Differences in Chemical Composition, Polyphenol Compounds, Antioxidant Activity, and In Vitro Rumen Fermentation among Sorghum Stalks

Simple Summary Polyphenol compounds are important physiological activity materials that resist corrosion and oxidation, can be maintained in a state of freshness, and can be used safely, among other advantages. In China, the most important cereal crop is sorghum, which is an important raw material for brewing. However, sorghum stalks are usually considered to have no value and are thrown away or burned, resulting in environmental pollution and the possible waste of a usable resource. Notably, the sorghum stalk contains an abundance of polyphenols that exhibit great development potential as unconventional resources. However, studies on sorghum stalks with respect to their polyphenol compounds and their effects on in vitro rumen fermentation in goats have been relatively rare to date. Accordingly, in the present study, six types of sorghum (Sorghum bicolor L. Moench) varieties used for brewing traditional Chinese liquor were selected, and we compared their stalks in terms of their chemical composition, polyphenol compounds, antioxidant activity, and effects on in vitro rumen fermentation in goats. Our findings provide new details regarding the use of this unconventional feed for goats, as well as theories for developing this kind of resource for use as ruminant feed. Abstract The aim of the study was to examine the differences in the chemical composition, polyphenol compounds, antioxidant activity, and in vitro rumen fermentation among six varieties of sorghum stalks. The results show that maoliangnuo 1 (M1) contained a higher (p < 0.05) level of dry matter, and jinzhong 405 (J4) contained a higher (p < 0.05) level of crude protein content. The concentrations of neutral detergent fiber, acid detergent fiber, and cellulose were significantly higher (p < 0.05) in stalk jinliangnuo (JN). The levels of chlorogenic acid, homoorientin, isovitexin, vitexin, rhoifolin, genistin, quercetin, apigenin, aloe emodin, emodin, and total polyphenols were all significantly (p < 0.05) higher in maohongnuo 6 (M6) than in the other stalks. Moreover, stalk M6 contained higher (p < 0.05) levels of total antioxidant capacity (TAC), glutathione peroxidase (GPX), catalase (CAT), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging capacity. There were significant (p < 0.05) positive correlations between total polyphenols and TAC, superoxide dismutase, GPX, CAT, and DPPH free-radical scavenging capacity. The total gas production was significantly (p < 0.05) influenced by the sorghum stalk variety and incubation time. Stalk J4 displayed higher values for the (p < 0.05) immediately soluble fraction and the potential extent of gas production, while stalk M6 exhibited a significantly lower (p < 0.05) insoluble fraction level. Furthermore, stalk M6 exhibited a significantly higher level of (p < 0.05) ruminal fluid propionic acid, but its level of butyric acid and its ratio of acetic acid to propionic acid were both significantly lower (p < 0.05). Taken together, the results reported in this paper indicate that the chemical composition, polyphenol compounds, antioxidant activity, and in vitro rumen fermentation all vary greatly among different varieties of sorghum stalks.