Grass silage versus maize silage effects on retail packaged beef quality A. O’Sullivan*, K. O’Sullivan†, K. Galvin*, A. P. Moloney‡, D. J. Troy‡, and J. P. Kerry* 1 *Department of Food Science, Food Technology and Nutrition, National University of Ireland, Cork; †Department of Statistics, National University of Ireland, Cork; and ‡Teagasc, National Food Centre, Castleknock, Dublin 15, Ireland ABSTRACT: The effects of three preslaughter diets on heifer beef quality were investigated. Heifers (n = 45) were divided into three groups and fed for ad libitum consumption either maize silage, grass silage, or a 50:50 mixture of maize silage and grass silage. Meat quality was determined by measuring color, lipid oxidation, α- tocopherol levels, and fatty acid composition. Beef from the maize silage group had poorest color stability (P < 0.05), whereas beef from the grass silage diet had best (P < 0.05) color stability. The visual panel least pre- ferred the maize silage group after 2 or more days of display, and lipid oxidation was significantly (P < 0.001) higher in this group compared to the 50:50 maize:grass silage and grass silage groups. There was a significant (P < 0.001) difference in the α-tocopherol levels detected Key Words: Beef Quality, Grass Silage, Maize Silage, Polyenoic Fatty Acids, Rancidity, Vitamin E 2002 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2002. 80:1556–1563 Introduction The main factors influencing the eating quality of meat are tenderness, color, and flavor (Buckley et al., 1995). At the point of sale, color and color stability are the most important attributes of meat quality. Consum- ers equate an attractive bright red color with long shelf- life and good eating quality, and various approaches have been used to meet this expectation (Hood and Mead, 1993). Of the production factors affecting meat color and quality, the dietary regime of the animals is one of the most important. Studies on forage finishing of beef have produced mixed results on carcass charac- teristics and palatability attributes. Fortin et al. (1985) found no differences in palatability attributes between forage- and grain-finished beef. Crouse et al. (1984) reported that steaks from grass-fed heifers were similar 1 Correspondence: phone: +353-21-4903798, fax: +353-21-4276318; E-mail: joe.kerry@ucc.ie. Received May 4, 2001. Accepted November 9, 2001. 1556 in the meat from the three dietary groups. α-Tocopherol levels increased in the order: maize silage < 50:50 maize:grass silage < grass silage, at levels of 2.08, 2.95, and 3.84 g/g meat, respectively. Fatty acid analysis indicated 18:3 was significantly (P < 0.001) lower in the maize silage-fed group than in the maize:grass silage and grass silage groups. However, 18:3 was signifi- cantly (P < 0.001) higher in the grass silage group than in the other two groups. There were no significant differ- ences in all other fatty acids among the three dietary groups. It was concluded that beef from grass silage- fed animals had better overall quality in terms of color, lipid oxidation, and α-tocopherol levels than beef from maize silage fed animals. to those from grain-fed heifers in terms of tenderness, juiciness, and flavor but darker in color during retail display. Smith (1990) discouraged forage finishing of beef due to its lower dressing percentage, decreased quality grade, yellow fat color, dark muscle color, and decreased flavor and tenderness in favor of grain-fin- ished beef. Grass silage is the predominant forage in the diet of Irish beef cattle finished indoors, and a number of stud- ies (French et al., 2000a, Steen and Kilpatrick, 2000) have examined the effects of feeding grass silage-based diets to beef cattle. In recent years, however, there has been increased interest in growing forage maize in new geographical areas, which are climatically favorable, conserving it as silage and using it as a forage that is complementary or alternative to grass silage in the diet of beef cattle. Because there is little information on the effect of maize silage on meat quality, this experiment was designed to determine the impact of substituting grass silage with maize silage in the diet of cattle on the quality of beef held under two forms of retail packaging: overwrapping and modified atmosphere packaging (MAP).