A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef

Abstract

Growing consumer interest in grass-fed beef products has raised a number of questions with regard to the perceived differences in nutritional quality between grass-fed and grain-fed cattle. Research spanning three decades suggests that grass-based diets can significantly improve the fatty acid (FA) composition and antioxidant content of beef, albeit with variable impacts on overall palatability. Grass-based diets have been shown to enhance total conjugated linoleic acid (CLA) (C18:2) isomers, trans vaccenic acid (TVA) (C18:1 t11), a precursor to CLA, and omega-3 (n-3) FAs on a g/g fat basis. While the overall concentration of total SFAs is not different between feeding regimens, grass-finished beef tends toward a higher proportion of cholesterol neutral stearic FA (C18:0), and less cholesterol-elevating SFAs such as myristic (C14:0) and palmitic (C16:0) FAs. Several studies suggest that grass-based diets elevate precursors for Vitamin A and E, as well as cancer fighting antioxidants such as glutathione (GT) and superoxide dismutase (SOD) activity as compared to grain-fed contemporaries. Fat conscious consumers will also prefer the overall lower fat content of a grass-fed beef product. However, consumers should be aware that the differences in FA content will also give grass-fed beef a distinct grass flavor and unique cooking qualities that should be considered when making the transition from grain-fed beef. In addition, the fat from grass-finished beef may have a yellowish appearance from the elevated carotenoid content (precursor to Vitamin A). It is also noted that grain-fed beef consumers may achieve similar intakes of both n-3 and CLA through the consumption of higher fat grain-fed portions.

Differences in intramuscular fatty acid profiles amongBos indicusand crossbredBos taurus × Bos indicusbulls finished on pasture or with concentrate feed in Brazil

“…Other authors, however, have reported less consistent results when the amount of SFA was compared among different feeding systems in cattle, as reviewed by Daley et al (2010). The increased amount of SFA in grain-finished animals in our study, especially of the B. indicus type, was mostly due to an increased amount of 18:0, 16:0 and 14:0.…”

“…The increased amount of SFA in grain-finished animals in our study, especially of the B. indicus type, was mostly due to an increased amount of 18:0, 16:0 and 14:0. While higher levels of 16:0 and 14:0 are commonly detected in grain-finished animals (Daley et al 2010), the higher amount of 18:0 reported here for this type of animals was somewhat unexpected, as this FA usually has a higher concentration in pasture-finished animals Nuernberg et al 2005;Alfaia et al 2009). …”

“…In general, the amount of PUFA is expected to be higher in pasture-finished animals (French et al 2000;Daley et al 2010;Scollan et al 2014), but the response seems to be breed dependent (Bressan et al 2011). However, individual PUFA respond differently to the finishing system, such that 18:2 n-6 tends to be higher in grain-finished animals, while 18:3 n-3 increases with pasture-finishing (Nuernberg et al 2005), as was also observed in our study, and total PUFA should reflect the relative importance of these components.…”

“…In general, meat from beef cattle finished on pasture has a more desirable fatty acid profile than when finishing is with grain (French et al 2000;Alfaia et al 2009;Daley et al 2010;Rossato et al 2010;Bressan et al 2011;Rosa et al 2014). On the other hand, genetic effects play an important role in fatty acid profiles of ruminant tissues and products (Pitchford et al 2002;De Smet et al 2004), e.g.…”

Production factors influence fresh lamb longissimus colour more than muscle traits such as myoglobin concentration and pH

“…Daley et al (2010) reported that fat yellowness in ruminants is primarily determined by their dietary intake of carotenoids, which varies substantially within and between feed types and thus would have varied considerably between sites in this study.…”