Understanding Hypoglycemia in Hunting and Field Trial Dogs
Glucose (blood sugar) is the major source of metabolic energy in our canine athletes. The brain and red blood cells depend on glucose as their sole source of energy whereas many of the other body tissues can utilize fats or proteins as an energy source. Glucose concentrations are closely regulated in the blood stream to maintain a constant ready and healthy state. Normal glucose levels in the dog are between 70 and 140 mg/dL. Blood sugar levels are determined by intake of foods and production within the body. Production within the body can come from the utilization of proteins, amino acids, stored fats and glycogen (stored glucose) reserves in the liver and skeletal muscles.
The canine pancreas plays a decisive role in glucose metabolism by producing the hormones insulin and glucagon in its alpha and beta cells. These hormones work synergistically (insulin from beta cells decreases glucose levels while glucagon from alpha cells increases blood glucose levels) to keep the sugar levels in the blood stream between the normal range of 70 to 140 mg/dL. Insulin’s role is to get glucose into the cells for energy and for storage of the sugar in the form of glycogen and fat whereas the role of glucagon is to remobilize or release those storages for energy during times of hunger or during stressful exercise. The storage form of glucose is glycogen and it is stored mainly in the liver and skeletal muscles of our dogs.
Hunting dog hypoglycemia occurs when a canine athlete exerts itself in strenuous exercise thereby rapidly depleting their blood sugar (glucose) before their reserves can be remobilized or released from glycogen storages from the muscle and liver resulting in extreme lethargy, muscle weakness and twitching, incoordination, trembling, dilated pupils and in most instances seizures (remember that the brain and red blood cells depend strictly on glucose as their energy source).
Diagnosis can be tricky because the dog’s blood sugar will return to normal before a blood sample can be evaluated in a clinical setting. Diagnosis is generally made by history associated with the episodes and rule out of other diseases such as Addison’s Disease, Epilepsy, Exercise-Induced Collapse (EIC is a genetic disease seen mostly in Labs), Insulinomas (beta cell tumors of the pancreas) or other metabolic/endocrine disorders. A dog experiencing any of these clinical signs should have a thorough examination and blood work done by your veterinarian.
Emergency treatment in the field is to give the affected dog a highly digestible form of glucose on the oral mucous membranes because the enzyme salivary amylase starts to break down starches into rapidly usable sugars. This can come from any source as simple as Karo syrup, jelly/jam, or maple syrup just to name a few. I like a product called Nutri-Cal that is dense in protein, fats and carbohydrates as well as minerals, vitamins and fatty acids. Nutri-Cal can be acquired from any local pet supplier or online at amazon.com. Once the dog has recovered, get them to eat and let them rest comfortably for the remainder of the day. Be careful with excessive sugars in their food because they can trigger a large release of insulin from their pancreas that can drive blood sugars back down into the low range (below 70 mg/dL)
Prevention is the most important component to hunting dog hypoglycemia. The current literature states this is most common in non-conditioned or out of shape dogs but this simply is not the truth. I’ve seen it happen in very well conditioned canine athletes. Carb loading 30 to 60 minutes prior to exercise using complex carbohydrates such as pastas or bread can help but their stomach should not be fully loaded. Feeding these dogs a calorically dense, high energy diet (low carbs and higher protein ~ 30%/fat ~20%ratios ) is a good way to train the mitochondria to utilize fats and proteins and not rely so much on sugars. Other people have tried feeding their dogs 10% of their calculated diet every 2 hours during strenuous exercise with good success. Finally a popular product that has recently surfaced on the market is the maltodextrin products. One source stated that they’ve had great success giving 1 g/kg of body weight (or 0.5 g/pound of body weight) in the am prior to exercise and then repeat 2 to 3 hours after strenuous exercise.