Broiler Breast Muscle Research Articles

Changing the incubation temperature during embryonic myogenesis influences the weight performance and meat quality of male and female broilers

Eggs of broilers were initially incubated at 37.8°C, then at 38.8°C (group H) and 36.8°C (groupL) between embryonic days 7 to 10 (time A) and days 10 to 13 (time B) and further incubated at 37.8°C until hatching. The chicks were fattened until day 35 and then slaughtered. The effect of treatment, time, and sex and their interactions on carcass and meat quality traits were determined. No significant impact of the "treatment time" was analysed, but "treatment" and "sex" and their interactions influenced (P < 0.05) the different parameters. After hatching, group L broilers were heavier (P < 0.05), followed by slower growth compared to group H chicken. At slaughter day, body, carcass, and leg weights of group H broiler were higher (P < 0.05) and yield results lower (P<0.05) compared to group L animals. pH, drip loss, shear force, and lightness values of group H broiler breast muscles were higher (P < 0.05) and grill loss and redness values lower (P < 0.05) compared to group L Musculus pectoralis superficialis (MPS). Body, carcass, MPS, and leg weights, leg yields and grill loss and lightness values of the male broiler were higher (P < 0.05) and drip loss results lower (P<0.05) than the female birds. Male group H broiler showed lower (P < 0.05) carcass and MPS yields compared to the control and group L males, whereas females group H birds had higher (P < 0.05) carcass and MPS weights and lower leg yields (P < 0.05) than the female group L animals. The study shows that an increasing incubation temperature during early embryogenesis positively influences the growth and carcass traits of the broilers, accompanied with a partly negative impact on meat quality (drip loss, shear force, lightness). The growth effects were sex-dependent, as significant weight differences could be only found in female broilers. The results indicate that incubation temperature alteration influences molecular mechanisms in the muscle and other tissues with an impact on growth after hatch.

Histopathologic and Myogenic Gene Expression Changes Associated with Wooden Breast in Broiler Breast Muscles.

The wooden breast condition is a myopathy affecting the pectoralis major (p. major) muscle in fast-growing commercial broiler lines. Currently, wooden breast-affected birds are phenotypically detected by palpation of the breast area, with affected birds having a very hard p. major muscle that is of lower value. The objective of this study was to compare the wooden breast myopathy in two fast-growing broiler lines (Lines A and B) with incidence of wooden breast to a slower growing broiler Line C with no phenotypically observable wooden breast. One of the characteristics of the wooden breast condition is fibrosis of the p. major muscle. Morphologic assessment of Lines A and B showed significant fibrosis in both lines, but the collagen distribution and arrangement of the collagen fibrils was different. In Line A, the collagen fibrils were tightly packed, whereas in Line B the collagen fibrils were diffuse. This difference in collagen organization may be due to the expression of the extracellular matrix proteoglycan decorin. Decorin is a regulator of collagen crosslinking and is expressed at significantly higher levels in Line A wooden breast-affected p. major muscle, which would lead to tightly packed collagen fibers due to high levels of collagen crosslinking. Furthermore, expression of the muscle-specific transcriptional regulatory factors for proliferation and differentiation of muscle cells leading to the regeneration of muscle in response to muscle damage was significantly elevated in Line A, and only the factor for differentiation, myogenin, was increased in Line B. The results from this study provide initial evidence that the etiology of the wooden breast myopathy may vary between fast-growing commercial broiler lines.

Fatty Acid Profile, Cholesterol and Oxidative Status in Broiler Chicken Breast Muscle Fed Different Dietary Oil Sources and Calcium Levels

The aim of the present study was to evaluate the effects of three feeds containing 6% oils: palm oil (PO), soybean oil (SO) and linseed oil (LO); and three calcium levels (NRC recommendation, 1.25% and 1.50%) on the fatty acid profile, lipid oxidation and cholesterol concentrations of broiler breast meat in a 3 × 3 factorial experiment. A total of 378 one-day-old chicks were randomly assigned to the diets and fed for six weeks. Birds fed diet supplemented with LO, SO and PO had higher proportions of α-linolenic, linoleic and oleic acids, respectively. The LO diet increased the total n-3 fatty acids and decreased the n-6 : n-3 compared with the PO and SO diets. Birds fed the PO diet had higher oxidative stability and cholesterol compared with those fed the SO and LO diets. However, the level of cholesterol in all treatments was within the normal range. The level of calcium and interaction between source of oil and calcium level did not influence lipid oxidation, fatty acid profile and cholesterol level of broiler breast muscle. It can be concluded that dietary LO and SO enhanced n-3 and n-6 polyunsaturated fatty acids, respectively, while dietary PO enhanced the oleic acid and oxidative stability of broiler breast muscle. Thus, this study showed that PO can be used as an alternative oil source in broiler diets with a positive effect on the oxidative stability of chicken meat refrigerated at seven days when compared with vegetable oils that are rich in linoleic and α-linolenic acid.

