Assessment of the economic relevance of the treatment of subclinical mastitis during lactation in dairy cows

High somatic cell counts in bulk-tank-milk generate economic losses and justify the implementation of control schemes. Currently under French conditions, such schemes do rarely include lactational treatment of subclinical intramammary infections (LT). A bioeconomic simulation model was used to examine the economic consequences of control strategies including LT of young cows. The core-model 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 simulation 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 1-quotum dairy herd with 100 year-present cows under the context of western France. Results showed that, to be profitable, LT control strategies had to be able to create a sufficient decrease in the incidence of new infections (obtained by improved prevention). Strategies based on strong culling rules resulted in rapidly improved herd SCC but led quasi systemically to not to fill up the quota, implying lower revenue. Finally, except for borderline unsatisfactory statuses (levels of SCC penalties <1% of the milk price), implementing LT, without any strong culling policy but with an improved prevention, was profitable in most cases.