Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

Dogs are scavengers. Cats less so – let’s call them opportunists. Dogs are not obligate carnivores, so they can get nutrition and energy out of carbohydrates and legumes as well as meat and fat. They are also inclined to get into all sorts of rubbish and rotten food. But that doesn’t mean that they are immune from getting ill due to dietary indiscretion.

The dog has a simple, very acidic gut, typical of a carnivore, designed to process large quantities of meat and bone. The dog’s stomach is most acidic (pH <1) when it is digesting and can remain at this low level for five hours. This is very acidic and can be compared to battery acid. The human stomach has a pH averaging 1.35–3.5, slightly higher than that of the dog.

Omnivores have less acidic digestive juices than carnivores due to their larger inclusion of alkaline-forming legumes and vegetables. Carnivores, on the other hand, spend their time eating protein and fat and the more protein in a meal, the lower the stomach pH. In an acidic environment, meat and bones are broken down and softened in one hour.

The stomach lining has rapidly dividing cells to repair any minor damage and also secretes a large amount of bicarbonate-rich mucus to protect itself from the acidity of the gastric juices. After digestion has occurred, the stomach juices become neutral as food is passed through to the small intestine, which is not designed to withstand acid.

The pH of food bolus will increase to a near neutral pH 6-7 in the duodenum, but as high as pH 8.3 by the time it reaches the colon. The very acidic environment in the carnivore’s stomach makes it very inhospitable to the majority of meat-borne pathogens such as Salmonella and E. coli. This is why dogs can dig up an old bone, nibble away and not get sick.

Bacteria called Clostridium can cause diarrhoea in dogs and it is picked up from eating rotten meat. These bacteria can also exist in a dog’s intestine without causing disease and start producing a toxin when stress or other disease occurs. The condition is generally easily managed with antibiotics and IV fluids.

We used to call this infection garbage disease. It’s difficult to diagnose exactly, as bacteria are often normally present, but specialised new tests can identify DNA which is designed to produce toxin.

Raw diets may be a source of Salmonella and resistant E. coli species. Owners should be aware of the risks, especially households with members, both human and canine, who are very young, elderly or immune-compromised.

The processed food typically has higher bacterial counts than acceptable for human consumption. Package warnings about preparation and hygienic handling of these raw pet foods are commonly absent and packaging may be defective and leaky.

Heat treatment is a critical control step in the elimination or marked reduction of bacteria arising from livestock sources, which is not available to producers of raw food as it is with processed pellets. Care should be taken when handling and preparing this food.

So, infection is of a lesser concern when a dog is eating stuff. Of more importance is intestinal obstruction as well as excess fat intake, causing pancreatitis in smaller breed dogs. Additionally, large amounts of onions are also toxic. They cause the blood to break down, similar to biliary.

Bones and ‘mielie’ cobs are the most common intestinal obstructions we see. If a bone is still in the stomach, there is a chance it will get digested. Once it is in the intestine, that option is over.
If the object has passed into the large intestine, we can often monitor and allow it to pass naturally.

Small intestinal obstructions require surgical removal. The earlier the better; once the object has perforated the intestine, inflammation decreases the prognosis of the surgery. If diagnosed early, the object is just removed through an incision into the intestine.

If the obstruction has been present for several days, then it is likely that that segment of the intestine will need to be removed and the ends sewn together. Dogs do remarkably well with this type of surgery. Compared to humans, they have much fewer complications. However, the risk of complications increases dramatically when there is infection.

Feeding fatty meals to small dogs will dramatically increase their risk of getting pancreatitis, a very painful condition in the upper abdomen adjacent to the stomach. Severe disease can cause death.

Milder disease is managed with fluids and pain control. Vets often see this condition. Once a patient has been affected with this, they are forever predisposed.

Although we don’t need to be overly concerned about our dogs getting food poisoning, they can still get ill from what they eat and we still need to be careful.