Use of naturally sourced feed additives (lactobacillus fermentation products and enzymes) in growing and finishing steers: Effects on performance, carcass characteristics and blood metabolites

An experiment was conducted to evaluate the use of naturally sourced feed additives that consisted of lactobacillus fermentation products (LFPs), plant based enzymes and prebiotics as alternatives to antibiotics in the diets of growing and finishing beef steers. The feed additives were two commercial products: Bio-Lac Plus (BL) and Boviglo (BG). During growing, 75 crossbred steers (initial body weight, 279 ± 4.9 kg) were blocked by weight and randomly allocated into five treatments: control; implant (IM; Elanco-Component TE-100 with Tylan); implant + antibiotics (330 mg monensin +110 mg chlortetracycline/steer/d; IMAT); implant + BL (30 g/steer/d BL; IMBL); and BG (5 mL/steer/d). Steers were fed a basal diet consisting of 600 g/kg corn silage, 350 g/kg dry-rolled barley grain, and 50 g/kg protein, vitamin and mineral supplement (dry matter [DM] basis). When the 112 d growing period finished, steers were maintained on the same treatments and gradually adapted to finishing diet within one month. Steers were not implanted during the 112 d finishing period. The finishing diet consisted of 100 g/kg corn silage, 870 g/kg dry-rolled barley grain, and 30 g/kg vitamin and mineral supplement (DM basis). Steers were housed in individual pens with feed intake measured individually over the 224 d experiment. During the growing period, no treatment effect on DM intake was observed; however, final body weight, ADG and G:F were highest (P < 0.05) with IM, IMAT and IMBL, intermediate with BG and lowest with control. A treatment × day on feed interaction (P < 0.05) occurred for ADG, which was higher (P < 0.01) with IMBL than control or other treatments during first 14 days on-feed. Feeding BG improved (P < 0.01) ADG and G:F versus control animals. In addition, the need to use therapeutic antimicrobials was lower (P < 0.01) for all treatments, in particularly with BL versus control. During finishing, s neither BL or BG effected growth performance or carcass characteristics. Greater (P < 0.05) antioxidant capacities were observed in steers fed IMAT than steers fed IMBL and BG. These results indicate that supplementation of BL or BG improved ADG and feed efficiency during the stressful, early portion of the growing phase, but had no effect during finishing. The results suggest that both BL and BG have the potential to be fed as alternatives to antimicrobial growth promoters in growing steers.