Effects of brewer's spent yeast inclusion level and ensiling duration on fermentative, fungal load dynamics, and nutritional characteristics of brewer's spent yeast-based silage

OBJECTIVE: This study was conducted to evaluate the effect of brewer's spent yeast (BSY) inclusion level and ensiling duration (ED) on fermentative, fungal load dynamics, and nutritional characteristics of brewer's spent-yeast based silage. MATERIALS AND METHODS: To prepare the silages materials, 4 BSY inclusion levels (0, 10, 20, and 30%) to replace BSG and 3 ED (2,4 and 6 weeks) were arranged in 4 × 3 factorial combination using a completely randomized design (CRD) in 5 replications. The ratio of brewery spent grain (BSG) to wheat bran (WB) used majorly as protein and energy sources, respectively was 30:69 with a 1% salt addition. Parameters measured include observation for surface spoilage, yeast and mold colony count, silage temperature, pH, total dry matter loss (TDML), major proximate, detergent fractions and permanganate lignin, in-vitro organic matter digestibility (IVOMD) and estimated metabolizable energy (EME) values. RESULTS: The study revealed that at any BSY inclusion level and ED, extensive mold growths and discolorations were not observed. However, slightly higher values of 6.5, 5.7, and 12.2 colonies forming unit (CFU)/g DM yeast, mold, and total fungal counts (TFC), respectively were recorded only at the 6 weeks of the fermentation period with 30% BSY inclusion level. Brewer's spent yeast inclusion level and ED had a significant (P < 0.05) effect on silage temperature (mean = 18.05 °C) and pH (mean = 4.16). Among proximate and detergent values, crude protein (mean CP g/kg DM = 204.5), neutral detergent fiber (mean NDF g/kg DM = 552.9), and acid detergent fiber (mean ADF g/kg DM = 115.9) responded significantly (P < 0.05) to both BSY inclusion levels and ED. CONCLUSION: Among nutritional quality, CP, IVOMD, and EME of silage samples were subjected to substantial improvements when silage masses were prepared from 20% BSY inclusion levels and when the same silage materials were allowed to ferment for four weeks. In addition, the lab-based experiment should be supported with additional silage quality parameters like volatile fatty acid content of the silage materials and supplementation of ruminant livestock under both on-station and on-farm conditions using either a pilot and/or target animals.