Many foods have adequate levels of fiber already provided. The ‘Guaranteed Analysis’ provided on your pets’ food bag should note the maximum crude fiber concentration. Most pet foods contain about 5% crude fiber, and this is often adequate for the average healthy dog. If your dog is constipated or has diarrhea, this could be something a simple stomach bug, parasites, other gastrointestinal diseases, or strain due to an enlarged prostate or mass impeding the passage of stool. Observe your dog to see if the symptoms persist for more than two days. The symptoms of constipation can overlap with those of urinary obstruction, which is very serious. If you see your pet repeatedly straining then a vet check is strongly advised. Ask your vet to include a rectal exam. If the primary issue turns out to be one of diet and digestion, your vet may suggest fiber supplementation.

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Write a summary of the previous text in Vietnamese:
Kiểm tra thức ăn hiện tại của chó. Quan sát chó. Đưa chó đến bác sĩ thú y.