PSXI-29 - Influence of a direct fed microbial on growth performance, carcass data, and immune function in feedlot finishing steers.

Abstract: One hundred and eighty crossbred beef steers (405.9 ± 2.3 kg) were used to determine the impact of a direct fed microbial (DFM) on growth performance, carcass characteristics, and immune response in finishing beef cattle. Steers were blocked by body weight and randomly assigned, within block, to 1 of 2 treatments (3 replicates/treatment: 30 steers/replicate). Groups within a replicate were randomly assigned to treatments. Treatments included: 1) no DFM (control) and 2) DFM supplementation at 50 mg/animal/d [BOVAMINE DEFEND^® Plus containing Lactobacillus animalis, Propionibacterium freudenreichii, Bacillus licheniformis, and Bacillus subtilis]. All steers were fed a high concentrate, steam-flaked corn-based finishing diet. Individual feed intake was recorded daily via the GrowSafe system. Body weights were collected every 28 d. Jugular blood samples were collected from all steers on day 0 and 112. On d 55 of the experiment, 10 steers per pen (30 steers per treatment) were randomly selected and injected, subcutaneously with 4.0 mg of ovalbumin (OVA). Jugular blood samples were collected from each steer on d 0, 7, 14, and 21 post injection. On d 112 of the experiment, the same steers were injected with the same dose of OVA and intramuscularly with 5ml of a 25 % pig red blood cell (PRBC) solution. Jugular blood samples were collected from each steer on day 0, 7, 14, and 21 post injection. After receiving the finishing diet for 185 d, cattle were transported to a commercial abattoir and slaughtered. Hot carcass weights were collected at the time of slaughter. Carcasses were allowed to chill for 24 h before carcass data were collected. Data were analyzed as a completely randomized block design and individual animal within pen was considered the experimental unit. Initial body weight, final body weight, and overall feed efficiency were similar across treatments. Steers receiving DFM had greater (P < 0.01) body weights and average daily gains on d 28 and 55 and greater (P < 0.04) dry matter intakes over the entire experiment compared to controls. Hot carcass weight, longissimus muscle area, quality grade, and marbling score were similar across treatments. However, dressing percentage (P < 0.02) was greater in steers receiving DFM compared to controls. Antibody titers to OVA and PRBC and d 112 interferon gamma concentrations were similar across treatments. However, red blood cell superoxide dismutase activity was greater (P < 0.05) in DFM-supplemented cattle compared to controls on d 112 of the experiment. These data suggest that BOVAMINE DEFEND^® Plus supplementation improves growth performance during certain periods of the finishing phase, increases overall dry matter intake and carcass yield, and may impact antioxidant status in beef cattle.