The pathology of deep pectoral myopathy of Turkeys

Evolutions in Commercial Meat Poultry Breeding

This paper provides a comprehensive overview of the history of commercial poultry breeding, from domestication to the development of science and commercial breeding structures. The development of breeding goals over time, from mainly focusing on production to broad goals, including bird welfare and health, robustness, environmental impact, biological efficiency and reproduction, is detailed. The paper outlines current breeding goals, including traits (e.g., on foot and leg health, contact dermatitis, gait, cardiovascular health, robustness and livability), recording techniques, their genetic basis and how trait these antagonisms, for example, between welfare and production, are managed. Novel areas like genomic selection and gut health research and their current and potential impact on breeding are highlighted. The environmental impact differences of various genotypes are explained. A future outlook shows that balanced, holistic breeding will continue to enable affordable lean animal protein to feed the world, with a focus on the welfare of the birds and a diversity of choice for the various preferences and cultures across the world.

Characterising the Influence of Genetics on Breast Muscle Myopathies in Broiler Chickens

This report provides the first estimates of the genetic basis of all key breast muscle myopathies (BMM) in broiler chickens [Deep pectoral myopathy, wooden breast, white striping and spaghetti breast] and their relationship with body weight and breast yield. Data from a pure bred high yielding commercial broiler line were analysed to estimate the genetic parameters using a multivariate animal model with the appropriate fixed effects and permanent environmental effect of the dam. Heritabilities of the BMM ranged from 0.04 to 0.25 and the genetic correlation of the BMM with body weight and breast yield ranged from -0.06 to 0.41. Here we highlight that the genetic variance of BMM accounts for a low proportion of the phenotypic variance and the BMM have a low genetic relationship with performance traits. The large contribution of residual variance to the phenotypic variance for the BBM was >71.5% which indicates the importance of the non-genetic effects on BMM. The data presented also show that the moderate to low genetic influence for the development of BMM can be used, through balanced selection, to reduce the myopathy incidence in the long term. The impact of genetic selection against BMM was tested empirically by comparing the incidence of WB and % breast yield of a commercial broiler with a high generation (HG) broiler. The HG broiler used represents 2 years of genetic improvement compared to the commercial broiler; the HG broiler had an 18.4% relative decrease in WB and a 1.02% relative increase in breast yield compared to the commercial broiler. This paper describes the relationship between the genetic and non-genetic factors influencing BMM highlighting the importance of understanding the non-genetic effects on myopathy incidence. It also shows that the genetic component of BMM can be reduced whilst at the same time improving breast yield as part of balanced breeding goals.

Muscle Abnormalities and Meat Quality Consequences in Modern Turkey Hybrids

Turkey meat is the second most consumed poultry meat worldwide and represents an economic source of high-quality protein for human consumption. To fulfill the increasing demand for turkey meat, breeding companies have been selecting genetic lines with increased growth potential and breast muscle proportion. Moreover, the progressive shift toward further processed products has emphasized the need for higher standards in poultry meat to improve its technological characteristics and functional properties (i.e., water-holding capacity). However, as observed for broiler chickens, a growing body of scientific evidence suggests that the intense selection for the aforementioned traits could be associated with a greater occurrence of growth-related myopathies and abnormalities and, consequently, to increased downgrading rates and overall reduction of meat quality characteristics. In the past, muscle abnormalities such as deep pectoral myopathy, pale-soft-and-exudative-like meat, and focal myopathy have been reported in turkey lines selected for increased growth rate. In addition, the presence of white striations in the superficial layer of pectoralis major muscle, as well as the tendency of muscle fiber bundles to separate resulting in an altered breast muscle structure, has been detected in commercial turkey abattoirs. Furthermore, past investigations revealed the presence of another quality issue depicted by an overall toughening of the breast muscle. These meat abnormalities seem to macroscopically overlap the white striping, spaghetti meat, and wooden breast conditions observed in pectoral muscle of fast-growing, high-breast-yield chicken hybrids, respectively. Considering the high economic impact of these growth-related abnormalities in broilers, there is an increasing interest of the turkey industry in estimating the occurrence and the impact of these meat quality issues also in the modern turkey lines. Studies have been recently conducted to assess the effect of the genotype on the occurrence of these emerging growth-related defects and to evaluate how meat quality properties are affected by white-striping condition in turkeys, respectively. Therefore, this review aims to provide a critical overview of the current understanding regarding the growth-related abnormalities and their impact on meat quality in modern turkey hybrids with the hope that this information may improve the knowledge concerning their overall effect on poultry meat.

