Variations in chicken breast meat quality: implications of struggle and muscle glycogen content at death

Residual feed intake breeding value associated with growth, carcass traits, meat quality, bone properties and humoral immunity in Japanese quail

Improved feed efficiency (FE) is one of the most important achievements in animal breeding programs. The present investigation aimed to determine the phenotypic correlations of residual feed intake (RFI) breeding value with some traits in growing Japanese quail. A total of 48 birds (24 males and 24 females) were selected from 220 quail chicks divided into three classes based on breeding values (BV) for RFI including low (LBV; n = 16), medium (MBV; n = 16), and high-BV (HBV; n = 16) were used to test FE. The effects of three groups of BV on the studied traits including carcass traits, meat quality, humoral immunity, and bone properties were evaluated. The BV for RFI was positively correlated with feed conversion ratio (FCR) and feed intake (FI) but not with metabolic BW (MBW^0.75). Live body weight, carcass, breast, and thigh weight in the LBV-RFI group were significantly greater than those in the HBV-RFI group. The BV for RFI had a negative correlation with live body weight and thigh weight. Our findings suggested that the selection of LBV-RFI quails may be useful to increase live body weight without any adverse impact on meat quality and bone properties, and live body weight can be implemented in breeding programs as an indirect selection indicator for improvement of FE in quails.

Carcass, visceral organ, and meat quality properties of two broiler hybrids differing in growth rates

This study aimed to determine the carcass, visceral organ, and meat properties according to the sex in slow growing broilers (SGB) and fast growing broilers (FGB). Six broilers from each genotype and sex group were slaughtered every week. It was determined that the difference between SGB and FGB in terms of carcass yield occurred at the highest level at 5 weeks and this difference continued until the age of 10 weeks. The weight percentages of all visceral organs examined in FGB were lower than in SGB. Higher values of pH, lightness, and cooking loss ​​were determined in breast and thigh meat of FGB compared with SGB (P < 0.05). The effects of genotype on protein levels of breast and leg meats were found to be insignificant. The fat level in breast meat was insignificant between genotypes after the fifth week of fattening period. There was no difference between the sexes regarding meat quality in both genotypes. When FGB and SGB were reared under the intensive conditions for 10 weeks, it was observed that visceral organs developed in harmony with body weight, especially in SGB during the 10 weeks of fattening period and SGB maintained their superiority in terms of meat quality.

Effects of Feeding Housefly (Musca domestica) Larvae on the Butchery Skills and Meat Sensory Characteristics of Local Chickens in Niger

The purpose of this work was to study the effects of substitution of fishmeal by housefly larvae at different rates and different physical states in the diet of local chickens. Five diets consisted of LFD, 25DL, 50DL, 25FL and 50FL, respectively, larval-free, 25%-dried-larvae, 50%-dried-larvae, 25%-fresh-larvae and 50%-fresh-larvae diet, in which 0, 25 and 50% of fishmeal was replaced by dried and fresh larvae, was formulated. A total of 165 local chickens of three weeks old, divided into 15 boxes in batches of 11 animals were raised. The experiment consists of three replications of five treatments. At 14 weeks of age, sixty chickens were slaughtered. Butchery skills and sensory characteristics were evaluated. Thus, a small variation of the ultimate pH from 5.63 to 5.55 between the different types of meat, and a carcass yield around 66%, was recorded. Any effects of substitution rate and physical state of housefly larvae on growth performance was not observed. Feet and proventriculus percentages increased in chickens fed 25% substitution. Liver and spleen percentage, and redder breast meat, increased in chicken fed dried larvae. Yellowness of the breast, thigh-and-drumstick meat and juiciness increased with 50% substitution. There is need of an investigation for liver and spleen enlargement and housefly larvae containing pigments. Thus, housefly larvae up to 50% substitution can be a suitable alternative to fishmeal in local chicken diets.

A comparative study of meat quality and vibrational spectroscopic properties of different chicken breeds

Chicken breed is one of the key factors that influence meat quality. The quality attributes of breast meat from commercial broiler (CB), Thai native chicken (NC, Leung Hang Khao), and the crossbred Korat chicken (KC) were investigated via synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy, Fourier transform Raman (FT-Raman) spectroscopy, and physicochemical analysis. The protein and carbonyl contents of KC and NC meats were higher than that of CB meat, but the lipid content was lower (P < 0.05). CB meat was characterized by high moisture, lightness (L*), and presence of taste-active nucleotides, namely, inosine 5′-monophosphate (IMP) and guanosine 5′-monophosphate (GMP). Moreover, NC meat had the highest insoluble collagen and inosine contents (P < 0.05). The predominant protein secondary structures of KC and NC meats were β-turns and random coils, whereas α-helices were mainly found in CB meat. Based on principal component analysis, the meat quality and spectra were clearly separated by breeds. The high moisture and lipid content of meat corresponded to O–H stretching (3,203 cm⁻¹) and C–H stretching (2,854 cm⁻¹) in the FT-Raman spectra, whereas PO₂⁻ stretching (1,240 cm⁻¹), measured via SR-FTIR, was well correlated with the IMP content. In addition, the FT-Raman wavenumber of 934 cm⁻¹, indicating C–C stretching, was correlated with high water-holding capacity (WHC) in KC meat. The quality of meat from slow- and fast-growing chickens significantly varies. Vibrational spectroscopy is a powerful technique that provides insightful molecular information correlated with various meat attributes.

Untargeted Metabolomics Reveals the Effect of Selective Breeding on the Quality of Chicken Meat

The selection for improved body weight is an effective approach in animal breeding. Guangxi Partridge chickens have differentiated into two lines under selective breeding, which include line S and line D that have shown statistically significant differences in body weight. However, the meat quality analysis in our study indicated that the quality of breast and thigh muscles in line S chickens changed, which included increased values of L*, b*, and drip loss and decreased a* value, pH, and shear force in skeletal muscles. To illuminate the effect of selection on skeletal muscles, LC-MS/MS metabolomics was performed to explore differentiated metabolites in divergent tissues from the two chicken lines. The results of principal component analysis and orthogonal projection to latent structures discriminant analysis suggested that metabolites of different groups were separated, which suggested that selective breeding certainly affected metabolism of skeletal muscles. KEGG analysis identified that valine, leucine, and isoleucine biosynthesis, glycerophospholipid metabolism, and glutathione metabolism noteworthily changed in breast muscle. Amino sugars and nucleotide sugar metabolism, ascorbate and aldarate metabolism, the pentose phosphate pathway, pentose and glucuronate interconversions, fructose and mannose metabolism, and glycerophospholipid metabolism were remarkedly identified in thigh muscle. These screened pathways suggested oxidative stress in breast and thigh muscles, which corresponded with our previous results. Therefore, this study determined that glycerophospholipid metabolism conservatively functioned in muscle flavor and development but exhibited different anti-oxidative patterns in different skeletal muscles. Overall, the present study identified several differentiated metabolites and pathways for exploring differences in meat quality between different broiler populations.

