I'm sure I've seen this question asked before but couldn't find it, so apologies!
Am I okay switching between flavours of one brand of food, without introducing it gradually as though it were a totally new food? HB currently eats JWB Junior fish and rice. Irritatingly, Zooplus only sell the turkey and lamb flavours, and its a tenner more for the same size bag of fish flavour on Viovet

.... I'm always over cautious with him and food as he had colitis when he was younger. Not sure if its worth the risk to change, but also, no point spending more than I have to!
Also, he doesn't get on with chicken at all. Is turkey likely to cause him similar troubles with it being a similar meat?
Thanks
R