The Effects of Bacterial Inoculants, Beet Pulp, and Propionic Acid on Ensiled Wet Brewers Grains

¹ Department of Animal Sciences, Dairy Forage Facility, Washington State University Puyallup 98371

The objective of this research was to determine whether microbial inoculants, propionic acid, or beet pulp would enhance the fermentation of wet brewers grains under short-term or long-term storage. In trial 1, three treatments (control and two amounts of lactic acid bacteria) were applied to wet brewers grains ensiled for 1, 2, 3, 28, and 57 d. Each added amount of lactic acid bacteria decreased pH faster, increased initial concentration of lactate, and reduced initial concentrations of acetate and butyrate compared with the control. In trial 2, four treatments (control, lactic acid bacteria, lactic acid bacteria plus enzymes, or propionic acid) were applied to wet brewers grains ensiled for 1, 2, 4, 6, 8, and 90 d. Benefits of the treatments were limited. Trial 3 utilized the same treatments as trial 2, and wet brewers grains were ensiled for 10, 25, 40, 55, and 75 d. All treatments increased production of lactate, enhanced the rate of pH decline, and limited production of butyrate. In trial 4, wet brewers grains were ensiled for 6 and 90 d as four treatments: 1) control, 2) added beet pulp (15% of wet weight), 3) high moisture grain inoculant, and 4) a combination of treatments 2 and 3. Treatment 4 resulted in the lowest concentration of acetate, NH3 N, and pH and the greatest concentration of lactate after 90 d of storage. Addition of microbial inoculants, acid, or beet pulp to wet brewers grains was beneficial in promoting a more efficient fermentation during long-term storage; however, results for short-term storage were limited.

Key Words: inoculants • propionic acid • wet brewers grains • fermentation

Submitted on January 6, 1994
Accepted on December 6, 1994

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