The influence of replacement policies on stability of production in a simulated cow‐calf farm system

Abstract This paper explores the dynamic consequences of different replacement policies on the production outcomes of pastoral cow‐calf systems using a simulation model of a cow‐calf farm at the INTA‐Balcarce Research Station, Argentina. The model is dynamic, mechanistic, climate driven, and implements management strategies with flexible rules. Three replacement policies were analysed: a) enough replacement heifers were retained each year to achieve a target number of cows; b) a constant number of replacements was retained each year; and c) no limit was imposed on the number of replacements, but the number of age‐culled cows was restricted. These policies were repeated (replicated) 50 times, using first an average climatic year from the Balcarce region and then a random sequence of 50 years drawn from the same dataset. The differences in performance indicators between the average values for the different replacement policies were small (1–5%), although statistically significant. The differences in standard deviation (SD) were greater, with Policy C being the most stable as indicated by the reduced standard deviation in animals and liveweight sold by 7 and 12%, respectively, in comparison with Policy A. Policy B produced more variable results (5 and 9%, greater SD in liveweight and animals sold, than Policy A, respectively). The differentiation between strategies was shown to be dependent on the environmental variability being simulated, due to complex interactions between the environment and the management strategy, specifically being exaggerated when environmental variability was artificially reduced by using average weather.