Dogs are not by nature very selective in their feeding habits and are therefore prone to develop disorders of the digestive tract through self-indulgence or by being fed incorrectly by their owners.
The digestive system of the puppy first comes under stress when the dog is weaned from the whole milk diet supplied by the mother to a mixed diet prepared by well-intentioned, but not always well informed, humans.
Supplementary feeding should take place slowly from 3 weeks of age to allow the puppy’s intestinal tract to adapt to the different source of milk proteins and cereals.
A common mistake is to incorporate too much meat or meat substitute too quickly. Although the puppy often eats this new food avidly its digestive tract cannot cope and the dog develops a potbelly and fails to gain weight.
Some dogs and cats are unable to tolerate everyday foods. It is not uncommon for a small puppy or kitten to develop diarrhea after being fed cows milk. Many dogs are quite unable to tolerate pork, and in others, fish can induce quite severe allergic symptoms.
Internal parasites can contribute to stomach disorders. Large numbers of roundworms in the small intestine can cause periodic vomiting and diarrhea.
In older dogs, the irritation of the bowel wall from whipworms can cause chronic diarrhea. Hookworms can cause severe gastrointestinal disorders as these worms actively burrow into the lining of the bowel. A severe anemia can result, with blood being passed in the bowel motions.
In recent years veterinarians have had to contend with an increasing number of dogs with an acute gaseous distension of the intestine, or bloat.
Large dogs seem more prone to this problem and once having had a severe attack seem more prone to further episodes. Typically, the dog is alright when put to bed at night but wakes the owner some hours later by howling and being in acute distress.
Prompt treatment is required if the dog is to be saved as the massive distension of the abdomen puts tremendous strain on the heart and respiratory system. Sometimes the veterinarian has to operate to relieve a torsion of part of the intestinal tract.
The condition is caused by very rapid fermentation within the stomach and small intestine producing large quantities of gas. Factors favoring this rapid fermentation are the eating of massive amounts of dry food or garbage containing putrid meat scraps.
Dogs that have suffered one attack should be fed small quantities of food (two or three times a day) and the amount of dry kibble food should be strictly controlled.
One of the most frequently occurring stomach disorders in older dogs is constipation.
By far the most important cause is the eating of large amounts of bone. Chicken bones, chop bones, lamb shanks all produce small sharp bone fragments that become compacted when they reach the large intestine.
Sharp fragments also irritate the bowel wall and cause the dog considerable pain when the muscle wall of the bowel contracts to attempt to expel the fecal mass.
Another cause of constipation in the dog is the feeding of a complete meat diet with no fiber.
Meat is almost completely digested and the residue that remains in the large bowel after digestion is quite small and hard. The muscle of the bowel has difficulty in moving this material along its length and irregular and small bowel actions result.
This type of constipation can easily be treated not by giving laxatives but by simply ensuring that there is some cereal included in the diet.
The severe constipation caused by bone fragments should be treated promptly by a veterinarian, as enemas and careful manipulations often are necessary to prevent damage to the bowel.
It is important that older dogs, whose intestinal muscles may be losing their strength, are not given too many bones of any type, especially small cooked bones.