## 4 Discussion
This decrease in acetate concentration might be caused by decreasing rumen pH through the hour of incubation in the present study, which agreed with the previous studies [21; 23]. The low rumen pH would inhibit the growth of fibrinolytic bacteria, where acetate was a result of structural carbohydrate degradation by these bacteria [21; 24]. The propionate was higher in the early hour of incubation by cultivated SB at 0 day. However, cultivated SB at 0 day had the lowest propionate concentration from 4 to 48 h. The higher propionate concentration of cultivated SB at 4 and 8 days might be caused by the change of starch into free sugar by germination [1; 2; 22], where free sugar was degraded by rumen microbe into propionate [21; 24]. The propionate showed a cubic pattern during incubation, which might be affected by the changing patterns of acetate and butyrate concentrations. It also could be partially supported by converting propionate into glucose [25] and lactate [26] through the gluconeogenesis of rumen microbes. Butyrate concentration increased slightly from 0 to 24 h of incubation. However, it was lower in SBs at 4 and 8 days compared to SB at 0 day on 48 h of incubation. In general, cultivated SB at 0 day showed a higher butyrate concentration with lower propionate concentration than cultivated SBs at 4 and 8 days during incubation. These results indicated that the germination could increase free sugar proportion and its degradation in the rumen. The IVDMD and IVNDFD of SB after 48 h of incubation showed the quadratic effect by cultivation stage, where cultivated SB at 4 days had the highest. These results in the present study agree with the previous studies that the germination increased rumen digestibility because of a change of polymer nutrients into monomer or oligomer nutrients [1; 2; 22]. The increased nutrient digestibility in cultivated SBs at 4 and 8 days were also supported by the previous study, which were tested in the animal trial [4; 5]. However, a more prolonged cultivation stage could decrease the digestibility of SB due to the increase of structural carbohydrates [1; 10]. Therefore, in the present study, IVDMD and IVNDFD increased in cultivated SB at 4 days and then decreased in cultivated SB at 8 days. In general, the results of IVDMD and IVNDF have supported by the results of [PERSON] and [PERSON] [2] that 1 to 4 days of SB cultivation were nutritionally superior for livestock diet including ruminants. After 48 h of incubation, the result of rumen pH was supported by the result of total VFA in the present study. A high concentration of total VFA resulting from microbial degradation would decrease the rumen pH. In addition, the ammonia-N concentration also influenced the rumen pH [21], but its concentrations did not differ among the cultivation stages after 48 h of incubation. Interestingly, the total VFA concentration was a contrast to IVDMD results in the present study. Cultivated SB at 0 day had the highest total VFA concentration but the lowest IVDMD. Even though the grain barley highly contained soluble carbohydrates, but it had a lot of hull (Figure 1) that could not degrade in the runen. It was a reason for the low IVDMD of cultivated SB at 0 day in the present study. The barley grain was faster to degrade but had a lower total degradable fraction than it sprouting form (Table 3). In addition, the soluble carbohydrate of cultivated SB at 0 day could be another reason for high total VFA concentration that is also in agreement with by the results of [PERSON] and [PERSON] [21]. In the present study, cultivated SBs at 4 and 8 days had a higher propionate and a lower butyrate. Similar to our discussion above, these results may be caused by the changes in nutrient forms due to germination. Supporting the IVDMD and IVNDFD results of the present study, the DM and NDF degradation kinetics results also indicated that 4 days was the best day for cultivating SB because it produced the highest total degradable fraction.