CT venography and pathological characterization of crus haemorrhage in Pekin ducks

The crus haemorrhage is one of the main causes of carcass defects in Pekin duck processing houses. However, its pathologic features are currently unclear. In order to examine the injury to the hind limb veins and illustrate the pathologic characteristics of crus haemorrhage in Pekin ducks, a total of 68 Pekin ducks with crus haemorrhage (test group) and 10 unaffected ducks (control group) were collected in this study. Five ducks randomly selected from each group were examined by computed tomographic venography with 2.0 mm thickness, 120 kVp, and 90 mA. Pathological changes were observed macroscopically, and under a microscope and electron microscope. The computed tomographic venography results showed no differences in the main hind limb veins between Pekin ducks with crus haemorrhage and the control. Macroscopic results demonstrated that the haemorrhage only occurred in crural muscles, most frequently in musculus gastrocnemius and musculus tibialis cranialis. In severe cases, muscular rupture and multiple intermuscular blood clots could be observed. Histological analysis showed rupture of myofibers and massive red blood cells between muscle bundles. Besides, infiltration of connective tissues and inflammatory lesions could be seen. However, no differences were observed in other organs between these two groups. The main ultrastructural characteristics were myofibrillar rupture and split, accompanied by mitochondrial membrane disintegration and vacuolization. All these results indicate that the haemorrhage in crus is a focal myopathy with the characteristics of bleeding, rupture, and inflammatory lesions. Research highlights CTV was a feasible method to evaluate the hind limb veins in Pekin ducks. The focal myopathy presented here only affected crural muscles. The focal myopathy was characterized by bleeding, rupture and inflammatory lesions.

Rapid growth rate results in remarkably hardened breast in broilers during the middle stage of rearing: A biochemical and histopathological study

The high incidence of meat of impaired quality poses a serious problem in the poultry industry. In recent years, the incidence of the pectoralis major muscle that appeared pale colored, remarkably hardened, and exudative, called "wooden breast" or "woody breast" has increased in slaughter houses. In the present study, 19-day-old Ross 308 broiler chickens affected (n = 10) and unaffected (n = 10) with remarkably hardened breast were selected from a commercial broiler farm, and reared to 55 days of age under a controlled environment. Among the affected birds, 5 of 10 birds appeared exhausted with markedly suppressed weight gain and 4 of 10 birds died during the rearing period. In contrast, all unaffected birds survived and most gained weight. Four of 10 unaffected birds lost the ability of back-to-back wing contact by the late stage of rearing. The biochemical analysis of blood plasma samples of 20-day-old birds revealed that creatine kinase and L-aspartate aminotransferase values in most affected birds were higher than those in unaffected birds; however, these values in unaffected birds increased rapidly with lost wing contactability and increasing age. Postmortem examinations revealed that the mean diameter of myofibers in affected birds was smaller than that in unaffected birds. Moreover, symptoms of degenerative and regenerative muscles were observed in most birds in both groups. Among them, a decrease in, or defect of, the characteristic polygonal shape of myofibers was the most common change within the pectoralis major muscles in both groups. The present study demonstrated that broilers affected with remarkably hardened breast during the middle stage of rearing would have suppressed physical status and weight gain, or would die. It was suggested that rapid growth in broilers might be a cause of remarkably hardened breast.

