JIA-2018-09

2092 TIAN Xing-zhou et al. Journal of Integrative Agriculture 2018, 17(9): 2082–2095 the range of 3.6–4.0 for the excellent silage (Guan et al . 2002). This was because LAB developed, leading to it became the predominant population during anaerobic phase, resulting in large amounts of organic acid (Kang et al . 2014). Particularly, anthocyanin-rich PSS displayed a lower pH value, perhaps because the structure of purple corn anthocyanin was bonded to sugar (Aoki et al . 2002), resulting in easy fermentation during storage in anthocyanin- rich PSS relative to the control. Generally, poor silage preservation had a high level of NH 3 -N. This was due to breakdown of the protein in forage (proteolysis) occurring as a result of the activity of plant enzymes prior to the establishment of anaerobic conditions (Acosta et al . 1991; Hu et al . 2015). However, wetter silage also had higher concentration of NH 3 -N because of the potential for clostridial fermentation (Kung and Shaver 2001). Thus, SSS had a relatively high level of NH 3 -N, perhaps owing to it had lower DM content in comparison to PSS. Additionally, since the sugar in anthocyanin was used as a substrate for lactic fermentation, which may have produced high LA content (Hosoda et al . 2009). AA and PA were the main energy sources for the harmful microorganisms during ensilage. Uniquely, the high level of soluble nutrients, especially NDF and ADF in plants was usually displayed high levels of AA, PA, and BA (Kung and Shaver 2001). In this report, two types of silage had similar levels of NDF andADF, thus there was no effect of treatments on AA and PA values. These findings were in agreement with Song et al . (2012) who showed that colored barley silage had a higher level of LA and similar levels of AA, PA, and BA compared to that of normal barley silage. 4.3. DPPH scavenging activity Anthocyanins, as a bioactive secondary plant metabolite, have been shown to have high antioxidant activity (Akula and Ravishankar 2011). DPPH was a free radical, which was able to produce a violet solution in an organic solvent and was stable at room temperature. The value of DPPH tended to decline under antioxidant molecule circumstances (Mensor et al . 2001). Accordingly, this was a handy and rapid way of being able to assay antioxidant activity by measuring DPPH scavenging activity (Cheng et al . 2006). In this experiment, anthocyanin-rich PSS extract had a stronger level of the DPPH scavenging activity than the control extract. One of the possible explanations was that anthocyanins could provide electrons to DPPH, so the solution was reduced to its non-free radical form to strengthen antioxidant activity (Jordão and Correia 2016). The amount of DPPH scavenging activity was in accordance with Hayashi et al . (2003). Indeed, anthocyanins are powerful antioxidants due to their special chemical structural formula, preventing free radicals from being oxidized nearby cells (Castañeda-Ovando et al . 2009). In addition, the IC 50 value was negatively associated with the DPPH scavenging activity (Yang and Zhai 2010). As expected, PSS extract had lower IC 50 level in this study, which was consistent with a previous report by Pedreschi and Cisneros-Zevallos (2006) who demonstrated that purple corn extract had a higher antioxidant activity, primarily depending on anthocyanins involved in enzyme inactivation and scavenging of electrophiles. 4.4. In vitro rumen fermentation Previous studies indicated that the incubation of anthocyanin- rich corn or colored barley with ruminal fluid had no effect on the degradation of anthocyanin (Hosoda et al . 2009; Song et al . 2012). Their results may be a definite explanation that anthocyanins in plants are not broken down in the rumen. In the current study, anthocyanin-rich PSS had a lower level of GP as well as a parameter, perhaps because it had the relatively high content of fiber content and relatively low level of WSC, resulting in slower degradation rate (Brebu and Vasile 2010). It is consistent with Mangan (1988) who reported that the flavonoid family can reduce the degradability of ruminal fluid nutrients to achieve the aim of preventing bloating. A similar conclusion was also given for the lower amount of GP in anthocyanin-rich grape pulp (Spanghero et al . 2009). Therefore, anthocyanins may only have potential value in improving ruminant health rather than providing individual bodies with access to nutrients. Correddu et al . (2015) demonstrated that the rumen metabolism of lactating dairy-ewe was markedly influenced by dietary supplementation with anthocyanin-rich grape. Similarly, the feeding of anthocyanin-rich purple corn silage may increase superoxide dismutase (SOD) activity in the plasma, but had no effect on rumen fermentation parameters in lactating dairy cows (Hosoda et al . 2012a). In short, it was safe to assume that anthocyanins had no negative impact on rumen fermentation, but they had the potential to inhibit GP for prevention of ruminant bloating. In this report, anthocyanins might be able to affect carbohydrate metabolism to provide more energy for ruminants by inhibiting AA production, increasing the proportion of PA. Hosoda et al . (2012a) reported that the feeding of anthocyanin-rich purple corn silage resulted in a lower AA to PA ratio in lactating dairy cows. However, Hosoda et al . (2012b) showed that the feeding of purple rice silage had higher ruminal fluid pH value and lower VFA because of poor nutrients and silage fermentative quality. As a consequence, nutrient composition could be one of the main factors affecting rumen fermentation, since anthocyanins may escape from the rumen to reach