As a normal part of my brooder program, I have put a little acv in the water. After reading some scientific sounding stuff that indicate I was wasting my time, I stopped and gave chicks plain old water. Almost immediately I had problems with stuck poop on their hineys. Scared me as the chicks in the brooder are very valuable to my flock goals. I put ACV back in the water and problem stopped. Besides the obvious result in chick health, I have better things to do than clean poop off chick butts.