I have been feeding my breeding females and youngsters a twice-weekly suppliment for about 9-10 years now.  It also helps to condition poorly and underweight chinchillas too.

Do not feed it in the same bowl as pellets, or you will find the chins will throw out their pellets in an effort to eat all the suppliment.

1 teaspoon per adult chin, twice a week, is sufficient.

Here is the basic recipe that I use (you can scale it up or down pro-rata!)

3kg oats - 3kg wheatgerm
500g barley flakes - 500g wheat flakes
500g rye flakes - 500g quinoa flakes
250g golden linseed - 500g oatbran

500g of dried herbs (and/or dried nettles)
15g-20g of Nutrabal (a high-calcium, broad-spectrum suppliment)

Sorry - Sales are Temporarily Suspended