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

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 m2 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.

Influence of Cutting Intervals and Transition Periods on Chemical Composition Variability of Selected Tropical Grasses under Flooded Savanna Conditions of Arauca, Colombian Orinoquia

“…Among the digestible components, DMD is positively correlated with potentially digestible chemical components such as CP, EE, TDN, and minerals present in the ash and corresponds to the proportion of plant material that can be digested by herbivores [11,34]. CP is rapidly degraded by ruminal microorganisms to increase the ammonia concentrations to favor microbial cell synthesis, while EE is degraded to produce energy due its caloric concentrations [12]. Likewise, TDN represents the utilizable energy content of a feedstuff, and its estimation relies on fractions like CP and EE, among others [35,36].…”

“…can be found in the physiographic positions of "banks". Introduced grasses of the Urochloa genus are also commonly found in both physiographic positions [11,12].…”

“…A major concern faced by floodplain savannah producers is the scarce knowledge about the yield and quality of the forage resources used to feed grazing animals in different physiographic positions, growth phases, and periods of the year. Some studies have evaluated the temporal variability of the nutritional characteristics of some grasses grown in the "bank" and "low" positions independently, showing that native grasses performed similarly or even better than some introduced grasses under the studied ecosystem [11,12]. Similarly, it has been found that "low" soils tend to present greater nutrient concentrations than "bank" soils [10], which should influence the nutritional statuses and forage availability of floodplain savannah grasses, according to age and growth periods.…”