Deep Sequencing Analysis of miRNA Expression in Breast Muscle of Fast-Growing and Slow-Growing Broilers.

Growth performance is an important economic trait in chicken. MicroRNAs (miRNAs) have been shown to play important roles in various biological processes, but their functions in chicken growth are not yet clear. To investigate the function of miRNAs in chicken growth, breast muscle tissues of the two-tail samples (highest and lowest body weight) from Recessive White Rock (WRR) and Xinghua Chickens (XH) were performed on high throughput small RNA deep sequencing. In this study, a total of 921 miRNAs were identified, including 733 known mature miRNAs and 188 novel miRNAs. There were 200, 279, 257 and 297 differentially expressed miRNAs in the comparisons of WRRh vs. WRRl, WRRh vs. XHh, WRRl vs. XHl, and XHh vs. XHl group, respectively. A total of 22 highly differentially expressed miRNAs (fold change > 2 or < 0.5; p-value < 0.05; q-value < 0.01), which also have abundant expression (read counts > 1000) were found in our comparisons. As far as two analyses (WRRh vs. WRRl, and XHh vs. XHl) are concerned, we found 80 common differentially expressed miRNAs, while 110 miRNAs were found in WRRh vs. XHh and WRRl vs. XHl. Furthermore, 26 common miRNAs were identified among all four comparisons. Four differentially expressed miRNAs (miR-223, miR-16, miR-205a and miR-222b-5p) were validated by quantitative real-time RT-PCR (qRT-PCR). Regulatory networks of interactions among miRNAs and their targets were constructed using integrative miRNA target-prediction and network-analysis. Growth hormone receptor (GHR) was confirmed as a target of miR-146b-3p by dual-luciferase assay and qPCR, indicating that miR-34c, miR-223, miR-146b-3p, miR-21 and miR-205a are key growth-related target genes in the network. These miRNAs are proposed as candidate miRNAs for future studies concerning miRNA-target function on regulation of chicken growth.

25-Hydroxycholecalciferol Enhances Male Broiler Breast Meat Yield through the mTOR Pathway1–3

Background: In recent years, there has been a growing body of evidence indicating that replacing cholecalciferol (vitamin D3) with 25-hydroxycholecalciferol [25(OH)D3] through dietary supplementation enhances breast meat yield in broiler chickens. However, the underlying molecular mechanisms are still unknown.Objective: We investigated the effect of 25(OH)D3 on male broiler growth performance (body weight, feed intake, feed conversion ratio, and breast meat yield), muscle protein synthesis, and the potential underlying molecular mechanisms.Methods: Male Cobb 500 broiler chickens were divided into 4 body weight–matched groups and received a control diet with normal cholecalciferol (2760 IU/kg feed) for 42 d, a diet with high concentrations of cholecalciferol (5520 IU/kg feed) for 42 d, or a diet with 25(OH)D3 (5520 IU/kg feed) for 42 d (HyD-42). A fourth group consumed the HyD-42 for 21 d and then control feed for 21 d (HyD-21) (n = 360 birds, 12 replicates/treatment). Food and clean water were available for ad libitum consumption. At the end of the 42-d experiment, protein turnover was measured by phenylalanine flooding dose. Breast muscle tissues were collected and protein synthesis–related gene and protein expression were measured by real time polymerase chain reaction and Western blot, respectively. Functional studies were performed in vitro with the use of a quail myoblast (QM7) cell line. QM7 cells were treated with 2 doses (1 nM and 10 nM) of cholecalciferol or 25(OH)D3 alone or in combination with 100 nM rapamycin, and cell proliferation was determined by cell proliferation assay. Protein synthesis–related gene and protein expression were also determined.Results: The HyD-42 increased 25(OH)D3 circulating concentrations by 126% (P < 0.05), enhanced breast meat yield (P < 0.05), and increased the fractional rate of protein synthesis by 3-fold (P < 0.05) compared with the control diet. Molecular analyses revealed that breast muscle from chickens consuming the HyD-42 expressed significantly higher concentrations of vitamin D receptor (VDR), phospho mechanistic target of rapamycinSer2481, phospho ribosomal P70 S6 kinase (RPS6K)Thr421/Ser424, and antigen Ki-67 (Ki67) compared with the other groups. In line with the in vivo data, in vitro functional studies showed that cells treated with 25(OH)D3 for 24 h had increased VDR expression, and activated the mechanistic target of rapamycin (mTOR)/S6 kinase (S6K) pathway, enhanced Ki67 protein concentrations, and induced QM7 cell proliferation compared with untreated or cholecalciferol-treated cells. Blocking the mTOR pathway with rapamycin reversed these effects.Conclusion: Taken together, our findings provide evidence that the effects of 25(OH)D3 on male broiler breast muscle are likely mediated through the mTOR-S6K pathway.

