Prevalence and Age-Associated Bacterial Chondronecrosis with Osteomyelitis Lesions in Commercial Broiler Flocks in Central Java, Indonesia

In tropical countries, broiler chickens are exposed to elevated ambient temperatures and humidity, which are sometimes exacerbated by high stocking densities and poor litter quality, thereby predisposing birds to severe stress, weakening immune function, and promoting BCO lameness progression. BCO lameness causes tremendous economic losses to the poultry industry and increases the risk of foodborne disease. BCO is frequently underdiagnosed in live populations, resulting in an iceberg phenomenon in which subclinical lesions are more prevalent than clinically apparent lameness. Therefore, a total of 500 Cobb500 broiler chickens from five commercial broiler flocks in Central Java, Indonesia, were randomly selected, weighed, slaughtered, and necropsied to evaluate the prevalence of BCO lameness lesions in the proximal femoral and tibial heads across distinct market ages ranging from 33 to 43 days. The ambient housing temperature in the region can reach 28-29 °C during the day. The results showed that more than 80 of the samples had normal femora at 33 days of age with an average body weight of 1.9 kg. A significant increase in the frequency and severity of femoral and tibial lesions was recorded at 35 to 36 days of age, when the average body weight reached approximately 2.5 kg. The high frequency of worsening BCO lesions observed during the 5th week suggests an age-related pattern in BCO occurrence during the late stages of grow-out. These findings suggest that improvements in nutrition, environment, and production management strategies before 36 days of age are necessary to mitigate the impact of BCO lameness in the poultry industry. © 2026 by the authors.