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

• Fabio Garrido-Ricoveri University of Zulia, Faculty of Agronomy, Maracaibo, Venezuela. https://orcid.org/0009-0005-1512-609X
• María Román University of Zulia, Faculty of Agronomy, Maracaibo, Venezuela. https://orcid.org/0009-0001-6322-4023
• Rover Maldonado-Cruz El Guayabo Local Station, National Institute for Agricultural Research (INIA), Venezuela. https://orcid.org/0009-0008-6763-7299
• Luis Cordero Animal Nutrition Laboratory, Faculty of Agronomy, University of Zulia, Maracaibo, Venezuela. https://orcid.org/0009-0005-5629-4567
• Alonso Fossi Department of Animal Science, Faculty of Agronomy, University of Zulia, Maracaibo, Venezuela. https://orcid.org/0009-0007-7709-4403
• Juan Vergara Department of Animal Science, Faculty of Agronomy, University of Zulia, Maracaibo, Venezuela. https://orcid.org/0000-0002-4358-0151
• Rosa Razz Department of Animal Science, Faculty of Agronomy, University of Zulia, Maracaibo, Venezuela. https://orcid.org/0000-0003-2188-6659
• Jorge Ortega Department of Statistics, Faculty of Agronomy, University of Zulia, Maracaibo, Venezuela. https://orcid.org/0000-0002-4358-0151

Keywords: season, pastures, defoliation frequency, nutritional value, bromatology, regrowth

Abstract

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 (CV) was evaluated
during the dry and rainy seasons (SE) under two (4 and 6 weeks) defoliation frequencies (DF) 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 SE 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.

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