Effect of various levels of dietary curcumin on meat quality and antioxidant profile of breast muscle in broilers.

The aim of this study was to determine the effects of curcumin on meat quality and antioxidant profile of breast muscle in broilers. In experiment 1, birds were fed basal diet with an additional 0, 50, 100, or 200 mg/kg curcumin, respectively. The results showed that dietary curcumin significantly increased the redness values of meat, catalase activity, and ABTS radical scavenging activity and decreased drip loss at 48 h. In experiment 2, birds reared under heat stress were assigned to similar treatments as experiment 1. Significant differences in the redox status of breast muscle were observed between the control and heat stress groups. The various levels of curcumin significantly prevented reactive oxygen species overproduction, enhanced the antioxidant defense system, and alleviated the abnormal change of antioxidant-related gene expression of muscle in heat-stressed birds. It was concluded that curcumin, as a potential antioxidant, improved meat quality and oxidant stability of muscle in broilers, whereas the inclusion of 50 and 100 mg/kg would be more efficient.

Effects of methionine supplementation on the expression of protein deposition-related genes in acute heat stress-exposed broilers.

The objective of this study was to evaluate the effect of heat stress and methionine supplementation on the gene expression of insulin-like growth factor I (IGF-I), growth hormone receptor (GHR), phosphatidylinositol 3-kinase, and regulatory 1 (PI3KR1) in the liver, as well as the expression of the atrogin 1 and cathepsin L2 (CTSL2) genes in the breast muscle of broilers. Broilers from 1–21 and 22–42 days of age were divided into three treatments related to methionine supplementation as follows: without methionine supplementation (MD), recommended level of methionine (DL1), and excess supplementation of methionine (DL2). The animals were either maintained at a thermal comfort temperature or exposed to heat stress (HS) (38°C for 24 hours, starting on day 20 or day 41 for experiments 1 and 2, respectively). The heat stress increased the body temperature at both ages. Starter period: The HS animals presented increased plasma creatinine content (P<0.0001) and the highest CTSL2 gene expression (P<0.0001). The methionine supplementation increased the IGF-I (P = 0.0144) and GHR (P = 0.0011) gene expression and decreased the CTSL2 (P = 0.0004) and atrogin 1 (P = 0.0012) gene expression. Grower period: Significant effects for the interaction between supplementation and environment were observed for GHR (P = 0.0252) and CTSL2 (P = 0.0011) gene expression. The highest GHR expression was observed in animals that remained in thermal comfort on the DL2 diet, and the lowest expression occurred in the HS animals fed the MD diet. For CTSL2, the HS animals fed the MD diet presented the highest CTSL2 gene expression, and the lowest expression was observed in the animals maintained at thermal comfort on DL1 and DL2 diets. Only methionine supplementation had effect on atrogin-1 gene expression (P<0.0001), with higher methionine content in the diet lower atrogin-1 gene expression was observed. Our results suggest that heat stress induces greater protein degradation and that methionine supplementation could induce protein deposition because methionine increased the expression of genes related to protein synthesis and decreased the expression of genes related to protein breakdown.

