I'm sorry to hear that Schroeder has diarrhea. Any change in diet, stress and parasites are primary considerations for causes of diarrhea. Fresh blood and/or mucous, if present in the feces, suggests the colon is very irritated and an exam by your vet is indicated: generally they will prescribe an antibiotic such as metronidazole to avoid translocation of bacteria from the colon into the bloodstream and prevent bacterial overgrowth (e.g. clostridial diarrhea). Alternatively, dark tarry feces (i.e. much like coffee grounds) suggests digested blood in the feces which can mean ulceration in the stomach or small intestine and I would advise seeing your vet promptly.
Assuming no fresh blood, mucous or dark tarry appearance and a reasonable appetite without vomiting, you can try a bland diet such as white chicken with no skin or fat and boiled white rice and unflavored Metamucil at 1 teaspoon twice daily to Schroeder's meal to resolve his diarrhea:
You can also try a canine probiotic (i.e. Purina Fortiflora is my favorite) at 1 packet mixed with food daily. Most dogs love the taste:
If Schroeder's diarrhea persists despite using the above measures for about 72 hours OR if he develops other symptoms at any point (i.e. vomiting, refusal to eat), then a trip to the vet is necessary. They should perform a test for parasites so do bring a stool sample with you. Most monthly heartworm preventatives cover major/common parasites but others exist that require specific treatment and of course when diarrhea becomes chronic it is worthwhile to run lab work to rule-out metabolic causes and consider temporary use of a prescription dog food, metronidazole (as mentioned above) and potentially deworming with a broad spectrum product like Panacur as presumptive treatments if your dog's lab work is all normal.
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