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Characterization of dorsal recumbency syndrome associated with woody breast in broiler flocks from Ontario, Canada

2022 CPRF,Broilers
We recently described dorsal recumbency syndrome (DRS) in market-age broiler chickens in Ontario. These broilers fall onto their backs and are unable to right themselves, described by some as “turtle chickens”. These broilers can eventually die on the farm and represent a significant economic loss. A previous report sug–gested that breast myopathies such as the woody breast (WB), which is characterized by scarring of the pectoral muscles, may be associated with this syndrome. We aimed to characterize the pathological, serological, and transcriptomic changes in broiler chickens affected by dorsal recumbency. A total of 64 broilers (Ross 708), 33 affected and 31 unaffected, were sampled at 42 to 48 days of age from 4 different commercial farms. Pectoralis major muscle samples were collected from all broilers and scored histologically to determine the presence and severity of myopathies. All 64 samples were used to determine the level of aspartate aminotransferase (AST) and creatine kinase (CK). Transcriptomic abundances of 19 genes were measured from 16 samples during one visit using droplet digital PCR. Recumbent birds displayed a significantly higher severity (p < 0.05) of myodegeneration, inflammation, and accumulation of fibro-fatty tissue in the P. major compared to unaffected birds. The level of AST and CK of recumbent chickens was significantly higher (p < 0.05) compared to those of unaffected birds, suggesting muscular damage. Mild hydropericardium was observed in 33.3% (95% CI: 19.1 – 51.4) and 25.8% (95% CI: 13.1 – 44.5) of affected and unaffected birds, respectively; right ventricular hypertrophy was observed in 12.1% (95% CI: 4.5 – 28.9) and 9.7% (95% CI: 3.0 – 26.9) of affected and unaffected broilers, respectively. HIF1A, MTOR, and MYF5 were over-expressed in affected broilers, whereas PRKAA2, PRKAB2, PRKAG3 were over-expressed in unaffected broilers. Histopathological, serological, and transcriptomic changes in the P. major suggest an association between WB and DRS.
Tags :
dorsal recumbency,woody breast
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University of Guelph

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