Effects of Tannic Acid on Performance and Fatty Acid Composition of Breast Muscle in Broiler Chickens Under Heat Stress

One hundred twenty day-old broiler chicks (Cobb 500) were randomly assigned into 4 treatment groups to investigate the effects of tannic acid supplementation (TA) on fatty acid composition in breast muscle of broilers under chronic heat exposure conditions. Five pen replicates of 6 chicks each were assigned to each of the following 4 dietary treatments: i) basal diet containing no TA at 25°C (CL); ii) basal diet containing no TA at 35°C (CH); iii) basal diet supplemented with 1% TA at 25°C (TL); and iv) basal diet supplemented with 1% TA at 35°C (TH). At the end of the 5-week experiment, breast muscle samples were collected to examine the fatty acid composition. Results showed that temperature, TA and their interaction effect significantly decreased body weight gain and feed intake. In addition, feed conversion ratio (FCR) significantly increased under high temperature, and addition of TA under high temperature did not improve the FCR. The effects of temperature, TA and their interaction on the saturated and unsaturated fatty acids were not significant (P<0.05). However, monounsaturated fatty acids significantly reduced by adding TA to the diet. Generally, TA improved the fatty acid profile of breast muscle of broilers under heat stress in comparison to the heat stressed chickens, which did not receive TA. Hence, it seems that dietary TA supplementation can be applied as a biological antioxidant for poultry nutrition in hot climatic conditions.

Influence of Dietary Histidine, Hybrid Line and Gender on Chicken Meat Quality and Carnosine Concentration

The aim of the investigation was to determine influence of L-histidine dietary supplementation (P1 0.0%, P2 0.1%, P3 0.2% and P4 0.3%), hybrid line (Cobb 500 and Hubbard Classic) and gender on meat quality and carnosine concentration in chicken breast and thigh muscles. The research was carried out on 184 one day old broiler chickens as 4x2x2 factorial design. Chicken live weight, carcass weight, dressing percentage, absolute and relative shares of main body parts in the carcass, pHi, pHu, colour, drip loss, cooking loss and share force of breast muscle, and carnosine concentration in breast and thigh muscles were determined. L-histidine dietary supplementation significantly affected live weight, carcass weight, weight of drumsticks and thighs, backs and wings, share of back and the CIE a* value (P<0.05), as well as the content of carnosine in breast muscle (P=0.003). Hybrid line influenced relative shares of main body parts in the carcasses, except for wings, and the CIE a* value of breast muscle (P < 0.001). Chicken gender affected live weight of chickens, carcass weight, as well as weight of main parts (P<0.001), except for breast. The results of the investigation showed that dietary L- histidine significantly increased carnosine content in broiler breast muscle. Cobb 500 female chickens of the P4 group had higher carnosine concentrations in breast muscle by 156.61 and male chickens by 150.49 µg/g of tissue than the control group. Cobb 500 broiler chickens deposited more carnosine in meat than Hubbard Classic broilers.

Physicochemical and Functional Properties of Chicken Meat

The physicochemical and functional properties of chicken meat under commercial processing in Serbia were studied. Samples (n = 48) of broiler breast and thigh muscles from two farms during 2012 were collected for subsequent meat quality analyses. The farm treatments modify significant growth performance, feed intake and the physicochemical properties of chicken meat. Fatty acid (FA) composition in tissues reflected the FA pattern of the diets, although the predominant FAs were monounsaturated FA (MUFA), in comparison to saturated FA (SFA) and polyunsaturated FA (PUFA). Therefore, our results suggest that quality of poultry meat is a complex and multivariate property.

Influence of dietary replacement of sunflower oil with milk thistle (Silybum marianum) oil on chicken meat quality and antioxidant status of liver

The research focused on the effects of dietary replacement of 3% sunflower oil (SO group) with 3% milk thistle oil (MTO group) on the technological quality of meat, such as pH value, colour (CIE L*, CIE a*, CIE b*), drip loss (%), shear force (N), and cooking loss (%), as well as on the content of fatty acid lipids in broiler breast and thigh muscles. Significant difference (P&lt; 0.05) was determined for pHi, pHu, CIE a*, CIE b* values between groups, although the values for the stated indicators were within the standard range. Lipids of breast meat of the MTO group contained more arachidic acid (P&lt; 0.001), octadecenoic acid isomer B (P= 0.047) and eicosatrienoic acid (P= 0.041), and less α-linolenic acid (P&lt; 0.001) and Σn-3PUFA. Lipids of thigh meat of the MTO group contained more ΣSFA, myristoleic acid, eicosatrienoic acid (P&lt; 0.05) and eicosenoic acid (P&lt; 0.001), and less α-linolenic acid, and had narrower Σn-3/n-6 PUFA ratio than the SO group. According to the antioxidant status of broiler liver, there was significantly higher catalase activity determined in the MTO group.

