I've also used goat kefir in place of the whey with excellent results, so it is a fun recipe to work with. (kingarthurflour.com)
I used whey from my homemade goat kefir... most excellent! (kingarthurflour.com)
You may use plain, whole milk goat kefir or homemade goat yogurt in place of the milk portion of the milk if raw goat milk is not available in your area. (thehealthyhomeeconomist.com)