Myotendinopathy of Unknown Etiology in Broiler Breeder Males.

This case series describes an emerging and ongoing lameness condition observed in broiler breeder males in flocks owned by a broiler integrator in the United States between February 2021 and April 2023. The lameness is characterized by an upright, penguin-like posture and gait. Affected flocks are typically 12-22 wk of age at presentation, but birds with similar stance and gross lesions can be observed as early as 1 day of age. Male mortality associated with this condition ranges from 0.01% to 6% per flock. The condition is infrequently observed in pullets from the female line but has not been observed in males (sex slips) from the female line. On postmortem examination, affected birds have bilateral hemorrhage due to a tearing of the iliotibialis muscles and fascia. In one case, a higher proportion of affected birds had unilateral lesions concurrently with broken legs or severe inguinal vaccine reaction. In this case, the affected leg was the weight-bearing leg. Histopathology confirmed the presence of hemorrhage in fascial sheaths surrounding major muscles, in addition to muscle fiber necrosis, edema, fibroplasia, and dissociation of tendon collagen. Bacteriology, histopathology, and clinical presentation identified no factors that were suggestive of an infectious etiology for this condition. No etiology has been established, but a suggested pathogenesis involves excessive biomechanical force resulting in tendon structural stress, leading to separation of tendon collagen fibers and associated muscle fiber stretching, separation, necrosis, and hemorrhage. The condition has been reported in multiple genetic lines, but the role of inheritance in the condition has not been fully evaluated.

Miotendinopatía de etiología desconocida en machos reproductores pesados. Esta serie de casos describe una condición de cojera emergente y recurrente observada en parvadas de machos reproductores pesados propiedad de un integrador de pollo de engorde en los Estados Unidos entre febrero del 2021 y abril del 2023. La cojera se caracteriza por una postura y desplazamientos corporales en forma erguida, parecidos a los de los pingüinos. Las parvadas afectadas suelen tener entre 12 y 22 semanas de edad en el momento de la presentación, pero se han podido observar aves con similar postura corporal y lesiones macroscópicas tan temprano como al primer día de edad. La mortalidad de los machos asociada con esta condición oscila entre el 0.01% y el 6% por parvada. La condición se observa con poca frecuencia en pollitas de la línea hembra, pero no se ha observado en machos provenientes de la misma línea hembra (errores de sexado). En el examen post mortem, las aves afectadas presentan hemorragia bilateral debido a un desgarramiento de los músculos iliotibiales y la fascia. En un caso, una mayor proporción de aves afectadas tuvieron lesiones unilaterales simultáneamente con patas rotas o una reacción postvacunal severa en la región inguinal. En este caso, la pierna afectada era la misma que soportaba peso. La histopatología confirmó la presencia de hemorragia en las vainas fasciales que rodean los músculos principales, además de necrosis de fibras musculares, edema, fibroplasia y disociación del colágeno del tendón. Mediante la bacteriología, la histopatología y la presentación clínica no se identificaron factores que sugirieran una etiología infecciosa para esta afección. No se ha establecido una etiología, pero una patogénesis sugerida implica una fuerza biomecánica excesiva que produce estrés estructural del tendón, lo que lleva a la separación de las fibras de colágeno del tendón y al estiramiento, separación, necrosis y hemorragia de las fibras musculares asociadas. La afección se ha informado en múltiples líneas genéticas, pero no se ha evaluado completamente el papel de la genética en esta condición.

Dietary guanidinoacetate reduces spaghetti meat myopathy risk in the breast muscle of broiler chickens.

