Chemical Composition and In Vitro Ruminal Fermentation Characteristics of Native Grasses from the Floodplain Lowlands Ecosystem in the Colombian Orinoquia

SIMPLE SUMMARY: The floodplain ecosystem of the Colombian Orinoquia has a diversity of native grasses; however, there is little information on its agronomic and fermentation characteristics. The aim of this study was to determine the chemical composition and fermentation parameters of the grasses Leersia hexandra, Acroceras zizanioides, Hymenachne amplexicaulis, and Urochloa arrecta (Tanner grass, “introduced”) as a control group. Green forage samples were taken in a 1 m(2) frame at 30, 40 and 50 days of age and biomass production was estimated. The chemical composition was analyzed by infrared spectroscopy, and the fermentation parameters by the in vitro gas production technique. Data were analyzed using a mixed model for repeated measures. The nutritional characteristics variations were: dry matter (DM, 0.7–2.0 ton/ha), crude protein (CP, 6.1–12.2%), neutral detergent fiber (NDF, 56.6–69.6%), ash (5.8–15.8%) and dry matter digestibility (DMD) between 20.8 and 60.6% from 12 to 48 h of fermentation. L. hexandra and A. zizanioides presented higher biomass, CP, ash, cellulose and Ca production. During the experimental period (30 to 50 days), the grasses did not present significant changes in nutrient availability. L. hexandra increased the concentrations of ammonia and total volatile fatty acids (VFA) and butyric acid. This last effect was also observed in the A. zizanioides grass. L. hexandra and A. zizanioides grasses constitute an alternative forage resource for ruminants during the flood seasons of the studied ecosystem. ABSTRACT: Grasses from lowland ecosystems in flooded savannahs are useful to feed extensive grazing animals; however, scarce information about its agronomic and fermentation characteristics exists. This study aims to determine the chemical composition and fermentation parameters of native grasses from the floodplain lowlands ecosystem in the Colombian Orinoquia. Three native grasses (Leersia hexandra, Acroceras zizanioides and Hymenachne amplexicaulis) and a “control” grass (introduced Urochloa arrecta—Tanner grass) were sown and sampled at 30, 40 and 50 days of age. On each sampling date, biomass production in a 1 m(2) frame was estimated, and the chemical composition and fermentation parameters were analyzed using near-infrared spectroscopy and the in vitro gas production technique, respectively. Data were analyzed using a mixed model for repeated measures and the least significant difference (LSD) was used for mean differentiation (p < 0.05). The grasses’ nutritional characteristics varied as follows: dry matter (DM, 0.7–2.0 ton/ha), crude protein (CP, 6.1–12.2%), neutral detergent fiber (NDF, 56.6–69.6%), ash (5.8–15.8%) and dry matter digestibility (DMD) between 20.8 and 60.6% from 12 to 48 h of fermentation. Native plants such as L. hexandra and A. zizanioides presented higher biomass production, CP, ash, cellulose, and Ca levels than the control plant. During the experimental period (30 to 50 days), the grasses did not present significant nutrient availability changes. In terms of fermentation characteristics, L. hexandra increased ammonia concentrations and total volatile fatty acids (TVFA) and butyric acid. This latter effect was also observed in A. zizanioides grass. L. hexandra and A. zizanioides grasses constitute a valuable alternative forage resource during the flooding times of the studied ecosystem.