Influence of Involuntary Culling on Optimum Culling Rates and Annualized Net Revenue

Abstract

Dynamic programming was used to make optimum insemination and culling decisions. Revenue depended on the sale of milk, calves, and cull cows. Costs were based on feed costs, health costs, replacement costs, housing costs, and interest. Conception probabilities, genetic improvement, variation in production, and repeatability of production and involuntary culling probabilities were considered when making the optimum decisions. Annualized net revenue, optimum culling rates, and the optimum average productive life were determined for various involuntary culling rates. Results indicated that involuntary culling probabilities have a large impact on annualized net revenue. Reducing involuntary culling rates by 2.9% (marginal involuntary culling rates by 20%) resulted in about $22 more net revenue per cow per year. Increasing average mature equivalent milk yield by 122kg resulted in the same increase in net revenue. Value of lowering the overall rate of involuntary culling was not affected by assuming that higher yielding cows were more prone to culling for involuntary reasons; however, optimum voluntary culling patterns were altered. Less intense culling in young cows was optimum when compared with the situation where the probability of involuntary culling was independent of production. Management and breeding policies should be directed toward increasing milk yield and decreasing the causes of involuntary culling.