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 forage vs grain feeding on carcass composition and palatability attributes of beef when time on feed was controlled. Diets included a 95% alfalfa silage ration (AS) or a 68% high-moisture corn, 25% alfalfa silage ration (HMC). These were incorporated into six treatments to allow comparisons of end points based on similar days on feed or backfat finish. Dietary treatments included 1) HMC (4 mm), or cattle allowed ad libitum intake of HMC until slaughter at 4 mm ultrasound backfat; 2) AS (HMC-4), or cattle allowed ad libitum intake of AS until slaughter, regardless of finish, when HMC (4 mm) cattle were slaughtered; 3) AS (4 mm), 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 until 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 allowed ad libitum intake of AS ration until slaughter at 8 mm backfat. Grain feeding generally increased (P < .01) ADG, carcass weight, grade fat, and intramuscular fat content when compared with forage feeding at similar times on feed. Palatability attributes of ribeye roasts and ground beef were generally unaffected (P > .10) by diet with the exception of slightly less beef flavor and more off-flavor in forage-fed vs grain-fed beef. Higher (P < .01) concentrations of linolenic acid and lower (P < .10) concentrations of oleic acid in forage-fed beef may be partially responsible for diet differences in flavor.