Meta-analysis to estimate the economic losses caused by reduced milk yield and reproductive performance associated with bovine paratuberculosis in Switzerland

Especially in regions with intensive cattle farming, paratuberculosis in ruminants can cause considerable economic losses for example through loss of sick animals, reduced milk yield and decreased reproduction performance. Although quantifying the actual economic losses is complex, this study attempts to quantify the losses caused by paratuberculosis in infected dairy farms in Switzerland by means of meta-analyses. For this purpose, in an elaborate selection process, data from 12 studies on milk yield and from three studies on the calving to conception interval were finally selected for further calculations. In addition, data from eight studies each on milk fat concentration and milk protein concentration were evaluated. For the meta-analyses, only studies in which «sick» (seropositive) and «healthy» (seronegative) animals based on the results of serum ELISA tests were compared at the individual animal level were considered. With a paratuberculosis prevalence of 5,99 % in cattle in Switzerland, a total loss of CHF 12 034 329,96 (95 % CI [CHF 8 625 406,02; CHF 16 409 276,30]; 11 095 652,20 € [7 952 624,35 €; 15 129 352,70 €]) per year was calculated for a population of 559 900 dairy cows. The main part of the losses is caused by an extended calving to conception interval: Seropositive animals need an average of 14,93 days longer (95 % CI [1,73; 28,13]) from calving to successful insemination as seronegative animals. This results in total costs for the extended calving to conception interval due to paratuberculosis of CHF 7 365 591,21 per year (95 % CI [CHF 900 394,95; CHF 14 838 087,61]; 6 791 075,10 € [830 164,14 €; 13 680 716,80 €]). Milk yield reduction based on a lactation period of 305 days results in an economic loss of CHF 4 668 738,75 per year (95 % CI [CHF 1 571 188,69; CHF 7 725 011,07]; 4 304 577,13 € [1 448 635,97 €; 7 122 460,21 €]). Milk fat and milk protein content were not found to be significantly changed. Despite a large number of studies in the screening phase, it was not possible to calculate all types of losses attributable to paratuberculosis due to lack of comparability between the studies, which is essential for meta-analyses. Nevertheless, it was possible to carry out four different meta-analyses, the results of which give a first impression of the economic importance of paratuberculosis in dairy cows in Switzerland.