The global demand for white chicken meat along with the increase in the occurrence of growth-related breast muscle myopathies (BMMs) [namely white striping (WS), wooden breast (WB), and spaghetti meat (SM)] highlights the need for solutions that will improve meat quality while maintaining the high productivity of modern broilers. Guanidinoacetate (GAA), a precursor of creatine, is used as a feed additive and has previously shown the potential to affect the quality of breast meat. This study investigated growth performance, meat quality and the risk ratio for the development of BMMs in broilers assigned to two dietary treatments: control (CON) group, fed a commercial basal diet, and supplemented GAA (sGAA) group, receiving the control diet supplemented on top with 0.06% GAA. Growth performance indicators such as BW, daily weight gain, daily feed intake, feed conversion ratio and cumulative feed conversion ratio were recorded on a pen basis. As a trait affecting animal welfare, the occurrence of foot pad dermatitis was also evaluated. At day 43, birds were processed, and breasts were scored for the incidence and severity of BMMs (n = 166 and 165 in CON and sGAA groups, respectively). Quality traits (ultimate pH, colour) and technological properties (i.e., drip and cooking losses, marinade uptake, shear force, and oxidation levels of the lipid and the protein fractions) of breast meat were assessed in both treatments on samples not showing any macroscopic sign of BMMs (n = 20 breast fillets per group). Data of myopathy risk ratio were analysed as the risk for each group to develop WS, WB, and SM myopathies. Our results show that while sGAA and control groups did not differ significantly in growth performance, a remarkably beneficial effect of GAA was observed on the incidence of BMMs with significantly reduced risk of sGAA group to develop SM myopathy. The risk of sGAA group to develop SM was 30% lower compared to CON (P = 0.028). Finally, a significantly lower drip loss was observed in sGAA in comparison with CON (1.78 vs 2.48%, P = 0.020). Together, our results show that the inclusion of 0.06% GAA in feed can improve the water-holding capacity of meat and reduce the risk to develop SM myopathy without compromising the performance of broilers.

Proteomic analyses on chicken breast meat with white striping myopathy.

White striping (WS) is an emerging myopathy that results in significant economic losses as high as $1 billion (combined with losses derived from other breast myopathies including woody breast and spaghetti meat) to the global poultry industry. White striping is detected as the occurrence of white lines on raw poultry meat. The exact etiologies for WS are still unclear. Proteomic analyses of co-expressed WS and woody breast phenotypes previously demonstrated dysfunctions in carbohydrate metabolism, protein synthesis, and calcium buffering capabilities in muscle cells. In this study, we conducted shotgun proteomics on chicken breast fillets exhibiting only WS that were collected at approximately 6 h postmortem. After determining WS severity, protein extractions were conducted from severe WS meat with no woody breast (WB) condition (n = 5) and normal non-affected (no WS) control meat (n = 5). Shotgun proteomics was conducted by Orbitrap Lumos, tandem mass tag (TMT) analysis. As results, 148 differentially abundant proteins (|fold change|>1.4; p-value < 0.05) were identified in the WS meats compared with controls. The significant canonical pathways included BAG2 signaling pathway, glycogen degradation II, isoleucine degradation I, aldosterone signaling in epithelial cells, and valine degradation I. The potential upstream regulators include LIPE, UCP1, ATP5IF1, and DMD. The results of this study provide additional insights into the cellular mechanisms on the WS myopathy and meat quality.

Research Note: Prospects for early detection of breast muscle myopathies by automated image analysis.

White Striping (WS), Wooden Breast (WB), and Spaghetti Meat (SM) are documented breast muscle myopathies (BMM) affecting broiler chickens' product quality, profitability and welfare. This study evaluated the efficacy of our newly developed deep learning-based automated image analysis tool for early detection of morphometric parameters related to BMM in broiler chickens. Male chicks were utilized, and muscle samples were collected on d 14 of rearing. Histological procedures, including microscopic scoring, blood vessel count, and collagen quantification, were conducted. A previous study demonstrated our automated image analysis as a reliable tool for evaluating myofiber size, conforming with manual histological measurements. A threshold for BMM detection was established by normalizing and consolidating myofiber diameter and area into a unified metric based on automated measurements, also termed as "relative myofiber size value." Results show that severe myopathy broilers consistently exhibited lower relative myofiber size values, effectively detecting myopathy severity. Our study, aimed as proof of concept, underscores the potential of our automated image analysis tool as an early detection method for BMM.