Effect of white striping on turkey breast meat quality

In the past decades, the intense selection practices carried out in order to develop fast growing and high breast-yield turkey hybrids profoundly modified the muscle physiology leading to the development of growth-related alterations and muscular abnormalities. White striations of variable thickness have been particularly observed on the ventral surface of Pectoralis major muscle belonging from heavy male turkeys since several years. However, although the effects of white striping (WS) have been extensively studied on broilers, this condition was not considered as a main quality issue by both turkey producers and meat industry. Thus, this study aimed at evaluating whether the occurrence of WS in heavy male turkeys affects the quality traits and technological properties of meat to the same extent previously observed for broilers. In two replications, 72 Pectoralis major muscles were classified as: normal (NORM), moderate WS (MOD) and severe WS (SEV) cases. The whole muscle was weighed and cut in order to assess colour, ultimate pH, water holding (drip and cooking losses) and binding (marinade uptake) capacities, NMR relaxation properties, shear force as well as proximate composition of meat. The Pectoralis major muscles affected by WS (both moderate and severe cases) exhibited a one-fifth increased weight in comparison with their NORM counterpart. However, the occurrence of WS only partially affected the proximate composition of the meat. In detail, although moisture, collagen and protein contents did not differ among the groups, if compared with NORM, higher lipid levels were found in SEV muscles, whereas MOD had intermediate values. On the other hand, both MOD and SEV exhibited lower ash content. Despite these variations in proximate composition, both water holding and binding capacities of turkey breast meat were not affected by WS. Indeed, quality traits of raw (pH, colour, cooking losses and shear force) and marinated (uptake, cooking losses and shear force) meat as well as water distribution within the muscle tissue did not differ between NORM and WS cases. Overall, if compared with broilers, WS only marginally affected quality traits of turkey breast meat. It might thus be hypothesised a diverse specie-specific physiological response to the pressure in muscle tissue induced by the selection in turkeys that, although analogously led to the occurrence of WS, results in limited effects on meat quality.

Response of Turkey Muscle Satellite Cells to Thermal Challenge. II. Transcriptome Effects in Differentiating Cells

Background: Exposure of poultry to extreme temperatures during the critical period of post-hatch growth can seriously affect muscle development and thus compromise subsequent meat quality. This study was designed to characterize transcriptional changes induced in turkey muscle satellite cells by thermal challenge during differentiation. Our goal is to better define how thermal stress alters breast muscle ultrastructure and subsequent development. Results: Skeletal muscle satellite cells previously isolated from the Pectoralis major muscle of 7-wk-old male turkeys (Meleagris gallopavo) from two breeding lines: the F-line (16 wk body weight-selected) and RBC2 (randombred control line) were used in this study. Cultured cells were induced to differentiate at 38°C (control) or thermal challenge temperatures of 33 or 43°C. After 48 h of differentiation, cells were harvested and total RNA was isolated for RNAseq analysis. Analysis of 39.9 Gb of sequence found 89% mapped to the turkey genome (UMD5.0, annotation 101) with average expression of 18,917 genes per library. In the cultured satellite cells, slow/cardiac muscle isoforms are generally present in greater abundance than fast skeletal isoforms. Statistically significant differences in gene expression were observed among treatments and between turkey lines, with a greater number of genes affected in the F-line cells following cold treatment whereas more differentially expressed (DE) genes were observed in the RBC2 cells following heat treatment. Many of the most significant pathways involved signaling, consistent with ongoing cellular differentiation. Regulation of Ca2+ homeostasis appears to be significantly affected by temperature treatment, particularly cold treatment. Conclusions: Satellite cell differentiation is directly influenced by temperature at the level of gene transcription with greater effects attributed to selection for fast growth. At lower temperature, muscle-associated genes in the satellite cells were among the genes with the greatest down regulation consistent with slower differentiation and smaller myotubes. Fewer expression differences were observed in the differentiating cells than previously observed for proliferating cells. This suggests the impact of temperature on satellite cells occurs primarily at early points in satellite cell activation.

