for more information
phone: 850-971-5806 or 850-948-6202
email: deeprootsmeat@yahoo.com
This Website is Maintained Naturally with Alternative Energy
Kathy's Web Design - Copyright 2009 - All Rights Reserved by Domain Owner
GOOGLE         YAHOO          BING
Ranching the Natural Way - Caring for our Environment
Proceedings from the National Grass-fed Beef Conference, Feb. 2007, PA

Fatty Acid Profiles in Grass-Fed Beef and What They Mean

Susan Duckett1 and Enrique Pavan2
1Clemson University, Clemson, SC and 2INTA, Balcarce, Argentina
Home:
Fat and cholesterol are required by the human body to function everyday. Cholesterol is found in foods of animal origin and serves as a precursor to all other steroids in the body including corticosteroids, sex hormones and vitamin D. Essential fatty acids cannot be synthesized in the human body and give rise to eicosanoids including prostaglandins, thromboxanes and leukotrienes. So what’s problem with fat and cholesterol in our diet? Cholesterol levels in the bloodstream are important. High cholesterol levels increase the risk for heart disease. Cholesterol can buildup in plaques inside arteries, a process called atherosclerosis, and block blood flow to the heart. This limits flow of nutrients and oxygen and can lead to heart attack or stroke if the plaques rupture. The National Cholesterol Education Program (NCEP) recommends for adults age 20 years and greater that total cholesterol levels be less than 200 mg per deciliter.
Dietary cholesterol consumption has little effect on blood cholesterol levels. The reason for this is due to the fact that dietary cholesterol contributes only about 25% of total cholesterol, whereas the human body produces about 75% of total blood cholesterol. A 150 mg reduction (from current U.S. average 450 mg/d to recommended level 300 mg/d) in dietary cholesterol intake will reduce blood cholesterol levels about 2% (i.e. blood cholesterol of 240 mg/dL will have a 4.8 mg/dL reduction). In contrast, medications called statins (i.e. Lipitor) reduce blood cholesterol levels by 40% (240 mg/dL x 40% = 96 mg/dL) through reductions in cholesterol synthesis.
One of the most important factors in regulating blood cholesterol levels is the type of dietary fat consumed. The type of fat consumed influences the lipoproteins that carry cholesterol in the blood. Two main lipoproteins are Low-density lipoprotein (LDL) and High-density lipoprotein (HDL). Low-density lipoprotein carries cholesterol from the liver to the rest of the body. If there is too much LDL, it can be deposited in the arteries and therefore referred to as “Bad” cholesterol. High-density lipoprotein carries cholesterol from the blood back to the liver for elimination from the body and is therefore considered “Good” cholesterol. The NCEP recommends that HDL cholesterol levels greater than 40 mg/dL and LDL cholesterol levels less than 100 mg/dL. Because the type of dietary fat consumed directly influences the levels of LDL and HDL cholesterol in the blood, one must alter the type of dietary fat intake in order to make significant changes in blood cholesterol levels.
Fat and Cholesterol
Fatty acids are characterized and typed by the number of carbons, number of double bonds, double bond location and configuration. The main types of fatty acids are: saturated, trans, monounsaturated, and polyunsaturated. Saturated fatty acids (SFA) raise total blood cholesterol levels; however, not all saturated fats are equal. One saturated fat called stearic acid (C18:0) does not elevate blood LDL cholesterol level and is considered neutral. Consumption of diets rich in shorter-chain, saturated fatty acids like lauric (C12:0), myristic (C14:0), and palmitic (C16:0) acids increase blood LDL-cholesterol and are considered cholesterol-elevating or hypercholesterolemic.
Trans fatty acids are receiving attention lately and are even being banned from the menu in some U.S. cities. Trans fatty acids are produced during the hydrogenation of unsaturated vegetable oils (40-60% of total fatty acids as trans) and are found in margarines or processed products that list partially hydrogenated vegetable oil in the ingredient list. This process of hydrogenation increases shelf life of the oil by reducing polyunsaturated fatty acid levels. In this process, many short chain trans fatty acids are produced (trans bonds in 6-16 position) and consumption of these artificial trans fatty acids increases bad (LDL) cholesterol and decreases good (HDL) cholesterol. Results from the Nurses’ Health Study found that women who consumed 4 teaspoons of margarine containing artificial trans fat had a 50% greater risk of heart disease than women who ate margarine only rarely (Willet et al., 1993). Mensink and Katan (1990) compared the effects of a trans or saturated fatty acid rich diet in humans and demonstrated that trans fats have a more negative effect on serum cholesterol levels than saturated fats. Clifton et al. (2004) reported high correlations (r = 0.66) between dietary trans fat intake from margarine and level of trans fat in adipose tissue, and that the level of trans fat in adipose tissue was associated with increased risk of coronary artery disease.