Gross and histopathological findings in hindlimb paralysis syndrome in wild Carnaby's black cockatoos (Zanda laitirostris).

The aim of this study was to describe the gross and histopathological features of a neurological syndrome in endangered Western Australian Carnaby's black cockatoos (Zanda laitirostris) that was first observed in 2012. The syndrome, named hindlimb paralysis syndrome in Carnaby's cockatoos (CHiPS), is characterized by annual outbreaks of hindlimb paralysis with occasional loss of deep pain and cloacal tone, typically occurring between January and March. Previous limited investigations suggested a possible toxic aetiology. Full gross necropsy and histopathology examinations were performed on 17 CHiPS cases and on 11 control birds for reference. Histopathological examination was carried out on all major organs including brain, spinal cord, brachial plexus, sciatic nerve and wing and hindlimb muscles. Gross and histopathological examinations did not elucidate a definitive cause of the clinical signs seen in CHiPS cases. There were no substantial gross or histopathological changes within the brain, spinal cord, sciatic nerve or brachial plexus that could explain the hindlimb paralysis. The most noteworthy changes were seen in the hindlimb and wing muscles, with a monophasic to polyphasic myopathy present in the hindlimb muscles of 15 of the 17 CHiPS cases and in the wing muscles in 11 of those cases. The cause and significance of the myopathy is unclear and requires further investigation. Based on the above findings, the most likely differential diagnoses include neurotoxicoses (eg, organophosphate, organochlorine and carbamate) and, less likely, myotoxicosis (eg, ionophore toxicosis), nutritional myopathy (eg, vitamin E/selenium deficiency) or botulism.

Allele frequency of muscular genetic disorders in bull-catching (vaquejada) quarter horses.

Quarter horses (QH), a prominent athletic breed in Brazil, are affected by muscular genetic disorders such as myosin-heavy chain myopathy (MYHM), polysaccharide storage myopathy (PSSM1), hyperkalemic periodic paralysis (HyPP), and malignant hyperthermia (MH). Bull-catching (vaquejada), primarily involving QH, is a significant equestrian sport in Brazil. Since the allele frequencies (AF) of MYHM, PSSM1, HyPP, and MH in vaquejada QH remain unknown, this study evaluated the AF in 129 QH vaquejada athletes, specifically from the Brazilian Northeast. These variants were exclusively observed in heterozygosity. The MYHM exhibited the highest AF (0.04 ±0.01), followed by PSSM1 (0.01 ±0.01) and the HyPP variant (0.004 ±0.01), while the MH variant was not identified in this study. This study represents the first identification of these variants in vaquejada QH, emphasizing the need to implement measures to prevent the transmission of pathogenic alleles and reduce the occurrence of clinical cases of these genetic diseases.

Spatial transcriptomics reveals alterations in perivascular macrophage lipid metabolism in the onset of Wooden Breast myopathy in broiler chickens.

This study aims to use spatial transcriptomics to characterize the cell-type-specific expression profile associated with the microscopic features observed in Wooden Breast myopathy. 1 cm3 muscle sample was dissected from the cranial part of the right pectoralis major muscle from three randomly sampled broiler chickens at 23 days post-hatch and processed with Visium Spatial Gene Expression kits (10X Genomics), followed by high-resolution imaging and sequencing on the Illumina Nextseq 2000 system. WB classification was based on histopathologic features identified. Sequence reads were aligned to the chicken reference genome (Galgal6) and mapped to histological images. Unsupervised K-means clustering and Seurat integrative analysis differentiated histologic features and their specific gene expression pattern, including lipid laden macrophages (LLM), unaffected myofibers, myositis and vasculature. In particular, LLM exhibited reprogramming of lipid metabolism with up-regulated lipid transporters and genes in peroxisome proliferator-activated receptors pathway, possibly through P. Moreover, overexpression of fatty acid binding protein 5 could enhance fatty acid uptake in adjacent veins. In myositis regions, increased expression of cathepsins may play a role in muscle homeostasis and repair by mediating lysosomal activity and apoptosis. A better knowledge of different cell-type interactions at early stages of WB is essential in developing a comprehensive understanding.

