Beef cattle production on Piatã grass pastures in silvopastoral systems

Tropical beef cattle production involving animals grazing in a shaded and biologically diverse environment, surrounded by high-quality edible biomass, is achievable through silvopastoral systems (SPSs). However, it is necessary to assess the effects of the presence of trees on forage and animal performance over time. In the Brazilian Cerrado, we evaluated the effects of 2 densities of eucalyptus trees in 2 SPSs (8 years of age SPS22: 227 trees/ha; SPS14: 357 trees/ha) on forage morphology, production and nutritive value of Urochloa brizantha cv. BRS Piatã grass plus performance of Nellore heifers, compared with a grass-only pasture, over a year from 2015 to 2016. On the one hand, SPSs improved (P<0.001) forage nutritive value as reflected in higher crude protein and digestibility and lower neutral and acid detergent fiber concentrations compared with a grass-only pasture. On the other hand, the grass-only pasture had higher (P<0.001) herbage mass and accumulation rate than the SPSs. Forage growth and animal production decreased with higher tree density. Increasing competition from trees with age could be a serious issue limiting pasture and animal production and should be monitored. The suitability of eucalyptus trees for planting in SPSs may be questionable after the 8th year of establishment and further studies are warranted.