I've had a bottle baby for 10 days now. He's 4 weeks old and growing like a weed. I had a freezer full of milk from last year that I assumed would last him awhile. He gets 16oz 3x day. I only have a few more days worth of milk for him. My question is this; Should I start mixing store bought whole cow's milk with the remaining goats milk or wait and switch over to cow's milk completely all at once?