Further research on this subject has lead me to two very different view points on ACV use age in livestock,

One opinion is

– acetic acid (the main component of ACV) will stimulate the rumen microbes that are the subset that breaks down CELLULOSE, HEMICELLULOSE, and LIGNIN. These long-chain hydrocarbons are the un-mined “gold” of forages, basically locked-up but, when broken down, capable of yielding thousands of units of sugars and starch molecules. In essence, the rougher the hay, the stemmier the hay, the better the results from ACV. Vinegar breaks down acid detergent and neutral detergent fiber and turns it into energy.

Another opinion –

Microbes break down the fiber in forages and one of their waste products (poop) is acetate. It’s like ammonia (fish waste product) in a fish tank. Putting more ammonia in will kill the fish. The cow cleans up the environment for her resident rumen microbes by absorbing that acetate across the rumen wall and into her system. Like a human cleaning a fish tank, or microbes there converting the toxic ammonia to less toxic nitrate. The rumen system is a tightly balanced system. If too much acetate is in the rumen, microbes die. Adding more microbe poop to the rumen won’t stimulate those microbes. If you add enough acetic acid to fiber to cause it to break down, that level will be toxic to the microbes that normally produce acetate as a waste product.

There may be value of ACV in other ways, but this proposed mechanism of action is faulty thinking.

Both seem very plausible to me but which is correct?

W