JIA-2018-09

2090 TIAN Xing-zhou et al. Journal of Integrative Agriculture 2018, 17(9): 2082–2095 metabolism during the whole ensilage period, thus reducing its value (Sanderson 1993). The interaction between silage and storage day for WSC was the result of the high level of WSC found in fresh SS compared to the fresh anthocyanin- rich PS. Owens et al . (1999) demonstrated that sugars remaining in silage could be derived from the hydrolysis of structural carbohydrates or starch. In the current study, structural carbohydrates did not differ in two treatments, probably indicating that the starch content was the main factor that affected the level of WSC. However, the exact reasons remain unclear and further observation is required. Fiber content was a major component of the plant cell wall and was insoluble in water, making it difficult to be exploited by microorganisms during the storage period (Mertens 2003). Hence, the concentrations of NDF and hemicellulose of SSS and PSS did not differ between silages and remained fairly constant throughout the experiment. On the contrary, ensilage treatment could accelerate the growth of lactic acid bacteria (LAB), but the ensilage treatment lacked proteolytic enzyme and relevant ash/OM degrading enzyme; thus, ash and OM values also did not differ among treatments and have been quite stable during the entire ensilage period. Moreover, the levels of GE and ADF tended to increase during the ensilage period, which was reported to be related to the strength of silage fermentation, in which the loss of moisture is induced, leading to high DM, with consequent concentration of the GE and ADF (McDonald and Edwards 1976; Meineri and Peiretti 2005). Additionally, we also found the concentration of CP in PSS was significantly higher than that of SSS. The reason may be that in purple plant response to environmental stresses through anthocyanin metabolism, plant nutrients can be improved under anthocyanin protection (Chalker-Scott 1999). These results were consistent with a previous report by Hosoda et al . (2012a) who reported that anthocyanin-rich purple corn Table 5 Comparison of DPPH scavenging activity of sticky corn stover silage (SSS) and anthocyanin-rich purple corn stover silage (PSS) extracts (%) Type 1) Dilution Mean1 2) SEM P -value 3) 1/5 1/4 1/3 1/2 1 Silage Dilution S×D SSS 59.7 67.6 71.3 72.2 73.5 68.9 B 1.68 <0.0001 <0.0001 0.601 PSS 70.9 75.4 78.4 79.8 81.1 77.1 A 1.12 Mean2 65.3 c 71.5 b 74.9 a 76.0 a 77.3 a SEM 0.827 0.186 1.92 1.44 0.536 1) Mean2, values represent the means of 6 replicates ( n =6); SEM, standard error of the mean. 2) Mean1, values represent the means of 15 replicates ( n =15). 3) Silage, effect of silage extract; Dilution, effect of dilution; S×D, effect of silage extract and dilution interactions. Values represent the means of 3 replicates ( n =3). Means with different lowercase letters within the same row are significantly different ( P <0.05); means with different uppercase letters within the same column are significantly different ( P <0.05). Table 6 Comparison of in vitro gas production (GP) of sticky corn stover silage (SSS) and anthocyanin-rich purple corn stover silage (PSS) for 96 h Type 1) Incubation time (h) 2) Mean1 3) SEM P -value 4) 3 6 9 12 24 48 72 96 Silage Time S×T SSS 18.7 24.3 31.3 39.3 61.3 80.0 88.7 90.7 54.3 A 1.41 <0.0001 0.0002 0.960 PSS 15.4 20.7 29.0 35.7 57.3 79.0 85.8 88.5 51.4 B 1.30 Mean2 17.0 g 22.5 f 30.2 e 37.5 d 59.3 c 79.5 b 87.3 a 89.6 a SEM 0.833 1.27 1.16 1.30 1.70 1.33 1.80 1.20 1) Mean2, values represent the means of 6 replicates ( n =6); SEM, standard error of the mean. 2) Values represent the means of 3 replicates ( n =3). 3) Mean1, values represent the means of 24 replicates ( n =24). 4) Silage, effect of silage; Time, effect of incubation time; S×T, effect of silage and incubation time interactions. Means with different lowercase letters within the same row are significantly different ( P <0.05); means with different uppercase letters within the same column are significantly different ( P <0.05). Table 7 Comparison of gas production (GP) kinetics, OMD, ME, and ED of sticky corn stover silage (SSS) and anthocyanin-rich purple corn stover silage (PSS) Item 1) SSS PSS SEM 2) P -value a (mL) 7.26 3.71 0.0190 <0.0001 b (mL) 85.2 86.9 0.530 0.145 a+b (mL) 92.4 90.6 0.534 0.139 c (% h) 0.04 0.04 0.0002 0.684 OMD (%) 71.9 68.0 1.68 0.176 ME (MJ kg –1 ) 9.94 9.39 0.237 0.176 ED (%) 54.9 52.3 1.07 0.0966 1) a, gas production from the immediately soluble fraction; b, gas production from the insoluble fraction; a+b, potential extent of gas production; c, gas production rate constant; OMD, organic matter digestibility; ME, metabolizable energy; ED, effective degradability. 2) SEM, standard error of the mean. Values represented the means of 3 replicates ( n =3).