Lactic Acid Bacteria and Formic Acid Improve Fermentation Quality and Beneficial Predicted Functional Characteristics in Mixed Silage Consisting of Alfalfa and Perennial Ryegrass

Abstract

The purpose of the present study was to investigate the effect of additives on the fermentation properties of ensiled mixed alfalfa and perennial ryegrass silage in the karst terrain of Southwest China. A mixture of alfalfa and perennial ryegrass was ensiled at a ratio of 3:7 using three experimental treatments: (1) CK (without additives) and distilled water (5 mL kg−1 fresh weight (FW)); (2) FA and formic acid (88%) (5 mL kg−1 FW); and (3) LAB combined with the application of Lactiplantibacillus plantarum and Lentilactobacillus buchneri (2 × 107 cfu/g FW). All samples were packed manually into polyethylene bags, and three polyethylene bags from each treatment were sampled on days 7, 15, and 45. The findings demonstrated that the pH values of all the mixed silages gradually decreased during ensiling. The lactic acid (LA) and acetic acid (AA) contents increased gradually with ensiling time and peaked after 45 days of ensiling. After 45 days of ensiling, the FA and LAB groups effectively preserved the nutrient content of the mixed silage, which presented a reduced neutral detergent fiber and acid detergent fiber content (p < 0.05) and higher water-soluble carbohydrate content (p < 0.05) than the CK group. The fermentation quality of the mixed silages in the FA and LAB groups improved, as indicated by higher (p < 0.05) LA contents and lower (p < 0.05) pH and ammoniacal nitrogen contents after 45 days of ensiling compared to those in the CK group. As fermentation progressed, the abundance of harmful microorganisms (Hafnia obesumbacterium, Enterobacteriaceae, and Sphingomonas) and beneficial microorganisms (Lactiplantibacillus and Lentilactobacillus) decreased and increased, respectively. In addition, compared to those in the CK group, the FA group had higher abundances of “lipid metabolism” and “biosynthesis of antibiotics” and lower abundances of “membrane transport”. Briefly, the results of this study suggest that the incorporation of FA and LAB additives could improve the quality of fermented mixed silage, and that FA is better than LAB. This information is useful for combining forage resources to satisfy the requirements for high-protein feed and for manufacturing ruminant feed annually.

Effect of Chemical and Microbial Additives on Fermentation Profile, Chemical Composition, and Microbial Populations of Whole-Plant Soybean Silage

“…Chemical additives reduced NH 3 -N content in WPS silage indicating lower proteolysis during silage fermentation, which is further confirmed by the greater concentration of CP observed in these silages when compared to other treatments. Aligning with the current study, authors have reported that chemical additives with organic acids are able to decrease ammonia N content in mixed legume-grass silage [28]. It is important to note that fermentation parameters and metabolites were assessed at the opening of the silos, and they cannot represent the fermentation dynamics throughout the silage storage period.…”

“…In whole-plant corn silage, WSC concentration and pH at opening were similar between silage treated with LAB and with organic acids [27]. In a mixed silage (alfalfa and perennial ryegrass), the pH was lower and WSC was greater in silages treated with formic acid regardless of the storage period (7, 15, or 45 d) in comparison with those treated with LAB [28]. Regarding comparisons between chemical additives, silages treated with FA type had greater concentrations of NFC than those silages treated with PA type, aligning with lower silage pH at opening for FA silos in comparison with PA type.…”