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Chemical characterization and in vitro fermentation activity of tropical legumes
Leguminous species are relevant as feed resources for grazing ruminants in a diversity of agro-ecosystems. Foliage from Albizio lebecoide, Ormosia panamensis, Centrosema pubescen, C. pubescen cv Bani, Pongania pinnata and Albizia lebbeck from the oriental region of Cuba was chemically characterized and the in vitro fermentation activity evaluated. Plots from various locations at the Rio Cauto´s Valley were demarcated and fifteen plants at a vegetative stage were randomly selected. Small leaves and twigs were collected simulating animal grazing. Samples were composite, dried and milled. Chemical composition, in vitro dry matter digestibility (IVDMD), total polyphenols and antioxidative activity using 1,2-diphenyl-2-picrylhydrazyl (DPPH) were determined. Glass syringes were used and gas production recorded at 0, 3, 6, 9, 12, 24, 48, 72 and 96h after incubation initiated. Inoculum from three rumen fistulated sheep fed alfalfa hay and comercial concentrate (70:30) was utilized. Kinetic parameters such as the asymptotic gas production (b) and the rate of gas production (k) were obtained by the exponential model G = b × (1 − e−k(t−L)). Data related to kinetic parameters b and k, chemical composition, total polyphenols and antioxidative activity were analyzed according to ANOVA for a completely randomized design. Significant variation (P < 0.05) was registered among legume species in all the studied variables. Except for O. panamensis, all species had a CP content greater than 15% (P < 0.05). Values related to NDF ranged from 51.1% in O. panamensis to 59.1% in C. pubescens cv bani. Intermediate values were obtained in P. pinnata (P < 0.05). In vitro dry matter digestibility varied (P < 0.05) from 37.3% in A. lebbek to 61.5% in C. pubescens cv bani. Centrosema species exhibited the greatest asymptotic gas production (P < 0.05; mean values for Centrosema= 182 ml gas/ g DM). Rate of gas production (k) ranged from 0.0154 % h-1 to 0.0549 % h-1. Centrosema species had superior k values as well (P < 0.05). Total polyphenols ranged from 1.62% in A. lebbeck to 0.29% in both Centrosema species (P < 0.05). Accordingly, antioxidative activity (overall mean = 92.7%) was greatest in those species containing superior levels of total polyphenols (P < 0.05). Among species, Centrosema species were of reasonably good quality (CP, 17.7%, IVDMD, 61.5%, DM basis). Moreover, the greatest values regarding the extent (b) and rate (k) of gas production observed in such species which indicate better nutrient availability for rumen microorganisms, might support their potential in marginal tropical and subtropical regions.
Keywords: Legumes, In vitro gas production, chemical composition