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Partial budget analysis of selective dry cow therapy strategies.

S. M. Rowe




Partial budget analysis of selective dry cow therapy strategies.
A. K. Vasquez1, S. M. Rowe*2, S. M. Godden2, P. J. Gorden3, A. Lago4, E. Royster2, J. Timmerman2, M. J. Thomas5, R. A. Lynch1, D. V. Nydam1. 1Cornell University Ithaca, NY, 2University of Minnesota St. Paul, MN, 3Iowa State University Ames, IA, 4Dairy Experts Tulare, CA, 5Dairy Health & Management Services Lowville, NY.

This study conducted partial budget analysis using MonteCarlo simulation with @Risk software to estimate the net economic impact for herds that switch from blanket dry cow therapy (BDCT) to culture- or algorithm-guided selective dry cow therapy (SDCT). Initial models assumed no differences in health outcomes between strategies, as was concluded in a previous trial by the authors. 10,000 iterations using expenditures associated with dry-off procedures and health outcomes during 1—30 DIM were used to model net economic herd-level impacts. Fixed values were inserted for variables expected to have minimal variation on US dairies and appropriate distributions were used for components that were assumed to vary. Costs for fixed or variable inputs and distribution types were derived from previously published models, current industry databases, or from professional experience. For culture-guided SDCT, on average, producers could expect to save $2.14 per cow-dry-off as compared with BDCT. For algorithm-guided SDCT, the mean net impact was $7.85. Seventy-six and 100% of iterations had a net impact ≥ $0 for culture- and algorithm-guided SDCT, respectively, indicating that the strategies were profitable in most of the herd conditions evaluated. The largest contributors to variance (~75% and ~25%) in both models were the percent of quarters treated at dry-off and the cost of antibiotics. Next, we investigated the economic impact in situations where SDCT increased mastitis cases during the next lactation. For this sensitivity analysis, subclinical and clinical mastitis were both set to increase by 1%, 2%, or 5% and net economic impacts were determined at fixed values of 20, 40, 60 and 80% antibiotic use at dry-off. Analysis indicated that if a 1% or 2% increase in mastitis resulted, in many situations SDCT continued to have net benefits over BDCT, particularly when use of these strategies resulted in lower levels of antibiotic use for the herds. At each level of evaluated antibiotic use, when mastitis was increased by 5%, mean economic impacts were negative for 95% of iterations. This partial budget analysis found that in the majority of situations, 2 SDCT strategies produce a positive net economic impact over BDCT.