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Title: Fatty acid metabolism and deposition in subcutaneous adipose tissue of pasture and feedlot finished cattle

Author
item Fincham, J - Virginia Polytechnic Institution & State University
item Fontenot, Joseph
item Swecker, Jr., William
item Herbein, Joseph
item Neel, James - Jim
item Scaglia, Guillermo
item Clapham, William
item Notter, D - Virginia Polytechnic Institution & State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2009
Publication Date: 7/17/2009
Citation: Guay, J.F., Fontenot, J.P., Swecker, Jr., W.S., Herbein, J.H., Neel, J.P., Scaglia, G., Clapham, W.M. 2009. Fatty acid metabolism and deposition in subcutaneous adipose tissue of pasture and feedlot finished cattle. Journal of Animal Science. doi: 0:jas.2008-1277.

Interpretive Summary: The most common practice of finishing beef cattle in the United States is to feed high-concentrate diets in feedlots. However, beef from such animals is high in fat and saturated fatty acids (SFA), and there is concern among consumers regarding consumption of this meat. The U.S.D.A. recommends that consumption of SFA be limited to less than 10% of caloric intake. Consumption of lean meat and avoidance of "marbled steaks" are recommended. Pasture-finished beef may be a healthier product, as it is lower in SFA, higher in omega-3 (n-3), and lower in omega-6 (n-6) polyunsaturated fatty acids. The objectives of this research were to determine the differences in the fatty acid composition of adipose tissue from pasture-finished versus high-concentrate finished cattle, and to determine the time required for changes in fatty acids to occur. In the high-concentrate diet, linoleic and linolenic acids averaged 57% and 2% of total fatty acids, respectively. The pasture forages contained 9% linoleic acid and 66% linolenic acid. Concentrations of linolenic acid were higher in ruminal fluid, serum, and adipose tissue of the pasture-finished steers, compared to the high-concentrate finished steers. Concentrations of 18:2 cis-9, trans-11 conjugated linoleic acid (CLA), a fatty acid with numerous human health benefits, were higher in adipose tissue of the pasture-finished steers than high-concentrate finished steers. Concentrations of 18:2 cis-9, trans-11 CLA declined in the high-concentrate finished steers from day 0 to day 28 to day 84. In the pasture-finished steers, concentrations in adipose tissue peaked on day 28, and remained high throughout the duration of the study. In the pasture-finished steers, linolenic acid concentrations tended to peak on day 28, and remained high throughout the study. Concentrations of linolenic acid gradually decreased over time in the high-concentrate finished steers. Thus, it appears that only a short time is needed to alter the omega-3 and CLA composition of adipose tissue in cattle finished on pasture.

Technical Abstract: An experiment was conducted to evaluate the effects of pasture finishing versus high-concentrate finishing, over time, on fatty acid metabolism in Angus crossbred (n = 24) steers. Ruminal fluid, serum, and adipose tissue biopsies were obtained on d 0, 28, 84, and 140. Pasture forages and diet ingredient samples were obtained at 14-d intervals to determine nutritive value and fatty acid composition. The high-concentrate diet consisted of corn silage, cracked corn grain, soybean meal, and a vitamin and mineral supplement. The pasture-finished steers grazed sequentially on triticale (×Triticosecale rimpaui)/annual ryegrass (Lolium multiflorum), alfalfa (Medicago sativa)/orchardgrass (Dactylis glomerata), and a cool-season grass/legume mixture. In the high-concentrate diet, linoleic and linolenic acids averaged 57% and 2% of total fatty acids. The pasture forages contained 9% linoleic and 66% linolenic acids. Concentrations of linolenic acid were higher (P < 0.05) in ruminal fluid, serum, and adipose tissue of the pasture-finished steers, compared to the high-concentrate finished steers. Concentrations of 18:2 cis-9, trans-11 conjugated linoleic acid (CLA), a fatty acid with numerous human health benefits, were higher (P < 0.05) in adipose tissue of the pasture-finished steers than high-concentrate finished steers. Concentrations of 18:2 cis-9, trans-11 CLA declined (P < 0.05) in the high-concentrate finished steers from day 0 to day 28 to day 84. In the pasture-finished steers, concentrations in adipose tissue peaked (P < 0.05) on day 28, and remained high throughout the duration of the study. In the pasture-finished steers, linolenic acid concentrations tended to peak (P = 0.06) on day 28, and remained high throughout the study. Concentrations of linolenic acid gradually decreased (P < 0.05) over time in the high-concentrate finished steers. Thus, it appears that only a short time is needed to alter the omega-3 and CLA composition of adipose tissue in cattle finished on pasture.