Grass finishing and the residual effect of pasture prior to concentrate finishingon the shelf stability of late-maturing bull beef

Context The finishing of late-maturing bulls on grass is economically more favourable than finishing on cereal concentrates but it may have a negative effect on oxidative stability. Aim To determine the effect of varying levels of pasture feeding during the finishing period on the oxidative stability of bull beef. Methods Groups of eight late-maturing breed sired bulls were assigned to one of the following production systems: (1) pasture only for 200 days (P), (2) pasture only for 100 days followed by pasture plus 50% of the dietary dry matter (DM) intake as concentrate for 100 days (P-C50), (3) pasture plus 50% of the DM intake as concentrate for 200 days (C50), (4) pasture only for 100 days followed by ad libitum concentrates for 100 days (P-C), (5) pasture plus 50% of the DM intake as concentrate for 100 days followed by ad libitum concentrates for 100 days (C50-C) and (6) ad libitum concentrates offered indoors for 200 days (C). The M. Longissimus thoracis et lumborum muscle was excised post-slaughter for proximate, fatty acid and α-tocopherol analysis and for measurement of lipid and protein oxidation and colour stability. Results The polyunsaturated fatty acid (PUFA) concentration and proportion in muscle were higher (P < 0.001) in C50 bulls compared with P, P-C50 and P-C bulls. The concentration of highly peroxidisable PUFA was at least 1.3-fold higher (P < 0.001) in the muscle of C50 bulls than of C and P-C bulls whereas the proportion was at least 1.5-fold higher (P < 0.001) in muscle of P, P-C50 and C50 bulls compared with C and P-C bulls. There was a higher (P < 0.001) concentration of saturated fatty acids and monounsaturated fatty acids in muscle of bulls fed on concentrate in the last 100 days (P-C, C50-C and C) compared with those fed on grass (fully or partially) in the last 100 days (P, P-C50 and C50). α-Tocopherol concentration was at least 1.5-fold higher (P < 0.001) in muscle of P bulls compared with C, C50-C and P-C bulls. Redness, redness stability, lipid and protein oxidation did not differ between treatments (P > 0.05). Conclusions The increase in highly peroxidisable PUFA in beef, by increasing pasture in the finishing ration did not increase susceptibility to oxidation, most likely due to a concomitant increase in α-tocopherol. Implications Beef can be produced from late-maturing bulls grazing on pasture for 200 days without impacting negatively on oxidative stability.

The scope for manipulating the polyunsaturated fatty acid content of beef: a review

Since 1950, links between intake of saturated fatty acids and heart disease have led to recommendations to limit consumption of saturated fatty acid-rich foods, including beef. Over this time, changes in food consumption patterns in several countries including Canada and the USA have not led to improvements in health. Instead, the incidence of obesity, type II diabetes and associated diseases have reached epidemic proportions owing in part to replacement of dietary fat with refined carbohydrates. Despite the content of saturated fatty acids in beef, it is also rich in heart healthy cis-monounsaturated fatty acids, and can be an important source of long-chain omega-3 (n-3) fatty acids in populations where little or no oily fish is consumed. Beef also contains polyunsaturated fatty acid biohydrogenation products, including vaccenic and rumenic acids, which have been shown to have anticarcinogenic and hypolipidemic properties in cell culture and animal models. Beef can be enriched with these beneficial fatty acids through manipulation of beef cattle diets, which is now more important than ever because of increasing public understanding of the relationships between diet and health. The present review examines recommendations for beef in human diets, the need to recognize the complex nature of beef fat, how cattle diets and management can alter the fatty acid composition of beef, and to what extent content claims are currently possible for beef fatty acids.