Relevance of Mastitis Control Strategies: Profitability of Lactational Treatment for Subclinical Infections in Dairy Herds, Assessed by a Bio-economic Simulation Model

Currently under French conditions, mastitis control schemes rarely include lactational treatment of subclinical intramammary infections (LT). A bioeconomic simulation model (ECOMAM) was used to examine the economic consequences of control strategies including LT of young cows. The core-model of ECOMAM was developed as dynamic (daily time stepping), mechanistic (individual representation of heifers and cows) and stochastic (using probabilities for simulation of both occurrence and consequences of mastitis). This model was used to study the economic worth of several control strategies based on LT applied to different udder health statuses of a 800 000 l-quotum dairy herd with 100 year-present cows under the context of western France. To be profitable, control strategies with LT had to be able to create a sufficient decrease in the incidence of new infections (obtained by improved prevention). Strategies based on strict culling rules resulted in rapidly improved herd SCC but led very often to not to fill up the quota, implying lower revenue. Finally, except for borderline unsatisfactory statuses (levels of SCC penalties <1.5% of the milk price), to implement LT, without any strong culling policy but with an improved prevention, was profitable in most cases. Key-words: Dairy Cow; Intramammary Infection; Lactational Treatment; Economics.