Fractionation of nitrogen compounds and carbohydrates in forages of different ages

Abstract

The objective of this study was to evaluate the chemical composition and protein and carbohydrate fractions in three forage species (Andropogon gayanus Kunth, Cenchrus ciliares L. and Panicum maximun x Panicum infestum) at four cutting ages: 21, 35, 49 and 63 days. Experiments were carried out at the Federal Institute of Education Science and Technology of Rio Grande do Norte - IFRN, located in the municipality of Apodi- RN, Potiguar West Meso-region. Materials collected in the field were analyzed in the Laboratory of Animal Nutrition (LANA), Federal Rural Semiarid University (UFERSA), Campus Mossoró, RN. Samples were processed, phenated, and analyzed. The analysis conducted included fractionation of nitrogen compounds and carbohydrates and chemical composition (dry matter, mineral matter, crude protein, lipids and fibers) was determined. The forages evaluated showed decreasing crude protein content with increasing cutting age, ranging between 14.9 and 6.2%. Andropogon grass showed the highest crude protein content. The fiber content increased with age. Fiber consisted of 62.4%–70.0% NDF and 30.07%–33.03% ADF. Highest fiber content was recorded for Massai grass, in which case, these two component species showed the highest fractions of intermediate degradation protein (B2), while Andropogon and Buffel Capins showed higher fractions of non-fibrous carbohydrates (A and B1). An increase in the concentration of cell-wall material in the detriment of the cellular content with increasing plant age was observed in the fodder studied. We also observed an increase in the indigestible fraction (C) of proteins and carbohydrates in the species studied.