RESUMEN
The utilization of solid-state fermentation (SSF) of cassava stem, "Manihot esculenta Crantz-MEC", is central in this study for its biochemical characterization and formulation of a new poultry feed using a starter culture of Rhizopus oligosporus strain at specified experimental conditions (26 ± 1 °C, 72 h and pH 6). The coupling of R. oligosporus strain to SSF of cassava stem caused significant increase (p < 0.05) in glucose, total reducing sugar (TRS) and total soluble protein (TSP) concentrations at variable but marked effect at 10% inoculum size of the fermented cassava stem, as compared with the unfermented type. Further evaluations of DPPH-radical scavenging activity, total phenolic and flavonoid contents (TPC and TFC), as indices of correlation to antioxidant activity in both fermented and unfermented cassava stems showed marked significant difference with prominence at 10% inoculum size (p < 0.05). Results of high α-amylase activities were observed in fermented cassava stem when compared with the unfermented type (p < 0.05) at increasing inoculum sizes (5-15%) but with marked dominance at 10%. Broiler chicks fed with formulated feed showed marked increase in weight gain at 10% inoculum size of the fermented cassava stem relative to a typical poultry feed. Also, examination of alkaline phosphatase (ALP) and alanine and aspartate aminotransferases (ALT and AST) showed no marked difference in their activities for fermented feed at increasing inoculum sizes when compared with typical poultry feed, respectively (p > 0.05). The study hereby suggests the use of fermented cassava stem as an alternative raw material during formulation of livestock feeds.