Its good to mix over the food gradually so start the PAH before whiskas run out
As mark says the ingredients are poor and this is what creates the pong, my lot have less stinky poos on better food and cats fed a raw diet are even better. They digest it all unlike the stinky carbs
IMO a dry diet isnt natural, convenient and good on the wallet but not great for cats. Cats need water and they never drink enough on a dry diet. Concentrated urine often leads to bladder problems
Cats shouldnt have crystals in their urine but vets consider it normal for them to have a few small ones due to modern diet. Something wrong there!!