Nutritional and logarithmic fungal count of brewery spent grain in different conservation techniques and brewery factories’

Abstract

The higher moisture level (70–80%) in wet brewer’s grain (WBG) poses two major difficulties when using it as a feed for different classes of animals. Firstly, transport of WBG is costly. Secondly, the rich polysaccharide and protein content and the high moisture content of WBG make it susceptible to microbial growth and spoilage. Therefore this study was planned to examine the effect of soaking, sun drying and ensiling on nutritional and fungal load dynamics of wet brewers’ grain. Wet brewers’ grain was collected from Meta Abo, Habesha, Dashen and Bedele breweries, Ethiopia. The sample was labeled and kept in a separate sterile bag and stored under − 20 °C. For soaking, 2 kg sample was uniformly treated with salt (3% on dry matter basis), placed in plastic container and covered with a lead for partial aerobic condition. Wet brewers’ grain (2 kg) was exposed to sun drying for the consecutive three days, eight hours per day. The sample (2 kg) with molasses (3% on dry matter basis) was ensiled in a plastic bottle. All samples except sun dried, were subjected to oven drying at 55 °C for 72 h. To evaluate insacco degradability, samples were incubated for 6, 12, 24, 48, 72 and 96 h in nylon bags (6.5 × 14 cm, 50 μm pore size) placed in ventral sac of three cannulated Boran-Friesian steers (550 ± 15 kg live weight). The samples (25 g) were dissolved in 225 ml of peptone water. Potato Dextrose agar medium was injected with 1 ppm per each 100 ml of agar with chloramphenicol and streptomycin to restrict bacterial growth. Plates were incubated aerobically at 28 ± 1 °C for 3 day and growing molds and yeast colonies were directly counted. The sample received from Meta Abo brewery factory had the higher (p < 0.05) acid detergent fiber, lignin and digestible organic matter but comparable dry matter (DM), ash, crude protein (CP) and neutral detergent fiber with other breweries. The minimal loss on DM and other nutrients, lower fungal, yeast and mold colony counts and the higher CP digestion kinetics was observed in ensiling techniques. If supply is not a constraint under local conditions, ensiling can be recommended as the best conservation practice.