Two experiments evaluated the effects of a Bacillus-based direct-fed microbial on in vitro dry matter (DM) and neutral detergent fiber (NDF; Exp. 1), and starch (Exp. 2) digestibility of a variety of ruminant feedstuffs. In Exp. 1, ten forage sources were evaluated: ryegrass, alfalfa hay, leucaena, corn silage, spinifex, buffel grass, flinders grass, Mitchell grass, rhodes grass hay, and Queensland bluegrass. Experimental treatments were a Control, forages with no probiotic inoculation; CON) or forages sources inoculated with a mixture containing Bacillus licheniformis and B. subtilis (3.2 × 10 9 CFU/g; DFM). In vitro DM and NDF digestibility were evaluated at 24- and 48-hours post-treatment inoculation. Treatment × hour interactions were noted for IVDMD and IVNDFD (P ≤ 0.05). More specifically, DFM inoculation increased (P ≤ 0.03) IVDMD at 24 hours in four forages and increased 48-hour IVDMD (P ≤ 0.02) in alfalfa hay, ryegrass, leucaena, and Mitchell grass hay, but opposite results were observed for Queensland bluegrass (P < 0.01). Twenty-four and 48-hour IVNDFD increased following DFM inoculation (P ≤ 0.02) in five forage sources, but reduced for Queensland bluegrass (P < 0.01). When the forages were classified according to their quality, main treatment effects were detected for IVDMD (P ≤ 0.02) and IVNDFD (P < 0.01). In Exp. 2, five common cereal grains were evaluated [high-density barley (82 g/100 mL), low-density barley (69 g/100 mL), corn, sorghum, and wheat] under the same treatments as in Exp. 1. In vitro starch digestibility was evaluated at 6- and 12-hours following treatment inoculation. Treatment × hour interactions were observed for starch digestibility in 3 out of 5 concentrate sources (P ≤ 0.001). Inoculation of DFM yielded greater 24-hour starch digestibility for high-, low-density barley, and wheat (P ≤ 0.02), but also greater at 48 hours in wheat (P < 0.0001). Moreover, mean starch digestibility improved for corn and sorghum inoculated with DFM (P < 0.01). Using a Bacillus-based DFM (B. licheniformis and B. subtilis) improved mean in vitro DM and NDF digestibility of different forage sources of varying qualities (based on CP content). Similarly, in vitro starch digestibility was also greater following DFM inoculation, highlighting the potential of this probiotic to improve nutrient digestibility and utilization into the beef and dairy cattle herd.

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Feeding cereal grain to cattle is common practice for optimal beef and milk production. High concentrations of starch and other soluble carbohydrates may cause acidosis. Information on the effect of processing on starch and protein degradability in the rumen are scarce. This study was to determine the ruminal degradation patterns of common grains and the effect of steam pelleting on starch and crude protein (CP) degradability in the rumen. The ruminal degradation pattern of dry matter (DM), starch, and CP of ground and pelleted sorghum, barley, wheat, and samples along with ground oats and triticale were determined using the in situ nylon bags method. Cereals were incubated for 0, 2, 4, 6, 8, 16, 32, and 60 h, and the fast and slowly degradable fraction, the effective degradation rate, and effective degradability (ED) of DM, starch, and CP were calculated. The starch ED of ground and pelleted sorghum, barley, and two wheat samples were 57.3, 93.6, 95.2, and 97.2%; and 61.5, 93.8, 93.8, and 95.6%, and their crude protein ED was 54.8, 82.3, 83.3, 82.6% and 51.9, 79.2, 81.8, and 78.1% respectively. The starch ED of ground oat and triticale were 98.3 and 94.7%, and that of CP were 93.7 and 75.2%, respectively. The degradability of sorghum was significantly lower than that of the other grains. Pelleting increased the fast-degradable DM and starch faction of sorghum and tended to improve its DM degradability (p = 0.081). Pelleting significantly reduced the fast-degradable fraction of DM and starch of wheat samples and numerically reduced its degradability.