A study was conducted using a continuous culture fermentation system to determine effects of probiotic supplementation on ruminal bacterial fermentation of hull-less barley- and corn-based diets. The probiotic contained both a fungal (Aspergillus oryzae) and yeast (Saccharomyces cerevisiae) culture along with several bacterial cultures. Treatments were arranged in a 2 × 2 factorial design with two sources of grain (hull-less barley, B and corn, C) with (+) or without (−) probiotic supplementation. Probiotic was added directly into the fermenter flasks. Diets consisted of (dry matter basis) 46% bromegrass silage, 5% alfalfa meal, and 49% barley- or corn-based concentrate mix. Probiotic supplementation decreased (P < 0.05) dry matter digestibility with the corn diet (C −, 58.6%; C +, 51.4%) but had no significant effect on the barley diet (B −, 48.7%; B +, 51.8%) Dry matter digestibility tended to be higher (P = 0.07) with corn- vs. barley-based diets. Protein degradation and fiber digestibility were not significantly (P > 0.05) affected by probiotic supplementation. Non-fiber carbohydrate digestibility was decreased (P < 0.05) with C + and tended to increase (P = 0.09) with B + compared to C − and B −, respectively (B −, 60.8%; B +, 67.1%; C −, 72.3%; C +, 63.4%). Probiotic supplementation had no significant (P > 0.05) effect on total or individual volatile fatty acids. Although limited, data suggest that type of grain used in the diet can influence the effectiveness of probiotics in altering ruminal metabolism. Key words: Continuous culture, corn, hull-less barley, probiotic, ruminal fermentation
Antimicrobial supplementation alters digestibility and ruminal fermentation in a continuous culture model