Differences in carcass composition and meat quality of conventional and slow-growing broiler chickens raised at 2 stocking densities

The fast growth rate of broiler chickens is a welfare concern that has increased consumer interest in chicken from slower growing (SG) broilers. Replacing conventional (CONV) broilers with SG broilers will reduce chicken supply and SG broilers require different management practices than CONV. This study evaluated the effects of 2 stocking densities on the carcass composition and meat quality of CONV broilers that reach market weight at 42 d and SG broilers that reach market weight at 63 d. Male broilers from each strain were exclusively stocked into 16 pens at a density of either 29 kg/m² or 37 kg/m². Live body, carcass without giblets (WOG), and part weights were recorded and used to calculate yield. Initial and 24-hour pH, color (L*, a*, and b*), cooking loss, and Warner Bratzler shear force of the breast and thigh muscles were measured. Birds from both strains reached similar live body and carcass WOG weights. CONV had 3.4%, 13.0%, and 2.8% greater (P ≤ 0.002), carcass WOG, breast, and tenderloin yields, while SG had 2.7%, 5.0%, 7.5%, and 1.2% greater (P < 0.0001) wings, leg quarters, frame, and skin yields, respectively. CONV breast 24-h pH and cooking loss were greater (P ≤ 0.04) than SG. While SG thigh shear force was greater than CONV (P = 0.008), breast shear force was the lowest for CONV stocked at 29 kg/m² and the greatest for SG stocked at 37 kg/m² (P = 0.04). SG had a paler breast than CONV, while CONV had a yellower breast than SG (P < 0.0001). While SG had a redder thigh than CONV (P = 0.002), SG stocked at 29 kg/m² had a redder breast than SG stocked at 37 kg/m², with both CONV groups intermediate (P = 0.04). These results indicate that differences in male broiler meat quality were affected more by strain than by stocking density. Compared with CONV, SG broiler meat quality was more affected by stocking density in this study.

Properties of broiler breast meat with pale color and a new approach for evaluating meat freshness in poultry processing plants

The current trend in monitoring meat quality is to move the quality measurements from the laboratory to the processing line. To provide better meat quality control in the commercial poultry processing plants, we evaluated the quality of broiler breast meat samples, observing different colors, and assessed their freshness using a Torrymeter. Different colors were classified based on the mean ± standard deviation of lightness (L*) values in 1,499 broiler breast fillets: Dark (L* < 56), normal (56 ≤ L* ≤ 62), and pale (L* > 62). To characterize the differences between the pale and normal color groups, we evaluated additional fillets for meat quality traits. Changes in meat quality during storage were also evaluated. The L* and Torrymeter values (freshness values) allowed us to distinguish between the pale and normal meat samples. Normal and pale fillets showed a significant difference in pH, Torrymeter values, and water-holding capacity (P < 0.001). The L* values were significantly correlated with cook and drip loss (P < 0.01) and were higher (paler, +1.2 L* unit) at 72-h postmortem than at 4-h postmortem. Torrymeter values were correlated with cook loss (P < 0.05) and pH (P < 0.001), and significantly decreased with the increase in storage period (P < 0.001). These results suggest the applicability of the Torrymeter, a fast and non-destructive device, in distinguishing stale and fresh breast fillets. With its portability and simplicity, the Torrymeter is expected to be a valuable tool to estimate meat freshness. Especially, the use of Torrymeter for evaluating pale breast fillets may allow easy identification and separation of fillets according to their pale, soft, and exudative properties in commercial poultry processing lines.

Influence of Post Mortem Muscle Activity on Turkey Meat Quality

Wing flapping and body movement can occur during the slaughter of poultry. Wing movement and flapping are driven primarily by the breast muscles (Pectoralis major and minor), and this muscle activity may have implications for meat quality. The objective of this study was to evaluate turkey post mortem activity during slaughter at a commercial poultry processing plant. Post mortem activity (during bleeding) was scored on 5,441 male turkeys, from six different genetic lines, using a 1–4 scale from none to severe wing flapping. Meat quality was measured on these birds in terms of pH (initial, ultimate, delta or change), color (L^*, a^*, b^*), and physiochemical traits (drip loss, cooking loss, shear force). Linear mixed models were used to analyze the effect of activity (score 1–4), genetic line (A–F), and season (summer vs. autumn) on the nine meat quality traits. Post mortem activity influenced a^*, drip loss, and shear force although the magnitude of the effects was small. There was an effect (P < 0.05) of genetic line on all the meat quality traits except for L^*, cooking loss, and shear force. In general, larger, faster-growing lines had higher pH, but the relationship between the lines for the other traits is not as clear. Season affected all the meat quality traits, except for pH_delta, with meat having a higher pH, L^*, b^*, drip loss, cooking loss, and shear force in the summer. This study provides an exploratory assessment of post mortem activity in turkeys and identifies meat quality traits which are most affected while also accounting for the effects of genetic line and season. Although identified effect sizes are small, the cumulative effect on turkey meat quality may be more substantial.

UHPLC-QTOF/MS-based comparative metabolomics in pectoralis major of fast- and slow-growing chickens at market ages

The molecular regulatory mechanism underlying meat quality between different chicken genotypes remains elusive. This study aimed to identify the differences in metabolites and pathways in pectoralis major (breast muscle) between a commercial fast-growing chicken genotype (Cobb500) and a slow-growing Chinese native chicken genotype (Beijing-You chickens, BYC) at market ages respectively based on ultra-high-performance liquid chromatography-quadrupole/time of flight mass spectrometry (UHPLC-QTOF/MS). Eighteen metabolites were identified as potential biomarkers between BYC and Cobb500 at market ages. Among them, L-cysteine exhibited a higher relative intensity in BYC compared with Cobb500 and was enriched into 10 potential flavor-associated KEGG pathways. In addition, the glycerophospholipid metabolism pathway was found to be associated with chicken meat flavor and the accumulation of sn-glycerol 3-phosphate and acetylcholine was more predominant in BYC than that in Cobb500, which were catalyzed by glycerophosphocholine phosphodiesterase (GPCPD1, EC:3.1.4.2), choline O-acetyltransferase (CHAT, EC:2.3.1.6), and acetylcholinesterase (ACHE, EC:3.1.1.7). Overall, the present study provided some metabolites and pathways for further investigating the roles of the differences in meat flavor quality in breast muscle between Cobb500 and BYC at market ages.

Comparison of the Automatic and Manual Broiler Pre-Slaughter Chain Based on Trailer Microclimate during Transportation and Its Effect on m. pectoralis major

Simple Summary

Improper pre-slaughter catching, loading/unloading, handling, and transport may cause negative effects on the welfare and meat quality of poultry. During the catch process, noisy, rough, or aggressive techniques can cause birds to panic, which can lead to injuries and lower meat quality. Fractures, joint dislocations, and bruises can be common and cause bird suffering, mortality, carcass degradation, and economic loss. Proper pre-slaughter processes can ensure the safety of poultry and workers. One way to prevent these problems is to use automatic catching machines (harvesters/chicken cat), handling machines (shuttles), and air-conditioned trucks (trailers) to collect and handle poultry. Microclimate in trailers is another important factor influencing welfare. Internal overheating may cause high mortality of the animals during transport and reduced meat quality. The use of modern air-conditioned trailers results in improved welfare conditions, reduced mortality and the incidence of injuries and fractures, and increased meat quality.

Abstract

This study aims to compare two broiler pre-slaughter chain methods: (i) the automatic pre-slaughter chain (APC) and (ii) manual pre-slaughter chain (MPC). The comparison is based on the evaluation of the trailer microclimate, number of injuries, and breast muscle (m. pectoralis major) quality. Transportation lasts 3.5 h, unloading 1 h. The selection of two hundred 39-day-old broilers (Ross 308 and Cobb 500 breeds) is random for each type of method. After slaughter, the pH value, electrical conductivity (EC), and color (lightness) of breast muscle tissues are determined at different post-mortem intervals. The MPC negatively affects the microclimate (p < 0.001), meat qualitative characteristics (p < 0.001), and places a greater strain on the body of chickens compared with APC. The average pH_15min value of MPC broiler breast muscle tissue, generally used as the main meat quality parameter, is 5.97 ± 0.12, in contrast to 6.36 ± 0.16 for APC. Higher pH_15min value of APC indicates better welfare and pre-slaughter handling. Values of EC and L* of breast tissues also confirms a difference between the methods of broiler handling (p < 0.001). No difference is found between the breed lines (p > 0.05).

