Combined Application of Probiotic and Phytobiotic Additives Improves Fermentation Quality and Amino Acid Preservation...

Preserving high-quality forage through silage is essential for continuous livestock production, yet protein degradation during fermentation remains a major challenge. To mitigate this nutrient loss, probiotics and phytobiotics are utilized as protective additives. This study investigated the synergistic application of lactic acid bacteria (LAB) and plant-derived bioactive compounds as deamination inhibitors to improve the fermentation quality and amino acid profiles of tropical forage silages. The experiment followed a 2 × 4 × 4 completely randomized factorial design with five replications. Factor A tested the inclusion of lactic acid bacteria (LAB) inoculum (Lactiplantibacillus plantarum). Factor B compared different plant extracts as additives (Acacia mangium, Swietenia macrophylla, and cumin essential oil), while Factor C evaluated various forage types (Pennisetum purpureum, Indigofera zollingeriana, Gliricidia sepium, and Stylosanthes guianensis). Statistical analysis revealed that LAB inoculation significantly reduced the pH level, suppressed fungal contamination, and improved physical traits (p < 0.05). Both the additive sources and forage types also exerted strong influences across all measured variables (p < 0.05). The interaction between microbes and plant extracts enhances protein preservation during ensiling. Among all the treatments tested, Indigofera zollingeriana showed the best response. The specific combination of L. plantarum and A. mangium extracts in Indigofera silage produced the best fermentation characteristics and a high ability to retain essential amino acids, particularly histidine, lysine, tryptophan, and valine. Lower NH₃-N concentrations and better amino acid preservation in this treatment indicate reduced protein loss due to proteolysis and deamination during fermentation. These findings confirm that the combination of probiotics and certain plant extracts is a highly effective strategy for maintaining the nutritional integrity of tropical forage preserved in silage form.