Vet Pete Wedderburn has the answers

We’ve owned two five-year-old indoor cats since they were kittens and have always fed them on a vet-recommended dry kibble cat food. The company has changed the formula, rebranding it as “anti-hairball indoor cat food”. How can we encourage the cats to enjoy this new food – and what happens if they don’t?

K&S, BRIXTON

The main rule when introducing pets to new foods is to do this gradually, over three or four days, by mixing an increasing proportion of the new food with a decreasing proportion of the old food. If you make a change too suddenly, a digestive upset can follow. You can’t force cats to enjoy eating a particular food: it’s trial and error to see what they enjoy. If the new formula is not to their liking, there’s a huge range available on the market now, so simply try another. All commercial pet food for cats provides complete nutrition, so the right choice is personal preference, finding out what best suits their individual taste and needs.

My 10-year-old parson russell terrier sometimes has a tremor in her back legs. My vet said it was inherent in the breed and that I didn’t need to worry about it. Can you give me any more information?

PO, LONDON

Tremors, or shivering, are common in dogs. The three common “normal” reasons are fear (perhaps of being at the vet), cold (shivering when outside) and dreaming while asleep. Some terriers suffer from “essential tremors”, which are a type of harmless trembling that can happen at any time, generally stopping when dogs start to walk about. There’s a long list of diseaselinked reasons, including brain diseases, metabolic disorders, pain (such as arthritis), toxins and viral infections. If you’re worried about a trembling pet, take a video and show your vet: this is the best way to explain to them what’s happening.

RESCUE PET

Bella is an independent nine-year-old cat who enjoys playing with rod toys. Contact Cats Protection’s Glasgow adoption centre on 0141 779 3341 or visit cats.org.uk/ glasgowac

To view outcomes of rescued pets, see petethevet.com/ rescues

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Send queries to petsubjects@ telegraph.co.uk or tweet @ PeteTheVet. All sick animals should be taken to a vet.