|Neel, James - Jim|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2005
Publication Date: 12/28/2005
Citation: Clapham, W.M., Foster, J.G., Neel, J.P., Fedders, J.M. 2005. Fatty acid composition of traditional and novel forages. Journal of Agricultural and Food Chemistry. 53:10068-10073.
Interpretive Summary: Recent research has shown the importance of certain fatty acids in our diet that are associated with reduced incidence of certain cancers and vascular diseases. These fatty acids are the conjugated linoleic acids, known commonly as the CLAs. Meat and milk from grazing ruminants are some of the most important sources of CLAs in our diet. Studies have shown that when cattle diets are supplemented with oils high in linolenic and linoleic fatty acids, more CLA is accumulated in the meat or milk. We conducted a study of thirteen forages, both traditional and novel, to determine the levels of fatty acids in the plant material over three harvests. Linolenic, linoleic and palmitic were the dominant fatty acids. Linolenic contributed between 43 and 72%, linoleic 8 to 22% and palmitic 12 to 25% of the total fatty acids depending on plant material and harvest time. The fatty acid levels were markedly different among the different forages. Galega and the grasses in the study had the highest levels of linolenic acid. Levels of linolenic acid were lower in turnip, rape, plantain, white clover and borage. Fatty acid levels declined with later harvests in all of the forages. These data suggest that we could manipulate the intake of fatty acids by grazing cattle through forage species selection and management.
Technical Abstract: Managing the fatty acid composition of grazing ruminant diets could lead to meat and milk products that have higher CLA concentrations, but forage fatty acid dynamics must be more fully understood for a range of forages before grazing systems can be specified. We determined the fatty acid profiles of 13 different forages, including grasses, legumes and forbs, grown under greenhouse conditions. Three separate harvests, at 3-week intervals, were made of each plant material. Alpha-linolenic [C18:3, 7.0-38.4 mg g dry matter (DM)], linoleic (C18:2, 2.0-10.3 mg g DM) and palmitic (C16:0, 2.6-7.5 mg g DM) acids were the most abundant fatty acids in all species at each harvest, together representing approximately 94% of the fatty acids present. Concentrations of fatty acids declined as plants developed, but the fractional contribution of each fatty acid to total fatty acids remained relatively stable over time. A ternary plot was created using concentrations for a-linolenic, a-linoleic and palmitic acids to illustrate species differences. Grasses (orchardgrass, ryegrass, tall fescue, and triticale) had a uniform composition (70% C18:3, 15% C18:2, 15% C16:0). In most forbs (rape, plantain, chicory and white clover), C18:3 was less than 70% and C18:2 was greater than 17%; borage had 50% C18:3 and 26% C18:2. All forages collected during the second harvest would provide adequate crude protein and energy balance for forage-finishing beef cattle. Forage fatty acid profiles indicate animal fat CLA content could be impacted by the forage species consumed during the finishing period.