Temperature effect on proliferation and differentiation of satellite cells from turkeys with different growth rates

Poultry selected for growth have an inefficient thermoregulatory system and are more sensitive to temperature extremes. Satellite cells are precursors to skeletal muscle and mediate all posthatch muscle growth. Their physiological functions are affected by temperature. The objective of the current study was to determine how temperature affects satellite cells isolated from the pectoralis major (p. major) muscle (breast muscle) of turkeys selected for increased 16 wk body weight (F line) in comparison to a randombred control line (RBC2) from which the F line originated. Pectoralis major muscle satellite cells were thermally challenged by culturing between 33°C and 43°C to analyze the effects of cold and heat on proliferation and differentiation as compared to control temperature of 38°C. Expression levels of myogenic regulatory factors: myogenic differentiation factor 1 (MYOD1) and myogenin (MYOG) were quantified by quantitative polymerase chain reaction (qPCR). At all sampling times, proliferation increased at a linear rate across temperature in both the RBC2 and F lines. Differentiation also increased at a linear rate across temperature from 33 to 41°C at all sampling times in both the F and RBC2 lines. Satellite cells isolated from F line turkeys were more sensitive to both hot and cold temperatures as proliferation and differentiation increased to a greater extent across temperature (33 to 43°C) when compared with the RBC2 line. Expression of MYOD1 and MYOG increased as temperatures increased from 33 to 41°C at all sampling times in both the F and RBC2 lines. These results demonstrate that satellite cell function is sensitive to both cold and hot temperatures and p. major muscle satellite cells from F line turkeys are more sensitive to temperature extremes than RBC2 satellite cells.

Structural alterations in oedematous and apparently normal skeletal muscle of domestic turkey

The morphology and histochemistry of oedematous and apparently normal turkey muscle were compared. Alterations in structural morphology were observed in the majority of the oedematous muscles and in about half the control muscles. Both the pectoralis thoracicus and biceps femoris were affected, with the former to a slightly greater extent. Histological features included proliferated endomysial and perimysial connective tissue, fatty replacement of necrotic areas of muscular tissue, evidence of fibre hypercontraction, necrosis of isolated fibres, shrunk and pyknotic nuclei and infiltration of the walls of blood vessels by mononuclear cells. In affected muscle, the histochemical reactions were weak and/or uniform amongst fibre types. There was no apparent association between the observed structural alterations and the oedematous condition.

The induction by muscle stimulation of a deep pectoral myopathy in the fowl

Thirty min occlusion of the subclavian artery of commercial strains of adult light-weight and broiler breeder fowls had no adverse effect on the supracoracoid muscle. When this temporary arterial occlusion was combined with electrically-induced contractions of the supracoracoid for a period of 4 min, myopathy occurred in both types of bird. A similar degree of muscle contraction without any interference with the arterial supply induced necrosis of the supracoracoid of the broilers but not of the light-weight strain. The superficial pectoral muscle of the broilers was not adversely affected by stimulation. The necrotic muscle resembled that in spontaneous deep pectoral myopathy. These findings are discussed with particular reference to the vascular supply to the muscle and although they are not considered to be due to pre-existing occlusive lesions of the arteries, the basic nature of the causative defect remains obscure. On the basis of this work carried out on commercial broiler breeder stock maintained at the Poultry Research Centre, we conclude that a relatively small number of electrically-stimulated contractions of the supracoracoid muscle will bring about necrotic myopathy.

Fibromuscular dysplasia in intramuscular arteries of Japanese quail (Coturnix coturnix japonica)

Fibromuscular dysplasia (FMD) was found in the intramuscular arteries of both commercial (normal) and mutant (LWC) strains of Japanese quail. The mutant strain LWC is afflicted with an inherited muscular dystrophy exhibiting myotonia. The arterial lesions were classified as medial fibroplasia or medial hyperplasia, both being subtypes of medial FMD. Some lesions showed extensive proliferation of medial smooth muscle into the vascular lumen, resulting in partial occlusion of the affected blood vessel. FMD occurred more frequently in the mutant LWC quail than in the commercial strain. Ischaemic changes were absent in the associated muscle structures in both strains. The significance of FMD in relation to the skeletal muscle changes in the mutant LWC strain remains unclear.

