PSIII-30 - Effects of a Bacillus-based direct-fed microbial on in vitro gas production and fiber digestibility of feedstuffs

Abstract: Direct-fed microbials (DFM) support the health and performance of the herd through different modes of action, including improvements on nutrient digestibility. In fact, Bacillus spp. has been identified as an important enzyme-producing bacteria that could benefit overall nutrient utilization by the beef and dairy cattle herd. Based on this rationale, we hypothesized that incubation of a Bacillus-based DFM would improve nutrient digestibility of feedstuffs often fed to ruminants. Therefore, our objective was to evaluate the effects of a Bacillus-based DFM on in vitro nutrient digestibility of different single feedstuffs. Six individual feedstuffs were sampled from China and South Africa and used herein. Feedstuffs were incubated or not (CON) with a Bacillus-based DFM (DFM; BOVACILLUS^TM; B. licheniformis and B. subtilis; 3.2 × 10⁹ CFU/gram; Chr. Hansen A/S., Hørsholm, Denmark) over a 48-h in vitro period. The dose of DFM was adjusted to the volume of the flasks being used and to represent the commercial dose of 3 grams/head per day (9.6 × 10⁹ CFU/head). In vitro gas production, dry matter (DM), and neutral detergent fiber (NDF) digestibility were evaluated at 24 and 48 h. Data were analyzed using PROC MIXED of SAS (version 9.4; SAS Inc., Cary, NC). Mean total in vitro gas production increased by 5.1 and 6.5% when DFM was incubated at 24 and 48 h, respectively (P < 0.01). At 24 h, NDF digestibility was 12.6% greater for DFM-treated feedstuffs vs. CON (P = 0.02; 27.7 vs. 24.6% for DFM and CON, respectively), but no effects were observed on DM digestibility (P = 0.26). Conversely, 48-h DM and NDF digestibility were greater for DFM vs. CON (P ≤ 0.05), with improvements that were in the order of 3.7 and 15.1%, respectively. In conclusion, we observed greater in vitro fiber degradability and gas production of feedstuffs collected from China and South Africa over a 48-h period when the DFM BOVACILLUS^TM was added at a dose representative of 9.6 × 10⁹ CFU per head. Greater improvements in fiber degradability are likely due to the enzymes produced by the DFM BOVACILLUS^TM.