The economic impact of mastitis control procedures in Scottish dairy herds
Mastitis is a costly disease. The recent changes in EU Milk Hygiene Regulations (EEC 92/46) have tremendously increased the importance of subclinical mastitis, hence the need for economically based mastitis control decisions in dairy farms. The majority of Scottish farmers use the widely recommended mastitis control procedures on the ground that cost benefit analyses of applying entire mastitis control programmes have shown substantial financial returns under experimental farm trials (Natzke et al., 1972; Scheper and Dijkhuizen, 1991). However, the usefulness of this traditional approach in terms of producing guidance on economic basis has been questioned since the economic law of 'diminishing marginal returns' applies to mastitis control expenditure (McInerney et al., 1992). Therefore, the mastitis control procedures which produce negative net returns cannot be detected by cost/benefit analysis of entire mastitis control programme since these would be masked by the positive effects of the other control procedures in the control programme. Subclinical mastitis cannot be seen but it is now identifiable by somatic cell count (SCC) records of which are becoming more widespread in Western countries. SCC records together with other mastitis control related records in Scotland now allow examination of marginal cost-effectiveness of a number of mastitis control programmes. The main objective of this study was therefore to use these records to test whether all mastitis control procedures used by Scottish dairy farmers are cost-effective. For this purpose multiple regression analysis was used to quantify the marginal impact of individual mastitis control procedures on milk yield depression and the probability of herds paying a bulk tank somatic cell count (BTSCC) penalty due to the presence of subclinical mastitis. Possible interactions between mastitis control procedures and other management variables were tested. From this statistical analysis an economically optimum disease loss and disease control expenditure mix for subclinical mastitis was established, and the technical and economic efficiencies of Scottish farmers were assessed.