Effects of feeding a Bacillus -based probiotic on feed intake, performance, carcass traits, and health of crossbred beef cattle fed sodium monensin and high-moisture corn-based diets during finishing1

Abstract

This experiment evaluated feed intake, performance, fecal nutrient concentrations, health, and carcass traits of crossbred beef cattle offered a high-moisture corn-based diet containing sodium monensin. On day 0 of the study, 402 crossbred steers [initial body weight (BW) 329 ± 69.5 kg] were blocked by BW and source into 1 of 28 feedlot pens (14 to 15 steers/pen). Within blocks, pens were assigned to high-moisture corn-based diets containing (BAC) or not (CON; n = 14) Bacillus licheniformis 809 and B. subtilis 810 (2 g/steer per day; n = 14). The experimental period lasted 118 days and BAC was added to a mineral-vitamin premix, which also contained sodium monensin. Throughout the experimental period, dry matter intake was determined daily, while individual BW was obtained on days 0, 35, and 118 of the study. Based on these measurements, average daily gain (ADG) and gain to feed (GF) were also calculated. Fecal samples were collected on days 20 and 70 of the study for determination of fecal starch and nitrogen (N). On day 122, animals were transported to a commercial slaughterhouse and carcass traits were determined. All data were analyzed with SAS (version 9.4) using pen as the experimental unit. Body weight on days 35 and 118 was greater (P ≤ 0.03) for BAC vs. CON, while no changes were observed on feed intake (P ≥ 0.40). Average daily gain was also greater for BAC from days 0 to 35 (P = 0.01) and 0 to 118 (P = 0.03). Hence, GF was improved by 8.4 and 2.9% when assessed from days 0 to 35 (P = 0.03) and 0 to 118 (P = 0.04), respectively. Hot carcass weight was also greater for BAC (+ 3.5 kg; P = 0.05), while Biceps femoris fat thickness tended to be greater (P = 0.07) for BAC. Carcass-adjusted final BW, ADG, and GF were also greater (P ≤ 0.05) for BAC. No differences were observed on fecal starch and N (P ≥ 0.42), but fecal score tended to be greater for BAC from days 35 to 118 and from days 0 to 118 (P ≤ 0.09). No treatment effects were detected for the incidence of bovine respiratory cases (P ≥ 0.12), while overall morbidity tended to be lower (P = 0.06) and fever occurrence in steers showing bovine respiratory disease was lower in steers fed BAC (P = 0.04). In summary, Bacillus spp. supplementation optimized performance, health, and carcass traits of feedlot cattle fed a high-moisture corn-based diet containing sodium monensin.