Effects of Replacing Mushroom By-Product with Tofu By-Product on Chemical Composition, Microbe and Rumen Fermentation Indices of the Fermented Diet

This study was aimed to estimate the effect of replacing mushroom by-product (MBP) with tofu by-product (TBP) on chemical compositions, microbes, and rumen fermentation indices of the fermented diet. The basal diet was formulated with MBP, TBP, rice bran, molasses, and inoculant at 32, 27, 37.5, 2.0, and 1.5% on dry matter (DM) basis, respectively. The inoculant mainly contained Lactobacillus acidophilus (1.2ｘ10¹⁰ cfu/g), Bacillus subtilis (2.1ｘ10¹⁰ cfu/g), and Sacaromyces cerevisiae (2.3ｘ10¹⁰ cfu/g). The MBP of basal diet was replaced with TBP at 0, 5, and 10% (DM basis) to mix the experimental diets. The experimental diets were ensiled into 10 L mini silo with 5 replications and incubated at 39°C for 48 h. After incubation, the fermented diets were subsampled for the chemical compositions, pH, microbes, and rumen fermentation indices. For rumen fermentation indices, the subsampled diets (0.5 g) were placed into the incubation bottles and mixed with rumen fluid mixture (40 ml) composed of Van Soest medium and rumen fluid collected from cannulated two Hanwoo heifers at 2:1 ratio. The mixtures were incubated in a CO₂ incubator at 39°C for 48 h with 5 replications and 3 blanks. The bottle content was centrifuged at the end of incubation. The supernatant used for rumen pH, ammonia-N, and volatile fatty acid, and the residue used for DM and neutral detergent fiber digestibilities. With increasing TBP replacement levels, crude protein of fermented diet increased (L, P<0.001) while crude ash decreased (L, P=0.002). The pH (L, P<0.001) and mold (Q, P<0.001) of fermented diets decreased by increases of TBP replacement levels, whereas lactic acid bacteria (L, P=0.020) increased. However bacillus subtilis and yeast were not affected by TBP replacement levels. In vitro rumen digestibility of DM (P=0.053) and neutral detergent fiber (P=0.024) increased linearly by increases of replaced TBP levels, while rumen pH changed quadratically (P=0.026). Rumen total volatile fatty acid decreased (L, P=0.001) by increases of TBP replacement levels, but rumen ammonia-N was not affected. With increasing TBP replacement levels, the contents (% of molar) of iso-butyrate (P=0.003) and butyrate (P=0.080) increased quadratically. However, the contents of acetate, propionate, valerate, and iso-valerate did not affected by TBP replacement levels. In conclusion, this study indicated that the replacement of MBP with TBP up to 10% could improve the quality of fermented diets by the results of increased crude protein, nutrient digestibility, and lactic acid bacteria, but decreased pH and mold.