I have a huge jar (well, its not really, just seems to be as it takes so long to get through!) of brewers yeast powder.
I put a couple of teaspoons into warmish water to make abit of a paste, then mix it into their water bowl ( a large washing up bowl)
the "instuctions" say............
"cattle & horses up to 4 teaspoons daily
Sheep & goats up to 2 teaspoons daily
Poultry 1 level teaspoon per 12 birds once a week"
And that its "a natural source of vitamin B group vitamins to correct deficiencies such as poor skin, feather and coat, loss of appetite etc!
cost me £3.00 for 500g from
www.smallholdersupplies.co.ukit looks like fine sand and smells like... a brewery!!