Meta-analysis to predict the effects of temperature stress on meat quality of poultry

Temperature stress (TS) is a significant issue in poultry production, which has implications for animal health and welfare, productivity, and industry profitability. Temperature stress, including both hot (heat stress) and cold conditions (cold stress), is associated with increased incidence of meat quality defects such as pale, soft, and exudative (PSE) and dark, firm, and dry (DFD) meat costing poultry industries millions of dollars annually. A meta-analysis was conducted to determine the effect of ambient TS on meat quality parameters of poultry. Forty-eight publications which met specific criteria for inclusion were identified through a systematic literature review. Temperature stress was defined by extracting 2 descriptors for each treatment mean from the chosen studies: (1) temperature imposed for the experimental treatments (°C) and duration of temperature exposure. Treatment duration was categorized for analysis into acute (≤24 h) or chronic (>24 h) treatments. Meat quality parameters considered were color (L*-a*-b* scheme), pH (initial and ultimate), drip loss, cooking loss, and shear force. Linear mixed model analysis, including study as a random effect, was used to determine the effect of treatment temperature and duration on meat quality. Model evaluation was conducted by performing a k-fold cross-validation to estimate test error, and via assessment of the root mean square prediction error (RMSPE), and concordance correlation coefficient (CCC). Across both acute and chronic durations, treatment temperature was found to have a significant effect on all studied meat quality parameters. As treatment temperature increased, meat demonstrated characteristics of PSE meat and, as temperature decreased, meat demonstrated characteristics of DFD meat. The interaction between treatment temperature and duration was significant for most traits, however, the relative impact of treatment duration on the studied traits was inconsistent. Acute TS had a larger effect than chronic TS on ultimate pH, and chronic stress had a more considerable impact on color traits (L* and a*). This meta-analysis quantifies the effect of ambient TS on poultry meat quality. However, quantitative effects were generally small, and therefore may or may not be of practical significance from a processing perspective.

Review: Production factors affecting poultry carcass and meat quality attributes

Poultry meat mainly comes from standard production system using high growth rate strains reared under indoor intensive conditions. However, it is possible to find also different alternative systems using outdoor extensive rearing conditions and slow-growing lines. These different production systems can affect carcass and meat quality. In this review, quality has been broken down into six properties: commercial, organoleptic, nutritional, technological, sanitary and image, the latter covering the ethical, cultural and environmental dimensions associated with the way the meat is produced, as well as its origin and being particularly valued in many quality labels. The quality of meat is built and can deteriorate along the continuum from the conception of the animal to the fork. Our review details the different factors implicated in the determinism of poultry meat properties and pinpoints critical periods, such as the preslaughter and slaughter periods, and key factors, such as the feeding regimen, via its direct effect on the fatty acid profile, the antioxidant and volatile compound contents, and indirect effects mediated via the growth rate of the bird. Our review also highlights potential antagonisms between different dimensions of quality. The genetic selection for breast meat yield, for example, has been effective in producing carcasses with higher meat yield, but resulting since a decade in the increased occurrence of quality defects and myopathies (white striping, wooden breast, spaghetti meat and deep pectoral disease). Outdoor access has positive effects on the image and nutritional properties (through its effect on the fatty acid profile of meat lipids), but it increases the exposition risk to environmental contaminants and pathologies (parasites, virus, bacteria); it also increases the variability in meat quality linked to the variability of animal performance and slaughter age. The orientation towards more agro-ecological low-input farming systems may present benefits for the image and nutritional properties, but also risks for the commercial (low carcass weight and low breast yield, irregularity in supply), organoleptic (stronger flavour, less tender and darker colour of the meat) and in terms of variability of the different properties that constitute quality. Efforts should be made in the future to better take into account the various dimensions of quality, in consumer information, payment to farmers and genetic selection.

Gastrocnemius Muscle Structural and Functional Changes Associated with Domestication in the Turkey

Selection for increased muscle mass in domestic turkeys has resulted in muscles twice the size of those found in wild turkeys. This study characterizes muscle structural changes as well as functional differences in muscle performance associated with selection for increased muscle mass. We compared peak isometric force production, whole muscle and individual fiber cross-sectional area (CSA), connective tissue collagen concentration and structure of the lateral gastrocnemius (LG) muscle in wild and adult domestic turkeys. We also explored changes with age between juvenile and adult domestic turkeys. We found that the domestic turkey's LG muscle can produce the same force per cross-sectional area as a wild turkey; however, due to scaling, domestic adults produce less force per unit body mass. Domestic turkey muscle fibers were slightly smaller in CSA (3802 ± 2223 μm2) than those of the wild turkey (4014 ± 1831 μm2, p = 0.013), indicating that the absolutely larger domestic turkey muscles are a result of an increased number of smaller fibers. Collagen concentration in domestic turkey muscle (4.19 ± 1.58 μg hydroxyproline/mg muscle) was significantly lower than in the wild turkeys (6.23 ± 0.63 μg/mg, p = 0.0275), with visible differences in endomysium texture, observed via scanning electron microscopy. Selection for increased muscle mass has altered the structure of the LG muscle; however, scaling likely contributes more to hind limb functional differences observed in the domestic turkey.

Broiler genetics influences proteome profiles of normal and woody breast muscle

Wooden or woody breast (WB) is a myopathy of the pectoralis major in fast-growing broilers that influences the quality of breast meat and causes an economic loss in the poultry industry. The objective of this study was to evaluate growth and proteome differences between 5 genetic strains of broilers that yield WB and normal breast (NB) meat. Eight-week-old broilers were evaluated for the WB myopathy and divided into NB and WB groups. Differential expression of proteins was analyzed using 2-dimensional gel electrophoresis and LC-MS/MS to elucidate the mechanism behind the breast myopathy because of the genetic backgrounds of the birds. The percentages of birds with WB were 61.3, 68.8, 46.9, 45.2, and 87.5% for strains 1-5, respectively, indicating variability in WB myopathy among broiler strains. Birds from strains 1, 3, and 5 in the WB group were heavier than those in the NB group (P < 0.05). Woody breast meat from all strains were heavier than NB meat (P < 0.05). Within WB, strain 5 had a greater breast yield than strains 1, 3, and 4 (P < 0.0001). Woody breast from strains 2, 3, 4, and 5 had a greater breast yield than NB (P < 0.05). Six proteins were more abundant in NB of strain 5 than those of strains 2, 3, and 4, and these proteins were related to muscle growth, regeneration, contraction, apoptosis, and oxidative stress. Within WB, 14 proteins were differentially expressed between strain 5 and other strains, suggesting high protein synthesis, weak structural integrity, intense contraction, and oxidative stress in strain 5 birds. The differences between WB from strain 3 and strains 1, 2, and 4 were mainly glycolytic. In conclusion, protein profiles of broiler breast differed because of both broiler genetics and the presence of WB myopathy.

Physicochemical Changes of Deep-Fat-Fried Chicken Drumsticks Treated with Quercetin-in-Edible Coating during Storage Time

In this study, 10% of chicken protein isolate (CPI) and quercetin (1 mg/mL) were used to develop an edible coating to improve the oxidative stability of deep-fat-fried chicken drumsticks during refrigerated storage (4 °C) for 10 days. Chicken samples with edible coating formulated with only 10% CPI served as the control. Although the thiobarbituric acid reactive substances (TBARS) values of the treated samples were lower than the control samples, no significant differences were observed. Quercetin-treated samples were generally harder than control samples. The pH was reduced by quercetin incorporation (p < 0.05). L* and b* values increased, while there was no significant variation in a* values during storage (p > 0.05).