A new inherited muscular disorder in Japanese quails (Coturnix coturnix japonica)

Thirteen adult mutant (LWC strain) Japanese quails (Coturnix coturnix japonica), between the ages of 8 and 60 weeks were examined for a progressive muscular disorder. The disorder, inherited as an autosomal dominant trait, was clinically apparent as early as 28 days of age; it was characterized by generalized myotonia, muscle stiffness, and muscle weakness. Affected birds were identified by their inability to lift their wings vertically upward and by their inability to right themselves when placed on their dorsum. Electromyographic studies in two mutant quails showed high-frequency repetitive discharges comparable to those of myotonic runs. These discharges persisted after nerve resection. The distinctive histopathologic changes in the various muscles examined were ring fibers, sarcoplasmic masses, and internal migration of sarcolemmal nuclei. A slight decrease in the size of type IIB muscle fibers and a slight increase in the size of type IIA fibers were observed in the M. pectoralis thoracicus of affected quails. In older affected birds, inter- and intrafascicular fatty infiltration with replacement of type IIB fibers by fat cells was seen in the pectoral muscles. Single fiber necrosis, nonspecific lymphorrages, and variations in the muscle fiber size and shape were also noted. The typical muscle lesions and multisystem involvement, which was manifested by testicular degeneration and atrophy in the male LWC specimens and bilateral lenticular cataracts in 6 of 13 affected mutant quails, suggest resemblance of this new inherited muscular disorder to myotonic dystrophy in man.

Histopathological and ultrastructural alterations of turkey skeletal muscle

The pectoralis thoracicus and biceps femoris muscles were obtained from 30 18-wk-old Large White turkey males at the time of slaughter. The birds had no observable mobility or postural problems, and the meat appeared normal. Samples were processed for histology, histochemistry, and electron microscopy. Degenerative features were found in muscle from 10 of the 30 birds. Four of the 10 had alterations in both muscles. The degenerative changes included scattered focal necrosis, hypercontraction of muscle fibers, infiltration by mononuclear cells, formation of fibrous tissue scars, and Z-band streaming. These structural alterations appear to be related to muscle ischemia.

Incidence of microscopically detectable degenerative characteristics in skeletal muscle of turkey

1. The incidence of microscopically detectable degenerative characteristics in 5 skeletal muscles (m. pectoralis thoracicus, m. supracoracoideus, m. biceps femoris, m. semitendinosus, m. femorotibialis medius) of turkeys was investigated. 2. Samples were obtained from 30 Large White turkey males 14, 16 and 18 weeks old. Hyaline degeneration, infiltration of mononuclear cells and necrotic fibres were observed. 3. Individual fibres varied greatly in size and muscle fibre nuclei were often shrunken and pyknotic. 4. Weak and/or uniform reaction for Ca++-ATPase and SDH in all types of muscle fibres and loss of alkaline phosphatase activity in cell membranes were noted. A positive reaction for acid phosphatase occurred in regions of perivascular infiltration and in necrotic muscle fibres. The majority of muscle fibres possessed high activity for phosphorylase a and b. 5. Based on the use of fluorescein alpha-bungarotoxin conjugate, motor end-plates appeared to be morphologically intact. Direct immunofluorescence with anti-chicken IgG showed positive reaction in muscle fibres undergoing necrosis and in the involved connective tissue. 6. Degenerative changes varied with age and were most marked in the oldest birds. 7. Because gross degenerative symptoms were absent from both the birds and the meat from them, the condition appears to be either different from or a precursor to the degenerative myopathy characterised by other authors.

Deep pectoral myopathy: a penalty of successful selection for muscle growth

Deep pectoral myopathy (DPM) is a disease that affects commercial poultry selected for large breast muscle development. The muscle affected by the disease is the supracoracoid muscle and usually one side of the breast musculature atrophies. The necrotic muscle has a characteristic pale green color. Heavy breeds of turkeys and broilers can be induced to show DPM by electrical stimulation of the breast muscle itself or by vigorous wing flapping; older birds are more susceptible. The cause of DPM is a fascial compartment too small to accommodate the enclosed supracoracoid muscle during vigorous exercise when the muscle increases its weight (and overall size) by about 20%. The inelastic compartment essentially strangulates the swollen, activated muscle. A possible means of correcting DPM is to train or exercise the flight muscles during the rapid growth phase of chicks or poults. Feed, for example, could be positioned above floor level so that birds would have to flutter up to reach it. There is also evidence to suggest a genetic component to the disease. Hence, an indicator such as high plasma creatine kinase levels may be used as a selection criterion.

