Cat has hard pebbly faeces after diet improvement

My 2 year old 3kg female cat (spayed) was initially eating some kibble that had a low meat content. She was producing well formed log-shaped faeces. I then changed her diet to a higher quality kibble with higher meat content and grain free. Since then she is enjoying her food much more, but producing hard pebbles as faeces. She is drinking slightly less than before but still regularly. She is still very energetic during playtime and has had no other behavioural changes except really begging for food compared to before. I am feeding her the same amount of calories as before (I adjusted the amount of food based on the different nutritional values of the new food).

Hello and thankyou for this intriguing question.  There area lot of unknowns, the first of which is:  How true is it - and on what basis - that your second kibble was of higher quality?  Packaging and pricing can be very deceptive in the pet-food industry; per-centage meat content is not the only factor in determining the quality of a diet; what of the fibre and water content?  Was the initial diet suiting your cat on all levels?  For what reason was the change made?  It it one thing if your vet had to put your cat on a special diet for a specific reason; quite another if your cat is in fine fettle and the first diet was a perfectly appropriate.  The second thing to understand is, whether the change in faeces is definitely attributable to the change in diet; might they have concurrently developed some illness (is this the reason you changed the diet?)  If the change is reversed, will the quality of the faeces return to its former grade?  These are all things to speak to your vet about and we would firmly recommend doing so as a matter of importance; because your are not my client and I know so little of the context here, I cannot tell you what to do.  Some changes to diets can have serious consequences, so I am pleased that you haven't ignored this change.

Hi Liz, thank you for your reply. Just to supplement with more information, the only reason why I made the change was because I thought that the kibble I had bought was possibly too cheap to be good quality (£3 for 2kg) and I saw that the meat content was exceptionally low (6%). Mel was also not really enjoying her food and if I fed her a portion in the evening there would still be kibble left the next morning. There were no signs of illness that prompted the switch. Neither of the two kibbles were advised by the vet, who just said that kibble is fine as long as it is the right amount for her to maintain her weight, but didn’t recommend a particular brand or type of kibble.

Thank-you for this supplementary info.  If Mel was not enjoying her food, I wonder whether there was some underlying cause of that - particularly if she had enjoyed the food previously, so would definitely recommend looking into this.  Reduced interest in food can be an early stage of various conditions in cats, include kidney disease.  It is hard to tell from here whether yours is simply one of those cats who self-regulates well, or whether the food is at fault.  In nutritional terms, I would not see the price-tag as the most relevant clue to this.   It may be time to call your vet and make enquiries about the food by name.  Cats are obligate carnivores i.e. there are certain amino acids (protein molecules) that it is important for them to consume, so I am glad that you are interested in getting to the bottom of it.