Microbial dynamics in combinations of forage cactus and sorghum silage as a function of aerobic exposure and faecal contamination

Abstract This study evaluated the dynamics of the bacterial community in mixtures of forage cactus and sorghum silage at different proportions, subjected to aerobic exposure periods, without or with faecal contamination. The experimental design was completely randomized in a 2 × 2 × 4 factorial arrangement, with two forage cactus proportions (20% and 80%), absence or presence of faecal contamination, and four aerobic exposure times (0, 6, 12, and 24 h). Fermentation profile, chemical composition, microbial populations, and bacterial diversity were evaluated. A higher proportion of forage cactus resulted in increased pH and greater proliferation of enterobacteria, with detection of Escherichia coli after aerobic exposure. In contrast, mixtures containing 20% forage cactus and 80% sorghum silage showed greater fermentative stability, characterized by higher lactic acid production, reduced growth of potentially pathogenic microorganisms, and lower abundance of undesirable bacterial groups after 24 h of exposure. The combination of 20% forage cactus and 80% sorghum silage was more effective in preserving the microbiological and fermentative quality of the mixture during aerobic exposure.