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?:abstract
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The health status of broilers raised at lower stocking density and limited antimicrobial use but routine anticoccidials was assessed, in order to identify prevalent causes of disease, mortality and reduced performance. \'Dead-on-farm\'(DOF) broilers from 145 commercial flocks were investigated at two different time points (TP1:7-14 and TP2:28-35 days of age); per sampling, 6-10 DOF broilers were selected for post-mortem investigation and gross pathomorphological changes were assessed, in total from 2,717 birds. Post-mortem findings were substantiated by bacteriological, virological and parasitological investigations. Furthermore, production data of all flocks were collected and used to perform comprehensive statistical analysis. Overall, colibacillosis was found most important with a significant negative impact on flock health, productivity and profitability through all ages of broiler production. At TP1, primary reasons for mortality comprised yolk sac infections, generally found together with fibrinous polyserositis due to E. coli. Furthermore, femoral lesions, which correlated with increased flock mortality, were associated with detection of E. coli. At TP2, ascites was detected frequently in DOF broilers, correlating with increased production losses in the 4th and 5th week of life. No etiological link between the presence of ascites and the detection of the investigated pathogens was observed.A positive correlation was noticed between the prevalence of ascites within flocks and the sea level of the farm, and with the sex of the birds. These disease conditions could not be linked with the housing system. Presence of Infectious Bronchitis virus, avian reovirus and fowl adenovirus did not correlate with macroscopic lesions or a specific disease. Research Highlights ï· In young broilers lesions of visceral organs due to bacterial infections dominated. ï· Colibacillosis impacts broiler health, productivity and profitability independent of the age of birds. ï· Disorders of the locomotor system were frequently observed throughout production. ï· Older broilers frequently showed pathologic changes due to metabolic disorders. ï· Overall, a shift from infectious towards metabolic disease conditions was noticed.
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