Today's Veterinary Practice

SEP-OCT 2016

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

Issue link: http://todaysveterinarypractice.epubxp.com/i/715668

Contents of this Issue

Navigation

Page 85 of 115

T O day' S Ve T erinary Prac T ice | September/October 2016 | tvpjournal.com ac V n n u T ri T i O n nOT e S Peer r eviewed 84 BASIC PROPERTIES OF FATTY ACIDS Fatty acids are classified as lipids, a larger macronutrient class that serves a structural role and provides energy, among other functions. l ipids include phospholipids and cholesterol as well as fats, oils, and fatty acids. Classification of Fatty Acids The functions of different fatty acids depend on their structure and composition. Fatty acids are classified based on: • l ength of the hydrocarbon chain • n umber of double bonds present in the chain • l ocation of the first double bond relative to the methyl, or omega, end of the hydrocarbon chain (Figure). Fatty acids are considered short-chain (< 8 carbons in length), medium-chain (8–12 carbons), or long- chain (> 12 carbons). The number of carbons in the chain gives the fatty acid different properties in terms of digestion, absorption, and usage. 1 Fatty acids are further defined by the number of double bonds: saturated fats contain no double bonds, monounsaturated fats contain 1 double bond, and polyunsaturated fats contain 2 or more double bonds. Fatty acids with double bonds are called omega-9, omega-6, or omega-3 based on the location of the first double bond from the methyl (omega) end of the hydrocarbon chain. For example, omega-6 fatty acids, often found in animal tissue and in sunflower and safflower oils, have their first double bond between carbons 6 and 7 from the omega end, whereas omega-3 fatty acids, derived from plant and marine sources, have their first double bond between carbons 3 and 4. Essential Fatty Acids d ogs and cats require omega-6 and omega-3 fatty acids in the diet because they cannot produce these essential fatty acids on their own. 1 e ssential fatty acids and their numeric formulas are listed in Table 1. The omega-6 essential fatty acids are linoleic acid ( la , containing 18 carbons with 2 double bonds [18:2]) and arachidonic acid ( aa , 20:4). la is essential for both dogs and cats, whereas aa is essential only for cats. c ats require aa due to the lack of delta-6 desaturase, an enzyme required for endogenous conversion of la to the longer and more unsaturated fatty acid aa . 3 i t is important to note that these omega-6 fatty acids cannot be endogenously produced in sufficient quantities. They must be provided in the diet to prevent signs of deficiency. d eficiency of omega-6 fatty acids can cause skin and coat abnormalities, reproductive problems, and failure to thrive. 1 The omega-3 essential fatty acids are alpha- linolenic acid ( ala , 18:3), eicosapentaenoic acid ( e P a , 20:5), and docosahexaenoic acid ( d H a , 22:6). e P a and d H a are found primarily in marine sources, including fish oil as well as phytoplankton and other marine plants. a s a result of the poor conversion of ala to e P a and d H a , 4-7 the nrc lists dietary requirements for e P a and d H a for both dogs and cats. 8 However, requirements vary among different life stages; for example, growing puppies and kittens require more d H a than adult dogs and cats. Omega-3 fatty acid deficiency may result in neurologic abnormalities, such as decreased visual acuity. 1 Figure. Chemical structure of linoleic acid (18:2, omega-6), with important features noted. Table 1. Essential Fatty Acids with Numeric Formula Commo N N A m E (Abbreviation) Num E ri C Formul A (chain length:double bonds) l o CA tio N o F First d oubl E b o N d (relative to omega end of chain) l inoleic acid (LA) 18:2 Omega-6 Alpha-linolenic acid (ALA) 18:3 Omega-3 Arachidonic acid (AA) 20:4 Omega-6 Eicosapentaenoic acid (EPA) 20:5 Omega-3 d ocosahexaenoic acid (DHA) 22:6 Omega-3

Articles in this issue

Links on this page

Archives of this issue

view archives of Today's Veterinary Practice - SEP-OCT 2016