Abstract
This study aimed at analysing the temporal aspects of foot-pad dermatitis in Swedish broilers. The information on disease prevalence and severity was based on a 2-year foot-health surveillance programme where information on producer, breed, feed manufacturer, region, abattoir, date of slaughter and several other variables was recorded. The seasonal effects were evaluated using classical multiplicative decomposition time series analysis. This study shows that there has been a significantly consistent decrease in the prevalence of severe foot-pad lesions during the first 2 years of the programme. Looking at the development over time we found a trend-cycle component of 10.4% and a seasonal component of 48.7% resulting in a total adjusted R-square value of 58.5% for the total foot-pad score. This means that almost 60% of the variation in flock foot-pad score can be explained by the variable 'time', and that this variation was mainly related to seasonal effects but also to a general decreasing trend over the study period. However, substantial differences in temporal patterns among slaughterhouses, feed suppliers and regions were found. The time series analysis approach was found to be useful for this type of investigation when evaluating the effects of an intervention programme, and it can also be applied for projecting the future development of disease status in a stable population.
Keywords: chicken, feed, feet, poultry, region, relative humidity, season, slaughterhouse, surveillance programme, time series
Sammanfattning
Denna studie syftade till att analysera de tidsmässiga aspekterna på förekomsten av trampdynedermatit (“fotskador”) hos svenska slaktkycklingar. Informationen om lidandets prevalens och omfattning baseras på material insamlat under två år inom ett fothälsoprogram som omfattat drygt 97% av de svenska slaktkycklingbesättningarna. Inom ramen för programmet har upplysningar om uppfödare, hybrid, foderleverantör, län, slakteri, slaktdatum och ett antal andra variabler inhämtats. De säsongsmässiga effekterna har utvärderats med hjälp av klassisk multiplikativ analys för tidsserier (classical multiplicative decomposition analysis). Studien visar att det har skett en signifikant nedgång i förekomsten av grava fotskador under de första två åren av fothälsoprogrammet. Vid analys av utvecklingen över tiden fann vi en trend-cyklisk komponent på 10.4% och en säsongskomponent på 48.7%, resulterande i ett totalt justerat R2-värde på 58.5% för den totala trampdynepoängen. Det fanns dock stora skillnader mellan de olika slakterierna, foderleverantörerna och regionerna. Tidsserieanalys befanns vara en användbar metod för denna typ av utvärdering av effekterna av ett interventionsprogram, och kan även användas för att projicera en framtida utveckling av sjukdomsläget i en stabil population.
Full Text
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Acknowledgments
The authors thank the Swedish Meteorological and Hydrological Institute (SMHI) for supplying the weather data and the Swedish University of Agricultural Sciences and the Swedish Poultry Meat Association for funding this project.
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