A model to predict the numbers of pigs weaned per week

A spreadsheet was developed to predict the numbers of pigs weaned per week 19 weeks after the sows were served. The prediction was based on 3-week rolling averages of sows served and 12-week rolling averages of litter size, preweaning mortality, and farrowing rate. The spreadsheet can be used to manage the future flow of pigs on a given farm. A model of the component parts of pigs weaned per week was used to determine the relative impact of each production parameter. The farrowing rate, litter size, and preweaning mortality had little impact on the variation of pigs weaned per week. The numbers of sows served explained 62% of the variation in pigs weaned per week. We recommend that producers keep the numbers of sows served within a farm-specific minimum and maximum to produce a steady flow of pigs through the system. This will require an adequate gilt pool for weeks when there are too few sows in estrus, and will require that producers allow sows to remain open for another estrus cycle if the maximum number of sows has been served for the week.