Susceptibility of 4 commercial broiler crosses to lameness attributable to bacterial chondronecrosis with osteomyelitis

Abstract

Growing broilers on wire flooring provides an excellent experimental model for exposing susceptibility to lameness attributable to bacterial chondronecrosis with osteomyelitis (BCO). Two independent experiments (E1, E2) were designed to compare the susceptibilities of broilers from 4 commercial crosses (W, X, Y, and Z). The standard crosses (W and Y) grow rapidly at an early age, whereas high-yield crosses (X and Z) initially tend to grow more slowly. Chicks were obtained from a commercial hatchery for E1, or were hatched at the University of Arkansas Poultry Research Hatchery for E2. Males and females were reared together (E1; n = 360/cross) or separately (E2; n = 390/cross) in 3 × 3 m pens on litter or wire flooring (wire). Necropsies revealed lesions that were pathognomonic for BCO in ≥94% of the birds that became lame. The SigmaStat Z-test was used to compare cumulative lameness incidences at 8 wk of age. For birds reared on litter, lameness incidences were low and did not differ between crosses or sexes (range: 2.2 to 4.6%; P ≥ 0.6). When males were reared on wire, their lameness incidences (by cross) were E1 = 52% for W(b); 42% for X(c); 69% for Y(a), and 44% for Z(bc); E2 = 31% for W(b); 19% for X(c); 49% for Y(a); and 25% for Z(bc). For females reared on wire, the lameness incidences were E1 = 40% for W(b), 30% for X(c), 49% for Y(a), and 28% for Z(c); E2 = 16% for W; 15% for X; 16% for Y; and 15% for Z (ns). Accordingly, the hierarchical ranking for BCO susceptibility by broiler cross was X ≤ Z ≤ W < Y for males in E1 and E2, for females in E1, and for males and females pooled in E1 and E2. Standard broiler crosses developed higher incidences of lameness than high-yield crosses, implicating an association between rapid early growth and susceptibility to BCO. Rearing the females separately on wire in E2 led to uniformly low incidences of BCO, regardless of cross. Stress-mediated immunosuppression contributes to the pathogenesis of BCO; perhaps female broilers experience less social or competitive stress when reared separately from their male hatch mates.

Incidence of Bacterial Chondronecrosis with Osteomyelitis (Femoral Head Necrosis) Induced by a Model of Skeletal Stress and its Correlation with Subclinical Necrotic Enteritis

“…We observed a greater incidence of BCO during Experiment 2 (birds evaluated at 59 days of age) compared to Experiment 1 (birds evaluated at 50 days of age). This is consistent with previous studies [9,10,[31][32][33] reporting that, after 30 days of age, the incidence of BCO progressively increases with age up to 62 days. In an attempt to synchronize the timing of possible bacterial translocation with increased susceptibility to skeletal microfractures, we timed the intestinal challenge such that the intestinal lesions typical of SNE would develop after 30 days of age.…”

“…Indeed, the low incidence of lameness observed in Experiment 1 prompted us to extend the duration of Experiment 2, in an effort to reveal any latent lameness. Several factors could explain the variation in the incidence of lameness among studies, including unintentional pathogen exposure (from water lines, litter, hatchery, breeders, farm environment), diet composition (final body weights of the animals), diet contaminants (mycotoxins), and genetic lines of the animals [6,32]. Consistent with other studies [8], we found a large proportion of birds that did not show evident signs of lameness even in the presence of advanced necrotic lesions in their bones, highlighting the relevance of the subclinical presentation of BCO [39].…”

Genome Analysis of Staphylococcus agnetis, an Agent of Lameness in Broiler Chickens

“…The exposed musculature was drenched with 70% ethanol, then incisions were made with an ethanol sterilized scalpel at the joints which were then bent at an acute angle to expose either the articulated surfaces. The proximal femora and tibiae were visually scored for lesion type [ 2 , 3 ] then sampled with a Sterile Cotton Tip Applicator (Puritan Medical Products, Guilford, MA). Depending on the experiment, the applicator was then used to either inoculate 3 ml of broth or directly rubbed over the surface of agar plates.…”

“…Lameness in this model is predominantly associated with bacterial chondronecrosis with osteomyelitis (BCO) of the proximal tibiae and femora. Different broiler lines have been shown to be susceptible but there may be some line differences and sire-effects [ 2 , 3 ]. A model for BCO susceptibility based on the vasculature and growth plate dynamics has been described [ 4 , 5 ].…”

Genetic selection of broilers and welfare consequences: a review

“…Although the pathogenesis is still not completely understood, Wideman et al (2014) demonstrated a significant genetic predisposition in the susceptibility of broilers to BCO. Another study by the same authors found standard broiler crosses that grew rapidly at an early age developed higher incidences of BCO compared to crosses that grew more slowly (Wideman et al 2013). A more recent study by Petry et al (2018) identified 10 differentially expressed genes between normal and BCO-affected broilers and concluded that these genes are strong candidates for the development of BCO.…”