Forage legumes included in diets with tropical grasses. I. Chemical composition and in-vitro digestibility

Abstract

An experiment was conducted to determine the effects of including legume species (Leucaena leucocephala, Stylosanthes guianensis, Centrosema pubescens Benth or Neonotonia wightii) at levels of 0, 5, 10, 20, and 40% of the dry matter on the chemical composition (crude protein, CP neutral detergent fiber, NDF; acid detergent fiber, ADF) and on in vitro dry matter digestibility (IVDMD) of mixtures of each legume with four grass species (Cynodon nlemfuensis Vanderyst, Panicum maximum jacq., Pennisetum purpureum Schum., or Sorghum bicolor (L.) Moench). Of the legume species included, Leucaena leucocephala and Centrosema pubescens had the highest CP content and IVDMD, respectively. For the legumes, the mean CP and IVDMD values, respectively, were Leucaena leucocephala, 21.98 and 68.09; Stylosanthes guianensis, 13.70 and 63.44; Centrosema pubescens, 18.29 and 68.60; and Neonotonia wightii, 16.72 and 66.64%. For the grasses, they were, respectively, Cynodon nlemfuensis, 8.27 and 61.38; Panicum maximum, 7.64 and 60.06; Pennisetum purpureum, 8.02 and 53.47; and Sorghum bicolor, 7.57 and 59.62%. Neutral detergent fiber and ADF contents were higher in the grasses (Cynodon nlemfuensis, 73.03 and 44.45; Panicum maximum, 65.27 and 49.06; Pennisetum purpureum, 69.26 and 51.88; and Sorghum bicolor, 60.24 and 50.99%, respectively) than in the fegumes (Leucaena leucocephala, 50.52 and 28.50; Stylosanthes guianensis, 52.57 and 36.63; Centrosema pubescens, 58.43 and 34.84; and Neonotonia wightii, 54.11 and 33.23%, respectively). The chemical composition of the forages varied according to the relative proportions of the species included, as expected. However, the effects on IVDMD were not additive; rather, associative effects, mainly antagonistic, were observed in most of the mixtures.