The economic optimisation of sow replacement decisions by stochastic dynamic programming

A stochastic dynamic programming model is designed to determine the economic optimal replacement policy in swine breeding herds. This optimal policy maximises the present value of net revenues from sows present in the herd and from subsequent replacement gilts over a given planning horizon. The model also calculates the total extra profit to be expected from trying to retain an individual sow until her optimal lifespan and not replacing her immediately. This total extra profit is an economic index which makes it possible to rank sows within the herd on future profitability and, therefore, can be used as a management guide in culling decisions. For typical Dutch values the optimal replacement decisions result in an average herd life of 3.34 parities. The maximum economic life of sows of average productivity turns out to be 10 parities. All data can easily be adjusted to represent a specific herd or a different region of the world.