I believe it is the high calcium in the layer pellets that is more problematic rather than the protein percentage (unless you are giving a game or turkey layer?)The type of protein also plays a big role (some ppl give their birds fish and meat from the table or cat food/dogfood) ...only laying hens need layer formulation...chickens dietary needs also vary dependent upon their individual circumstances (not every backyard or field is the same) and age and breed...that having been said what I do for my roos is to put out a separte feeder of grower/finisher for the boys so they have an alternative to the layer pellets (which they avoid like the plague). When you are giving ACV the natural PH of your water plays a most decisive role in how much you use...ideally you should test this at least once if you suspect your water is either highly acidic or highly alkaline in order to determine the amount of ACV needed... I have a good article on this and when I find it I shall come back and edit the link into this post. (If the water is
too acidic it will kill your birds...use with caution/precision when giving to chicks)
EDTED TO ADD:
http://www.thepoultrysite.com/articles/246/effects-of-water-acidification-on-broiler-performance
Effects of Water Acidification on Broiler Performance
Comments and Conclusions
This research project found no significant improvement in average weights, feed conversion or water consumption when the drinking water pH was lowered to 3, 4 or 5. The results indicate that birds are very tolerant of a wide range of pH water. The findings that the crop pH was significantly lowered by reducing the water pH might explain why producers have reported that bird droppings become more firm when acidifiers are added to the water. The crop serves as a storage compartment for consumed particles.
Nature designed the crop to store whole bugs and seeds, not the finely ground, easily digested feed utilized by broilers for efficient feed conversions. If the crop is full of feed and poor quality water is added, then there is an increased risk for the development of harmful bacterial and mold that could impact the rest of the digestive tract. However,
research done in Alabama by Hardin and Roney (no date) found that a pH range of 4 was not favorable for bacteria such as E. coli, Salmonella and Clostridium to grow and thrive.
The current research indicates that it is possible to decrease the drinking water pH to a range that would lower the crop pH to almost 4, thus creating an environment that is hostile for undesirable microbes. However,
given the diversity of drinking water sources it is a very good idea to measure the pH of the drinking water when using acidifiers at manufacturers recommendations because the natural buffering capacity of water may result in reduced impact of the acidifier on pH. It may even be necessary to add more acidifier to the stock solution to achieve a lower drinking water pH.