Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Clyde isn't feeling himself, with a decrease in appetite and increased noise from his stomach and eating grass.
These noises you are hearing are the result of ingesta moving through the gastrointestinal tract and gas bubbles. In most cases they are completely normal and seem to cause the dog no distress. But in cases where the dog acts uncomfortable it is likely that the pup is experiencing some reflux or abnormal motility, or painful intestinal spasms that are more than the usual. In severe cases this can be linked to pancreatitis which is a painful inflammation of the pancreas leading to increased enzyme leakage.
Dogs with nausea or gastroesophageal acid reflux often eat grass or foreign material to make themselves vomit. They will often swallow repeatedly and lick things trying to soothe their nausea and acid burn. If they can rid themselves of whatever is irritating their stomach that way then all is good.
But when they continue to be uncomfortable then we need to stop them from eating any more grass. It becomes a vicious cycle where the more they eat grass the more their stomach acid refluxes and burns their esophagus, and the worse they feel.
Possible causes of his symptoms include a change in diet, dietary sensitivities or allergies, or eating things that they should not like too many fatty table scraps or garbage, bones etc. Metabolic organ failures (kidney or liver disease), Addison's disease (hypoadrenocortisim), pancreatitis, inflammatory bowel disease or even infiltrative cancers are other possible causes.
Ideally because this has persisted for several days I would recommend checking basic blood tests on him including a complete blood count, biochemistry panel and a blood test for pancreatitis called can spec PL (canine specific pancreatic lipase) which is highly specific for pancreatitis. If his electrolyte levels seem unbalanced (high potassium and low sodium) then testing for Addison's disease with a test called an ACTH response test.
If those things are normal then the next step diagnostically would be an abdominal ultrasound when he is showing symptoms and endoscopy to collect intestinal biopsies.
Has he been fed anything different or gotten into anything different that you know of?
In the meantime to help with gastrointestinal upset and reflux you can give either:
1) Pepcid ac (famotidine) at a dose of one 10mg tablet per 20 to 40 pounds of body weight every 12 hours
2) Prilosec (omeprazole) at a dose of one 20mg tablet per 40 to 80 pounds of body weight every 24 hours
These are acid reducers and should help him feel more comfortable. They are quite safe and can be used for a few days if needed. In some cases dogs remain on them long term if this is a repeated problem.
I would pick up all food for now and water for a couple hours to allow his stomach to settle after the acid reducers. In a couple hours when you give him water or low salt clear broths like low salt beef or chicken broth to drink but make sure it is in small amounts only. If he drinks too much too quickly that can lead to nausea and vomiting. To get some electrolytes in you can also offer him a 50:50 mix of pedialyte and water.
If he seems to feel better later today offer a bland diet mix of 1/3 boiled, minced, white, skinless chicken or boiled, lean hamburger and 2/3 boiled, plain, white rice or pasta mixed with some low salt chicken or beef broth to make it easy to lap up and swallow as well as increase his fluid intake. If he refuses that you can offer a little meat baby food. Probiotics such as Fortiflora, Proviable, or Benebac can help replace appropriate bacteria. You can add those to the bland diet mix.
If things go well and he does eat and doesn't vomit feed him the bland diet for 2 to 3 days then slowly start to mix back in his regular food, a little more at each meal. It should take about 5 to 7 days to slowly convert him back to his regular diet.
If he continues to refuse to eat, begins to vomit, runs a fever (more than 103F rectally), has a tense painful belly then he is not a candidate for home therapy and must see a veterinarian for an examination, diagnostics, injectable anti-nausea drugs intravenous fluids and supportive care.
Please let me know if you have any further questions.