Hi Joanne,
its hard to know 100% what a dog has reacted too, but since he was doing OK on Pro Plan Lamb & Rice formula, then you introduced the Chicken & Rice & all this has happened, I’d say it was the Pro Plan Chicken & Rice formula, it might of had something wrong with it?? could have been left in hot truck when being transported to pet shop or online store, the Chicken formula might have more prebiotics ingredients then the Lamb & Rice formula has & unbalanced his gut flora??…
If your dog is OK starting a new food without introducing with the old food then just start him on another brand that has limited ingredients, with ingredients you know agree with him but try & stay away from dry foods that are higher in Prebiotic ingredients…. Still feed his beef & rice cooked meal he’s doing well on for 1 meal & the other meal feed the new dry formula..
