Abstract
Wooden breast (WB) syndrome has emerged as a global myopathy in modern commercial broiler chickens, mainly affecting the pectoralis major muscle. Recent evidence suggests that WB myopathy is a systemic disease, which might be accompanied by other physiological disparities and metabolic changes. This study was conducted to systemically investigate the potential physiological changes in liver tissues as well as the possible mechanisms involved to enhance the understanding of the etiology. A total of 93 market-age Arbor Acres male broiler chickens were sampled and categorized into control (CON) and WB groups based on the evaluation of myopathic lesions. Liver samples were collected (n = 10 in each group) for histopathological evaluation and biochemical analyses. Results indicated that WB birds exhibited significantly higher plasma aspartate amino transferase, alkaline phosphatase, and gamma glutamyl transpeptidase activities. Histopathological changes in hydropic/fatty degeneration, inflammatory cell infiltration, intrahepatic hemorrhages, elevated myeloperoxidase activity, and overproduction of nitric oxide were observed in WB liver compared with CON, suggesting the occurrence of liver injury in birds affected by WB myopathy. The WB group showed increased levels of reactive oxygen species, oxidative products, as well as enhanced antioxidant capacities in the liver. These changes were associated with impaired mitochondria morphology and mitochondrial dysfunction. WB myopathy also induced mitochondria-mediated hepatic apoptosis by upregulating levels of caspases 3 and 9, altering the expressions of apoptotic B-cell lymphoma-2 family regulators, as well as increasing the release of cytochrome c. The activation of nuclear factor kappa-light-chain-enhancer of activated B cell signaling enhanced the mRNA expression of downstream inflammatory mediators, contributing to the production of inflammatory cytokines in WB liver. Combined, these findings suggest that hepatic disorders may be conjoined with WB myopathy in broiler chickens and indicating systemic physiological disparities, and other metabolic changes accompanying this myopathy need further assessment.
Highlights
Over the past few decades, the demand for poultry meat has increased notably
We stained the liver tissues using hematoxylin and eosin (H&E) and Masson staining to reveal the damage caused by wooden breast (WB) myopathy (Figure 1A)
This study provides evidence of liver damage in birds affected by WB myopathy primarily by impaired liver morphology as well as elevated serum AST, alkaline phosphatase (AKP), and γ-GT activities
Summary
Over the past few decades, the demand for poultry meat has increased notably. genetic selection of modern commercial broiler chickens has been pushed toward fast growth and enhanced breast muscle yield (Petracci et al, 2015). This selection pressure accompanied with the modern intense breeding programs have caused the increasing incidence of spontaneous breast muscle abnormalities. These emerging myopathies have drawn worldwide attention due to their high occurrence and negative impacts on meat quality (Petracci et al, 2019). Wooden breast (WB) myopathy, is macroscopically characterized by hardened areas, pale ridge-like bulges, as well as occasional appearance of clear viscous fluid, small hemorrhages, and white striping in the pectoralis major (PM) muscle (Sihvo et al, 2014). WB myopathy seriously impairs the quality and nutritional value of breast meat (Mudalal et al, 2015; Soglia et al, 2016), thereby causing substantial economic losses to the poultry industry
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