The farm I got my pullets from recommended using cider vinegar in between worming treatments to help keep the worms at bay as it slightly alters the gut environment (makes it more alkaline?? - my chemistry is rusty!) which makes it less hospitable to worms.
ACV is I believe acidic and a chickens digestion system is very acidic to the point ACV would have little or no effect on acidity. If a chx digestion system is acidic why is it assumed it needs to be made more alkaline? Surely if it's evolved to be acidic that's what it needs to be why attempt to "correct" it by tinkering with it?
The truth is the benefits of ACV, if any, are far from clear. ACV became popular in the 1950's, post war, when an American alternative medicine author wrote a book on herbal and folksy dietry remedies and supplements which were supposed to be cure all for all manner of ailments. It became a cult craze and ACV was one of the things which caught on. People used to drink the stuff as a health tonic!. I suppose anything that vile must do some good
It's now sold mostly for animals, horses and the like.
HF
It's interesting to read the supposed list of benefits ACV has, it is claimed to be a cure, or usually "helpful in the treatment of", as modern advertising law requires some credible proof of a claimed benefit and it's easier to get away with vague claims. The list is long and includes some types of cancer, and heart problems to name a couple of the biggies. If you are losing your hair it also will grow hair on a billiard ball or at least "help" as a hair restorer.
I'm reminded that some wag once produced a well supported petition calling for the abolition of
hydrogen dioxide dihydrogen monoxide a chemical which is all around us and can cause death by suffocation in some animals, and one of it's many "bad" associations was it is found in all cancer cells. The list of bad sounding facts about it was long and impressive. Of course for those more conversant with chemistry will know it's water. An essential ingredient for life.
Chx and some animals appear to like a bit of ACV in their drinking water or at least they appear to initially drink more but wouldn't it also make you thirsty and want to drink more? Long term I've found chx will drink fresh water just as well if not better than ACV treated. Just put two drinkers out side by side with ACV in one and fresh water in another and monitor it longterm to see which they prefer. Anything which encourages them to drink particularly in hot weather can be useful.
HF