Effects of graded levels of potato by-products in barley- and corn-based beef feedlot diets: I. Feedlot performance, carcass traits, meat composition, and appearance.

To measure effects of diet on feedlot performance, carcass characteristics, and beef appearance, 144 crossbred beef steers (333+/-.44 kg) were allotted within weight block (3) to a randomized complete block design with a 2 x 3 factorial arrangement of dietary treatments. Main effects were grain (barley or corn) and level of potato by-product (PB) (0, 10, or 20% of diet DM). Steers were fed diets containing 83% concentrate (grain plus PB), 10% supplement, and 7% alfalfa on a DM basis for an average of 130 d. Level of PB quadratically affected (P < .10) DM intake and gain such that steers fed 10% PB ate more and gained faster. Corn-fed steers were more (P < .05) efficient (5.8 vs 6.3 kg DM/kg gain) and had more (P < .05) kidney, pelvic, and heart fat (2.2 vs 2.0%) than barley-fed steers. A grain x PB interaction was detected (P < .10) for marbling score, which was minimized in steers fed barley diets (small 0) but maximized in those fed corn diets (small 30) at 10% PB. Diet did not affect beef firmness or beef color score. Barley-fed beef had whiter fat (P < .05) than corn-fed beef (2.6 vs 2.9 on a 1 to 7 scale); however, fat luster score was not affected by diet. Small differences were noted in fatty acid profile, purge, drip loss, and muscle pH. No differences were noted in color measurements due to dietary treatment over 7 d of retail shelf life. Overall, differences were small and probably not biologically important. These results indicate that these diets had minimal effects on beef appearance and carcass characteristics, meat composition, and water retention properties.