JIA-2018-09

2083 TIAN Xing-zhou et al. Journal of Integrative Agriculture 2018, 17(9): 2082–2095 1. Introduction Anthocyanins, a group of flavonoid compounds that are naturally occurring plant pigments responsible for color change from red through purple to blue, are present in a wide variety of plants, such as blackcurrant, wild blueberry, concord grape, and purple corn (Zhao et al . 2009; Silva et al . 2016; Zhang et al . 2016). Typically, anthocyanins have been reported to exhibit potent antioxidant activity (Owoade et al . 2015). Thus, they may remove excessive free radicals to alleviate oxidative stress in ruminants when the animal’s antioxidant system balance is disrupted during metabolic disorder (Jomova and Valko 2011; Georgiev et al . 2014). Thailand is a special tropical country with a different climate than other countries and areas due to its long dry season from November to March (Hashimoto et al . 2004). Thus, roughage must be provided to ruminants since it is not available during that period. The process of making silage has become common; silage has been an increasingly important source of ruminant forage feedstuff (Lounglawan et al . 2011; Lukkananukool et al . 2013). Purple corn is a rich and economical source of anthocyanin colorants for human consumption (Jing and Giusti 2007). Previous studies demonstrated that purple corn by-products, such as the husk, cob, silk and tassels also had abundant anthocyanins (Cevallos-Casals and Cisneros-Zevallos 2004; Dykes and Rooney 2007; Khampas et al . 2013). Consequently, purple corn by-products seem to be a suitable functional ingredient for ruminants (Hosoda et al . 2012c). However, those by-products are usually buried or burned after the corn kernels are harvested, which pollute the environment, it is not in line with the goal of sustainable development. In addition, purple corn is a type of field crop that is widely grown in Thailand (Harakotr et al . 2014; Phinjaturus et al . 2016). Recently, farmers and researchers in Thailand are looking for new ways to improve ruminant health from the perspective of animal nutrition in terms of antioxidant activity. There has been little information reported about anthocyanin in purple corn stover silage (PSS) on forage yield, silage fermentative quality, anthocyanin stability, and antioxidant activity or on rumen fermentation in ruminants. Accordingly, in order to provide a preliminarily understanding of the potential of anthocyanin-rich PSS as a roughage for ruminants, we investigated its chemical composition, silage fermentative parameters, anthocyanin composition, antioxidant activity during different lengths of ensilage and in vitro incubation with ruminal fluid. 2. Materials and methods 2.1. Plant management and silage making A field experiment was conducted from June 16, 2016 to September 1, 2016, during the rainy season at the Suranaree University of Technology (SUT) farm, Nakhon Ratchasima, Thailand (14°53´37.9´´N, 102°01´22.0´´E). F 1 hybrid purple waxy corn and F 1 hybrid sticky waxy corn were cultivated in 0.5 m distance under the same fertilizer conditions (N-P 2 O 5 -K 2 O, 50:50:50 kg ha –1 ; Hydro Thai Limited, Bang Kruai, Thailand) using a completely randomized design with three duplicates per treatment. Corn grain was harvested at the yellow ripe stage, and then corn stover (without the corn grains) was cut into pieces approximately 6–8 cm in length above the soil surface by a cutting machine (SCB- 2800, Fermier Engineers Private Limited, Tamil Nadu, India). The fresh materials were immediately transferred to the laboratory and chopped into pieces 2–3 cm in length by an electric automation grinder (Model 5222, Mitsubishi, Tokyo, Japan). Next, the materials were placed into 0.5 L mini-silos, which were kept in the dark at 15–25°C ambient temperature for a period of 0, 7, 14, 21, 42, 63, 84, and 105 d, respectively. 2.2. Chemical analysis After ensilage, 20 g of fresh silage samples were placed into a 150-mL beaker, covered with 100-mL of distilled water, and blended for 30 min at room temperature before being filtered through filter paper (Whatman™ No. 1441-125, GE Healthcare Life Sciences, Marlborough, MA, USA), then pH determination was done immediately by a portable pH meter. Meanwhile, the filtrate solution was stored at –20°C displayed lower levels of immediately soluble fraction and ratio of acetic acid (AA) to PA at 12 h, but the other parameters were unaffected ( P >0.05) relative to the control. Taken together, the results indicated that: (1) anthocyanins could be stable in silage; (2) anthocyanin-rich PSS showed better silage fermentative quality and stronger antioxidant activity; and (3) anthocyanin-rich PSS had no negative effect on rumen fermentation parameters. Keywords: anthocyanin-rich purple corn stover silage, anthocyanin stability, silage fermentative quality, antioxidant activity, rumen fermentation