*3.2.1 Bacterial inoculants*

LAB plays a major role in the fermentation process of silage, whose main strains include *Lactococcus* (*Streptococcus faecalis*, *Staphylococcus lactis*, *Lactobacillus lactis football*, etc.) and *Lactobacillus* (*Lactobacillus plantarum*, *Lactobacillus brucei*, *Lactobacillus casei*, *Lactobacillus brevis*, etc.). Inoculated LAB in silage can be divided into two types: homozygous and heterotypic fermentation. Homotypic fermentation mainly includes *Lactobacillus plantarum* and *Pediococcus lactis*, while heterotypic fermentation is mainly *Lactobacillus brucei* at present. The advantages of homozygous fermentation are that one glucose is converted into

two lactic acids, which have strong acid-producing ability, fast pH value reduction, and less DM loss during fermentation. However, its disadvantage is that it produces a large amount of lactic acid, resulting in poor aerobic stability after cellar opening. After exposure to air, the silage pH value increases rapidly and the silage temperature increases accordingly. Heterotypic fermented convert 1 mol of glucose into 1 mol of lactic acid and 1 mol of acetic acid. Because the acidity of acetic acid is less than that of lactic acid, the speed of reducing pH value in fermentation is slower than that of the same type, and the loss during fermentation is higher than that of the same type of LCB. However, due to the production of a large amount of acetic acid, the aerobic stability after cellar opening is very good, up to 100 hours.

*Lactobacillus* inoculum, or LAB starter, is widely recognized and commercialized, mainly because it can reduce the loss of DM in the early stage of fermentation. However, during silage opening, this microbial inoculum failed in preventing thermal deterioration of silage and did not improve the aerobic stability of silage. What bother producers is certain yeasts that have a strong utilization of lactic acid, which are insensitive to high concentrations of lactic acid, are highly tolerant to low pH environments, and cannot inhibit its activity in acidic environments. They grow well in the acidic environment of silage. When the silage is opened, they are twice as active after exposure to air as in the sealed environment of silage. During the period of aerobic exposure, these yeasts can utilize lactic acid as an energy substance. The aerobic activity of yeasts will lead to the increase of silage pH due to the utilization and consumption of lactic acid, which weakens the acidic environment. In such an environment, other aerobic bacteria and molds will also activate, while the degree of silage corruption will deepen. Ultimately, the activity of aerobic microorganisms can not only lead to the loss of sugar, starch, and protein but also produce a lot of heat because of the large number of microbial reproduction and activity.

Nowadays, widely used and recognized inoculants contain mixed microbial inoculants of both homotypic LAB (to reduce pH) and heterotypic *Lactobacillus brucelli* (to inhibit yeasts), which can ensure both successful fermentation during anaerobic fermentation of silage and reduction of fever, deterioration, and spoilage during open pit.

### *3.2.2 Enzyme*

Additional enzymes mainly refer to a variety of cell wall degrading enzymes, such as cellulase, hemicellulase, amylase, and pectinase. The purpose of adding enzymes is to reduce the fiber content in silage. In addition, more sugars can be degraded by enzymes for LAB fermentation. As enzymes contribute to the degradation of acidic and neutral washing fibers, lactic acid fermentation, dry matter recovery, and storage life are improved. Because of the large demand and high cost of enzyme preparation in the process of adding, it is seldom used in the actual production process.

### *3.2.3 Antiseptic additives*

In order to reduce the pH value quickly, soften the silage, and facilitate the digestion of materials, dilute sulfuric acid or hydrochloric acid can be added to the silage. Preservatives are added to make the silage sink quickly, compact easily, increase the storage capacity, and make the silage crops stop breathing (biological oxidation) quickly, thus improving the success rate. Formic acid and propionic acid are commonly used. Benzoic acid and its sodium salt also have good bacteriostatic effect on molds in silage with dosage not exceeding 0.1%. In the United States and
