One of my cats insists on eating the dog’s food. Will this damage the cat at all? Should I stop her eating this?

F Simmons, Abingdon Eating the dog food occasionally in addition to her normal diet should not cause any problems. If your cat doesn’t get an upset stomach after eating the dog food, it should do her no harm. However, there are some differences in the body’s requirement for vitamins and essential proteins between dogs and cats. In particular, cats need the amino acid taurine in their food, which dogs’ bodies can make from other substances. A cat fed exclusively on dog food will develop taurine deficiency, which can lead to serious problems, including heart disease and blindness. The large pet food manufacturers have spent millions of pounds researching the best foods for our pets, and generally speaking, feed dog food to your dog, and cat food to your cat.

My two-year-old guinea pig has developed lumps in each armpit. They are quite firm and about the size of a bean. My vet says she has never seen this before, but didn’t seem to think it was sinister. They have grown slightly since then. Have you encountered this before? Peter Waverley, Oxford

I have seen many lumps and bumps on guinea pigs but never in the armpits. I suspect these may be swollen lymph nodes (often called glands). These glands will swell when fighting infection but usually they will reduce in size quite quickly when the infection is gone. If they continue to grow, or they do not reduce within a couple of weeks, please take him back to your vet who may decide to take a sample from each lump and have this checked by a laboratory to determine exactly what is going on.