Enterobacteriaceae and Enterococcaceae are the dominant bacterial families translocating to femur heads in broiler chicks

As a result of rapid growth of broilers, bacterial chondronecrosis with osteomyelitis has emerged in the last decade, with bacterial translocation from the gut to internal organs, including the femur head. In this study, we isolated translocated bacteria in femur heads, blood, and liver, during ageing of broilers, and identified the bacteria using 16S rDNA sequencing. We also provided histopathological descriptions of femur head lesions. Bacteria were isolated from blood, liver, and femoral head samples. In the femoral heads, an age-related presence of bacteria was observed, with high prevalence at 2 days post-hatch, and no bacteria isolated from femoral heads of broilers older than 14 days. Bacterial identification using 16S rRNA gene sequencing demonstrated that bacteria present in blood, liver, and femur belonged to different taxonomic groups. Bacteria isolated from blood and liver samples belonged predominantly to the Enterobacteriaceae, Enterococcaceae, and Staphylococcaceae, while Escherichia/Shigella and Enterococcus spp. were the most prevalent taxa in femoral head samples. No bacteria were isolated from the femoral head of any of the birds with histopathological lesions. All 19-day-old and 22-day-old birds in this study showed cartilage retention in both legs, and had signs of separation between the articular cartilage and the growth cartilage in one or both legs. This study shows that young clinically healthy broilers have a higher prevalence of bacteria in the femoral head compared to older broilers and that presence of bacteria in blood and liver is common during ageing of broilers.RESEARCH HIGHLIGHTS center dot Large number of bacteria isolated from femoral heads of clinically healthy broilers.center dot The prevailing taxa in femoral heads were Escherichia/Shigella and Enterococcus spp.center dot Continuous presence of bacteria in blood and liver of clinically healthy broilers.center dot Enterobacteriaceae, Enterococcaceae, and Staphylococcaceae prevail in blood and liver.