Changes in gene expression in the intestinal mucus of broilers with woody breast myopathy.

Previous work has shown that dietary treatments affect woody breast (WB) incidence differently, which indicates that gut conditions such as gut barrier function, inflammation, and oxidative stress are likely related to WB. In this study, dietary supplementation with antibiotics (bacitracin) or probiotics (Bacillus subtilis) was investigated for their effects on the expression of transcripts related to gut barrier function, inflammation, and oxidative stress in the mucus lining of the jejunum from broilers with or without WB. A split-plot experimental design was used in this study. The dietary treatments served as the main plot factor and the breast muscle condition was the subplot factor. On d 41, jejunum mucus was collected from 1 bird from each of 3 replicate pens in each 3 dietary treatment groups that exhibited WB and an additional bird that contained a normal breast (3 biological replicates/treatment/phenotype; 3 × 3 × 2, total N = 18). Total RNA was extracted using a commercial RNA extraction kit. The expression levels of CLDN1, MUC6, TLR2A, TLR2B, TLR4, IFN-γ, IL-1ß, IL-8L1, IL-10, NOS2, and SOD were determined using 2-step RT-qPCR analysis. The gene expression difference in ΔCt values was determined after normalizing with the chicken 18S rRNA gene. When the significant differences occurred between treatments, the relative fold change was calculated using the ΔΔCt method and the significance level was calculated. The PROC GLM procedure of SAS 9.4 was used, and the level of significance was set at P ≤ 0.05. There were no significant interactive effects between diet and the breast muscle condition on the expression of any of the genes tested. However, birds with WB exhibited higher MUC6 (P < 0.0001) gene expression levels than birds with normal breast muscles. In addition, the expression of SOD decreased in birds that were fed the antibiotic diet when compared to birds that were fed the probiotic diet (P = 0.014). In conclusion, WB identified in broilers tested in the current study is attributed to increased expression of mucin, indicating a correlation between WB incidence and gel-forming mucin secretion and pathogen signaling.

Large-scale genomic and transcriptomic analyses elucidate the genetic basis of high meat yield in chickens.

INTRODUCTION: Investigating the genetic markers and genomic signatures related to chicken meat production by combing multi-omics methods could provide new insights into modern chicken breeding technology systems. OBJECT: Chicken is one of the most efficient and environmentally friendly livestock, especially the fast-growing white-feathered chicken (broiler), which is well known for high meat yield, but the underlying genetic basis is poorly understood. METHOD: We generated whole-genome resequencing of three purebred broilers (n = 748) and six local breeds/lines (n = 114), and sequencing data of twelve chicken breeds (n = 199) were obtained from the NCBI database. Additionally, transcriptome sequencing of six tissues from two chicken breeds (n = 129) at two developmental stages was performed. A genome-wide association study combined with cis-eQTL mapping and the Mendelian randomization was applied. RESULT: We identified > 17 million high-quality SNPs, of which 21.74% were newly identified, based on 21 chicken breeds/lines. A total of 163 protein-coding genes underwent positive selection in purebred broilers, and 83 genes were differentially expressed between purebred broilers and local chickens. Notably, muscle development was proven to be the major difference between purebred broilers and local chickens, or ancestors, based on genomic and transcriptomic evidence from multiple tissues and stages. The MYH1 gene family showed the top selection signatures and muscle-specific expression in purebred broilers. Furthermore, we found that the causal gene SOX6 influenced breast muscle yield and also related to myopathy occurrences. A refined haplotype was provided, which had a significant effect on SOX6 expression and phenotypic changes. CONCLUSION: Our study provides a comprehensive atlas comprising the typical genomic variants and transcriptional characteristics for muscle development and suggests a new regulatory target (SOX6-MYH1s axis) for breast muscle yield and myopathy, which could aid in the development of genome-scale selective breeding aimed at high meat yield in broiler chickens.

