You would expect your dog to be full of energy and happy after mealtime, instead your dog appears weak, dazed and listless even to the point of staggering, making you wonder what may cause a dog to be lethargic after eating. As with many health conditions in dogs, the only reliable way to know exactly what may be going on is to see the vet. In the meanwhile, it may be worthy recording the behavior so the vet can see it and accordingly decide what diagnostic tests to run. If your dog appears debilitated after eating but then, after a while he snaps out of it, you may find it interesting reading about a few conditions that may play a role in this behavior.
A Matter of Ammonia
One possible cause for a dog acting lethargic after eating is an issue with the dog's liver. One of the many tasks of the dog's liver is to filter the blood, converting ammonia (a breakdown product of protein in food) into urea so that it can be effectively excreted through the kidneys.
In an impaired liver, this task may not be carried out effectively leading to several problems affecting the brain, that fall under the term of hepatic encephalopathy.
In a dog with a liver problem known as a portosystemic shunt, the blood bypasses the dog's liver which means the ammonia isn't removed as it should. This accumulation of high ammonia levels in the dog's body triggers several neurological problems as it reaches the dog's brain resulting in tremors, seizures, weakness and staggering.
These symptoms tend to be more pronounced in dogs about 30 minutes after a meal because the protein content in food results in the production of more metabolic waste, explains veterinarian Dr. Todd Lawmaster.
A portosystemic shunt is in many cases a birth defect and it is often noticed in puppies; however, it can also develop over time when the dog's liver functionality starts gradually declining.
In normal, healthy dogs, there are blood vessels that connect the intestines to the liver, but in a dog with a portosystemic shunt, these blood vessels bypass the liver. Another variation, yet, less common that a portosystemic shunt, is a condition known as microvascular dysplasia where toxins once again don't get filtered as they should.
A Matter of Glucose
A dog that appears lethargic after eating may in some cases suffer from lowered levels of glucose. This may not seem to make much sense, considering that dogs with low blood sugar, usually feel better with a meal, but there can be exceptions to the rule.
Some dogs may be affected more than others just like some people get drowsy after a Thanksgiving dinner, explains veterinarian Dr. Drew. This lethargy may simply derive from the drop in blood sugar one experiences from the insulin being released during the digestive process. The effect may be more significant after eating foods that are particularly rich in carbs.
In some cases, periodic low blood sugar levels may be indicative of a dog suffering from a tumor of the pancreas medically known as an insulinoma, explains Dr. Lawmaster. Affected dogsmay develop lowered levels of insulin which trigger the onset of periodic episodes of shakiness and lethargy.
At the Vet's Office
If your vet determines that your dog may be suffering from a problem with the liver, he or she may decide to run a battery of tests. An x-ray along with a complete blood count and a blood chemistry profile is a good starting point. However, the numbers of liver enzymes only provide information about whether the liver is damaged or not and will not provide information pertaining how well the liver is functioning.
Diagnosing liver problems such as a portosystemic shunt requires a specific test that is known as a fasted bile acid test. This blood test is done when the dog is on an empty stomach (usually for 12-18 hours) and then it is done again after feeding the dog. High levels of bile acids are indicative that the liver's functionality has decreased.
A bile acid test can be followed by an ultrasound to look for the presence of a shunt, or a portogram study which uses a dye which is injected into a vessel of the liver and x-rays are then taken to follow the path of the dye.
Based on the findings, the vet may recommend a low protein diet (usually a prescription diet such as L/D made by Hills) along with medications that are meant to increase the dog's tolerance to protein by binding it, such as lactulose. Antibiotics like neomycin may also be prescribed since they alter the bacterial metabolism in the dog's digestive tract, considering that bacteria excrete ammonia as a byproduct.
It's helpful to also add fiber such as bran or plain canned pumpkin along with thiamine and vitamin K, explains veterinarian Dr. Salkin. Your vet may also suggest giving your dog intravenous fluids so to help expedite the excretion of ammonia through the kidneys.