Fish Nutrition & Feed Technology

Unit 4 - Lipids

4.3.Classification

Lipids may be classified into two basic groups as glycerol based lipids and non-glycerol based lipids, according to the presence or not of the alcohol glycerol. The following gives a bird’s eye view of the classification of lipids.

Lipids are important sources of metabolic energy (ATP) and the energy value of lipid is higher (9.5 kcal/g) when compared to protein (5.6 kcal/g) and carbohydrate (4.1 kcal/g). Thus, dietary lipids may be used to spare the more valuable protein for growth. In particular, free fatty acids derived from triglycerides (fats and oils) are the major aerobic fuel sources for energy metabolism of fish muscle.

Lipids are a source of essential fatty acids, which in turn are essential for the maintenance and integrity of cellular membranes. They are also a source of essential steroids, which in turn perform a wide range of important biological functions (i.e. the sterol cholesterol is involved in the maintenance of membrane systems, for lipid transport, and as a precursor of vitamin D3, the bile acids, and the steroid hormones - androgens, estrogens, adrenal hormones, and corticosteroids).

From a feed technology viewpoint, lipids act as lubricants for the passage of feed through pellet dies, which reduce the dustiness of feeds, and play a role in feed palatability.