How old is Mr Bumper?
how long is he spitting up like this?
what is the name of his food?
In a boy Bumpers age he may be getting a bit of acid reflux. He could also have a dental problem as well as a hormonal imbalance.Sometimes older cats build up a sensitvity to the corn that is used as fillers in dry food or have difficuty chewing and digesting. Purina is loaded with unnessary fillers that can be harmful to cats. Try discntinuing the Deli cat and see if the spitting up stops. Also put a little hairball remedy or even plain vaseline on Bumpers foot once at night for him to lick off. That will coat his GI tract and help prevent reflux. He can als have a quarter of a pepsid tablet once a day - at night is best.
If this still continues, have a vet look at his mouth. If he does have a dental problem, he will be scripted an antibiotic to resolve the infection.A ca his age should have a well kitty exam at least once a year. If he is dehydrated at all, he can have droppers of plain pedilate a few times a day.
Mr Bumper sounds like wonderful boy - and you are the purrfect kitty parent. He is very lucky to have you. Please let me know how hings are going. I will always be happy to help.