I've read that both vinegar and garlic will help boost their immune system, and the garlic may help with internal parasites. I haven't noticed any particular difference, but I've also never had any disease or bug problems with my hens, so nothing really to compare it to. Just makes sense to me and an inexpensive preventative measure. I put one capful of vinegar and a clove of garlic in 2 gallons of water.
I feed with Purina. The other choices my feed store offers are a less expensive brand and then several high end brands. I find it laughable to give chickens a 'vegetarian' feed (I'm fairly certain they would eat worms and bugs over plants if given the choice), and found the cheaper brand to be inferior. So...middle of the road for me. Plus plenty of time free ranging. Dandelions seem to be a favorite, and while they do kick dirt around and nibble on my plants, I haven't had any major damage. But, I only have 8 hens, a large yard, and surrounding fields - so they have plenty to choose from.
Good luck in your future endeavor. I sure love fresh eggs, and also enjoy giving them away.
