Effects of increasing levels of dried corn distillers grains with solubles on growth performance, carcass characteristics, and meat quality of yearling heifers

Three hundred forty-seven crossbred heifers (330 +/- 11 kg initial BW) were used in a randomized complete block study to identify the optimal level of dried corn distillers grains with solubles (DGS) in flaked corn finishing diets. Fifty-four pens were used, with 9 pens per treatment and 6 to 7 heifers per pen. Finishing diets were steam-flaked corn-based and were fed once daily for 148 d. Dietary treatments consisted of 6 levels of DGS (0, 15, 30, 45, 60, and 75%, DM basis). Dry matter intake, ADG, and final BW responded quadratically (P <= 0.03) to increasing levels of DGS and were maximized at 15% DGS. However, G: F decreased linearly (P = 0.01) as level of DGS increased. Longissimus muscle areas were not different (P >= 0.27), whereas 12th-rib fat thicknesses decreased linearly (P = 0.05) for heifers fed increasing levels of DGS. Marbling score and USDA yield grades were not different (P >= 0.06) for heifers fed different levels of DGS. Number of carcasses grading USDA Prime or Choice were not different (P >= 0.07), whereas number of carcasses grading USDA Select increased (P = 0.02; linear) as dietary level of DGS increased from 0 to 75%. Myofibrillar and overall tenderness increased linearly (P = 0.01) as dietary level of DGS increased from 0 to 75%. Juiciness, off-flavor intensity, and thiobarbituric acid reactive substances were not different (P >= 0.16) among treatments. Redness of steaks (i.e., a*) was not different (P >= 0.13) for steaks collected from heifers fed different levels of DGS as evidenced by similar instrumental color measurements after d 0, 3, and 5 of display. However, on d 7, steak color was less red (P = 0.04) and had more metmyoglobin. Concentration of linoleic acid (18:2n-6cis), total n-6 fatty acids, and total PUFA linearly increased (P = 0.01) with increasing levels of DGS.