Ruminant animal products (beef, lamb, butter, ice cream, cheese, etc.) also contain low levels (1-8% of total fatty acids as trans) of trans fatty acids. These trans fatty acids are produced naturally during the biohydrogenation of unsaturated fatty acids in the rumen. These naturally produced trans fatty acids (trans bonds predominately in 9-11 position) are receiving distinction from their artificial counterparts present in partially hydrogenated vegetable oil. One reason for this is that the major trans fatty acid in most ruminant products is vaccenic acid (C18:1 t11; VA), which can be converted to conjugated linoleic acid (CLA) and has cancer-fighting properties. Turpeinen et al. (2002) reported that on average 19% of dietary VA is converted to CLA, cis-9 trans-11 isomer, in humans. As a result, it has been suggested that dietary consequences of VA in beef products should be considered separately from other trans fatty acids (Lock et al., 2005). Monounsaturated fatty acids (MUFA) contain one, cis double bond. Oleic acid (C18:1 c9), a MUFA, is the predominant fatty acid in ruminant animal products and comprises from 30-50% of the total fatty acids present. Consumption of diets rich in monounsaturated fatty acids increases good (HDL) and lowers bad (LDL) cholesterol levels (Mensink and Katan, 1989). Canola and olive oils contain predominately MUFA at levels of 58% and 72% of total fatty acids, respectively.
Polyunsaturated fatty acids (PUFA) are subdivided into two categories, omega-6 and omega-3, based on location of the double bonds in the fatty acid chain. Omega-6 fatty acids are common in grains and vegetable oils. Omega-3 fatty acids are common in plant lipids and fish oils. Diets containing omega-6 or omega-3 fatty acids lower blood total and LDL cholesterol; however, omega-6 PUFA also tend to lower HDL cholesterol (Mensink and Katan, 1989). Consumption of diets high in omega-3 fatty acids is associated with reduced risk of heart disease, stroke and cancer (Kris-Etherton et al., 2002). Currently, Americans consume greater amounts of omega-6 PUFA than omega-3 PUFA, which has dramatically altered the omega-6 to omega-3 ration in the human diet. Health professionals recommend that we consume a diet with a more balanced ratio (< 4:1) of omega-6 to omega-3 PUFA. The World Health Organization recommends a daily intake of 1.1 g/d of omega-3 fatty acids with approximately 0.8 g/d of linolenic acid and 0.3 g/d of EPA and DHA.
Cancer-Fighting Compounds
In cattle, dietary unsaturated fatty acids are biohydrogenated (BH) in the rumen to saturated end products. However, this process of ruminal BH is sometimes incomplete yielding various trans-octadecenoic acids and conjugated linoleic acid (CLA) isomers. Conjugated linoleic acid, specifically the cis-9 trans-11 isomer, has been shown to possess anticarcinogenic effects (Ha et al., 1987). Evidence from in vitro and rodent experiments suggests that a minimum dietary level of 0.5% CLA cis-9 trans-11 isomer is needed to help reduce the incidence of cancer (Ip et al., 1994). If the average American adult consumes a 2200 kcal diet with about 40% of calories from fat (assuming 60% diet digestibility), we estimate that the average dietary intake for adults would be about 600 g per d and the level of CLA needed would be 300 mg of CLA cis-9 trans-11 per d. Beef products in the human diet are reported to contribute about 25% of total dietary CLA with dairy products as the primary sources (Ritzenthaler et al., 2001). Research now shows that over 80% of the CLA present in milk (Griinari et al., 2000) and beef (Gillis et al., 2003) is formed by desaturation of VA to CLA cis-9 trans-11 in mammary and adipose tissues. In humans, estimates are that about 19% of VA from enriched butter is desaturated to CLA cis-9 trans-11 isomer with ranges from 0 to 30% (Turpeinen et al., 2002). Thus, levels of both CLA and VA in beef products are important in determining the potential levels of CLA in humans.
Grass-fed Beef
