EFFECTS OF FORAGE VS GRAIN FEEDING ON CARCASS CHARACTERISTICS, FATTY-ACID COMPOSITION, AND BEEF QUALITY IN LIMOUSIN-CROSS STEERS WHEN TIME ON FEED IS CONTROLLED

Limousin-cross steers (n = 135; 258 +/- 26 kg) were used to compare fo rage vs grain feeding on carcass composition and palatability attribut es of beef when time on feed was controlled. Diets included a 95% alfa lfa silage ration (AS) or a 68% high-moisture corn, 25% alfalfa silage ration (HMC). These were incorporated into six treatments to allow co mparisons of end points based on similar days an feed or backfat finis h. Dietary treatments included 1) HMC (4 mm), or cattle allowed ad lib itum intake of HMC until slaughter at 4 mm ultrasound backfat; 2) AS ( HMC-4), or cattle allowed ad Libitum intake of AS until slaughter, reg ardless of finish, when HMC (4 mm) cattle were slaughtered; 3) AS (4 m m), or cattle allowed ad libitum intake of AS until slaughter at 4 mm backfat; 4) HMC (AS-4), or cattle allowed ad libitum intake of HMC unt il slaughter, regardless of finish,when AS (4 mm) cattle achieved 4 mm backfat; 5) HMC (RES), or cattle fed HMC at restricted intakes until slaughter at 4 mm backfat with feed offered at 75% of intake achieved by HMC (4 mm) and HMC (AS-4) cattle; and 6) AS (8 mm) or cattle allowe d ad libitum intake of AS ration until slaughter at 8 mm backfat. Grai n feeding generally increased (P < .01) ADG, carcass weight, grade fat , and intramuscular fat content when compared with forage feeding at s imilar times on feed. Palatability attributes of ribeye roasts and gro und beef were generally unaffected (P > .10) by diet with the exceptio n of slightly less beef flavor and more off-flavor in forage-fed vs gr ain-fed beef. Higher(P < .01) concentrations of linolenic acid and low er (P < .10) concentrations of oleic acid in forage-fed beef may be pa rtially responsible for diet differences in flavor.