Concentration of lipids, cholesterol, and fatty acid profile in chicken breast meat affected by wooden breast myopathy frozen for up to 12 mo.

The aim of this study was to examine the effects of frozen storage for 12 mo on the concentrations of lipids and cholesterol and fatty acid profile of wooden chicken breast meat. A total of 120 samples of chicken breasts were selected, according to the degree of "wooden breast" myopathy ["severe," "moderate," and "normal" (absence of myopathy)], from male chickens slaughtered at 42 d of age, from Cobb 500 strain. Part of the samples (n = 20/grade of severity) were evaluated on the day of collection and the remainder were packaged, frozen and stored at -18°C for up to 12 mo. At the beginning (collection day) and at the end of the proposed freezing period (12 mo), analyses of lipid, cholesterol, and fatty acid profile were carried out. Percentage of saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids were evaluated. Meats affected by wooden breast myopathy had lower levels of PUFA that exert beneficial effects on health, such as DHA, EPA and ARA, and this profile is impaired by prolonged storage (12 mo), which results in important nutritional losses for the consumer.

Time course evaluation of collagen type IV in Pectoralis major muscles of broiler chickens selected for different growth-rates.

Collagen type IV (COL4) is one of the major components of animals' and humans' basement membranes of several tissues, such as skeletal muscles and vascular endothelia. Alterations in COL4 assembly and secretion are associated to muscular disorders in humans and animals among which growth-related abnormalities such as white striping and wooden breast affecting Pectoralis major muscles (PMs) in modern fast-growing (FG) chickens. Considering the high prevalence of these myopathies in FG broilers and that a worsening is observed as the bird slaughter age is increased, the present study was intended to evaluate the distribution and the expression level of COL4 protein and its coding genes in PMs of FG broilers at different stages of muscle development (i.e., 7, 14, 21, 28, 35, and 42 d of age). Medium-growing (MG) chickens have been considered as the control group in consideration of the lower selection pressure on breast muscle growth rate and hypertrophy. Briefly, 5 PM/sampling time/genotype were selected for western blot, immunohistochemistry (IHC), and gene expression analyses. The normalized expression levels of COL4 coding genes showed an overexpression of COL4A2 in FG than MG at d 28, as well as a significant decrease in its expression over their rearing period. Overall, results obtained through the gene expression analysis suggested that selection for the hypertrophic growth of FG broilers may have led to an altered regulation of fibroblast proliferation and COL4 synthesis. Moreover, western blot and IHC analyses suggested an altered secretion and/or degradation of COL4 protein in FG broilers, as evidenced by the fluctuating trend of 2 bands observed in FG over time. In view of the above, the present research supports the evidence about a potential aberrant synthesis and/or degradation of COL4 and corroborates the hypothesis regarding a likely involvement of COL4 in the series of events underlying the growth-related abnormalities in modern FG broilers.

Monensin poisoning outbreak in free-ranging and captive birds.

Monensin poisoning is uncommon and has been rarely reported in birds. This work aimed to described clinical-pathological aspects of an outbreak of monensin poisoning in captive and free-ranging birds. Thirty-seven of 600 captive birds fed a diet containing 893.19 mg/kg of monensin died within 10 days (mortality 6.17%). There was no ionophore antibiotics on the feed label supplied to captive birds, which established an error in feed production. Necropsies were performed on twelve animals: Muscovy duck (Cairina moschata) (2/12), greater rhea (Rhea americana) (2/12), black-necked swan (Cygnus melancoryphus) (2/12), garganey (Anas querquedula) (1/12), ostrich (Struthio camelus) (1/12), and common pigeon (Columbus livia) (4/12). These four common pigeons were free-ranging birds and died after eating the same contaminated feed. Birds were mainly found dead, however in animals which clinical signs were observed (Columba livia, Rhea americana, Cairina moschata, Anas querquedula, and Struthio camelus), they included incoordination, inability to stand, and intense prostration, that ranged from 24 to 72 h until death. Grossly, five birds had focally extensive pale firm areas in the myocardium and two had in the skeletal muscles, one being concomitant lesions. Histologically, muscle necrosis and degeneration were observed in striated musculature (skeletal and/or heart) in all birds analyzed. Monensin poisoning outbreaks can affect free-ranging birds that are fed on external feeders, as well as captive birds, due to an error in the feed formulation.

