Embryo Lethality Assay for Evaluating Virulence of Isolates from Bacterial Chondronecrosis with Osteomyelitis in Broilers

We used an embryo lethality assay (ELA) to assess virulence for different isolates from cases of bacterial chondronecrosis with osteomyelitis (BCO) in broilers. ELA has been used to measure virulence and lethal dosage of Enterococcus faecalis and Enterococcus cecorum. We hypothesized that ELA could substitute for more laborious and costly assessments of BCO isolate pathogenicity using live birds. We evaluated two different levels of bacteria injected into eggs from layer and commercial broiler embryos. Significant findings include a) Escherichia coli from neighboring farms operated by the same integrator had very different embryo lethality, b) isolate Staphylococcus agnetis 908 had low virulence in ELA, even though this isolate can induce more than 50% BCO lameness, c) Enterococcus cecorum 1415 also had low pathogenicity; even though it was recovered from severe bilateral tibial dyschondroplasia, d) human and chicken isolates of S. aureus had significant pathogenicity, e) virulence for some isolates was highly variable possibly corresponding with quality of the embryos/fertile eggs used, and f) ELA pathogenicity was much lower for our BCO isolates than previous reports which may reflect maternal environment. Overall, ELA virulence and BCO virulence are not always concordant indicating that that ELA may not be an effective measure for assessing virulence with respect to BCO.ImportanceLameness is among the most significant animal welfare issues in the poultry industry. Bacterial infections are a major cause of lameness and different bacterial species have been obtained from lame broilers. Reliable lab-based assays are required to assess relative virulence of bacteria obtained from lame broilers. Embryo Lethality Assays have been used to compare virulence. Our results suggest that this assay may not be an effective measure of virulence related to lameness.

Role of Oxidative Stress and Antioxidants in Thiram-induced Tibial Dyschondroplasia

Tetramethyl thiuram disulfide (thiram) is an important dithiocarbamate bactericide; it has been widely used for the control of various diseases in fruits, vegetables, seeds and food grains. However, it also causes environmental pollution problems and poses a threat to human health to a certain extent. Thiram induces tibial dyschondroplasia (TD) by causing oxidative stress and antioxidants imbalance in tibial growth plate in poultry. TD is a skeletal abnormality in fastgrowing poultry birds. It has been considered an economically important disease in poultry that affects poultry industry by carcass loss at meat processing plant due to decrease in disease resistance, production performance, and carcass quality and induces breast cysts and osteomyelitis worldwide. Oxidative stress is developed due to the imbalance of free radical oxygen, which disrupts the equilibrium state of oxidant and antioxidant tending to oxidation. This review is based on the current research, mainly to explore the relationship and mechanism between tibial dyschondroplasia and oxidative stress induced by thiram, which provides a new theoretical foundation for the further research of the related mechanism.