Spatial influence on breast muscle morphological structure, myofiber size, and gene expression associated with the wooden breast myopathy in broilers

Abstract

The wooden breast (WB) myopathy is identified by the palpation of a rigid pectoralis major (p. major) muscle and is characterized as a fibrotic, necrotic p. major disorder in broilers. The objective of the current study was to determine spatial morphological and gene expression differences at 4 locations within WB affected muscle from different genetic lines. Morphology was evaluated in 2 broiler lines expressing the WB myopathy (Lines A and B) and a line without WB (Line C) at 3 ventral locations and one anterodorsal location in the p. major muscle. In WB affected muscle of Line A, fibrosis was greatest in the anterior locations of WB affected muscle. In Line B muscle, fibrosis was greatest in the anteroventral region and minimal in the anterodorsal or posterior regions. Average p. major myofiber diameter was 30% larger in Lines A and B compared to Line C. However, in Line A there were no differences between the percentage of large fibers (diameter >70 μm) in unaffected and WB affected muscles at any sampling region. The percentage of small fibers (diameter <10 μm), likely small regenerating fibers, and expression of myogenic determination factor 1 (MYOD1) and myogenin were increased in Line A WB affected muscle compared to unaffected muscle. In Line B, the percentage of small fibers and MYOD1 expression in WB affected muscle was not different from unaffected muscle. Connective tissue organization within WB affected muscle was also different in Lines A and B, which may be attributed to decorin, a proteoglycan that mediates collagen crosslinking, growth factor signaling, and cell growth. Decorin expression was increased at all locations within Line A. However, in Line B decorin was increased only in the fibrotic regions of the p. major. The compiled results provide evidence that the WB myopathy is not uniform throughout the entire p. major muscle and the anterior end of the p. major muscle was more affected by the condition.

Wooden‐Breast, White Striping, and Spaghetti Meat: Causes, Consequences and Consumer Perception of Emerging Broiler Meat Abnormalities

“…They also reported that only breast WS/WB presented lower DPA and EPA contents. Changes in the chemical composition of WB and WS/WB meats are consistent with the replacement of fibers by adipose tissue (lipidosis) and the accretion of extracellular water as a result of edema and inflammatory processes (Clark & Velleman, ; Kawasaki, Iwasaki, Yamada, Yoshida, & Watanabe, ).…”

“…This condition might even be exacerbated by the physiology of the pectoralis major muscle: its impressive development (with particular reference to thickness) might compress the pectoral artery thus further reducing oxygenation and nutrients transportation to the muscle. This hypothesis is further supported by the evidence that the severity of the histological lesions, associated with the occurrence of WS, WB, and SM, gradually decreases moving from the skin-facing surface towards the inner section of the pectoralis major (Baldi et al, 2018;Clark & Velleman, 2016;Soglia et al, 2016a). In addition, hypoxic conditions seem to be exacerbated by the reduced blood vessel density observed in WB affected muscles (Sihvo et al, 2018) as well as by tissue swelling likely due to the accumulation of compounds having osmotic properties (that is, taurine and alanine) (Boerboom et al, 2018).…”

“…Consistently, recent studies carried out in modern broiler strains selected for rapid growth and muscle yield revealed that the pectoralis major muscles were entirely composed of type IIB fibers and the authors hypothesized whether this condition may increase their susceptibility to the development of muscular abnormalities (Petracci et al., ). In this context, an overall impairment in muscle regeneration in fast‐growing broilers was recently demonstrated to be a consequence of a reduction in satellite cells number and in their altered abilities to proliferate and differentiate (Clark & Velleman, ; Daughtry et al., ). In addition, it was recently found a strong genetic determinism of the WS condition in fast‐growing chickens ( h 2 = 0.65; Alnahhas et al., ), even if Bailey, Watson, Bilgili, and Avendano () previously reported lower heritability levels in two commercial pure lines of broiler chickens selected for high ( h 2 = 0.34) or moderate ( h 2 = 0.18) breast meat yield.…”

Evidence and role of phlebitis and lipid infiltration in the onset and pathogenesis of Wooden Breast Disease in modern broiler chickens

“…With the knowledge that WBD presents itself bilaterally, in this study, the upper 1/3 or craniolateral aspect of right superficial pectoral muscle was used consistently as the sampling site on all samples. The choice for this specific location was guided by the knowledge that clinical, gross and histological changes associated with WBD are largely known to start from the cranial aspect of the muscle before becoming apparent caudally (Clark & Velleman, 2016). Further, muscle samples excised from this site were about 2-3 cm deep from the outer aspect of the muscle.…”

Insights into the molecular basis of wooden breast based on comparative analysis of fast- and slow-growth broilers

“…The breast muscle was palpated to examine birds for hardness, before euthanasia. This approach has been used as a diagnostic method in several recently published studies [10,26,27]. Birds were then euthanized by cervical dislocation and dissected for the collection of tissues for genetic analysis.…”