Understanding the Determination of Meat Quality Using Biochemical Characteristics of the Muscle: Stress at Slaughter and Other Missing Keys

Despite increasingly detailed knowledge of the biochemical processes involved in the determination of meat quality traits, robust models, using biochemical characteristics of the muscle to predict future meat quality, lack. The neglecting of various aspects of the model paradigm may explain this. First, preslaughter stress has a major impact on meat quality and varies according to slaughter context and individuals. Yet, it is rarely taken into account in meat quality models. Second, phenotypic similarity does not imply similarity in the underlying biological causes, and several models may be needed to explain a given phenotype. Finally, the implications of the complexity of biological systems are discussed: a homeostatic equilibrium can be reached in countless ways, involving thousands of interacting processes and molecules at different levels of the organism, changing over time and differing between animals. Consequently, even a robust model may explain a significant part, but not all of the variability between individuals.

Supplementing flaxseed oil for long periods improved carcass quality and breast fatty acid profile in Japanese quail

The efficient time for supplementing flaxseed oil to meat-type quail to produce n-3 fatty acid fortified meat has not been determined. This study was conducted to find out the effects of different periods of flaxseed oil supplementation in the Japanese quail diet on the subsequent growth performance, carcass characteristics, fatty acids profile of breast, and functional properties of the Japanese quail meat. Totally, 720 one-day-old Japanese quail were studied in a 35-day experiment using a completely randomized design. Substituting sunflower oil with flaxseed oil had no significant effect on weight gain and feed intake in Japanese quails. Supplementing flaxseed oil for the whole 35-day growth period significantly reduced abdominal fat proportion. Flaxseed oil addition to the quail diet just a week before slaughter resulted in a 4.97-fold increase in the n-3 fatty acid content of the breast muscle. Feeding flaxseed oil decreased the activity of delta-9-desaturase in quail's breast compared to sunflower oil. The greatest thrombogenic index observed in the breast meat from control while consumption of flaxseed oil significantly decreased the thrombogenic index. Supplementing flaxseed oil to quail's diet for 21 and 35 days before slaughter significantly increased breast malondialdehyde content. Feeding flaxseed oil for long periods had no significant impact on the breast meat pH while water holding capacity was decreased. The breast lightness was increased when the flaxseed oil was fed for longer periods. Generally, feeding flaxseed oil in the last week of the growth period improved the feed conversion ratio and the fatty acid profile of quail breast meat with the minimum deterioration effects on meat quality characteristics.

Comparison of performance and carcass composition of a novel slow-growing crossbred broiler with fast-growing broiler for chicken meat in Australia

Slow-growing broilers offer differentiation in the chicken meat market for consumers who have distinct preferences based on perceived higher welfare indices and willingness to pay a higher price for the product. Although breeding for slow-growing broilers is relatively advanced in Europe and the United States, it is limited in Australia. Crossbreeding is one of the approaches taken to developing slow-growing broiler strains. Thus, the aim of this study was to compare performance, immune response, leg health, carcass characteristics, and meat quality of a novel crossbred slow-growing broiler breed (SGB) with the conventional, fast-growing Cobb 500 broiler (CB) to assess their suitability as an alternative for chicken meat production in Australia. A total of 236 one-day-old broiler chicks (116 SGB and 120 fast-growing CB) were reared on standard commercial diet in an intensive production system. Birds and feed were weighed on a weekly basis and feed intake and feed conversion ratio calculated. At 21 d of age, a 2% suspension of sheep red blood cells was injected subcutaneously into 8 broilers of each breed to compare their antibody response. Birds from both breeds were grown to a final live weight of 2.0–2.2 kg, before a latency-to-lie (LTL) test, carcass analysis and apparent metabolizable energy (AME) assay were performed. The SGB reached the target weight at 55 d of age compared with 32 d in CB. However, SGB stood for longer during LTL, had higher thigh, drumstick, and wing yields (as a percentage of carcass weight) as well as darker and redder meat in comparison with the CB. The CB had better feed conversion efficiency, higher antibody (IgM) production, higher AME, heavier breast yield, and lower meat drip loss than the SGB. Although fast-growing CB outperformed the SGB for traditional performance parameters, the crossbred in this study was comparable with other slow-growing broiler breeds and strains across different countries and is thus a suitable candidate for a slow-growing alternative in Australia.

Nutritional Properties and Oxidative Indices of Broiler Breast Meat Affected by Wooden Breast Abnormality

Wooden breast (WB) abnormality adversely impacts the quality of chicken meat and has been linked with oxidative stress. In this study, breast samples were taken from carcasses of 7-week-old Ross 308 broilers 20-min and 24-h postmortem. Five WB and seven non-WB control samples were assigned based on palpatory hardness (non-WB = no unusual characteristics and WB = focal or diffused hardness). WB exhibited lower contents of protein and the amino acids, i.e., isoleucine, leucine and valine, lighter surface color, lower shear force, greater drip loss and altered mineral profiles (p ≤ 0.05). Despite no difference in lipid oxidation, a greater degree of protein oxidation was found in the WB meat (p ≤ 0.05). Absolute transcript abundances of superoxide dismutase, hypoxia inducible factor 1 alpha and pyruvate dehydrogenase kinase 1 were greater in WB (p ≤ 0.05), whereas lactate dehydrogenase A expression was lower in WB (p ≤ 0.05). The findings support an association between oxidative stress and the altered nutritional and technological properties of chicken meat in WB.

The role of histidine dipeptides on postmortem acidification of broiler muscles with different energy metabolism

It is generally held that the content of several free amino acids and dipeptides is closely related to the energy-supplying metabolism of skeletal muscles. Metabolic characteristics of muscles are involved in the variability of meat quality due to their ability to influence the patterns of energy metabolism not only in living animal but also during postmortem time. Within this context, this study aimed at establishing whether the concentration of histidine dipeptides can affect muscle postmortem metabolism, examining the glycolytic pathway of 3 chicken muscles (pectoralis major, extensor iliotibialis lateralis, and gastrocnemius internus as glycolytic, intermediate, and oxidative-type, respectively) selected based on their histidine dipeptides content and ultimate pH. Thus, a total of 8 carcasses were obtained from the same flock of broiler chickens (Ross 308 strain, females, 49 d of age, 2.8 kg body weight at slaughter) and selected immediately after evisceration from the line of a commercial processing plant. Meat samples of about 1 cm³ were excised from bone-in muscles at 15, 60, 120, and 1,440 min postmortem, instantly frozen in liquid nitrogen and used for the determination of pH, glycolytic metabolites, buffering capacity as well as histidine dipeptides content through ¹H-NMR. Overall results suggest that glycolysis in leg muscles ceased already after 2 h postmortem, whereas in breast muscle continued until 24 h, when it exhibited significantly lower pH values (P < 0.05). However, considering its remarkable glycolytic potential, pectoralis major muscle should have exhibited a greater and faster acidification, suggesting that its higher (P < 0.05) histidine dipeptides' content might have prevented a potentially stronger acidification process. Accordingly, breast muscle also showed greater (P < 0.05) buffering ability in the pH range 6.0–7.0. Therefore, anserine and carnosine, being highly positively correlated with muscle's buffering capacity (P < 0.001), might play a role in regulating postmortem pH decline, thus exerting an effect on muscle metabolism during prerigor phase and the quality of the forthcoming meat. Overall results also suggest that total histidine dipeptides content along with muscular ultimate pH represent good indicators for the energy-supplying metabolism of chicken muscles.

