PARTIAL BUDGET OF THE DISCOUNTED ANNUAL BENEFIT OF MASTITIS CONTROL STRATEGIES

The objective of this study was to rank the benefits associated with v arious mastitis control strategies in simulated herds with intramammar y infections caused by Streptococcus agalactiae, Streptococcus spp. ot her than Strep, agalactiae, Staphylococcus aureus, coagulase-negative staphylococci, and Escherichia coli. The control strategies tested wer e prevention, vaccination for E. coli, lactation therapy, and dry cow antibiotic therapy. Partial budgets were based on changes caused by ma stitis control strategies from the mean values for milk, fat, and prot ein yields of the central herd and the number of cows that were culled under. fixed mastitis culling criterion. Each annual benefit (dollars per cow per year) of a mastitis control strategy was compared with th e revenue for the control herd and was calculated under two different milk pricing plans (3.5% milk fat and multiple-component pricing), thr ee net replacement costs, and three prevalences of pathogen-specific i ntramammary infection. Twenty replicates of each control strategy were run with SIMMAST (a dynamic discrete event stochastic simulation mode l) for 5 simulated yr. Rankings of discounted annual benefits differed only slightly according to milk pricing plans within a pathogen group but differed among the pathogen groups. Differences in net replacemen t costs for cows culled because of mastitis did not change the ranking of control strategies within a pathogen group. Both prevention and dr y cow therapy were important mastitis control strategies. For herds pr imarily infected with environmental pathogens, strategies that include d vaccination for mastitis caused by E. coli dominated strategies that did not include vaccination against this microorganism.