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