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Combined Ensiling of Tropical Beans and Sugarcane Stalks: Effects on Their Secondary Metabolites

Abstract:

In this study, the effect of mixed silage on the chemical composition, ensilability, in vitro cellulase digestibility and some of their plant secondary metabolites (PSM) were assessed. The lab-scale silage mixes were made in triplicate from sugarcane (Saccharum spp.) stalk and Canavalia ensiformis or Mucuna pruriens beans (Santa Clara, Cuba). Sugarcane stalks and beans were mixed at a ratio of 40:60 (on DM basis), respectively, in combination with a mixture of microbial inoculants (Lactobacillus acidophilus, and two Kluyveromyces fragilis strains, 4 × 105 colony forming units (CFU)/g of fresh matter). Before and after ensiling, the chemical composition, ensilability and contents of some PSM (trypsin inhibitor, L-canavanine, total tannins, L-dopa and phytic acid) were determined. A complete factorial design to assess the effect of the ensiling time (30, 60 or 90 days), the legume type (LT) and their interactions on the assessed parameters were performed. A better silage fermentation quality of the M. pruriens–sugarcane mixed material [e.g., lower (p < 0.05) pH and ammonia N content and higher (p < 0.05) concentration of lactic acid] was observed as compared with the C. ensiformis–sugarcane mixed material. The ensiling process reduced (p < 0.001) the studied PSM, being higher (p < 0.001) in the M. pruriens–sugarcane silages than in the C. ensiformis–sugarcane silages [trypsin inhibitor (86 vs. 76%); L-canavanine (70 vs. 53%); total tannins (54 vs. 50%); L-Dopa (89 vs. 86%)], except for phytic acid (65 vs. 68%), respectively]. It was concluded that ensiling enhances the quality of the feeds by pbkp_redigestive reduction of the amount of secondary plant metabolites.