Inducing experimental bacterial chondronecrosis with osteomyelitis lameness in broiler chickens using aerosol transmission model

Abstract

Lameness disease attributed to bacterial chondronecrosis with osteomyelitis in broilers affects production, animal welfare, and food safety in the poultry industry. The disease is characterized by necrotic degeneration of the rapidly growing femora and tibiae due to bacterial translocation from the respiratory or gastrointestinal tracts into the blood circulation, eventually colonizing the growth plate of the long bones. To investigate the etiology, pathogenesis, and intervention measures for BCO, developing an experimental model that reliably induces BCO lameness is of the utmost importance. In the past, we have employed a wire-flooring model and a litter-flooring model administered with a bacterial challenge to investigate strategies for mitigating BCO. However, multiple issues on labor-intensive barn setup and cleanout efforts for the wire-flooring system and concern of direct pathogenic exposure to the broilers for the litter-flooring models rendered these research models less effective. Thus, we investigated a new approach to induce experimental BCO lameness using an aerosol transmission model employing a group of birds reared on wire-flooring pens as a BCO infection source, and the disease is further disseminated through the airborne transmission to other birds reared on litter flooring in the same housing environment. The effectiveness of the aerosol transmission model in inducing BCO lameness was concluded from 4 independent experiments. The cumulative lameness generated from the BCO source group on the wire floors versus negative control treatments on the litter floors from Experiments 1, 2, 3, and 4 were 84% vs. 69.33%, P = 0.09; 54.55% vs. 60%, P = 0.56; 78% vs. 73.50%, P = 0.64; 81% vs. 74.50%, P = 0.11. Overall, the cumulative lameness generated from the wire floors was successfully transmitted to the birds on litter floors without significant statistical differences (P > 0.05). The effectiveness of the aerosol transmission model for experimentally triggering BCO lameness provides a reliable system for evaluating practical intervention strategies for BCO lameness in broilers.

Keywords: aerosol; broiler; chondronecrosis; lameness.