16.12.2023

Bacterial chondronecrosis with osteomyelitis (BCO) is an important cause of severe lameness in fast-growing broilers. The rapid growth of broilers has contributed to the emergence of bacterial BCO in several ways. The intensive genetic selection for economic traits, such as rapid weight gain and feed use efficiency, has led to a significant increase in broiler growth rates. As a consequence, the developing cartilage in broilers is susceptible to microfractures in the growth plates of the proximal femur and tibia, which can be colonized by haematogenous opportunistic bacteria. These microfractures, combined with the compromised skeletal integrity, provide an environment conducive to the development of bacterial chondronecrosis with osteomyelitis. Bacterial translocation through the epithelial lining of the gastro-intestinal tract, and bacteraemia, are of significant importance in the pathogenesis of BCO. Therefore, reducing the number of opportunistic pathogenic bacteria that can pass the intestinal barrier, improving the integrity of the intestinal barrier, and supporting the host’s immune system in order to efficiently eliminate translocated bacteria from the systemic circulation are of importance in the prevention of this disease.
A new study published in Avian Pathology indicates that Enterobacteriaceae and Enterococcaceae are the main bacterial families translocating to femur heads in broiler chicks. These bacterial families were found to be the dominant taxa in the femoral heads of broiler chicks, with Escherichia/Shigella and Enterococcus spp. being the most prevalent taxa in femoral head samples. An age-related effect on the presence of bacteria in the femoral heads was observed. Almost all 2-day-old chicks had bacteria present in the femoral heads. While some only had a few colonies, others had over 100 CFUs in the femoral samples. This number decreased drastically as the broilers got older and, after the age of 2 weeks, no colonies were found in the femoral samples. These results indicate that bacteria may be present in the circulation, without noticeable colonization of the femoral head at later ages. This knowledge can aid in the development of targeted strategies to mitigate the impact of BCO on broiler health and welfare.