Association of residual feed intake with growth performance, carcass traits, meat quality, and blood variables in native chickens

Improving feed efficiency is a primary goal in poultry breeding strategies. Residual feed intake (RFI) in chickens typically calculated during the growing period is a measure of feed efficiency that is independent of the level of production. The objective of this study was to evaluate phenotypic correlations of growth performance, carcass traits, meat quality, and blood variables with RFI in growing native chickens. A total of 1,008 chickens were selected for the experiment to derive RFI. After the RFI measurement period of 42 d, 25 chickens with low RFI values, 25 chickens with medium RFI values, and 25 chickens with high RFI values were selected. The RFI was significantly positively correlated with feed conversion ratio and average daily feed intake, while it was not significantly correlated with initial body weight (BW), final BW, average daily body weight gain, and metabolic BW0.75. The abdominal fat weight and yield of high RFI group were significantly greater than those of medium and low RFI groups, and the abdominal fat yield was significantly positively correlated with RFI. Moreover, the plasma insulin-like growth factor 1 (IGF-1) content of low RFI group was significantly greater than those of high and medium RFI groups. The plasma concentrations of adrenocorticotropic hormone, triiodothyronine (T3), and cortisol of high RFI birds were significantly greater than that of low RFI birds. RFI was significantly positively correlated with plasma concentrations of T3 and cortisol, while it was significantly negatively correlated with plasma concentration of IGF-1. In addition, the serum levels of glucose and triglyceride of high RFI birds were significantly lower than that of low RFI birds. The serum low-density lipoprotein cholesterol (LDL-C) content of high RFI group was significantly greater than that of medium and low RFI groups, and it was significantly positively correlated with RFI. Our data suggested that selection of chickens with low RFI values may be beneficial to reduce fat deposition in native chickens without affecting the meat quality. Circulating IGF-1, T3, cortisol, and LDL-C concentrations can be used as indirect selection indicators of feed efficiency in native chickens. The effect of IGF-1, T3, cortisol, and LDL-C on feed efficiency of native chickens should be carefully examined and validated in future breeding programs.

Effects of reducing dietary amino acid density and stocking density on growth performance, carcass characteristics, meat quality, and occurrence of white striping in broiler chickens

A 49-day trial was conducted to determine the impact of dietary amino acid (AA) density and stocking density (SD) on growth performance, carcass traits, meat quality, and white striping (WS) occurrence in broiler chickens. Two hundred eighty-eight Ross 308 male broilers consisting of 6 replicate cages with 8 broilers per replicate were used. Treatments were arranged in a 3 × 2 factorial and consisted of 3 AA densities (normal, 10, or 20% lower than normal) and 2 different SD (high 35 kg/m² or low 26 kg/m²). Breasts were classified as normal, moderate, and severe for WS. Data were analyzed as a completely randomized design using the GLM procedure. Decreasing AA density decreased overall growth performance, carcass, breast yields, and fillet dimensions linearly, while leg and rib cage yields increased linearly (P < 0.01). High SD decreased hot carcass, breast, wings, and rib cage weights in birds fed normal AA diets (P < 0.05). High SD increased the length of breast fillet (P < 0.05). Cooking loss, breast lightness (L∗), and redness (a∗) at 48 h postmortem increased linearly with decreasing AA density, while ultimate breast pH (pH_u) and nitrogen content decreased linearly (P < 0.05). The occurrence of normal, moderate, and severe WS fillets was 45.3, 49.1, and 5.6%, respectively. As the dietary AA density decreased, the occurrence of no WS breast fillets increased linearly, whereas the occurrence of moderate WS fillets and mean WS score decreased linearly (P < 0.05). SD did not affect the occurrence of WS. Severe WS fillets were heavier and had higher cranial thickness, pH_u, and fat content and lower yellowness (P < 0.05), but water-holding capacity, nitrogen content, L∗, and a∗ value did not differ among different WS scores. Taken together, WS occurrence and severity increased with higher growth rate. Growth depression created by lowering dietary AA density regardless of SD resulted in a decrease in mean WS score, but it also compromised the growth and meat quality.

Short cold exposures during incubation and postnatal cold temperature affect performance, breast meat quality, and welfare parameters in broiler chickens

Cold stimulations during egg incubation were reported to limit the occurrence of ascites in broilers subjected to cold temperature after 14 d of age. However, data are lacking on the impacts of such strategy in case of cold temperature conditions at start. This study aimed to evaluate the effects of incubation and posthatch cold challenge on performance, breast muscle integrity, and meat processing quality in broiler chickens. Ross 308 eggs were incubated under control temperature (I₀, 37.6°C) or subjected to 15°C during 30 min on day 18 and 19 of incubation (I₁). Chicks from each group were reared in floor pens either at standard rearing temperature (T₀), from 32°C at 0 d to 21°C at 21 d of age, or exposed to colder rearing temperature (T₁), from 29°C at 0 to 21°C at 21 d of age. All birds were then kept at 21°C until slaughter (day 40), when body weights (BW), feed conversion ratio (FCR), breast muscle yield, meat processing quality, and the occurrences of meat defects, hock burns, and pododermatitis were recorded. No significant impact of incubation conditions on hatchability was observed. At day 40, BW was more under T₁ than under T₀ conditions, with T₀ females (but not males) presenting more BW after I₁ than after I₀ conditions. In the whole period, T₁ chickens presented lower FCR than T₀ chickens and higher breast meat yields at day 40. The occurrence of white striping was more in I₁T₁ males than in all other groups, except for the I₀T₁ males. Hock burns were more frequent in I₁T₁ males than in all females and I₀T₀ males, whereas the occurrence of pododermatitis was lower in T₀ males than in other groups. Despite some positive effects of I₁ incubation on growth after starting under low ambient temperature, this study reveals the limits of such strategy concerning chicken health and welfare, demonstrating that early thermal environment is a major component of the quality and sustainability of chicken meat production.

Effect of galactooligosaccharides delivered in ovo on meat quality traits of broiler chickens exposed to heat stress

A study was carried out to evaluate meat quality traits in fast-growing chickens stimulated in ovo with trans-galactoolighosaccarides (GOS) and exposed to heat stress. On day 12 of egg incubation, 3,000 fertilized eggs (Ross 308) were divided into prebiotic group (GOS) injected with 3.5 mg GOS/egg, saline group (S) injected with physiological saline, and control group (C) uninjected. After hatching, 900 male chicks (300 chicks/treatment) were reared in floor pens in either thermoneutral (TN; 6 pens/group, 25 birds/pen) or heat stress conditions (HS, 30°C from 32 to 42 D; 6 pens/group, 25 birds/pen). At 42 D of age, 15 randomly chosen birds/treatment/temperature were slaughtered and the pectoral muscle (PM) was removed for analyses. Data were analyzed by GLM in a 3 × 2 factorial design. In ovo treatment had no effect on PM weight, pH, water-holding capacity, and shear force. GOS and S birds had lighter (L*, P < 0.01) PM than C group, whereas the latter showed a higher (P < 0.05) yellowness index (b*) compared to S group. Proximate composition, cholesterol, and intramuscular collagen properties were not affected by treatment. As for fatty acid composition, only total polyunsaturated fatty acids (PUFA) content and n-6 PUFA were slightly lower in GOS group compared to S. Heat stress had a detrimental effect on PM weight (P < 0.01) and increased meat pH (P < 0.01). PM from HS chickens was darker with a higher b* index (P < 0.05) and had a higher (P < 0.01) lipid content and a lower (P < 0.05) total collagen amount. Total saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and PUFA were similar among groups. Significant interactions between factors were found for fatty acid composition: GOS decreased (P < 0.01) SFA and increased (P < 0.05) MUFA contents in HS birds. In conclusion, in ovo injection of GOS could mitigate the detrimental effect of heat stress on some meat quality traits.

Genetical Genomics of Tonic Immobility in the Chicken

Identifying the molecular mechanisms of animal behaviour is an enduring goal for researchers. Gaining insight into these mechanisms enables us to gain a greater understanding of behaviour and their genetic control. In this paper, we perform Quantitative Trait Loci (QTL) mapping of tonic immobility behaviour in an advanced intercross line between wild and domestic chickens. Genes located within the QTL interval were further investigated using global expression QTL (eQTL) mapping from hypothalamus tissue, as well as causality analysis. This identified five candidate genes, with the genes PRDX4 and ACOT9 emerging as the best supported candidates. In addition, we also investigated the connection between tonic immobility, meat pH and struggling behaviour, as the two candidate genes PRDX4 and ACOT9 have previously been implicated in controlling muscle pH at slaughter. We did not find any phenotypic correlations between tonic immobility, struggling behaviour and muscle pH in a smaller additional cohort, despite these behaviours being repeatable within-test.

