Carbohydrates

Carbohydrates normally serve as the most important source of bodily energy. (Carbohydrates provide approximately 4 kcal per gram.) The utilizable ones are found mostly as sugars and starches. In animal feeds, corn is often used as an ingredient because it is rich in carbohydrates. Crude fiber, or roughage, is also considered to be a source of carbohydrates, but its precise usefulness to an animal depends upon the particular food the fiber comes from and how well the animal is able to digest that fiber. Ruminant animals have microorganisms to aid in fiber digestion; monogastric animals are less efficient in digesting fiber, but may need fiber for other purposes.

For analytical purposes, the level of carbohydrates in a product is determined by analyzing for moisture, fat, protein, crude fiber and ash, then assuming that the carbohydrates are what is left over. This portion is called the nitrogen-free extract, or NFE. More precise analysis is difficult because there are so many different compounds that make up the carbohydrate category. The product fact sheets for the LabDiet^® products include a break-out of some carbohydrate sources. The levels of starch and four of the sugars (sucrose, glucose, fructose and lactose) are given. When nourishment is withheld from the body, energy is derived from the carbohydrate glycogen.

Carbohydrates in Purified Diets

Typically, the sources of carbohydrates in purified diets are sucrose (“table sugar,” a simple carbohydrate metabolized quickly) and dextrin (“cornstarch,” a complex carbohydrate metabolized far more slowly). Depending upon the research purpose of the diet, the ratio of these carbohydrates will vary.

For example, certain diets have been formulated to provide all the carbs from sucrose, with a matching diet obtaining all the carbs from cornstarch in order to study the diabetogenic effect of simple and complex carbohydrates.