Chemical composition of Urochloa and Megathyrsus maximus cultivars under tropical humid forest conditions

Urochloa and Megathyrsus maximus comprise the most widely sown grasses in Venezuela, and their composition is influenced by management practices and the rainfall regime in the region. The chemical composition of seven grass cultivars was evaluated during the dry and rainy seasons under two defoliation frequencies (4 and 6 weeks) in tropical humid forest conditions of the Catatumbo municipality, Zulia state, Venezuela. Dry Matter (DM), Ash (ASH), Ether Extract (EE), Crude Protein (CP) and Crude Fiber (CF) were measured. A randomized complete block design with a split-plot arrangement and four replications per cultivar was used. Highly significant effects (p<0.01) of season were observed on ASH, EE and CF contents. Defoliation frequency significantly affected (p<0.01) all evaluated variables, with notable CP contents in cultivars BR02/0465 (10.36 %) and CIAT 606 (10.17 %). Considering SE, CV and DF together, highly significant effects (p<0.01) were determined on EE contents of M. maximus cv. Tanzania (2.59 %) and CIAT BR02/0465 (2.39 %) during the dry SE at DF 4 weeks. Regarding CF, significant decreases (p<0.01) were recorded as the age advanced from 4 to 6 weeks in cultivars Tanzania (26.87 % to 26.66 %), BR02/0465 (25.03 % to 21.68 %) and Mulato II (24.81 % to 20.46 %). From a bromatological perspective, the evaluated cultivars demonstrated high nutritional value, particularly CIAT BR02/0465, identifying it as a promising option for the tropical humid forest of El Guayabo.