The genetic basis of pectoralis major myopathies in modern broiler chicken lines

Abstract

This is the first report providing estimates of the genetic basis of breast muscle myopathies (BMM) and their relationship with growth and yield in broiler chickens. In addition, this paper addresses the hypothesis that genetic selection for increase breast yield has contributed to the onset of BMM. Data were analyzed from ongoing recording of BMM within the Aviagen breeding program. This study focused on three BMM: deep pectoral myopathy (DPM; binary trait), white striping (WS; 4 categories) and wooden breast (WB; 3 categories). Data from two purebred commercial broiler lines (A and B) were utilized providing greater than 40,000 meat quality records per line. The difference in selection history between these two lines has resulted in contrasting breast yield (BY): 29% for Line A and 21% for Line B. Data were analyzed to estimate genetic parameters using a multivariate animal model including six traits: body weight (BW), processing body weight (PW), BY, DPM, WB, and WS, in addition to the appropriate fixed effects and permanent environmental effect of the dam. Results indicate similar patterns of heritability and genetic correlations for the two lines. Heritabilities (h2) of BW, PW and BY ranged from 0.271–0.418; for DPM and WB h2 <0.1; and for WS h2 ≤0.338. Genetic correlations between the BMM and BW, PW, or BY were ≤0.132 in Line A and ≤0.248 in Line B. This paper demonstrates the polygenic nature of these traits and the low genetic relationships with BW, PW, and BY, which facilitates genetic improvement across all traits in a balanced breeding program. It also highlights the importance of understanding the environmental and/or management factors that contribute greater than 65% of the variance in the incidence of white striping of breast muscle and more than 90% of the variance of the incidence of wooden breast and deep pectoral myopathy in broiler chickens.

Classification of wooden breast myopathy in chicken pectoralis major by a standardised method and association with conventional quality assessments

“…Here, we describe three categories of WB as no, moderate and severe including reference dummies. Similar attempts have recently been presented to categorise severity of white striping (Bailey et al ., ; Trocino et al ., ), and the separate and combined occurrences of white striping and wooden breast (Mudalal et al ., ; Soglia et al ., ). It should be emphasised that the samples categorised as severe WB in this study may not be fully comparable to previous studies, as in the present study some PMs with extreme WB are discarded at the slaughter line.…”

White striping prevalence and its effect on meat quality of broiler breast fillets under commercial conditions

“…White striping (WS) is one of the most important emerging problems for the poultry industry, and its appearance, particularly in breast meat, has been rapidly increasing (Bailey, Watson, Bilgili, & Avendano, ; Kuttappan, Hargis, & Owens, ; Petracci et al, ). White striping (WS), the quantity and thickness of which changes from bird to bird, is characterized by white parallel lines in the same direction of the muscle fibres.…”

Simple Method for Screening the Affected Birds with Remarkably Hardened Pectoralis Major Muscles among Broiler Chickens

“…However, a new type of myopathy, referred to as "white striping" or "wooden breast", which occurs without nutritional deficiencies or infectious diseases and only in the pectoralis major muscles of commercial broiler chickens has frequently been reported in recent years in the worldwide broiler industry (Sihvo et al, 2014;Velleman and Clark 2015). The white striping is characterized by visible white lines parallel to the direction of the muscle fibers, while the wooden breast is characterized by hardening and an exudate of the breast muscle (Bailey et al, 2015). However, the difference in pathogenesis between the two phenotypes has not been strictly classified.…”

“…Pale-colored exudative meat has been found in both broiler chickens and turkeys (Woelfel et al, 2002;Owens et al, 2009;Bailey et al, 2015;Velleman and Clark 2015). Smith and Northcutt (2009) reported that this pale-colored exudative avian muscle differed from pale, soft, and exudative porcine meat.…”