Bottle calves - Holstein

Question: I have two new Holstein bottle calves. Took them straight from the dairy before they were 8 hours old. Both of them got their colostrum and a clostridium shot. They are healthy, happy little buggers with no problems...so far...I'm still waiting for the other shoe to drop!

My question is that I'm raising them on goat's milk. They are 5 days old now and approximately 80 - 90 pounds each, though one is obviously bigger than the other. I am giving them 1 1/2 quarts in the morning, 1 quart in the afternoon and 1 1/2 quarts in the evening, to total one gallon each. With goat's milk, is that enough? Obviously, like any calf, they think they're starving to death. But I understand that goat's milk is more easily digestible. Do they need more than the standard gallon a day or is that enough with goat's milk? So far they don't have anything else, but I was going to get them some calf starter and a water bucket later this week.

Anything else I should be doing? No scours yet (first year trying goat's milk and I'm impressed with the lack of scours - last year it only took three days before I had them scouring and lost one, despite best efforts at treating).

Thanks,

Sarah