Comparison of rebreeding policies for Ontario dairy herds

Net-revenues of rebreeding policies that differed in the maximum allowable days after calving for breeding were compared using data generated by a dynamic stochastic simulation model of Ontario dairy herds. Such comparisons benefit farmer decision support, as rebreeding decisions are important management choices. Rebreeding up to 168 d after calving only was least optimal. Hence, the rebreeding period should not be too short. At average and high herd fertility, a rebreeding policy under which cows with a mature equivalent milk production level lower than 80%, between 80 and 100%, and greater than 100% of the herd average were not rebred, bred up to 168 d after calving, and bred up to 250 d after calving, respectively, resulted in higher net-revenue than rebreeding policies that used a single cut-off for all cows. Differences in net-revenue between the optimal and the least optimal policy were $217.90 and $114.40 per cow per year for the lowest and highest simulated reproductive performance, respectively. At low herd fertility, rebreeding up to 364 d postpartum was optimal. However, at this level of performance emphasis should be given to improving fertility, rather than choice of rebreeding policy. Key words: Dairy cattle, simulation, economics, insemination policy, rebreeding policy