Mapping of QTL for chicken body weight, carcass composition, and meat quality traits in a slow-growing line

Slow-growing chicken lines are valuable genetic resources for the development of well-perceived alternative free-range production. While there is no constraint on increasing growth rate, breeding programs have to evolve in order to include new traits improving the positioning of such lines in the growing market for parts and processed products. In this study, we used dense genotyping to fine map QTL for chicken growth, body composition, and meat quality traits in view of developing new tools for selection of a slow-growing line. The dataset included a total of 836 birds (10 sires, 87 dams, 739 descendants) and 40,203 SNP. QTL for the 15 traits analyzed were detected by 3 different methods, i.e., linkage and linkage disequilibrium haplotype-based analysis (LDLA), family-based single marker association (FASTA), and Bayesian multi-marker regression (Bayes Cπ). After filtering for QTL redundancy, we found 16, 16, and 9 QTL when using the FASTA, LDLA, and Bayes Cπ methods, respectively, with a threshold of 2.49 × 10-5 for FASTA and LDLA, and a Bayes factor of 150 for the Bayes Cπ analysis. They comprised 17 QTL for body weight, 9 QTL for body composition, and 15 QTL for breast meat quality or behavior at slaughter. The 3 methods agreed in the detection of highly significant QTL such as that detected on GGA24 for body weight at 3, 6, and 9 wk, and the 2 QTL detected on GGA17 and GGA18 for breast meat yield. Several significant QTL were also detected for the different components of breast meat quality. This study provided new locations for investigation in order to improve our understanding of the genetic architecture of growth, carcass composition, and meat quality in the chicken and to develop molecular tools for the selection of these traits in a slow-growing line.

Mobile Poultry Processing Unit as a Resource for Small Poultry Farms: Planning and Economic Efficiency, Animal Welfare, Meat Quality and Sanitary Implications

Simple Summary

Poultry meat production is now based on fast-growing strains, with consequences for animal health and welfare. There is also an increasing demand for products from extensive rearing systems; there are, however, several criticisms including the difficulty of slaughtering chickens from a logistic, legislative and economic point of view. A possible solution could be represented by the use a Mobile Poultry Processing Unit (MPPU), which directly reaches the poultry farms. The aim of this review is to analyse the requisites and economic efficiency of a MPPU prototype in Italy; further, the related animal welfare aspects and the qualitative and sanitary implications are discussed.

Abstract

Nowadays there is an increasing demand for poultry products from alternative rearing systems. These systems, commonly named pastured poultry production (PPP), are more expensive than intensive rearing system but sustain biodiversity, local economies and farm multi-functionality besides providing meat to which consumers attribute high ethical value and quality. PPP generally uses large outdoor runs, small number of animals and requires chickens adapted to natural environment. One of the most relevant obstacles to further development of PPP systems is related to the slaughtering of animals economically and at the same time complying with the sanitary regulations to maintain food safety standards. A possible solution could be represented by a Mobile Poultry Processing Unit (MPPU), which directly reaches the poultry farms. MPPU can consider a good compromise for the niche production providing an opportunity to small farmers to exploit the full potential of their production system. The aim of this review is to analyse the essential requisites and MPPU economic viability in an Italian system. Qualitative, societal aspects are discussed together with bird welfare and hygiene implications. The case study indicates the viability of MPPUs but notes that up scaling to medium sized operations would not be permissible under current EU regulations.

Effects of method and duration of restraint on stress hormones and meat quality in broiler chickens with different body weights

Objective

The study was designed to investigate the effects of restraint method, restraint duration, and body weight on stress-linked hormones (corticosterone, adrenaline, and noradrenaline), blood biochemical (namely glucose and lactate), and the meat quality in broiler chickens.

Methods

A total of 120 male broiler chickens (Cobb 500) were assigned to a 2×3×2 factorial arrangement in a completely randomized design using two restraint methods (shackle and cone), three durations of restraint (10, 30, and 60 s), and two categories of live body weight (1.8±0.1 kg as lightweight and 2.8±0.1 kg as heavyweight).

Results

Irrespective of the duration of restraint and body weight, the coned chickens were found to have lower plasma corticosterone (p<0.01), lactate (p<0.001), lower meat drip loss (p<0.01), cooking loss (p<0.05), and higher blood loss (p<0.05) compared with their shackled counterparts. The duration of restraint had significant effects on the meat initial pH (p<0.05), ultimate pH (p<0.05), and yellowness (p<0.01). The lightweight broilers exhibited higher (p< 0.001) blood loss and lower (p<0.05) cooking loss compared to the heavyweight broilers, regardless of the restraint method used and the duration of restraint. However, the interaction between the restraint method, duration of restraint, and body weight contributed to differences in pre-slaughter stress and meat quality. Therefore, the interaction between the restraint method and the duration of restraint affected the meat shear force, lightness (L*) and redness (a*).

Conclusion

The duration of restraint and body weight undoubtedly affect stress responses and meat quality of broiler chickens. Regardless of the duration of restraint and body weight, the cone restraint resulted in notably lower stress, lower meat water loss, and higher blood loss compared to shackling. Overall, the findings of this study showed that restraint method, duration of restraint, and body weight may affect the stress response and meat quality parameters in broilers and should be considered independently or interactively in future studies.

The Incidence of Muscle Abnormalities in Broiler Breast Meat - A Review

The dramatic improvements in the growth rate and breast muscle size and yield in broilers through the intensive genetic selection, and the improvement in nutrition and management over the past 50 years have introduced serious abnormalities that influenced the quality of breast meat. The abnormalities include pale-soft-exudative (PSE) conditions, deep pectoral muscle (DPM) myopathy, spaghetti meat (SM), white striping (WS), and woody breast (WB) that have serious negative implications to the broiler meat industry. The incidences of PSE and DPM have been known for several decades, and their prevalence, etiology and economic impact have been well discussed. However, other abnormalities such as SM, WS and WB conditions have been reported just for few years although these conditions have been known for some time. The newly emerging quality issues in broilers are mainly associated with the Pectoralis major muscles, and the incidences have been increased dramatically in some regions of the world in recent years. As high as 90% of the broilers are affected by the abnormalities, which are expected to cause from $200 million to $1 billion economic losses to the U.S. poultry industry per year. So, this review mainly discusses the histopathological characteristics and biochemical changes in the breast muscles with the emphasis on the newly emerging abnormalities (SM, WS, and WB) although other abnormalities are also discussed. The impacts of the anomalies on the nutritional, functional, mechanical and sensory quality of the meat and their implications to the poultry industry are discussed.

Carcass and meat quality characterization of indigenous and improved variety of chicken genotypes

A study was conducted to examine four genotypes of chicken for their carcass and meat quality characteristics. From each genotype, 20 birds were slaughtered at their respective age of maturity. Breast and thigh muscles were evaluated for meat quality characteristics. Transport loss and carcass weight were highest in the white commercial broiler (WBR) and lowest in Aseel (ASL) and Indbro Aseel (ASR). Dressing percentage ranged between 66.41 and 72.56 and was not significantly different among genotypes. The yield of various cut-up parts for different genotypic birds was significantly different (P < 0.05). Highest percent yield for breast (29.15), thigh (15.57), drumstick (13.82) and wings (18.44) were observed in WBR, rainbow rooster (RR), ASR and rainbow rooster Plus (RRP), respectively. Giblet % was highest in RR and meat:bone ratio of thigh portion was highest in WBR. Higher ultimate pH was recorded for RR, RRP, and WBR, and higher water-holding capacity was detected in ASL and ASR. Further, bound water was higher in RR, RRP, and WBR, and free water was maximum in ASL and ASR. A significant (P < 0.05) higher shear force was observed in ASL and higher muscle fiber diameter in WBR. Cooking yield did not differ significantly among genotypes. The breast meat from ASL showed significantly (P < 0.05) higher redness value and WBR showed the lower redness. Further, ASL and ASR meats were darker and red in color than broiler meat. Meat from two indigenous birds (ASL and ASR) had significantly (P < 0.05) lower fat content compared to broilers and other crosses. ASL gave a slightly firmer meat as liked by consumers. The sensory evaluation showed breast meat from RR birds and ASL birds had better flavor scores than other birds. These results indicated that meat of indigenous chickens (ASL and ASR) has some unique features over commercial fast-growing birds that would increase their demand by consumers who prefer chewy, low-fat chicken meat.

