Histopathology of Wooden Breast

Transcription

1 Histopathology of Wooden Breast Canadian Poultry and Egg Processors Council Aviagen Frederic J. Hoerr, DVM, PhD June 10, 2016 Halifax, Nova Scotia FJ Hoerr 1

2 Normal Veterinary Diagnostic Pathology, LLC Normal skeletal muscle has a few hyper eosinophilic fibers (white arrow), basophilic fibers with internalized prominent nuclei(green arrow), and a necrotic muscle fibers infiltrated FJ with Hoerrmacrophages (blue arrow). 2

3 Broiler muscle Number of fibers set at hatch Fibers grow by hypertrophy (increase size) Genetic selection promotes progressively greater hypertrophy Corresponding decreases in Endomysial space around fiber Perimysial space around muscle bundle Blood supply per unit of muscle mass Veterinary Diagnostic Pathology, LLC FJ Hoerr 3

4 Wooden Breast FJ Hoerr 4

5 Early lesion. Many hyper eosinophilic fibers; consistent with low ph due to lactic acid build up (blue arrows). Also edematous fibers with early fragmentation (green arrows). Veterinary Diagnostic Pathology, LLC CF Rpt_Template 5

6 Pectoral muscle Predominance of type IIB white fibers have been selected Fast twitch, glycolytic Lactic acid produced Relative decrease in vascular supply in high-yield strains Increased anaerobic respiration Lactic acid retention Lower ph of fibers (acidophilic) H&E stain Acidophilic = Eosinophilic/Red Basophilic = Blue Veterinary Diagnostic Pathology, LLC FJ Hoerr 6

7 Satellite Cells Veterinary Diagnostic Pathology, LLC FJ Hoerr 7

8 Satellite cells Mediate muscle growth by hypertrophy Regeneration and repair Pluripotent Myogenesis, osteogenesis, adipogenesis Require vascular environment for proper signaling and activation Proliferate close to capillaries In turn, satellite cells can stimulate angiogenesis Regeneration requires angiogenesis and myogenesis Insufficient vascularization promotes fibrosis Veterinary Diagnostic Pathology, LLC FJ Hoerr 8

9 Blood supply and satellite cells Interdependence Decreased blood supply, decreased satellite cells Muscle fibers are stressed by retention of lactic acid Predisposes to degeneration and necrosis Decreased satellite cells Reduction in fiber maintenance Reduction in fiber regeneration Smaller muscle fibers Fibrotic muscle Veterinary Diagnostic Pathology, LLC FJ Hoerr 9

10 Muscle and fat deposition Satellite cells have adipogenic capability Feed restriction first week (Velleman et al, 2014) Increased myofiber necrosis Increased intramuscular fat deposits Feed restriction moved to second week Eliminated increased myofiber necrosis and fat deposits Veterinary Diagnostic Pathology, LLC FJ Hoerr 10

11 More advanced lesion. Fragmented, necrotic fibers (blue arrows). Widened perimysium with fatty dysplasia (green arrow). Veterinary Diagnostic Pathology, LLC CF Rpt_Template 11

12 Fatty dysplasia (tiger striping). CF Rpt_Template 12

13 Marked increased width of the perimysium, with myxomatous change and collagen fibers (blue arrow). Fatty dysplasia (green arrow). Veterinary Diagnostic Pathology, LLC CF Rpt_Template 13

14 Higher magnification of degenerating and necrotic muscle fibers (blue), and widened perimysium (green) CF Rpt_Template 14

15 Images of mild (A), moderate (B), and severe (C) samples in the histological scale (ranging F1 to F3) used to score the levels of myodegeneration (Masson's Trichrome). F. Soglia et al. Poultry Science 2016;95: Severe fibrosis (wooden breast endstage lesion) 2015 Poultry Science Association Inc.

