Simulated comparisons of breeding plans for beef production - Part 1: A dynamic model to evaluate the effect of mating plan on herd age structure and productivity.

Abstract A computer program to simulate beef production is described. The model is based on the principles of industrial dynamics and constructed in the simulation language DYNAMO. This dynamic model is composed of subroutines that simulate herd structure for a cow herd and a production herd composed of calves from the cow herd. Additional subroutines model pre-weaning and post-weaning growth of the calves. The portion of the model that simulates the herd structure includes ten age classes of cow. The subroutine which models the portion of the herd between 2 and 9 years of age utilises twelve variables to describe the events that occur in the herd during the passage of a year. The age structure of the herd is influenced by the breeding system and the way in which the herd is managed. The production herd is modelled by sequential subroutines. These subroutines follow the number and growth of calves weaned from the cow herd until they are sold at 32, 52, 67 or 85 weeks of age. Mating plans utilising different breeds can be simulated in combination with various management options.