Changes in body composition and meat quality in response to dietary amino acid provision in finishing broilers

In order to control and optimize chicken quality products, it is necessary to improve the description of the responses to dietary amino acid (AA) concentration in terms of carcass composition and meat quality, especially during the finishing period. The aim of this study was to investigate the effects of Lysine (Lys, i.e. a limiting AA used as reference in AA nutrition) and AA other than Lys (AA effect). In total, 12 experimental diets were formulated with four levels of digestible Lys content (7, 8.5, 10 and 11.5 g/kg) combined with either a low (AA-), adequate control (AAc) and high (AA+) amount of other essential AA (EAA) expressed as a proportion of Lys. They were distributed to male Ross PM3 from 3 to 5 weeks of age. No significant AA×Lys interaction was found for growth performance or carcass composition. Body weight and feed conversion ratio were significantly improved by addition of Lys but were impaired in broilers receiving the AA- diets, whereas breast meat yield and abdominal fat were only affected by Lys. No additional benefit was found when the relative amount of other EAA was increased. There was a significant AA×Lys interaction on most of the meat quality traits, including ultimate pH, color and drip loss, with a significant effect of both AA and Lys. For example, AA- combined with reduced Lys level favored the production of meat with high ultimate pH (&gt;6.0), dark color and low drip loss whereas more acid, light and exudative meat (&lt;5.85) was produced with AA+ combined with a low Lys level. In conclusion, growth performance, carcass composition and meat quality are affected by the levels of dietary Lys and AA in finishing broilers. In addition, interactive responses to Lys and AA are found on meat quality traits, leading to great variations in breast pHu, color and drip loss according AA balance or imbalance.

Carcass Quality, Meat Quality and Sensory Properties of the Dual-Purpose Chicken Lohmann Dual

Over 40 million day-old layer line cockerels are culled in Germany each year, due to economic reasons, leading to a recently instigated research focus on the potential of dual-purpose breeds as an alternative to conventional poultry husbandry, especially the practice of culling. This paper aims to explore and assess the dual-purpose chicken breed “Lohmann Dual” (LD) performance (n = 30) and sensory characteristics (n = 48). Carcass and meat quality traits are evaluated, and descriptive sensory analysis of breast muscles is conducted. To define the scope of characteristics, a market sample of “Ross” Line (n = 35) is adducted. LD carcasses are characterized by higher leg than breast yield; carcass, breast and leg weights are higher in Ross. LD meat has a lower pH, differs in color, has higher drip and thawing losses, but lower cooking loss. LD breast muscles are firmer as indicated by shear force measurements, which is confirmed through the sensory analysis. Appearance, odor and flavor differ between the lines. Overall, distinguishable differences are found between both breeds. Further research should focus on the marketing aspect of the dual-purpose line, as some characteristics could draw consumers to this product. Animal welfare and ethical concerns should further be considered when considering dual-purpose breeds as a feasible alternative to culling.

Physicochemical determinants of pH in pectoralis major of three strains of laying hens housed in conventional and furnished cages

1. Post-mortem decline in muscle pH has traditionally been attributed to glycogenolysis-induced lactate accumulation. However, muscle pH ([H⁺]) is controlled by complex physicochemical relationships encapsulated in the Stewart model of acid-base chemistry and is determined by three system-independent variables - strong ion difference ([SID]), total concentration of weak acids ([A_tot]) and partial pressure of CO₂ (PCO₂). 2. This study investigated these system-independent variables in post-mortem pectoralis major muscles of Shaver White, Lohmann Lite and Lohmann Brown laying hens housed in conventional cages (CC) or furnished cages (FC) and evaluated the model by comparing calculated [H⁺] with previously measured [H⁺] values. 3. The model accounted for 99.7% of the variation in muscle [H⁺]. Differences in [SID] accounted for most or all of the variations in [H⁺] between strains. Greater PCO₂ in FC was counteracted by greater sequestration of strong base cations. The results demonstrate the accuracy and utility of the Stewart model for investigating determinants of meat [H⁺]. 4. The housing differences identified in this study suggested that hens housed in FC have improved muscle function and overall health due to the increased opportunity for movement. These findings support past studies showing improved animal welfare for hens housed in FC compared to CC. Therefore, the Stewart model has been identified as an accurate method to assess changes in the muscle at a cellular level that affect meat quality that also detect differences in the welfare status of the research subjects.

Poultry Meat Quality in Relation to Muscle Growth and Muscle Fiber Characteristics

Variations in the definition of poultry meat quality exist because the quality traits are not solely based on intrinsic and extrinsic factors but also consumers’ preference. Appearance quality traits (AQT), eating quality traits (EQT), and reliance quality traits (RQT) are the major factors focused by the consumer before buying good quality of poultry meat. AQT and EQT of poultry meat are controlled by physical and biochemical characteristics of muscle fibers which can be categorized into a total number of fibers (TNF), cross-sectional area of fibers (CSAF), and fiber type composition (FTC). In poultry meat, it has been shown that muscle fiber properties play a key role in meat quality because numerous studies have reported the relationships between quality traits and fiber characteristics. Despite intensive research has been carried out to manipulate the muscle fiber to improve poultry meat quality, demand in a rapid growth of poultry muscle has correlated to the deterioration in the meat quality. The present paper reviews the definition of poultry meat quality, meat quality traits, and variations of meat quality. Also, this review presents recent knowledge underlying the relationship between poultry meat quality traits and muscle fiber characteristics.

Breast meat quality of chickens with divergent growth rates and its relation to growth curve parameters

Abstract. The effects of the increase of body weight of contemporary broilers during growth on functional meat quality and color characteristics of the chicken breast muscle are controversially debated. Therefore, male chickens (n = 264) of a fast-growing commercial broiler (Ross 308) and two slow-growing experimental meat-type chicken lines were compared at equal age and at similar body weight in order to investigate the effect of growth rate on selected functional breast meat traits and meat color. Additionally, the breast meat characteristics of birds with different growth profiles were compared within lines. When the body weight of commercial broilers reached about 40 to 60 % of their growth potential, they exhibited particularly high ultimate pH values compared with slow-growing lines. The ability of the meat of fast-growing broilers to retain water during cooking was impaired (5 to 16 percentage points increased cooking loss compared to slow-growing lines), which, in contrast to pH, was only marginally affected by body weight and/or age at slaughter. No unfavorable correlations of breast meat quality traits with the growth profile, represented by growth curve parameters derived from the Gompertz–Laird equation, were detected within any of the investigated chicken lines. It is noteworthy that the associations of ultimate pH and cooking loss with maximum growth speed indicate a non-linear relationship. Thus, some of the functional characteristics of breast meat of the fast-growing broiler resembled the white-striping defect described for poultry meat, but the hypothesis that selection on increased growth rates is detrimental for meat quality per se could not be confirmed. In fact, an elevated growth potential in particular, i.e., body weight at maturity, could have some beneficial effects for the water-holding capacity of breast meat, regardless of the genotypic growth rate.

