Abstract

In southern Brazil, beef cattle production systems generally rely on grazing on natural pastures. However, their forage production, and consequently metabolizable energy (ME) production, is seasonal and influenced by climatic events. Thus, there is a scientific and commercial interest in evaluating and understanding the biological impacts of intensification using pasture irrigation and the effects of El Nino-Southern Oscillation (ENSO) phenomena on the long term on the productivity of cow-calf systems. Therefore, our objective was to develop a simulation model to evaluate the effects of intensification levels, using cultivated pastures and irrigation, on the productivity and on the efficiency metabolizable energy utilization of beef cow-calf systems in a 10-year horizon. This period allows capturing the effects of several production cycles as influenced by ENSO events. The model includes three submodels: herd structure, herd ME requirements, and forage ME production. The results of the present study demonstrate that the proposed model is able to evaluate the influence of intensification of grazing systems on metabolizable energy production, carrying capacity, productivity and biological efficiency of beef cow-calf systems over a long-term horizon. Productivity was increased in 15.9% when 20% of the grazing area was intensified and irrigated compared with the modeled non-intensified system, independently of climatic events. The main productive response was the increase in the number of dams in the herd, especially as a result of the use of irrigation. This study proposes different alternatives for increasing the productivity of beef cow-calf systems in southern Brazil.