Fermentation Quality, In Vitro Digestibility, and Aerobic Stability of Total Mixed Ration Silage in Response to Varying Proportion Alfalfa Silage

Simple Summary Ensiling a total mixed ration (TMR) allows longer storage times for thoroughly mixed feed. In our previous study, we found that alfalfa silage could directly provide an acidic environment in fresh TMR and had a function comparable to that of lactic acid bacterial inoculants in improving fermentation quality during ensiling. However, the specific percentage of silage addition to the TMR has not been evaluated. In this study, we explored the effects of different proportions of alfalfa silage on the fermentation quality, in vitro digestibility, and aerobic stability of TMR silage and discussed the results in terms of the chemical composition of the feed. We found that the gradual development of an acidic environment during the ensiling process, which can be achieved with 40% alfalfa silage addition, can improve aerobic stability. However, the addition of 60% or 20% alfalfa silage might cause lower aerobic stability or clostridial spoilage in TMR silage. Our findings provide a more in-depth understanding of the effects of silage components on TMR silage and may guide farmers to apply a proper silage composition in rations to avoid the loss of feed value during storage or feeding stages. This study aimed to evaluate the effects of different proportions of alfalfa silage on the fermentation quality, in vitro digestibility, and aerobic stability of total mixed ration (TMR) silage. Three TMRs were prepared with different silage contents on a fresh matter basis: (1) 60% alfalfa silage (AS60), (2) 40% alfalfa silage (AS40), and (3) 20% alfalfa silage (AS20). The lactic acid in AS60 did not increase after 30 days of ensiling (p > 0.05). Butyric acid was detected in the AS20 group after 14 days of ensiling. The AS60 group showed significantly higher in vitro dry matter digestibility than the AS20 group (p < 0.05). The aerobic stability of TMR silage gradually increased with a decreasing percentage of alfalfa silage (p < 0.05). Unlike AS60, which directly gained an acidic environment from the alfalfa silage, AS40 developed a stable acidic environment during ensiling and further improved aerobic stability. However, when the percentage of alfalfa silage was reduced to 20%, a risk of clostridial spoilage occurred in the TMR silage. Therefore, the addition of 40% alfalfa silage to TMR is optimal and could achieve both good fermentation quality and considerable resistance to aerobic deterioration in TMR silage.