Possible impact of the "yellow card" antimicrobial scheme on meat inspection lesions in Danish finisher pigs

In 2010, the "yellow card scheme" which was adopted by the Danish Veterinary and Food Administration imposed restrictions on pig farmers who used more antimicrobials than twice the average. To study the potential impact on pig health, we looked into antimicrobial consumption and vaccine use data from the monitoring programme Vetstat, covering all treatments conducted on Danish pigs between January 2010 and July 2011. The decrease in antimicrobial consumption was pronounced for all age groups (sows/piglets, weaners and finishers) treated for either gastro-intestinal or respiratory disease. Evaluated over 12 months, use of vaccines increased in general: PCV2-related infections (+31%), gastro-intestinal disease (27%), respiratory infections (21%) whereas use of vaccines against other infections remained almost constant (-18%). Data from meat inspection of finisher pigs from before and after introduction of the scheme were compared. This included 1.7 million finisher pigs originating from 2765 pig farms, slaughtered on one large Danish abattoir and covered the first 9 weeks in 2010 and 2011, respectively. Nine lesions of chronic nature and infectious origin and the code "condemned" were selected. The prevalence of these lesions was calculated. Logistic regression models with year and week as explanatory variables were used to identify whether the prevalence of a lesion changed from 2010 to 2011. Possible clustering due to correlation within herds and between weekly shipments of animals originating from the same herd was taken into account in the models. The most common lesion seen was chronic pleuritis (∼23%) while the other lesions occurred less-commonly (<1%). For osteomyelitis, pleuritis, chronic arthritis and condemnation, no differences were observed between the 2 years. The prevalence of chronic peritonitis (OR=1.5), umbilical hernia (OR=1.2) and chronic enteritis (OR=1.2) were statistically higher in 2011 compared to 2010, whereas it was lower for tail bite infection (OR=0.6), chronic pericarditis (OR=0.6), and chronic pneumonia (OR=0.7) (P<0.001). Moreover, in the condemned carcasses, chronic pneumonia plummeted as a lesion found in 2011 compared to 2010 (OR=0.07, P<0.0001). Our results indicate that marked reduction in use of antimicrobials is associated with a short-term increase in the prevalence of specific lesions found during meat inspection and higher coverage of vaccines against respiratory diseases might impact the prevalence of chronic pneumonia positively. Other factors that impact on pig health were not included in the study. Moreover, effect of productivity was not evaluated.