Integrated application of transcriptomics and metabolomics provides insights into glycogen content regulation in the Pacific oyster Crassostrea gigas

BACKGROUND

The Pacific oyster Crassostrea gigas is an important marine fishery resource, which contains high levels of glycogen that contributes to the flavor and the quality of the oyster. However, little is known about the molecular and chemical mechanisms underlying glycogen content differences in Pacific oysters. Using a homogeneous cultured Pacific oyster family, we explored these regulatory networks at the level of the metabolome and the transcriptome.

RESULTS

Oysters with the highest and lowest natural glycogen content were selected for differential transcriptome and metabolome analysis. We identified 1888 differentially-expressed genes, seventy-five differentially-abundant metabolites, which are part of twenty-seven signaling pathways that were enriched using an integrated analysis of the interaction between the differentially-expressed genes and the differentially-abundant metabolites. Based on these results, we found that a high expression of carnitine O-palmitoyltransferase 2 (CPT2), indicative of increased fatty acid degradation, is associated with a lower glycogen content. Together, a high level of expression of phosphoenolpyruvate carboxykinase (PEPCK), and high levels of glucogenic amino acids likely underlie the increased glycogen production in high-glycogen oysters. In addition, the higher levels of the glycolytic enzymes hexokinase (HK) and pyruvate kinase (PK), as well as of the TCA cycle enzymes malate dehydrogenase (MDH) and pyruvate carboxylase (PYC), imply that there is a concomitant up-regulation of energy metabolism in high-glycogen oysters. High-glycogen oysters also appeared to have an increased ability to cope with stress, since the levels of the antioxidant glutathione peroxidase enzyme 5 (GPX5) gene were also increased.

CONCLUSION

Our results suggest that amino acids and free fatty acids are closely related to glycogen content in oysters. In addition, oysters with a high glycogen content have a greater energy production capacity and a greater ability to cope with stress. These findings will not only provide insights into the molecular mechanisms underlying oyster quality, but also promote research into the molecular breeding of oysters.

The effects of electrical stunning voltage on meat quality, plasma parameters, and protein solubility of broiler breast meat

This study was designed to compare the effects of different stunning voltages of pulsed direct current on meat quality of broilers. For this purpose, plasma parameters, blood loss, carcass damage, and meat water holding capacity, color, shear force, pH, and protein solubility were analyzed. A total of 400 broilers were divided into 5 treatment groups and stunned with 5, 15, 25, 35, and 45 V at 750 Hz and 10 s, respectively. Blood samples were collected immediately after cutting the neck. Pectoralis major muscles were removed from the carcass after chilling and placed on ice. Breast muscle pH and meat color were determined at both 2 and 24 h postmortem. Dripping loss, cooking loss, pressing loss, and cooked breast meat shear values were determined after 24 h postmortem. The 5 V treatment significantly increased (P < 0.05) blood plasma corticosterone and lactate concentration compared with the other groups. The carcass damage of wings, Pectoralis major, and Pectoralis minor was significant in the 5, 35, and 45 V groups. The pH of 2 h postmortem in the 5 and 45 V groups was significantly lower (P < 0.05) than in the 15 and 25 V groups. In the 5 and 45 V groups, the protein solubility and shear force value were significantly lower (P < 0.05) and dripping loss was significantly higher (P < 0.05) than the other groups.

Effect of housing environment on laying hen meat quality: Assessing Pectoralis major pH, colour and tenderness in three strains of 80-81 week-old layers housed in conventional and furnished cages

1. Meat quality is affected by factors such as stress, genetic strain and activity and is determined in part by measures of pH, colour and tenderness. In conventional laying hen cages (CC), lack of physical space and inability to perform highly motivated behaviours leads to stress and inactivity. Furnished cages (FCs) permit expression of highly motivated behaviours, but typically house larger group sizes than CC, thereby contributing to social stress. The objective of this study was to evaluate the effects of CC and FC laying hen housing environments and strain differences on meat quality of 80-81-week-old birds. 2. Pectoralis major meat quality was assessed for two flocks of Shaver White (SH), Lohmann Lite (LL) and Lohmann Brown (LB) hens housed in either 5-hen CC or 40-hen FC. Between 80 and 81 weeks, muscle samples were collected from randomly selected hens and analysed for muscle pH, colour and shear force (SF) using established methods. 3. In both flocks, the combined treatment body weights (BWs) were higher for CC than FC hens and the combined strain BWs were higher for LB than LL and SH hens. Flock 1 LB had lower initial and ultimate pH than SH and LL, and greater pH decline than SH. Muscle redness (a*) was higher for CC SH than FC SH in both flocks. Muscle a* was higher for LL than SH and LB in Flock 1, and higher than SH in Flock 2. Housing differences in muscle SF were absent. In CC, SF was higher for SH than LL and LB in Flock 1, and higher than LB in Flock 2. 4. Lack of housing differences suggests that environmental stressors present in both housing systems similarly affected meat quality. Strain differences for muscle pH, a* and SF indicate increased stress experienced by SH and LL hens. The absence of Flock 2 strain differences is consistent with the cannibalism outbreak that occurred in this flock and most severely impacted LB hens.

Effect of fast pH decline during the early postmortem period on calpain activity and cytoskeletal protein degradation of broiler M. pectoralis major

The objective of this study was to determine the effects of fast pH decline during the early postmortem period on calpain activity and the degradation of cytoskeletal proteins in broilers. Eighty broilers were randomly categorized into two groups: physical restraint (PR) and free struggle (FS). M. pectoralis major (PM) was used for determination of calpain activity, shear value, ultrastructure of myofibrils, and the degradation of desmin, titin, nebulin, and troponin-T. The pH (6.05) of FS group is significantly low than PR group (6.38) at 0.3 h postmortem. Fast pH decline during the early postmortem period led to a decrease of μ/m-calpain activities at 0.3 and 3 h postmortem (P < 0.05), but did not affect the ultimate μ/m-calpain activity. An initial fast decrease in pH increased the degradation of desmin, titin, nebulin, and increased the 30 kDa degradation fragments of troponin-T. Therefore, the fast pH decline during the early postmortem period decreased the μ/m-calpain activity and increased the degradation of cytoskeletal proteins in broiler muscle. It is possible that the fast pH decline experienced an earlier activation of calpains that resulted in earlier protein degradation and ultimately lower shear force.

Proximate composition and variation in colour, drip loss and pH of breast meat from broilers supplemented with Moringa oleifera leaf meal over time

This study investigated the breast meat proximate composition and quality indicators in relation to response of broilers to the following dietary treatments (T): positive control (+C; with 668 mg salinomycin and 500 mg zinc bacitracin per kg of feed); Moringa oleifera leaf meal (MOLM) was fed at a low level (ML; 1–5 g/kg feed, depending on growth stage), a medium level (MM, 3 times the low level) or a high level (MH, 5 times the low level); and a negative control (–C; without supplementation) for 35 days. At postmortem, the carcass weight, and breast muscle pH at 45 min (pH45) and 24 h (pH24) were recorded. At 36 h postmortem, breast muscles were excised, weighed and stored in a refrigerator at 4°C to measure pH, colour (CIE-L*, lightness; a*, redness; and b*, yellowness) and cumulative drip loss over eight consecutive days. Chroma (C*) and hue angle (h) were calculated. The –C had the highest (P > 0.05) dressing percentage and chilled carcass weight, and ML had the lowest. Breast meat fat and energy contents were highest (P < 0.05) in +C and MOLM supplemented diets, and lowest in -C. Dietary treatments had no effect on pH at postmortem and during storage over time. Cumulative drip loss increased with each day of storage, and it was highest (P < 0.05) in +C and lowest in MH. Dietary supplementation of MOLM significantly (P < 0.05) reduced lightness, but increased redness, yellowness, chroma and the hue angle during storage over time. In conclusion, dietary supplementation of M. oleifera leaf meal had positive effects on proximate composition and shelf-life quality indicators of broiler breast meat.