Temporal myosin heavy chain isoform expression transitions faster in broiler chickens compared with Single Comb White Leghorns

Physico-chemical properties of natural actomyosin from breast and thigh meat of fast- and slow-growing chicken: a comparative study

Physico-chemical behaviors of natural actomyosin (NAM) from slow-growing Korat chicken (KC) breast and thigh at low (0.2 M) and high (0.6 M) NaCl concentrations were evaluated and compared to those from their corresponding muscles in fast-growing broiler chicken (BC). NAM from KC breast and thigh meat showed higher solubility than their corresponding in BC (p < 0.05). Breast NAM from both chickens showed the highest solubility at 0.4 M NaCl, while thigh NAMs showed the highest solubility at 0.8 M (p < 0.05). SDS-PAGE revealed higher protein extractability for breast NAMs at low ionic strength, regardless of breed and structural protein, particularly troponin, appeared to vary within muscle and breed. NAM from KC showed higher Ca2+-ATPase activity, surface hydrophobicity, but lower total sulfhydryl groups content (p < 0.05). Particle size of NAM solutions varied with ionic strength, in which KC-NAM showed larger size than at lower ionic strength, while BC-NAM appeared to be greater at higher ionic strength. NAM from KC breast showed higher thermal stability as higher initial (T0) and maximum (Tmax) denaturation temperatures of 48.4 and 54.8°C, respectively, recorded by microdifferential scanning calorimetry. The KC-NAM, particularly from breast, exhibited lower turbidity within 40-50°C, while turbidity increased in BC samples at low ionic strength when heated at 60°C. Dynamic rheology revealed different storage modulus (G') depending on breed, muscle type and ionic strength. Breast BC-NAM formed more elastic gel with higher end point G' at 80°C (Ge'; p < 0.05). Ionic strength showed reverse effects on different breeds as a stronger Ge' value achieved in KC- NAM at low ionic strength, while high ionic strength induced stronger gel in BC samples. Aggregation of NAMs began at lower temperatures at higher ionic strength and actin dissociation probably occurred in breast NAM from KC as observed by a drop of G' at around 70°C. The results of this study revealed differences between NAM of the two breeds, by which higher gel elasticity are expected in KC at lower ionic strength.

Label-free liquid chromatography-mass spectrometry comparison of the breast muscle proteome profiles in two fast-growing broilers

Poultry meat-production is increasing worldwide; leading to the selection of chickens for meat-production that show a fast growth. A label-free quantitative proteomic-approach and Western-blot were applied to investigate the dynamics of muscle protein under rapid growth conditions in two common fast-growing broiler genetic-lines (Ross 508 and AZ Extra Heavy Red-chicken). Muscle exudate from chicken Pectoralis major was used as substrate to unveil the proteome of these genetic-lines. Six-hundred forty-five proteins were identified in total from all samples, and after statistical-analysis 172 proteins were found to be differentially-expressed, clearly distinguishing the two chicken genetic-lines. Several of these differentially-expressed proteins were involved with the proteasome and glycolysis/gluconeogenesis-pathways. Changes in meat-quality traits were also observed, which were reflected in the proteomic-profile. Proteins involved in the ubiquitin-proteasome system were associated with the bigger muscle mass of Ross 508, while phosphoglucomutase 1 was associated with a possible higher capability of AZ Extra Heavy Red-chickens to cope with stressors. This pilot proteomic-approach applied on muscle exudate samples provided key evidence about the pathways and processes underlying these two chicken genetic-lines and their meat-quality parameters. We also identified potential biomarkers that could determine the peculiar production potentials (e.g. breast-growth) of these broilers-lines, which arise from differences in their genetic-backgrounds.

Temporal embryonic transcription of chicken fast skeletal myosin heavy chain isoforms in the single comb white leghorn

There are numerous factors that can significantly influence embryonic development in poultry and thus make simple days of incubation (chronological age) a less than perfect metric for studying embryonic physiology. The developmental fast skeletal muscle myosin (MyHC), the predominant protein in the Pectoralis major (PM), is temporally expressed as a cadre of highly specific developmental isoforms. In the study described herein, a novel molecular technology (NanoString) was used to characterize the myosin isoform transcriptional patterns in the PM of Single Comb White Leghorn (SCWL) embryos. NanoString technology is based on quantitative analysis of the transcriptome through digital detection and quantification of target mRNA transcripts. Total RNA was isolated and gene transcription quantified using NanoString in embryonic muscle samples collected daily from 6 through 19 days of incubation. Data were analyzed using the LOESS smoothing function at a 95% confidence level. The temporal transcription of MyHC isoforms obtained in this study was consistent with the literature at higher specificity and resolution, thus validating NanoString for use in gene transcription analyses. The results support a hypothesis that the transcription patterns of the embryonic MyHC isoforms may be used as molecular clocks to further investigate the developmental relationships underlying embryonic fast skeletal muscle growth and development.

Skeletal muscle characterization of Japanese quail line selectively bred for lower body weight as an avian model of delayed muscle growth with hypoplasia

This study was designed to extensively characterize the skeletal muscle development in the low weight (LW) quail selected from random bred control (RBC) Japanese quail in order to provide a new avian model of impaired and delayed growth in physically normal animals. The LW line had smaller embryo and body weights than the RBC line in all age groups (P<0.05). During 3 to 42 d post-hatch, the LW line exhibited approximately 60% smaller weight of pectoralis major muscle (PM), mainly resulting from lower fiber numbers compared to the RBC line (P<0.05). During early post-hatch period when myotubes are still actively forming, the LW line showed impaired PM growth with prolonged expression of Pax7 and lower expression levels of MyoD, Myf-5, and myogenin (P<0.05), likely leading to impairment of myogenic differentiation and consequently, reduced muscle fiber formation. Additionally, the LW line had delayed transition of neonatal to adult myosin heavy chain isoform, suggesting delayed muscle maturation. This is further supported by the finding that the LW line continued to grow unlike the RBC line; difference in the percentages of PMW to body weights between both quail lines diminished with increasing age from 42 to 75 d post-hatch. This delayed muscle growth in the LW line is accompanied by higher levels of myogenin expression at 42 d (P<0.05), higher percentage of centered nuclei at 42 d (P<0.01), and greater rate of increase in fiber size between 42 and 75 d post-hatch (P<0.001) compared to the RBC line. Analysis of physiological, morphological, and developmental parameters during muscle development of the LW quail line provided a well-characterized avian model for future identification of the responsible genes and for studying mechanisms of hypoplasia and delayed muscle growth.