Are comprised of a straight hydrocarbon chain terminating with a carboxylic acid group. Fatty acids are components of more complex lipids (commonly called fat). They are of vital importance as an energy nutrient, but also in the production of bioactive compounds. Two fatty acids are considered essential, meaning they must be consumed through the diet, which is otherwise stated as – the animal does not have the ability to synthesize these fatty acids. The essential fatty acids are linoleic (18:2 n-6) and alpha-linolenic acid (18:3 n-3), an omega-6 and omega-3 fatty acid, respectively.
The essential status of the fatty acids linoleic acid and alpha-linolenic acid is due to the fact that some of the longer, more highly unsaturated fatty acids into which they can be converted are necessary 1) for the formation of cell membranes and 2) as precursors of compounds called eicosanoids.
There are a few different nomenclatures for fatty acids, but the most common designation is given as: x:y n-z where (x=number of carbon atoms):(y=number of double bonds) (n- z=the first carbon where double bond exists counted from the methyl, or omega end of the chain). For example, alpha-linolenic acid would be expressed as 18:3 n-3, meaning it is 18 carbons long, with 3 double bonds, starting at the third carbon when counting from the omega end.
The length of the chains of fatty acids found in foods and body tissues ranges from 4 to about 24 carbon atoms. They may be saturated (SFA), monosaturated (MUFA, containing one carbon-carbon double bond), or polyunsaturated (PUFA, having two or more carbon-carbon double bonds).
Nutritional interest in the n-3 (omega-3) fatty acids has escalated enormously because of their reported hypolipidemic and antithrombotic effects, which is of particular interest for horses with insulin resistance. Furthermore, immune system function is impacted by fatty acid composition of the diet. In very general terms, the omega-6 fatty acids are considered to be pro-inflammatory and the omega-3 anti-inflammatory based on their respective roles in prostaglandin synthesis.