## 4 Discussion  
All the sorghum silage samples were well fermented with low pH values (<4.2) because the WSC content of the raw material was high (70.31 g kg\({}^{-1}\) DM), adequate fermentable substrate is the basis for sufficient lactic acid production [27]. However, it was found that high temperature could cause a decline in the lactic acid content and increases the pH value previously [14], which also occurred in our study. The homofermative inoculants produced a sufficient amount of lactic acid, and the LAB-treated silages in this study all had lower pH values than the control. [PERSON] et al. [28] and [PERSON] et al. [29] also reported that the application of _Lactobacillus plantarum_ to sorghum silage significantly improved the lactic acid contents and reduced the acetic acid and propionic acid contents. The efficiency of the fermentation was promoted by the LAB treatments at 20 and 30 \({}^{\circ}\)C. The inoculants accelerated the process of lactic acid fermentation and suppressed the detrimental microorganisms such as clostridia, enterobacteria and yeasts, which reduced the consumption of WSCs [2]. The silages treated with homolac  
Figure 3: The phenolic acid extraction yields of sorghum silage. (**a**) Ferulic acid (FA) extraction yields. (**b**) \(p\)-coumaric acid (PCA) extraction yields. DM, dry matter; Control [12], LF18, _Lactobacillus fraciminis_ inoculant [23], LP23, _Lactobacillus plantarum_ inoculant [23]. Means within the same temperature (a, b) or within the same inoculant (A, B) with difference superscripts differ significantly from each other (\(p<0.05\)). Error bars indicate standard error of means. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline \multirow{2}{*}{**Item**} & \multirow{2}{*}{**Temperature**} & \multicolumn{3}{c}{**Inoculant**} & \multirow{2}{*}{**SEM**} & \multicolumn{3}{c}{**Significance**} \\ \cline{3-3} \cline{5-8}  & & **Control** & & & **LF18** & **LP23** & **I** & **T** & **I \(\times\) T** \\ \hline \multirow{3}{*}{DMD (\%)} & 20 \({}^{\circ}\)C & 47.71 & 47.42 & 48.78 & 0.78 & 0.866 & 0.485 & 0.966 \\  & 30 \({}^{\circ}\)C & 49.1 & 49.35 & 49.15 & & & & \\  & 40 \({}^{\circ}\)C & 48.9 & 51.53 & 50.5 & & & & \\ \hline \multirow{3}{*}{NDFD (\%)} & 20 \({}^{\circ}\)C & 35.61 & 36.96 & 34.52 & 0.30 & 0.042 & 0.876 & 0.018 \\  & 30 \({}^{\circ}\)C & 34.30  & 38.34  \\ \hline \hline \end{tabular}
\end{table} 
Table 3: In vitro digestibility of sorghum silages. had a higher ratio of lactic acid to acetic acid, which is usually used as a qualitative indicator of fermentation [30]. The LP23-treated silage had a significantly higher ratio of lactic acid to acetic acid than the control and LF18 groups at 20 and 30 \({}^{\circ}\)C, but at a temperature of 40 \({}^{\circ}\)C, the ratio of lactic acid to acetic acid in the LP23 group was significantly decreased. It is likely that LP23 does not exhibit its optimal growth at high temperature and becomes less competitive than enterobacteria at the higher temperature used in this study. In contrast to homofermatterative LAB, enterobacteria produce more acetic acid from glucose [31]. A lower temperature might reduce the propionic acid content. [PERSON] et al. [32] did not detect propionic acid in silage stored at a temperature below 25 \({}^{\circ}\)C. In China, sorghum is typically harvested during the hottest four months, when daytime temperatures can easily reach 40 \({}^{\circ}\)C, while tropical regions may maintain high temperatures for longer periods of time. In this study, the LAB-treated silages presented a higher Flieg's point than the control silages at 40 \({}^{\circ}\)C, which indicated that the inoculants could still improve the fermentation quality of sorghum silage at high temperature. Furthermore, increased proteolysis occurs in silages stored at high temperatures, which results in lower CP contents [33; 34]. In addition, increased proteolysis results in higher buffering and poorer fermentation, which might also alter the fermentation profile and the microbiology of sorghum silage [31].