Performance of two accessions of Urochloa humidicola managed under rotational grazing in the Antioquian Northeast (Colombia)

Livestock activity in the neotropics is carried mainly on soils characterized as acidic and of low fertility, and Urochloa humidicola is a perennial tropical grass option for use in such conditions. The objective of this study was to compare the forage and animal performance of the accessions U. humidicola CIAT-16886 versus CIAT-679 managed under rotational grazing systems in the northeastern region of Antioquia, Colombia. Between August 2016 and October 2017, at El Nus Research Center (Agrosavia), in a 5 ha area for each accession, biomass availability, plant height (PH) and cover (CO), the contents of crude protein (CP) and neutral detergent fiber (NDF), the in situ dry matter digestibility (ISDMD), the forage allocation (FA), and the cumulative (CLWG) and by cycle (LWGpC) live weight gain were measured, using cattle of the local Blanco Orejinegro (BON) breed. Generalized linear mixed models were used for data analysis. Significant differences (P<0.05) between both grass accessions were detected for forage biomass availability, PH, CO, CP and FA; whereas no differences between accessions were detected for NDF and ISDMD. A significant interaction between Accessions x Sex (P=0.033) was observed for CLWG, with females showing a higher LWG when grazing the CIAT-679 accession, while no significant differences between accessions were detected with males. Accession CIAT-679 showed a better performance for several agronomic variables and cattle live weight gain; hence, it could still be recommended for rational grazing systems under similar conditions to the ones of this study.