Impact of Wooden Breast myopathy on in vitro protein digestibility, metabolomic profile, and cell cytotoxicity of cooked chicken breast meat.

This study investigated the impacts of Wooden Breast (WB) abnormality on in vitro protein digestibility and cytotoxicity of cooked chicken breast meat. Chicken breasts without (non-WB, n = 6) or with severe WB condition (WB, n = 6) were cooked and subjected to static in vitro protein digestion. The results showed no significant differences in free-NH2, degree of hydrolysis and distribution of peptide molecular weight between non-WB and WB samples at late intestinal digestion (P5), suggesting no adverse effects of WB on protein digestibility. Based on peptidomic analysis, P5 fraction of WB showed greater content of peptides with oxidative modification than that of non-WB. Untargeted metabolomics did not find any metabolites with potential toxicity either in non-WB and WB. Hydrolyzed non-WB and WB (1.56-100 µg/mL) did not affect viability of Caco-2 and Vero cells but addition of WB samples reduced Caco-2 cell viability compared with non-WB.

Common and atypical presentations of Anaplasma phagocytophilum infection in equids with emphasis on neurologic and muscle disease.

BACKGROUND: Comprehensive descriptions of equids with granulocytic anaplasmosis (EGA) with neurologic or muscle disease and other atypical presentations are scarce in the literature. OBJECTIVE: Describe the clinical signs, laboratory findings, treatment, and outcome of equids with EGA with emphasis on neurologic and muscle disease. ANIMALS: Thirty-eight horses, 1 donkey. METHODS: Retrospective study. Equids with EGA were included. The electronic data base was searched from January 2000 to December 2022 using the words anaplasmosis, ehrlichiosis, granulocytic, and rickettsia. Signalment and clinical data were reviewed. Data were evaluated for normality using Shapiro-Wilk test. Parametric and nonparametric statistics were used for normally and non-normally distributed data. RESULTS: Common (41%) and other (59%) presentations were seen in horses ≥ 4 years of age (median, 14 years) with an overrepresentation of males (77%). Neurologic disease was common (41%), mainly presenting as diffuse symmetrical proprioceptive ataxia. Brain disease was less common manifesting as obtundation and cranial nerve deficits. Muscle disease was less common, with QH breeds with the variant causing myosin heavy chain myopathy (MYHM) having severe disease. Cavitary effusion, cardiomyopathy and disseminated intravascular coagulation (DIC) were uncommon. Clinical laboratory results varied depending on disease stage. Muscle enzyme activities were significantly higher in horses with muscle disease. Outcome was favorable with prompt tetracycline treatment. Death and long-term sequelae were not reported. CONCLUSIONS AND CLINICAL IMPORTANCE: Common and atypical presentations of EGA have a favorable outcome with prompt tetracycline treatment. Quarter horse breeds with muscle disease should be genotyped for MYHM.

Hypoxia promotes proliferation and inhibits myogenesis in broiler satellite cells.