Fatty acid composition as a percentage of total fatty acids of beef muscle from concentrate-finished versus grass-finished beef is shown in Table 1. The results are from the Appalachian Pasture Beef Systems Project and data was collected on 200 Angus-cross steers for a period of three years (Sonon et al., 2005). Steers (12 mo of age) were finished on either concentrate/corn silage diet in the feedlot or on pasture for 150 d. Steers on pasture treatment grazed “naturalized” pasture, which consisted of a mix of bluegrass, orchardgrass, endophyte-free tall fescue and white clover for majority of the time and hay meadow regrowth and triticale for short periods of time Steers were fed to an equal age in order to minimize confounding due to animal age or environmental factors. The percentage of SFA, odd-chain, or omega-6 PUFA did not differ between concentrate and grass finished beef. Monounsaturated fatty acid percentage was greater for concentrate than grass-finished. Omega-3 PUFA percentage was greater for grass- than concentrate-finished. This resulted in a lower, more desirable, ratio of omega-6 to omega-3 fatty acids in grass-finished beef (1.65) compared to concentrate-finished beef (4.84). The percentage of CLA, cis-9 trans-11 isomer, was greater for grass- than concentrate-finished. Vaccenic acid percentage was also greater for grass- than concentrate-finished beef. Fatty acid content (g per 3 oz. serving, broiled) of beef muscle from concentrate-finished versus grass-finished beef is shown in Table 2. Grass-finished beef contains half (2.1 g/serving) of total fatty acids compared to concentrate-finished beef (4.2 g/serving). Due to these differences in total fatty acid content of beef, the fatty acid composition on a per serving basis (3 oz. broiled) is also changed. Saturated fat content was lower for grass-finished than concentrate-finished beef. The amount of odd-chain and MUFA per serving was lower for grass-finished than concentrate-finished beef. Omega-6 PUFA content was lower and omega-3 PUFA content was higher for grass-finished than concentrate-finished beef. Because the percentage of CLA, cis-9 trans-11 isomer, in grass-fed was twice as high but total fatty acid content was half that of concentrate-finished, the amount of CLA per serving is similar among concentrate- and grass-finished beef. However, the amount of VA is 4-fold higher for grass-fed beef and this can be desaturated to CLA in the human body. Cholesterol content per serving did not differ among finishing systems. Overall, grass-fed beef produced from animals of the same age as concentrate-fed beef will have lower total, saturated, and monounsaturated fatty acid content with greater omega-3 fatty acid and vaccenic acid content.
Forage Species
The fatty acid composition of beef produced from finishing on various forage species versus concentrate finished beef is shown in Table 3. These results are from the Appalachian Pasture Based Beef Systems Project and represent 47 Angus-cross steers finished in fall of 2005 (Duckett et al., 2006). This project is on-going and additional data will be collected for another two-year period. Thirty-six steers (12 mo of age) grazed native pastures consisting of bluegrass and white clover for 110 d and then were randomly allotted to grazing paddocks containing alfalfa, pearl millet or native pastures. Steers grazed these paddocks containing the three forage species for an additional 40 d. Twelve steers were also finished on concentrate/corn silage diet for 150 d.
The percentage of SFA was greater for Native and Alfalfa-finished than concentrate-finished beef. Monounsaturated fatty acid percentage was greater for concentrate than forage finished, regardless of forage species. Omega-3 PUFA, CLA, and VA fatty acid percentages were greater for forage finished, regardless of forage species, than concentrate-finished. Ratio of omega-6 to omega-3 fatty acids was lower (1.3), more desirable for forage finished, regardless of forage species, compared to concentrate finished (6.4). Total fatty acid content was lower (2.5 g/serving) for forage-finished, regardless of forage species, compared to concentrate finished (6.0 g/serving). Cholesterol content did not differ among finishing systems. Overall, finishing on different forages resulted in minor changes in fatty acid composition.
Supplementation on Grass
Fatty acid composition of beef finished on endophyte-free tall fescue pasture only (PAST), pasture + 0.52% of BW (DM basis) corn grain (PAST-CORN) or pasture + 0.1% corn oil + 0.42% soybean hulls (PAST-OIL), compared to high concentrate grain finishing (15% grass hay; 85% concentrate; CONC) are shown in Table 4. Twenty-eight Angus steers were randomly allotted to three pasture treatments with or without supplementation for 197 d (Pavan and Duckett, 2006). Concentrate finished steers were allowed to graze endophyte-free tall fescue for 105 d and then were finished on a high concentrate diet for 92 d. Steers were slaughtered at a similar age endpoint to minimize confounding due to animal age or environment.
