Carbohydrates

These act as a third source of dietary energy. In addition to being cheap they also act as binding agents for feed and increase the palatability of proprietary diets.

Carbohydrates are divided into two main groups - the sugars and the non-sugars. The former includes such things as glucose, sucrose and lactose whilst the latter contains the more complex materials such as starch and various polysaccharides. From a fish feed aspect, glucose and starch are of importance. As carnivorous fish, salmonids lack sufficient quantities of the enzymes necessary for efficient digestion and metabolism of most carbohydrates. Levels in proprietary diets are consequently low, carbohydrates giving way to increases in other components such as oil. For herbivorous fish, the carbohydrate content of man-made diets is correspondingly higher.