...as with any other feed change, switch over slowly if you can-[especially with small breeds] - don't wait until you are already out of the hay they are used to and then begin the change over to a different hay. [some rabbits are more sensitive than others to hay changes- Small breeds are more prone to GI issues - so caution is especially important]
I also feed a lot of other feeds, or pellets-- I don't give a hay change with my rabbits a second thought...
JMHO...
-- Sat Aug 20, 2016 5:26 am --
Just an additional thought to explain my view of feeding grass hay.. [as opinions vary]
I feed grass hay primarily as a source of long stem fiber, not as a primary nutrient source for the rabbits.
I feel commercial pelleted feed is too low in long stem fiber for adult rabbits, especially older rabbits.
I do like Timothy because of its high protein content, but-- in older rabbits high protein is usually a negative. [especially for pet rabbits]
lactating does need a lot of energy, no grass hay will supply enough of that...