Saturated fatty acid percentage was higher for PAST-OIL and CONC than PAST. Monounsaturated fatty acid percentage was highest for CONC and lowest for PAST and PAST-OIL. Oil supplementation on pasture (PAST-OIL) increased the omega-6 fatty acid percentage in beef muscle to 8.8%, levels greater than PAST or PAST-CORN. Omega-6 fatty acid percentage was also greater for PAST and PAST-CORN than CONC. Omega-3 PUFA percentage was highest for PAST and lowest for CONC. Corn grain or oil supplementation lowered the percentages of omega-3 PUFA compared to PAST but levels were greater than CONC. The ratio of omega-6 to omega-3 ratio was lowest for PAST. Supplementation of corn grain or corn oil on pasture resulted in higher omega-6 to omega-3 ratios. Conjugated linoleic acid and VA concentrations were highest for PAST-OIL and lowest for CONC. Supplementation with corn grain on pasture lowered CLA and VA percentages compared to PAST but levels were greater than CONC. Total fatty acid content was greater for CONC than PAST-OIL, which were both greater than PAST or PAST-CORN. Cholesterol content did not differ among dietary treatments. Overall, oil supplementation on pasture increased CLA and VA concentrations; however, oil supplementation also increased omega-6 PUFA resulting in a high ratio of omega-6 to omega-3 PUFA. Corn grain supplementation on pasture reduced levels of CLA, VA and omega-3 PUFA compared to pasture only.
Summary
Grass-fed beef contains greater concentrations of conjugated linoleic acid, vaccenic acid, and omega-3 PUFA than concentrate-fed beef. Grass-fed beef also contains lower total fat content when finished to similar time endpoints. This reduction in total fat content results in lower saturated fat, monounsaturated fat, and omega-6 PUFA content in one 3 oz. serving of grass-fed beef. On a per serving basis, conjugated linoleic acid content is similar among grass-fed and concentrate-fed beef but vaccenic acid, which can be converted to conjugated linoleic acid, content is 4-fold greater for grass-fed. Omega-3 PUFA content per serving is higher; however, levels are low (45 mg/serving) compared to other sources of omega-3 PUFA (chinook salmon, 1821 mg/serving; bluefin tuna, 1415 mg/serving). Finishing cattle on various forage species appears to results in minor changes in fatty acid composition. Supplementation on pasture alters fatty acid composition depending on the type and amount of supplement offered.
References
Clifton, P. M. et al. 2004. Trans fatty acids in adipose tissue and the food supply are associated with Myocardial Infarction. J. Nutr. 134:874-879.
Duckett, S. K. et al. 2006. Effects of forage type on longissimus muscle fatty acid composition in forage-finished beef. J. Anim. Sci. 84(Suppl. 1):387.
Gillis, M. H. et al. 2003. Effect of rumen-protected conjugated linoleic acid (CLA) or linoleic acid on leptin and CLA content of bovine adipose depots. J. Anim. Sci. 81(Suppl. 2):12 (Abstr.).
Griinari, M., B. A. Corl, S. H. Lacy, P. Y. Chouinard, K. V. V. Nurmela and D. E. Bauman. 2000. Coonjugated linoleic acid is synthesized endogenously in lactating dairy cows by D9 desaturase. J. Nutr. 130:2285-2291.
Ha, Y. L. et al. 1987. Anticarcinogens from fried ground beef: heat altered derivatives of linoleic acid. Carcinogenesis 12:1881-1887. Ip, C., M. Singh, H. J. Thompson, and J. A. Scimeca. 1994. Conjugated linoleic acid suppresses mammary carcinogenesis and proliferative activity of the mammary gland in the rat. Cancer Res., 54:1212-1215.
Kris-Etherton, P. M. et al. 2002. Fish consumption, fish oil, omega-3 fatty acids and cardiovascular disease. Circulation 106:2747-2757.
Lock, A. L. et al. 2005. Butter naturally enriched in conjugated linoleic acid and vaccenic acid alters tissue fatty acids and improves the plasma lipoprotein profile in cholesterol-fed hamsters. J. Nutr. 135:1934-1939.
Mensink, R. P. and M. B. Katan. 1989. Effect of a diet enriched with monounsaturated or polyunsaturated fatty acids on levels of low-density and high-density lipoprotein cholesterol in healthy women and men. New Engl. J. Med. 321:436-441.
Mensink, R. P. and M. B. Katan. 1990. Effect of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects. N. Engl. J. Med. 323(7):439-445.
Pavan, E. and S. K. Duckett. 2006. Corn oil or corn grain supplementation to forage-finished steers. II. Effects on s.c. and i.m. fatty acid composition. J. Anim. Sci. 84(Suppl. 1):388 Ritzenthaler, K. L. et al. 2001. Estimation of Conjugated Linoleic Acid Intake by Written Dietary Assessment Methodologies Underestimates Actual Intake Evaluated by Food Duplicate Methodology. J. Nutr. 131:1548-1554.
Sonon, R. et al. 2005. Effects of winter stocker growth rate and finishing diet on beef longissimus fatty acid composition. J. Anim. Sci. 83(Suppl. 1):204.
Turpeinen, A. M., M. Mutanen, A. Antti, I. Salminen, S. Basu, D. L. Palmquist, and J. M. Griinari. 2002. Bioconversion of vaccenic acid to conjugated linoleic acid in humans. Am. J. Clin. Nutr. 75:504-510.
Willet, W. C. et al. 1993. Intake of trans fatty acid and risk of coronary heart disease among women. Lancet 341:581-585.
Table 1. Fatty acid composition (% of total fatty acids) of ribeye steaks from concentrate- or grass-finished beef (Sonon et al., 2005).


