I have pygmy and dairy goats. To be honest, I never feed any goats a lot of concentrates (as in goat mix) prefering high fibre diets - they have good quality chaff, and soaked sugar beet added to their goat mix, and plenty of hay or haylage.
I suppose I am cautious because many years ago, not long after I started breeding goats, I ....upped the in kid goats feed about a month before kidding, not overly, but what I thought was adequate. One of the females went off her legs, and was not well at all. Took her to the vet, and I got a right roasting for giving her concentrates - that had caused her illness.
To this day, that vets words ring in my ears"If you want to increase anything, increase her hay intake!"
It turned out ok - two weeks later Penny kidded twins