Before I adopted my two year old female cavies (2) I bought some Oxbow Timothy pellets. They were formerly eating an alfalfa based Kaytee food with lots of colored pieces. It looks like they are not eating the new pellet food as readily of course. (They love their veggies!) Should I buy a small bag of their former food and keep switching over more slowly? It has been two weeks and I only gave them the former food until it was gone (3-4 days). Thanks.