JIA-2018-09

2091 TIAN Xing-zhou et al. Journal of Integrative Agriculture 2018, 17(9): 2082–2095 silage showed a significantly higher CP value compared to the control. Anthocyanins are sensitive to high pH, light, and temperature during storage period (Markakis and Jurd 1974; Francis and Markakis 1989; Laleh et al . 2006; Li et al . 2011). However, light and temperature factors could be considered to be negligent in this study because all the samples were compressed under anaerobic conditions, placed in mini- silos, and kept a dark environment at 15–25°C ambient temperature. Reyes and Cisneros-Zevallos (2007) showed that the degradation rate of anthocyanins were positively correlated with the pH value under the same external conditions. Consequently, the silage had a lower pH value after 7 d of ensilage, which provided the necessary condition for the stability of anthocyanins. Specifically, anthocyanins consisted of anthocyanidin and sugar(s), which is the sugar structure used as a substrate during the ensilage period (Hosoda et al . 2009). Therefore, the decreased range of anthocyanins in PSS was greater compared to SSS, possibly indicating that more sugar in PSS took part in the silage fermentation for easier ensilage. These observations were in agreement with Song et al . (2012) who demonstrated that colored barley showed higher total anthocyanins content and maintained a level of 42% in storing silage. Moreover, Cya seemed to be the main anthocyanin composition in two types of silage, which is consistent with the findings of previous studies (Pedreschi and Cisneros-Zevallos 2007; Cuevas Montilla et al . 2011). Interestingly, an interaction between treatment and time for M3G, Cya, and total anthocyanins indicated a differential response to storage time for each of silage. One study did show that the color of the purple plant is due to anthocyanins (Aoki et al . 2002). Thus, the fresh anthocyanin-rich PS displayed high levels of M3G, Cya, and total anthocyanins relative to the fresh SS. In addition, two samples showed different levels of DM; the trend of declining pH during the storage period was similar, whereas anthocyanin-rich PSS had a lower level of pH compared to the control silage. Collectively, together these factors could cause an interaction between treatment and time for the amount of anthocyanins. The pH value declined rapidly at the fermentation phase when the silage became anaerobic, which was usually in Table 8 Comparison of ruminal fluid pH, NH 3 -N, and VFA values of sticky corn stover silage (SSS) and anthocyanin-rich purple corn stover silage (PSS) Item 1) Time (h) SSS PSS SEM 2) P -value pH 12 6.82 6.87 0.0217 0.208 24 6.65 6.67 0.0222 0.444 48 6.56 6.56 0.00666 1.00 Mean 6.66 6.70 0.0423 0.477 NH 3 -N (mg dL –1 ) 12 2.00 1.95 0.0267 0.323 24 2.01 1.91 0.0738 0.422 48 2.89 2.87 0.0504 0.789 Mean 2.34 2.20 0.166 0.573 AA (mmol L –1 ) 12 78.2 73.1 3.45 0.419 24 83.3 81.5 1.23 0.357 48 96.0 92.4 1.32 0.122 Mean 86.8 82.3 2.92 0.309 PA (mmol L –1 ) 12 70.4 69.5 0.920 0.577 24 79.7 75.6 1.13 0.0647 48 94.5 88.3 2.65 0.175 Mean 82.9 77.8 3.23 0.297 BA (mmol L –1 ) 12 14.7 13.9 0.198 0.0899 24 16.3 15.8 0.298 0.318 48 20.8 19.0 0.455 0.110 Mean 17.6 16.3 0.841 0.300 TVFA (mmol L –1 ) 12 163 156 3.13 0.264 24 179 173 2.45 0.142 48 211 200 3.66 0.0891 Mean 187 176 6.81 0.290 Ratio of acetate to propionate 12 1.11 1.05 0.00361 0.0033 24 1.05 1.08 0.0592 0.572 48 1.02 1.05 0.0310 0.522 Mean 1.05 1.06 0.0203 0.797 1) NH 3 -N, ammonia nitrogen; AA, acetic acid; PA, propionic acid; BA, butyric acid; TVFA, total volatile fatty acid. 2) SEM, standard error of the mean. Values represented the means of 3 replicates ( n =3).