellulose-digesting microbes in the hindgut, the only source of this being long, stemmy, cellulose-rich hay, and not about feeding an unrecognised microbe for what we think is good measure.
Also, we used to think that BY added in a generous measure of the B-Vits, but again this has been thrown out. Provided the horse is fed species-appropriate fibre forage, i.e. hay, the microbiome produces its own B-vits, including B12 and B6 in the hindgut, and in the ‘active’ form that the equine body can utilise, not in a synthetic, unnatural form that we usually add in as a supplement. Just for good measure the same applies to vit.C and vit.K.
So there we have it. BY is both inappropriate and potentially damaging to the equine physiological system.
For the record, as soon as I came across this I instantly removed it from my own horses' diets and interestingly, MacAttack - my most hindgut-challenged and very uncomfortable with it as in super-sensitive (which meant every time I reached under his belly for rug straps meant risking a severed arm), instantly softened and became hugely nicer to be around.
I can now get his sweet itch rug straps with no bother at all - literally no more cow-kicking which was previously a given - and he doesn't bite me at all now. Nothing else has changed so I can only put this down to removing the BY. He's literally turned from a bitey thug to a marshmallow softie who's happy to let me cuddle him. What's not to love about that?!