333 Effects of ruminally-protected lysine and Megasphaera elsdenii on performance and carcass characteristics of finishing cattle

Abstract

Abstract Crossbred steers (n = 448; 352 ± 25 kginitial body weight) were used to evaluate impact of Megasphaera elsdenii (ME; Lactipro advance, MS Biotec, Wamego, KS), alone or in combination with ruminally-protected lysine (RPL; USA Lysine, Kemin Industries, Inc., USA), on performance and carcass traits of finishing steers in a randomized complete block design. Steers were blocked by initial body weight and randomly assigned within block to one of 64 pens (7 steers/pen) in a 2 x 2 factorial treatment arrangement. Factors consisted of RPL (0 or 40 g/steer daily) and two step-up regimens (21-d without ME or 10-d with ME). Four step-up diets were used to transition cattle to finishing diets containing (dry basis) 60% steam flaked corn, 7% wheat straw, 30% sweet bran, and supplement. Diets were fed once daily ad libitum. Freeze-dried ME was re-hydrated and dosed orally (1x1010 CFU/steer) on d 1, and top-dressed (1x107 CFU/steer daily) onto diets daily thereafter. Data were analyzed using a mixed model with ME, RPL and the interaction as fixed effects, and block as the random effect. There were no interactions between ME and RPL (P > 0.05). Steers given ME consumed 16% less roughage compared to their counterparts without (P < 0.05), but gain, dry matter intake, and gain:feed were similar (P > 0.10). Administering ME tended to increase percentage of USDA Prime carcasses (0.5 vs 2.7%; P < 0.06). Feeding RPL did not affect feedlot performance, carcass weight, longissimus muscle area, marbling score, 12th-rib fat thickness, or liver abscess incidence (P > 0.10), but tended to increase yield grade (P < 0.07). In conclusion, use of Megasphaera elsdenii with an accelerated step-up program yielded feedlot performance and carcass traits comparable to those of cattle adapted with a conventional, 21-d step-up program, but supplemental lysine was without effect.