Breast muscle myopathies in broilers compromise meat quality and continue to plague the poultry industry. Broiler breast muscle myopathies are characterized by impaired satellite cell (SC)-mediated repair, and localized tissue hypoxia and dysregulation of oxygen homeostasis have been implicated as contributing factors. The present study was designed to test the hypothesis that hypoxia disrupts the ability of SC to differentiate and form myotubes, both of which are key components of myofiber repair, and to determine the extent to which effects are reversed by restoration of oxygen tension. Primary SC were isolated from pectoralis major of young (5 d) Cobb 700 chicks and maintained in growth conditions or induced to differentiate under normoxic (20% O2) or hypoxic (1% O2) conditions for up to 48 h. Hypoxia enhanced SC proliferation while inhibiting myogenic potential, with decreased fusion index and suppressed myotube formation. Reoxygenation after hypoxia partially reversed effects on both proliferation and myogenesis. Western blotting showed that hypoxia diminished myogenin expression, activated AMPK, upregulated proliferation markers, and increased molecular signaling of cellular stress. Hypoxia also promoted accumulation of lipid droplets in myotubes. Targeted RNAseq identified numerous differentially expressed genes across differentiation under hypoxia, including several genes that have been associated with myopathies in vivo. Altogether, these data demonstrate localized hypoxia may influence SC behavior in ways that disrupt muscle repair and promote the formation of myopathies in broilers.

Plants Causing Toxic Myopathies.

Boxelder and sycamore maple contain hypoglycin A (HGA), the toxic metabolite of which, MCPA-CoA, inhibits fatty acid ß-oxidation, causing seasonal pasture myopathy (SPM) or atypical myopathy (AM), respectively. White snakeroot and rayless goldenrod contain multiple benzofuran ketones (BFKs). The identity/toxicity of BFKs appear variable, possibly involving interactions between toxins/toxic metabolites, but ultimately inhibit cellular energy metabolism. Unthrifty horses grazing sparse pastures during the fall appear predisposed to these plant-associated, frequently fatal, toxic myopathies. Toxidromes are characterized by varying degrees of rhabdomyolysis and cardiac myonecrosis, with plant toxins remaining toxic in hay and being excreted in milk.

Effect of light restriction on productive results and behavior of broiler chickens.

The study aimed to evaluate the effect of light restriction (18L:6D vs. 14L:10D), genotype (A vs. B), and sex on performance, behavior, and meat quality, and the occurrence of wooden breast (WB) and white striping (WS) in broiler chickens. To this purpose 704 one-day-old chickens of 2 genotypes, half males and half females, were reared from hatching until slaughtering at 45 d of age in 32 collective pens (22 chickens per pen). Light restriction reduced growth rate and final live weight (LW), but improved feed conversion ratio (FCR) (P < 0.01) and reduced inactive behaviors of chickens (P < 0.001). Light restriction also reduced WS occurrence in breasts (89.5 to 64.6%; P < 0.001) and reduced meat shear force (2.64 to 2.20 kg/g; P < 0.05) and ether extract content (2.29 to 1.87%; P < 0.05). Regarding genotype, compared to genotype B, chickens of genotype A were heavier (3,242 g vs. 3,124 g; P < 0.01) with higher cold carcass weight and Pectoralis major muscle yield (12.9 vs. 12.0%; P < 0.001) and a higher FCR (1.63 vs. 1.61; P < 0.01). Finally, females had lower final LW (2,852 g vs. 3,513 g) and higher FCR (1.64 vs. 1.59) than males (P < 0.001), but a higher proportion of breast and P. major (P < 0.001), lower cooking losses (P < 0.001) and shear force (P < 0.01), and higher protein content (21.6 vs. 20.7%; P < 0.001). In conclusion, light restriction depressed growth, but was effective in decreasing WS occurrence and improved feed conversion. The decrease in inactive behaviors (sitting/laying) of light-restricted chickens can be positively considered in view of animal welfare.

Effects of genetic selection for fast growth on the development of wooden breast myopathy in broilers.