Optical characteristics of deep pectoral myopathy in turkey carcasses

When eviscerated turkey carcasses are illuminated with white light from a 100 W lamp in the body cavity dorsal to the sternum, about 90% of carcasses with deep pectoral myopathy can be detected subjectively. With this method, subjective detection is more reliable than photometric detection. When a fiber-optic probe is placed in direct contact with a lesion, the absorbance spectrum of reflected light is radically different to the spectrum from normal muscle, and three types of lesions can be identified (red-purple, green, and yellow). However, the presence of lesions is masked by even a shallow depth (approximately 1 cm) of normal muscle between the lesion and the probe. A combination of both optical methods might enable carcasses to be inspected without slashing the breast muscles of all the carcasses from flocks of suspect birds, but the whole length of the supracoracoideus on each side would have to be traversed by the fiber-optic probe. For a fiber-optic detection system in the abattoir, the simplest diagnostic characteristic would be the ratio of two wavelengths (480/550 nm). The average ratio for normal muscle was .68. The average ratios for lesions were from 1.17 to 1.38.

Early expression of hereditary deep pectoral myopathy in turkeys due to forced wing exercise

In a deep pectoral myopathy selected (DPMS) line, forced wing exercise (FWE) at 20 weeks of age resulted in the same level of expressed deep pectoral myopathy (DPM) as seen in unexercised DPMS turkey by 72 weeks of age. The FWE at 15 and 17 weeks of age in DPMS line females increased the incidence of DPM to 30 and 50% compared to 5% in unexercised controls. There is an apparent developmental age X exercise relationship in the expression of DPM. In varieties, lines, and crosses without a history of DPM, FWE does not induce the myopathy. Additional evidence confirms the modifier effect in the polygenic DPM defect. Body weight and breast width measurements in genetically susceptible turkeys were not closely or consistently associated with expression of the myopathy. The results suggest FWE of turkeys at 20 weeks of age or later as a method for detecting genetic carriers at prebreeding ages.

Plasma creatine kinase as an indicator of degenerative myopathy in live turkeys

1. Diagnosis for degenerative myopathy of the Musculus supracoracoideus (DMS) in the live bird was attempted from plasma creatine kinase (CK) [EC 2.7.3.2] activities in 70 female turkeys. The blood of each bird was sampled 18 to 20 times over an age span of 16 to 79 weeks. 2. DMS incidence was 15.7%. 3. After CK values were logarithmically transformed and corrected for bleeding date, 82% of the affected birds had one CK value that deviated 3 or more standard deviations from the mean of other values for the same bird. The results indicate that plasma CK activities can be used to identify affected birds with a high degree of reliability.

Pathology of deep pectoral myopathy of broilers

Deep pectoral myopathy occurred in 39 of 204 apparently healthy and 46 of 146 ill, adult broiler breeders from Poultry Research Centre flocks. Both sexes and two commercial strains were similarly affected. The myopathy was not associated with any disease except pododermatitis. The supracoracoid was the only muscle affected. It was bilaterally involved in 33 chickens. The lesions were grouped macroscopically into three categories: acute oedema progressing to a green necrosis, centrally located cicatrix, and replacement of the caudal region by fibroadipose tissue. Microscopcially the green lesion consisted of necrotic, anucleate muscle fibres devoid of inflammatory cells and surrounded by a fibrous capsule that had a reactive inner border and externally abutted on normal and regenerating muscle or fibro-adipose tissue. Considered with the ultrastructural findings of early loss of glycogen and disintegration of sarcoplasmic reticulum, mitochondria, nuclei and Z lines, these findings indicate that the condition is an ischaemic necrosis. There was no evidence that its primary cause was occlusive vascular lesions. The muscle was able to regenerate unless extensive secondary neurological lesions were present.