Downgrading of Heavy Broiler Chicken Carcasses Due to Myodegeneration of the Anterior Latissimus Dorsi: Pathologic and Epidemiologic Studies

Abstract

Recently, in some Brazilian poultry companies, a dorsal cranial muscular lesion has been increasingly detected in broilers, causing heavy economic losses due to carcass downgrading. The observed gross lesions located in the anterior latissimus dorsi (ALD) muscle are characterized by yellowish discoloration of the skin and swelling on the dorsal cranial region of that muscle. When the ALD muscle is cut, subcutaneous edema, muscular superficial hemorrhage, pallor, adherence, and increased thickness and density are observed. Microscopically, findings indicate degenerative and polyphasic features, variation in fiber size and splitting, presence of hyaline, necrotic and regenerative myofibers, extensive fibrosis, and adipose tissue with lymphohistiocytic infiltration in all ALD muscles affected. The etiology of the lesion is unknown, and no detailed report was found in literature. The highest frequency of carcass downgrading due to this lesion was found in the heaviest and the oldest males of high-yield broiler strains (P < 0.01). This study is the first to describe the pathologic and some epidemiologic aspects of this new myopathy.

Myodegeneration With Fibrosis and Regeneration in the Pectoralis Major Muscle of Broilers

“…5,10 The main histologic changes in these are very similar to our findings of myodegeneration and necrosis with fibrosis and regeneration within the wooden breast myopathy. 7,10 Overlapping of histologic changes with the white striping myopathy is not surprising, since white striping is clearly a feature also in the wooden breast myopathy. Macroscopic similarities between our findings and the ALD myopathy are striking as well: paleness, increased hardness and thickness of the muscle, and exudate on the muscle surface.…”

“…Macroscopic similarities between our findings and the ALD myopathy are striking as well: paleness, increased hardness and thickness of the muscle, and exudate on the muscle surface. 10 The ALD myopathy affected most severely the heaviest male birds; occurrence of severe white striping was particularly high in the heavy and rapidly growing birds. 5,10 In Finland, the weight of the broilers as well as breast fillets has increased in the past 3 years, together with the occurrence of the hard myopathy of the pectoralis major (Finnish poultry industry, personal communication, 2013).…”

“…10 The ALD myopathy affected most severely the heaviest male birds; occurrence of severe white striping was particularly high in the heavy and rapidly growing birds. 5,10 In Finland, the weight of the broilers as well as breast fillets has increased in the past 3 years, together with the occurrence of the hard myopathy of the pectoralis major (Finnish poultry industry, personal communication, 2013). Therefore, it is possible that the fast growth rate, together with the increased breast meat yield, indeed plays a significant role also in the development of the wooden breast myopathy.…”

Evaluation of Physiological Parameters of Broilers with Dorsal Cranial Myopathy

“…The etiology of myopathies, which affect the visual quality of broiler carcasses, has not been elucidated yet (Zimermann et al, 2012).…”

“…A gradual increase in carcass downgrading and condemnations due to DCM has been detected, particularly in winter, when its incidence may range from 1% (Amaral, 2014) to 6% (Zimermann et al, 2012). However, as the etiology of DCM has not been elucidated yet, and its effects on the systemic health of broilers are still unknown.…”