1. This study investigated the physiological and molecular mechanisms leading to wooden breast (WB) by comparing growth parameters, oxygen consumption rate, thyroid hormone and gene expression patterns in fast- versus slow-growing broiler lines (Cobb500 and L1986, respectively).2. WB was observed in Cobb500 broilers only and was first diagnosed on d 21 post-hatch. Compared to the slow-growing L1986, Cobb500 showed a significantly higher growth rate, relative breast weight, breast thickness, meat pH and water-retention capacity (drip loss). Correspondingly, there was significantly lower relative heart weight, relative right ventricular weight, triiodothyronine and thyroxine concentrations and oxygen consumption rate.3. Compared to No-WB Cobb500, the WB-affected samples exhibited higher relative breast weight, breast thickness and drip loss and lower plasma total thyroxine (T4) concentrations.4. Selection for fast growth was associated with differential expression of genes involved in hypoxia (PLOD2), energy metabolism (FABP3, FABP4, CD36, and LPL), endoplasmic reticulum stress, muscle regeneration (CSRP3) and fibre-type switching (ANKRD1). WB-affected samples exhibited an upregulation of CSRP3, PLOD2 and ANKRD1, while CD36 was downregulated. Taken together, selection for fast growth and muscle gain is not matched by adequate cardiac and metabolic support systems.

The incidence and associated risk factors affecting myopathies in broiler chickens in Lithuania.

The objectives of this research were to highlight the main factors, which have relevant significance for etiology of myopathies and to assess the incidence of myopathies in a representative population of broilers raised in Lithuania. Eighteen flocks were evaluated to assess the incidence of musculus pectoralis major myopathies (PMM) (total 54,000 broilers) and dorsal cranial myopathy (DCM) (total 124,200 broilers). Thirteen flocks (total 19,500 broilers) were evaluated to find out deep pectoral myopathy (DPM) occurrence in Lithuania. Investigated parameters of each flock were: average broiler live body weight (BW) at slaughter, average slaughter age, treatment and seasons. A correlation analysis was used to measure the strength of the linear relationship between the investigated traits and incidence of these myopathies. Overall, the incidence of PMM in Lithuania was 18.19%. DCM and DPM were 5.16% and 0.27%, respectively. The percentage of PMM in flocks was strongly associated with average broiler live BW at slaughter (r=0.898, p<0.001) and age at slaughter (r=0.693, p<0.001). The percentage of PMM in flocks was negatively related with treatment of broilers (rs=-0.535, p<0.05). The percentage of DCM was positively associated with average broiler live BW at slaughter (r=0.537, p<0.05) and with seasons (rs=0.658, p<0.01). However, our study results revealed, that the analyzed parameters are not so important in DPM etiology. Furthermore, predisposing factors of PMM, DCM and DPM are different. These findings suggest that not only broiler's heavy weight and age at slaughter could have influence for etiology of myopathies.

Physical, chemical, and microbiological evaluation of sausages produced with chicken meat affected by deep pectoral myopathy.

The purpose of the present study was to characterize the chemical composition, lipid oxidation, and physical characteristics of fresh sausages produced with meat from the pectoralis major muscle affected by deep pectoral myopathy. For the characterization of myopathy, samples were collected from broiler chickens slaughtered between 42- and 46-days old in a slaughterhouse in the state of São Paulo. The experiment consisted of samples from pectoralis major muscle of birds affected or not by DPM (normal-absence of myopathy and DPM category 3-progressive degeneration of the pectoralis minor with a greenish appearance). After classification of the samples, a part of raw products with the pectoralis minor removed, was submitted to microbiological and physical analyses for the characterization of DPM. Afterward, only the pectoralis major muscle was used to manufacture fresh sausages and 2 groups were established. The evaluated parameters were: color, pH, water-holding capacity (WHC), cooking loss (CL), shear force (SF), water activity (Aw), and chemical composition. Meat pH was higher (P < 0.05) in meats with DPM, however, WHC values were lower (71.92%), which made CL value increase (25.31%). In addition, the coloring increased and the technological characteristics of raw breasts were less favorable with the presence of DPM. All fresh sausages' color (except a* higher control group), pH, and Aw values were higher in DPM group. No effect on SF values was observed between fresh sausages. In chemical composition, only protein content increased in fresh sausages with DPM. Microbiological analyses did not indicate bacterial contamination of raw samples and fresh sausages. Data obtained in the present study suggest fresh sausages produced with breasts affected by DPM are a viable alternative and may confer more favorable qualitative characteristics to sausages than the raw marketed meat.