Economic evaluation of risks to producers who use milk residue testing programs

Obiective - To evaluate the decision to test for milk antimicrobial residues in milk from dairy cows treated with procaine penicillin G (PPG). Design-Economic-decision analysis after stochasic simulation. Sample Population - 1,000 computer-simulated cows/model. Procedure - Meta-analysis of the Food Animal Residue Avoidance Databank was used to generate PPG disappearance curves for cows given single PPG treatments IM of 6,600 U/kg (3,000 U/lb) of body weight or 26,400 U/kg (12,000 U/lb), and multiple treatments at 26,400 U/kg (12,000 U/lb), IM. These curves were entered into 1,000-replication stochastic Pharmacokinetic models, generating population-level milk PPG profiles for each treatment group for each day after treatment, which were subjected to economic-decision analyses of feasibility of residue testing. The model was evaluated for changes in herd size, proportion of herd available for testing, milk production test price, test sensitivity/specificity, and withdrawal periods. Results - For both single-treatment groups, a 2-day withdrawal period avoided violative residues. However, nearly two thirds of the cows risked false identification for violative residues. For the multiple-treated group, nearly 40% had violative residues after a 5-day withdrawal period, and an additional 10 to 15% risked false identification for violative residues. Economic analysis yielded a decision against testing mean cost was $2 (ie, 5% more than the mean cost of not testing). Clinical Implications - Complex dynamics of current milk residue tests discourage practitioners from recommending procedures to clients. In general increases in herd size, milk production, proportion of a herd available for testing, or milk price will increase the value of testing. Increasing test sensitivity decreases its desirability to producers.