A pooled analysis of seven large pen feedlot studies: influence of <i>Megasphaera elsdenii</i> NCIMB 41125 on late-term mortality and growth performance of feedlot steers and heifers following terminal processing

Large pen feedlot studies (n = 7) with heifers and steers (n = 17,571) were conducted in North America to determine the effects of orally administered Megasphaera elsdenii NCIMB 41125 (Lactipro; Axiota Animal Health, Fort Collins, CO, USA) on late feeding period mortality and growth performance. Study designs were randomized complete blocks, and treatments included no administration of Megasphaera elsdenii NCIMB 41125 (CON) and administration of a commercial dose of Megasphaera elsdenii NCIMB 41125 (LP). Treatments were administered 51 to 147 d on feed to coincide with terminal implant administration and/or sorting into marketing cohorts, on subsequent mortality and growth performance. Data were analyzed with linear mixed models to account for the hierarchical design structure and fitted for mortality and performance outcomes. Mortality incidence was reduced (P = 0.005) when dosing Megasphaera elsdenii NCIMB 41125 [0.011 vs. 0.007 (per 100 head days) ± 0.002 for CON versus LP cattle, respectively]. Thus, the death rate during the risk period was 1.57 times greater in cattle not administered LP. No treatment × sex interaction (P ≥ 0.53) was observed for any growth performance measures. A significant effect of sex (P < 0.01) was observed for dry matter intake (DMI), average daily gain (ADG), and gain:feed (G:F), with steers exhibiting increased performance across all outcomes. No difference (P ≥ 0.18) between treatments was noted for DMI, ADG, or G:F. Orally administering Megasphaera elsdenii NCIMB 41125 to steers and heifers at terminal implant processing can be a management strategy to decrease mortality following terminal processing and during the late finishing phase.