Computer simulation model of swine production systems: III. A dynamic herd simulation model including reproduction

A dynamic herd simulation model for a swine production unit has been developed. The model is discrete and stochastic and the appropriate random distributions have been defined from the literature or empirically estimated. Theoretical concepts and relationships presented previously are used to simulate growth and the overall life cycle of individual animals. Simulated animals are young pigs (from birth to slaughter age), gilts, and sows. Animal events are farrowing, weaning, mating, end-nursery (transfer from nursery to the growing-finishing facility), and slaughter and are processed individually using a next-event scheduling orientation package. Animals within the herd are culled for different health and reproductive reasons. Genetic parameters, diet composition, and herd management are input variables chosen by the user. The effects of nutrition, genetics, season, and other factors on several reproductive parameters are considered. Model evaluation is performed by studying the output of the model under specified herd situations. The herd model adequately simulates animal flow and dynamics of the herd.