ChileanJAR

A simulation model of beef cattle fattening systems based on grazing pastures was developed. The objective was to evaluate different pasture options under different management strategies, types of beef cattle, stocking densities, supplementation strategies and input prices. This model was structured based on a program, whose main module drives management input and generates result files. The dynamic section uses biological subroutines to solve equations simulating biological processes, the most important being the metabolizable energy intake and live weight change. Pasture growth and nutritive value were simulated empirically from the interpolation of monthly data of pasture growth and digestibility of different pasture types. The model also calculates processes related to pasture management, forage conservation and bioeconomic aspects. The physical grazing experiment, carried out during the 1979-1980 seasons was utilized to validate the animal sub-system, A coefficient of determination higher than 95% was obtained when simulated and real values measured in the respective experiments were correlated by regression analysis, verifying the non existence of bias in the estimations. The root mean square error (RMSE) was smaller than 6%, suggesting that this model is realistic and has a high degree of precision.