how long for a new food to be accepted?

My 4.5 month old kitten has been on Merrick kitten dry food since I adopted her, but after a vet visit today she's been prescribed the Royal Canin Gastrointestinal High Energy (wet and dry) for some chronic diarrhea problems. She likes the wet, but she has not yet touched the dry food. I've mixed some in with her old dry food, but she just sniffs it and walks away. I figure I should give it some more time, but how long has it taken your cats to accept a new food after introducing it?

My adult cat happened to steal some of the new dry food, so she clearly likes it haha. Guess my kitten is a picky eater... 

I assume the vet took a stool sample to get it lab tested? I'd be trying to work out the underlying cause. I'm by no means an expert on digestive complaints but I can answer your question.

I've tried mixing tiny amounts of the new to the old  and gradually increasing it. I've tried gradually increasing the amount over 7 and over 10 days (my cat has a sensitive stomach) with varying success. Often she just refuses it end of story. I wouldn't be worried that she won't eat the dry. 

Yeah she's had 3 separate stool tests in the last several months, all negative for parasites. One microscopic eval just showed lots of gram negative rods so she was treated for bacterial overgrowth previously.

I'll try the slow transition and hope she takes to it.

Some cats don't like RX foods. I personally think RX food is a gimmick and a waste of money. Kittens have sensitive digestive systems and get diarrhea easily from food. When my kittens were young I vet 100% wet food with probiotics mixed in their food twice a day and that solved the diarrhea issues. 

moorspede said:

 
I assume the vet took a stool sample to get it lab tested? I'd be trying to work out the underlying cause. I'm by no means an expert on digestive complaints but I can answer your question.

I've tried mixing tiny amounts of the new to the old  and gradually increasing it. I've tried gradually increasing the amount over 7 and over 10 days (my cat has a sensitive stomach) with varying success. Often she just refuses it end of story. I wouldn't be worried that she won't eat the dry.

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Success! Day 3 and she's started to take to the new food. And stools are bulking up thank goodness. 

That's wonderful! I'm so happy for you! Please keep us posted on how your kitty is doing.