Fatty acid, % of total fatty acidsConcentrate-finishedGrass-finished
n                                                                 103                           95
Saturated                                                    43.44                        44.24
Odd-Chain                                                  1.79                         1.74
Monounsaturated                                       41.99a                      33.97b
Polyunsaturated, omega-6                           3.71                         3.77
Polyunsaturated, omega-3                           0.79b                       2.32a
Ratio omega-6:omega-3                               4.84a                       1.65b
Conjugated Linoleic Acid, cis-9 trans-11    0.36a                       0.78b
Vaccenic acid                                              0.32a                       3.34b
abMeans in the same row with uncommon superscripts differ (P < 0.05).

Table 2. Fatty acid content (g/3 oz. serving, broiled) of ribeye steaks from grain-or grass-finished beef.


Fatty acid, g/3 oz. serving, broiledConcentrate-finishedGrass-finished
n                                                            103                           95
Total fatty acid content                          4.16a                        2.13b
Saturated                                               1.82a                        0.95b
Odd-Chain                                             0.073a                      0.037b
Monounsaturated                                  1.76a                         0.73b
Polyunsaturated, omega-6                     0.142a                       0.074b
Polyunsaturated, omega-3                     0.032b                       0.045a
Conjugated linoleic acid, cis-9 trans-11        0.016                         0.017
Vaccenic acid                                         0.014a                       0.072b

Cholesterol, mg/3 oz. serving                  64.17                        65.29
abMeans in the same row with uncommon superscripts differ (P < 0.05).

Table 3. Fatty acid composition of beef finished on three different forages species or a high concentrate diet (Duckett et al., 2006).


Fatty acid, % of total                              Native  Alfalfa  Pearl Millet  Concentrate
n                                                             12        12          12      11
Saturated                                             46.60a 47.42a   45.72ab 44.16b
Odd-Chain                                             1.55     1.51      1.47      1.59
Monounsaturated                                 35.24b 35.91b  37.18b   44.68a
Polyunsaturated, omega-6                      3.43     3.66     3.39       3.14
Polyunsaturated, omega-3                      2.55a   2.81a   2.56a     0.56b
Ratio omega-6:omega-3                         1.34b   1.29b   1.32b     6.37a
Conjugated linoleic acid, cis-9 trans-11 0.67a   0.65a   0.68a     0.26b
Vaccenic acid                                         3.15a   2.83a   2.82a     0.12b

Total fatty acids, g/serving                     2.54     2.66      2.22       6.03
Cholesterol, mg/serving                      66.21    62.78    64.54     64.26
abMeans in the same row with uncommon superscripts differ (P < 0.05).



Table 4. Fatty acid composition of beef finished on pasture with or without corn grain or corn oil supplementation compared to concentrate-finished beef (Pavan and Duckett, 2006).


                                        PasturePasture + CornPasture + OilConcentrate Rate
n                                               7                 7                      7               7
Saturated                               39.69b        41.38ab            42.34a      42.76a
Odd-Chain                              1.61            1.33                  1.15         1.74
Monounsaturated                  33.25c        36.42b              30.65c      43.04a
Polyunsaturated, omega-6       6.22b         6.53b                8.78a        3.54c
Polyunsaturated, omega-3       4.16a         2.61b                1.79c        1.08d
Ratio omega-6:omega-3          1.49d         2.49c                 4.95a       3.27b
Conjugated linoleic acid,
cis-9 trans-11                         0.92b         0.62c                 1.14a       0.36d
Vaccenic acid                         2.83b         2.04c                 5.40a       0.95d
Total fatty acids, g/serving     1.73c          1.95c                2.52b       4.62a
Cholesterol, mg/serving                 59.98        60.02                 59.74       63.70

abcdMeans in the same row with uncommon superscripts differ (P < 0.05).
   Troy Platt 850-948-6202             Harold Platt 850-971-5806
Farm Address:
11061 W. US 90
Greenville, Florida 32331
Billing Address:
701 NE Chaparral Way
Madison, Florida 32340