16 High vs. Low Expression of Wooden Breast Increased decoran expression proteoglycan/collagen crosslinking Increased muscle regulatory gene expression regeneration and repair FJ Hoerr 16

17 Minimal overall cellular inflammation Inflammation Few heterophils in myxomatous early fibroplasia Perivascular cuff of lymphocytes, within normal limits. Veterinary Diagnostic Pathology, LLC FJ Hoerr 17

18 Skeletal muscle is striated muscle FJ Hoerr 18

19 E Longitudinal orientation. Many hypereosinophilic fibers (E), and necrotic fibers (N). Fat dysplasia (arrow). N E CF Rpt_Template 19

20 Increased and ongoing fibrous connective tissue accumulation (fibrosis) (blue arrow). This is accompanied by only minimal cellular inflammation; predominately heterophils (green). CF Rpt_Template 20

21 Fiber regeneration (nuclear rowing) in presence of ongoing degeneration and necrosis. CF Rpt_Template 21

22 Other lesions in muscle Comparative pathology FJ Hoerr 22

23 Inactivated Vaccine Reactions Muscle Immature granulation tissue (scar tissue) with many vaccine/carrier granulomas FJ Hoerr 23

24 Inactivated Vaccine Reactions Muscle Muscle Inflammatory reaction around vaccine droplets (arrow). Veterinary Diagnostic Pathology, LLC 24

25 Inactivated Vaccine Reactions Coagulum of spent inflammatory cells on the surface of the muscle. Muscle Veterinary Diagnostic Pathology, LLC 25

26 Vitamin E/Se Deficiency Nutritional Myopathy Poultry production Clinical disease Meat quality Caged or confined birds Adequate diets Wild birds Predisposition to capture myopathy Photos D. Swayne FJ Hoerr 26

27 Salinomycin toxicity, broilers 27 & 44 days days 27 days Heart 44 days FJ Hoerr 27

28 Deep Pectoral Myopathy FJ Hoerr 28

29 Broiler, 59 days, Deep Pectoral Myopathy Sequestrum FJ Hoerr 29

30 Broiler, 59 days, Deep Pectoral Myopathy Shrunken muscle mass due to ischemic necrosis, with many small regenerating fibers (arrow). Muscle fibers with loss of nucler detail; likely a sequestrum of devitalized tissue.

31 Broiler, 59 days, Deep Pectoral Myopathy This shows demonstrate a chronic but ongoing muscle degeneration and tissue reactions. The blue bracket - increased fiber eosinophilia, and early acute reversible degenerative lesion. The green band of fibers are relatively normal. The yellow band - edema and early fibroplasia which constitutes part of the aseptic inflammatory reaction. The red band represents muscle fibers in various stages of degeneration including the blue fibers which are necrotic, collapsed, and infiltrated with macrophages. FJ Hoerr 31

32 Staphylococcal tenosynovitis & osteomyelitis with muscle involvement Photos K. Bessinger Joiner FJ Hoerr 32

33 Muscle, lymphoma x20 FJ Hoerr 33

34 Discussion Anatomic location of gross lesion Chickens selected for pectoral muscle mass Achieved by pectoral muscle fiber hypertrophy Type IIB, fibers, glycolytic, lactic acid produced and retained Relative reduction in vascular supply Satellite cells key to fiber hypertrophy, maintenance, and repair Vascular supply and satellite cells are interdependent Fat deposition may occur because of early stresses to satellite cells Directed to increase adipogenic differentiation Tiger-striped breast meat FJ Hoerr 34

35 Discussion II Wooden Breast is likely a metabolic development enhanced by genetic selection Muscle fiber necrosis has occurred in the pectoral muscle at a low level for many years Wooden breast represents an increased in incidence, severity and visibility Fiber necrosis Limited inflammation Edema Rapid onset of fibrosis No evidence of septic process or inflammation No evidence of bacterial or fungal disease Product quality and aesthetic concerns FJ Hoerr 35

36 Wooden Breast A variable percentage of the flock is affected Goal Minimize the subpopulation of overtly affected chickens Genetics, nutrition, and management are likely key intervention points, but the specifics points need to be defined. 1% 100%

37 Thank You