Effects of conventional and grass-feeding systems on the nutrient composition of beef1

Abstract

The objectives of this study were to determine the nutrient composition of grass-fed beef in the United States for inclusion in the USDA National Nutrient Database for Standard Reference, and to compare the fatty acid composition of grass-fed and conventionally fed (control) beef. Ground beef (GB) and strip steaks (SS) were collected on 3 separate occasions from 15 grass-fed beef producers that represented 13 different states, whereas control beef samples were collected from 3 regions (Ohio, South Dakota, and Texas) of the United States on 3 separate occasions. Concentrations of minerals, choline, vitamin B(12), and thiamine were determined for grass-fed beef samples. Grass-fed GB samples had less Mg, P, and K (P < 0.05), and more Na, Zn, and vitamin B(12) (P < 0.05) than SS samples. Fat color, marbling, and pH were assessed for grass-fed and control SS. Subjective evaluation of the SS indicated that grass-fed beef had fat that was more yellow in color than control beef. Percentages of total fat, total cholesterol, and fatty acids along with trans fatty acids and CLA were determined for grass-fed and control SS and GB. Grass-fed SS had less total fat than control SS (P = 0.001), but both grass-fed and control SS were considered lean, because their total fat content was 4.3% or less. For both GB and SS, grass-fed beef had significantly less (P = 0.001 and P = 0.023, respectively) content of MUFA and a greater content of SFA, n-3 fatty acids, CLA, and trans-vaccenic acid than did the control samples. Concentrations of PUFA, trans fatty acids, n-6 fatty acids, and cholesterol did not differ between grass-fed and control ground beef. Trans-vaccenic acid (trans-11 18:1) made up the greatest concentration of the total trans fats in grass-fed beef, whereas CLA accounted for approximately 15% of the total trans fats. Although the fatty acid composition of grass-fed and conventionally fed beef was different, conclusions on the possible effects of these differences on human health cannot be made without further investigation.

Finishing strategies for steers based on pasture or silage plus grain and time on feed and their effects on beef quality

“…The intramuscular fat from animals fed on pasture had a higher percentage of C18:1 t-11 (vaccenic acid) than that from the other finishing treatments (P≤0.05), which was consistent with other studies (Leheska et al, 2008;García et al, 2008). The C18:1 t-11 is an intermediate in the biohydrogenation of linoleic (C18:2 n-6) and linolenic (C18:3 n-3) acids and was higher in beef from pasture-fed cattle.…”

“…The concentration of conjugated linoleic acid c-9 t-11 in adipose tissue is higher when animals are fed on pasture than when fed on stored forage or grain (Schor et al, 2008). Other studies also showed that steers finished on pasture had higher beef contents of CLA c-9 t-11 than those finished on grain-based diets (Realini et al, 2004;Garcia et al, 2008;Leheska et al, 2008;.…”

Influence of α-tocopherol supplementation on trans-18:1 and conjugated linoleic acid profiles in beef from steers fed a barley-based diet

“…It is also important to note that, on average, t10-18:1 and t11-18:1 would constitute about 52% and 15% of total t18:1, respectively, in both regular ground beef and lean steak. Current results also indicate that feeding a high barley-grain diet like most concentrate-based diets (Dugan et al, 2007;Kraft et al, 2008;Leheska et al, 2008) increased levels of trans fatty acids other than t11-18:1 in beef compared with high-forage diets. In this context, it could, therefore, be important to re-examine the exclusion of t18:1 isomers from compulsory labelling of trans fatty acids in ruminant-derived foods.…”

Nutritional Quality of Beef Produced in Chile from Different Production Systems

“…In this sense, other studies have also found that steers fed on grass had higher C18:1 t-11 than those fed on grainbased diets (Leheska et al, 2008;Garcia et al, 2008). Moreover, some studies suggest a linear increase in CLA c-9, t-11 synthesis as the C18:1 t-11 content of the diet increased in human subjects (Salminen et al, 1998;Turpeinen et al, 2002a), whereas, the rate of conversion of C18:1 t-11 to CLA c-9, t-11 was estimated to range from 5 to 12% in rodents to 19 to 30% in humans (Turpeinen et al, 2002b).…”