Chondronecrosis with osteomyelitis in broilers: further defining lameness-inducing models with wire or litter flooring to evaluate protection with organic trace minerals

Abstract

The feed additive Availa-ZMC was investigated for the ability to reduce lameness in broilers using 2 alternative models for inducing lameness. The mixture of organic trace minerals was effective in reducing lameness by 20% in the wire flooring model and 25% in the litter flooring model with the bacterial challenge. Lameness in both models is overwhelmingly attributable to bacterial chondronecrosis with osteomyelitis. The reduction in lameness was associated, at least in part, with enhanced intestinal barrier integrity mediated by elevated expression of tight junction proteins and stimulation of bactericidal killing of adherent peripheral blood monocytes obtained from the birds treated with Availa-ZMC. Lameness is a major animal welfare concern in broiler production. The wire flooring model and litter flooring model with the bacterial challenge are effective models for evaluation of management strategies for mitigating infectious causes of lameness.

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

“…We performed ELA with different bacterial isolates isolated from lame broilers to estimate relative pathogenicity. We observed that S. agnetis 908 is not pathogenic in the ELA even though we have shown that this isolate readily infects young broilers when administered at 10 4 or 10 5 CFU/ml in drinking water at 20 and 21 days of age (1, 3, 6, 7). Broilers challenged with S. agnetis 908 begin to develop lameness by 41 days of age and by 56 days of age 50% of the birds will be clinically lame with BCO lesions in proximal femoral and tibial heads.…”

“…We therefore assessed different BCO isolates at 10 5 and 10 6 CFUs (Table 1). We included S. agnetis 908 recovered from a femoral BCO lesion on our research facility as this isolate can induce lameness ≥50% by day 56 when administered in drinking water for two days to 20-day old broilers (1, 3, 6, 7). Surprisingly, 908 injections of even 10 6 CFUs resulted in only 14% embryo lethality, a level not statistically different from 1xPBS control treatment (Figure 2A).…”

“…Our data suggest caution in drawing broad conclusions when using ELA for evaluation of relative virulence of BCO isolates. Concerns include: a) the lack of significant virulence by S. agnetis 908 which we have shown is hypervirulent in inducing lameness and spreading through a broiler facility (3, 6, 7), b) the lack of virulence of E. cecorum 1415 which should have been virulent based on earlier reports using ELA (33), and c) the variability of ELA results with different sets of embryos for hypo- or moderately virulent isolates (e.g., E. coli 1409). There remains a need to develop new, convenient, and reliable, laboratory assays for assessing pathogenicity for chicken bacterial isolates related to BCO.…”

“…S. agenetis 908 is closely related to isolates from sub-clinical mastitis in dairy cows (5). S. agnetis 908 can induce greater than 50% BCO lameness by 56 days of age when administered in a single dose in drinking water at 10 4 to 10 5 CFU/mL on day 20 (1, 3, 6, 7). Our current model for lameness etiology is that environmental stress can lead to increased leakage (translocation) of bacteria across the gut and pulmonary epithelia into the blood system (1–3, 8–10).…”

Analysis of Genomes of Bacterial Isolates from Lameness Outbreaks in Broilers

“…The predominant species was Staphylococcus cohnii (~95%) with 3-4% Staphylococcus lentus and 1-2% E. coli . Air sampling during our broiler experiments at the University of Arkansas Poultry Research farm typically identify predominantly S. cohnii but not E. coli (26, 27).…”