OP here...
I just though of something, my cat can be very sensitive to sudden changes
in diet - that is in terms of throwing up. A friend once gave him some
cooked (and smoked) beef (while I was away) and he threw up all over the
place. Also, I tried giving him a small amount of yoghurt for the diarrhea
(about a teaspoon, warmed) and he puked on that.

All this said, he didn't throw up when we switched from Hill's to IVB green
peas and rabbit - I put him straight on the new dry food (he's always had
dry) without doing it gradually and no puking.

So, I'm kind of concerned about putting him straight on chicken and rice for
fear that he'll puke it all up. Should I do a very gradual transition?

Hank