Elsevier

Meat Science

Volume 66, Issue 3, March 2004, Pages 567-577
Meat Science

Effect of pasture vs. concentrate feeding with or without antioxidants on carcass characteristics, fatty acid composition, and quality of Uruguayan beef

https://doi.org/10.1016/S0309-1740(03)00160-8Get rights and content

Abstract

Thirty Hereford steers were finished either on pasture (n=10) or concentrate (n=20) to determine dietary and antioxidant treatment effects on carcass characteristics, fatty acid composition, and quality of Uruguayan beef. Half of the steers finished on concentrate were supplemented with 1000 I.U. vitamin E head−1 day−1 for 100 days. Postmortem vitamin C was added to ground beef (0.05% v/w) displayed for 8 days at 2 °C. Carcasses from steers finished on concentrate had greater (P<0.05) carcass weight, conformation, degree of finishing, fat depth, and ribeye area than pasture finished animals. Carcasses from pasture-fed steers showed darker (P<0.05) longissimus color and yellower (P<0.05) fat at 24 h postmortem than concentrate-fed. Initial longissimus Warner-Bratzler shear force (WBSF) values were similar (P>0.05) between pasture- and concentrate-fed animals. However, beef from pasture-fed cattle had lower (P<0.05) WBSF values at 7 and 14 days postmortem. Longissimus α-tocopherol concentrations were greater (P<0.01) for pasture- and concentrate-fed animals that were supplemented with vitamin E compared to concentrate-fed. Steaks from pasture-fed and vitamin E supplemented cattle had similar (P>0.05) TBARS values, which were lower (P<0.05) than steaks from concentrate-fed steers during 21 days of display. Ground beef from vitamin E supplemented steers had the lowest TBARS values; whereas samples from pasture-fed animals had the lowest lipid stability with higher TBARS levels than other treatments. Vitamin C addition to ground beef did not (P>0.05) reduce lipid oxidation. Vitamin E supplementation of concentrate-fed cattle had no effect (P>0.05) on color stability of ground beef or steaks. The a (redness) and b (yellowness) values were higher (P<0.05) when vitamin C was added to ground beef. Longissimus fatty acid content of concentrate-fed animals was twofold greater (P<0.01) than pasture-fed. The percentages of C14:0, C16:0, and C18:1 fatty acids were higher (P<0.01) in the intramuscular fat of concentrate-fed steers, whereas pasture-fed cattle showed greater (P<0.01) proportions of C18:0, C18:2, C18:3, C20:4, C20:5, and C22:5. Total conjugated linoleic acid (CLA) and CLA isomer c9t11 were higher (P<0.01) for pasture- than concentrate-fed cattle. Vitamin E supplementation of concentrate-fed steers increased lipid stability of ground beef and steaks, but was unable to improve color stability; whereas vitamin C addition to ground beef increased color stability without altering lipid oxidation. Finishing cattle on pasture enhanced the unsaturated fatty acid profile of intramuscular fat in beef including CLA and omega-3 fatty acids.

Introduction

Beef cattle production systems in Uruguay rely almost exclusively on grazed pastures. However, more recently intensive beef production systems have gained increased interest by some beef producers. The focus is to produce a differentiated product in a vertically integrated manner to target both domestic, but particularly international markets. This production system, however, differs from a typical feedlot grain-based diet in the United States, in that the rations are formulated with 50% corn silage, and 50% grain.

Dietary recommendations for humans promoting the consumption of less saturated fat have led to an increased interest in meats containing more unsaturated fatty acids. Consumption of saturated fatty acids (SFA) has been associated with increased serum low-density-lipoprotein cholesterol concentrations, and increased risk of coronary heart disease (Keys, 1970). Ruminant fat has a higher SFA and a lower polyunsaturated:saturated fatty acid (PUFA:SFA) ratio than non-ruminant fat, due to hydrogenation of dietary unsaturated fatty acids in the rumen (French, Stanton et al., 2000). However, the nutritional background of meat-producing animals may alter the fatty acid composition of ruminant tissue fat.

Recent research has focused on the nutritional importance of the n-6:n-3 fatty acid ratio in the human diet, and on conjugated linoleic acid (CLA) isomers because of their anticarcinogenic properties (Ha et al., 1990, Ip et al., 1994). The nutritional value of n-3 PUFAs is well recognized, and increased consumption of these fatty acids has been recommended (Department of Health, 1994). Ruminant fats are among the richest natural sources of CLA, in particular the cis-9, trans-11 isomer, which arises from microbial hydrogenation of dietary linoleic acid in the rumen (Ha et al., 1990). In addition, CLA is synthesized from trans-11 octadecenoic acid by Δ9-desaturase in adipose tissue (Bauman, Baumgard, Corl, & Griinari, 1999). Previous research has shown that including grass in the diet of dairy and beef cattle increased CLA concentration in milk and beef intramuscular fat, respectively (French et al., 2000, Lawless et al., 1998, Yang et al., 2002).

Although an increase in the n-3 fatty acid concentration is desirable from a human health perspective, oxidative stability of meat is reduced. Lipid and muscle pigment oxidation are the major problems causing quality deterioration in meat. Thus, enrichment with antioxidants is necessary in order to prevent the risk of oxidative damage (Jakobsen, 1999).

The Uruguayan economy is strongly dependent on agriculture and the export of beef products, and there is no information available comparing the meat quality, fatty acid composition and product shelf life of beef from the traditional pasture-fed and the more intensive concentrate-based production systems. The objectives of this study were to compare carcass characteristics, beef quality, and longissimus fatty acid composition from cattle finished on pasture or on a concentrate-based diet; and to evaluate the effect of antioxidants, antemortem vitamin E and postmortem vitamin C, on product shelf life.

Section snippets

Animals and diets

Thirty Hereford steers backgrounded on pasture were finished either on pasture (n=10) or concentrate (n=20) during summer (November 2001–February 2002). Pasture- and concentrate-fed steers were fed in commercial operations run by the National Institute of Agricultural Research of Uruguay in conjunction with the Uruguayan Hereford Breeders Association, and the Uruguayan Association of Natural Intensive Beef Producers. The pasture consisted predominantly of perennial ryegrass (Lolium perenne),

Carcass characteristics

Vitamin E supplementation did not alter (P>0.05) any of the carcass characteristic measured. The effect of finishing beef cattle on pasture or concentrate on carcass characteristics is shown in Table 1. Carcasses from cattle finished on concentrate were heavier (P<0.05) than those finished on pasture. Conformation scores tended to be lower (P<0.10) indicating better conformation from carcasses finished on concentrate than pasture. Carcasses from concentrate-finished animals had greater (P<0.05)

Conclusions

Pasture-fed carcasses from Uruguayan cattle showed darker longissimus color and yellower fat at grading than concentrate-fed. Although pasture-fed carcasses were lighter and leaner than concentrate-fed, there were no differences in initial tenderness between the groups. Moreover, pasture-fed beef showed a greater potential for postmortem tenderization through aging, becoming more tender than concentrate-fed beef after 7 days of storage. Supplementation of α-tocopherol to cattle finished on

Acknowledgments

This research was funded by the Uruguayan National Institute of Agricultural Research (INIA), Inter-American Development Bank (IDB) and the Uruguayan Ministry of Livestock, Agriculture and Fishery (MGPA). We wish to thank the Uruguayan Hereford Breeders Association, the Uruguayan Association of Natural Intensive Beef Producers (AUPCIN), the Uruguayan Technological Laboratory (LATU), Roche Ltd., and Dr. R. Radi and Dr. H. Botti for their support and cooperation in this project.

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