Abstract:[Background] The development and utilization of cassava residues (CR) as feed resources can reduce environmental pollution and realize the local transformation of these resources. Microbial fermentation can reduce the crude fiber content of CR, improve their palatability, and increase feed conversion efficiency. [Objective] This study was conducted to screen microbial starter cultures with better fermentation effects on CR and their fermentation duration. [Methods] Three kinds of complex microbial starter cultures, including A (Bacillus, Lactobacillus, and Saccharomyces cerevisiae), B (Pediococcus pentosaceus, and Saccharomyces cerevisiae), and C (Lactobacillus plantarum, Saccharomyces cerevisiae, and Bacillus subtilis) were selected and mixed with fresh CR. Then, they were randomly divided into seven groups with five replicates per group. Samples were collected on days 0, 1, 3, 7, 14, 28, and 56 of the fermentation, respectively, to determine the nutritional composition. [Results] Compared with fresh CR, starter culture A and B increased (P<0.05) the crude ash content of CR; Starter culture C increased (P<0.05) the crude protein content of CR; The three kinds of starter cultures decreased (P<0.05) the neutral detergent fiber content of CR and increased (P<0.05) the crude fat content. [Conclusion] Microbial fermentation can effectively improve the nutritional value of CR, of which the use of starter culture C for short-term fermentation has the most significant increase in their nutritional value, especially crude protein and crude fat contents.