It is very well known that all animals require glucose to run metabolism. Carbohydrate metabolism is main energy source for all living animals. 

The dogs are capable of meeting their energy source from carbohydrate metabolism. The need for more carbohydrates during gestation and lactation has been debated before. Pregnant dogs need more glucose to support the growh of fetus. lactating dogs also require more glucose to produce lactose. The same is also assumed by female cats. 

Early studies for pregnant dogs showed that a varying amount of carbohydrate was given. The insufficient carbohydrate in the food caused the mothers to become hypoglycemic, ketotic, and deficient in the amino acid alanine in their blood. The end result was unfortunately a 63% successful pregnancy rate for the pregnant dogs with no carbohydrate in the diet. 

However, other studies refute this data. Alanine, glycine, and serine are the principal gluconeogenic amino acids for dogs. In other words, these amino acids allow the body to produce glucose. Insufficient amounts of it cause insufficient amounts of glucose if the dogs are fed a protein-rich diet. 

These results were further supported by another study that specified the required protein levels during a carbohydrate deficiency. Dogs require significantly more protein per metabolic body weight during a carbohydrate-free state. Therefore, we can come to the point that glucose is an essential nutrient for the body. We also should not forget that dogs and cats can produce enough glucose when given enough protein sources. 

For cats, things can be somewhat different. In the blog "Nutritional Idiosyncrasies of the Cat," we went over how a cat's digestive system is different. Cats are strictly carnivores. Carnivorous animals continuously engage in gluconeogenesis right after they eat. Their bodies locked onto gluconeogenesis, whether they were fasting or resting after a big meal. This claim is backed by the PEPCK enzyme level in the liver.  PEPCK is responsible for converting gluconeogenic amino acids to glucose. 

Because they are obligate carnivores, cats have special metabolic adaptations that enable them to use the gluconeogenic catabolism of amino acids to consistently deliver glucose and maintain normal blood glucose levels. 

Regarding all of the above, what will we consider for commercial pet food? Commercial dry pet food contains around 60 percent carbohydrates, and wet pet food may contain between 0% and 30 percent. Both cats and dogs can digest carbohydrates, in this case mainly starch, with the pancreatic amylase enzyme. Dogs have higher levels of this enzyme, but cats also have sufficient. Carbohydrate is a must-have for the extrusion process for dry pet food. Because of the starch, the kibble is expanded after the extrusion. It is made like cheese puffs but with a different recipe with protein and other ingredients. 

Cats and dogs can digest cooked starches, but lactose and dairy product digestion decreases with age. Kittens can digest lactose with an increased lactase enzyme in their intestine. Mature cats may lack or have insufficient amounts; therefore, mature cats can experience diarrhea from lactose. Similarly, very young animals have low levels of the sucrase enzyme. Feeding sucrose (table sugar) solutions is not recommended for very young cats and dogs. 

Fibers are also important. Nonfermentable fibers can facilitate peristalsis. This type of fiber can also help control hairballs in cats. Fermentable fibers can be used by colonic bacteria to produce short-chain fatty acids. These acids are important energy sources for colonocytes and mucosal cells of the colon.