## 3 Results and Discussion
### In Vitro Runnial Fermentation of Silages: Fermentative Parameters  
After 24 h of in vitro incubation of silages with ruminal fluid from sheep, the total VFA production was greater for UM (\(p<0.05\)) than for the other silages (Table 4), which may be due to a greater availability of degradable compounds, such as molasses and urea, for ruminal microorganisms. These results are in good accordance with the greater values of AGPR and PDMD observed for UM silage (Table 2). In agreement with our results, [PERSON] and [PERSON] [PERSON] and [PERSON] (2018) also observed a significant increase in total in vitro VFA production when Leucena silage was enriched with urea and molasses. Although [PERSON] et al. (2018) observed the same effect when including formic acid in ryegrass silage, no increase in total VFA concentrations was observed by [PERSON] et al. (2018) by including formic acid in ryegrass silages, which agreed with our results. The lack of differences in in vitro VFA production between CON and FA silages was consistent with the similar PGP and PDMD values observed for both silages (Table 2).  
There were significant differences among silages in all individual VFA. Compared with CON, all of the treated silages had greater (\(p<0.05\)) acetic and propionic proportions, but lower (\(p<0.05\)) butyric, isobutyric, isovaleric, and valeric proportions. As a consequence of these shifts in VFA profile, the acetate/propionate ratio was lower (\(p<0.05\)) for the silages treated with formic acid (FA and FAUM) than for the CON and UM silages. The effects of silage additives on VFA profile in their in vitro fermentation reported in the literature are controversial. [PERSON] et al. (2018) and [PERSON] et al. (2018) did not observe significant differences in the ruminal VFA profile when using formic acid as an additive for grass and drooping wild ryegrass silages, respectively. [PERSON] and [PERSON] [PERSON] and [PERSON] (2018) reported no shifts in VFA profile after including molasses and urea in Leucena silages, except for an increase in propionate proportion, which is in agreement with our results.  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Item 2**} & \multirow{2}{*}{**CON**} & \multirow{2}{*}{**FA**} & \multirow{2}{*}{**UM**} & \multirow{2}{*}{**FAUM**} & \multirow{2}{*}{**SEM 2**} & \multirow{2}{*}{\(p\) =} & \multicolumn{2}{c}{**Typha**} & \multirow{2}{*}{**Triticale Hay**} \\  & & & & & & & & \\ \hline Total VFA (mmol/g dry matter) & 4.33  & 5.31  & 0.105 & \(<\)0.001 & 4.00 & 5.74 \\  & & & & & &  
The lower proportions of isobutyric, valeric, and isovaleric acids observed for the treated silages compared with the CON silage might be indicative of reduced CP degradation, as these VFA were produced in the degradation of branched-chain amino acids [25], but the NH\({}_{3}\)-N concentrations were similar to CON for FA silage and greater for the UM and FAUM silages (Table 4). The greater NH\({}_{3}\)-N concentrations observed for UM and FAUM silages agreed well with previous studies using urea as a silage additive. In fact, [PERSON] et al. [22] and [PERSON] and [PERSON] [35] observed increased concentrations of NH\({}_{3}\)-N when napiergrass and Leucaen silages, respectively, were treated with urea.  
Compared with the pre-ensiling typha, all of the silages had numerically greater VFA production, but it was lower than that of triticale hay. These results are consistent with the lower gas production of the silages and indicate that the silages were fermented in vitro to a lesser extent than the triticale hay. However, the VFA profile of the silages was similar to that of triticale hay, especially for those treated with formic acid (FA and FAUM) that showed comparable acetate/propionate ratios (2.91, 2.83, and 2.74 for FA, FAUM, and triticale hay, respectively).