Hi again,Thank you for your patience. Jackson's symptoms are definitely a concern, and given his age we have to consider a range of possible issues here including everything from a food intolerance, to gastrointestinal parasites, fluid in the abdomen due to a heart issue, an internal organ problem, or even an abdominal tumor. Given he has been drooling alongside the gas and bloating, a gastrointestinal issue is very likely. He could potentially have a food allergy or intolerance to one of the proteins within the senior diet you changed him over to, so you could certainly try him back on the food he was on prior to this change to see if he improves, or try another company's senior diet. Hopefully both of your dogs are up to date with intestinal deworming treatments, and if not, please try and get that done over the weekend if you can. You will need their most recent weights in order to get the right dose for each of them. IF your boy is still drooling, bloated and uncomfortable, you are definitely going to need to continue to keep a close eye
on him over the coming few days. I really would encourage you to get him back to the vet if he seems painful or uncomfortable now. Here they can do more diagnostic tests including a full blood test, an abdominal ultrasound and xray to rule out an abdominal tumor or internal organ problem, and carry out a rectal exam to ensure all is ok there. In the meantime, do try him back on the diet he was on around 10 days prior to the current senior diet. In fact, you could try him with cooked, boneless, skinless chicken
breast and boiled white rice for a few days to see if that helps at all. For now, please keep a close eye on his mucus membranes, capillary refill time and respiratory rate as follows:Mucus membranes - flip his lip and look at the color of his gums. They should maintain a nice salmon pink color. Get him to the emergency Vet if they appear white or very pale pink, or if they are a dark deep red color.Capillary Refill time - this measures blood perfusion and test this by putting your thumb on his gum to apply pressure. After you release your thumb you will see the gum blanch. Capillary refill time is the amount of time it takes (in seconds) for the gum to return to a healthy pink color from the blanched white color. If 2 seconds or less don't worry - if it is taking significantly more time, again - off to the emergency Vet.Respiratory Rate - if he is continuously panting throughout the night, this is a sign of shock and or pain and a signal for a trip to the emergency Vet. Best of luck with Jackson and hopefully these symptoms settle soon. Definitely follow up with your vet if they continue so that further diagnostics can be run here. It doesn't sound like an infectious issue given your other dog is currently absolutely fine. I hope all of the above makes sense? If you have more questions or if I can help in any other way, please do not hesitate to ask! If you would like to accept my answer, please press RATE OUR CONVERSATION (I am not compensated in any other way). Bonuses are always welcome. Thanks! I hope to work with you again soon!Kind Regards,Dr EPS: If you have additional questions after you rate the question, you are welcome to request me for additional conversations if I am on-line or by beginning your question "Dr. E..." or "Pet-doc..." and others will leave the questions for me.