THE EFFECT OF BEE POLLEN ON BROILER BREAST AND THIGH MEAT COLOUR L* a* b*

The present study was aimed to investigate the impact of the addition bee pollen as supplements diet into the broiler feed mixture on broiler breast and thigh meat colour such as L* (lightness), a* (redness), and b* (yellowness) values. A total of the 180 chickens in one day old chickens hybrid combination Ross 308 which were divided into 6 groups (n=30): control, (I, II, III, IV and V) experimental groups. The value of L* in the control group was higher compared to the experimental groups except (II, IV) groups. The a* value in the breast was tended slightly to green in control and (I, V) groups only in (II, III, IV) groups which the value of the a* was tended slightly to redness colour and there were found significant differences (P≤0.05) between control and (II, III, IV) groups in breast and thigh muscles. Further, in the breast and thigh they were found that the b* value was higher in the control group compared to the experimental groups (I, II, III, IV and V) and there were found significant differences (P≤0.05) between control group and (II, III) groups. However, they were conclude that the bee pollen has no effect on broiler breast and thigh meat colour L* (lightness), otherwise they were found that the bee pollen in the amount (1500, 2500 and 3500 mg.kg-1) were tended the broiler breast muscles to redness coloour slightly compared to the experimental group.

Effect of the timing of posthatch feed restrictions on the deposition of fat during broiler breast muscle development

The effect of the timing of posthatch feed restriction on adipose deposition and adipogenic gene expression in the broiler pectoralis major muscle was studied by applying a 20% feed restriction either the first or second week after hatch. Broiler chicks at hatch were divided into a full-fed (control) group and a 20% feed restriction group. The expression of adipogenic genes, peroxisome proliferator-activated receptor gamma (PPARγ), and CCAAT/enhancer-binding protein alpha (C/EBPα) were measured. The expression of both PPARγ and C/EBPα was affected by the wk 1 feed restriction with expression significantly increased during the first week posthatch. The deposition of fat within the pectoralis major muscle was affected by the timing of the feed restriction. Extensive fat depots were present by 27 d of age in the pectoralis major muscle of the wk 1 restricted group compared with the control. Fat deposition was eliminated when the 20% feed restriction occurred in wk 2. Taken together, these results demonstrate that the timing of early posthatch feed restrictions in chicks is critical in the deposition of fat in the pectoralis major muscle and expression of adipogenic genes.

Influence of fermentation concentrate of Hericium caput-medusae (Bull.:Fr.) Pers. on performance, antioxidant status, and meat quality in broilers

This study was conducted to evaluate the effects of supplementation with the fermentation concentrate of Hericium caput-medusae (Bull.:Fr.) Pers. (HFC) on growth performance, antioxidant status, and meat quality of broilers. A total of 600 female Arbor Acres broilers were randomly divided into five dietary treatments (20 broilers per pen with 6 pens per treatment): CON (basal diet), ANT (basal diet supplemented with 5mg flavomycin/kg diet) and HFC (basal diet supplemented with 6, 12 and18g HFC/kg diets). The experiment lasted for 6 weeks. Performance parameters were recorded on days 21 and 42, and the other response criteria on day 42. The average daily feed intake was not affected by HFC inclusion during the entire experimental period. Incorporation of dried HFC in chicken diet improved the daily gain compared with the control and ANT treatments, and the average daily gain increased (P<0.001) quadratically when the HFC levels increased. The superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) values increased (P<0.05) quadratically, while the malondialdehyde (MDA) level in the serum, liver, and breast muscle of broilers decreased (P<0.001) quadratically with the increasing of dietary HFC level. The pH24h value of the breast muscle increased (P<0.001) quadratically, while the drip loss and cooking loss decreased (P<0.01) quadratically when the HFC levels increased. Dietary supplementation with HFC had no significant effects on shear force of broilers. The L* value decreased (P<0.01) quadratically, while the a* and b* values of the breast muscle increased (P<0.01) quadratically when the HFC levels increased. These results demonstrate that HFC has promising antioxidant potential to enhance oxidative status and meat quality of broiler chickens.

Effect of pH and postmortem aging on protein extraction from broiler breast muscle

This study determined the effects of extraction buffer pH and postmortem aging on the extraction of salt-soluble and water-soluble proteins from broiler pectoralis muscle. Deboned broiler breast fillets were collected at 4 h postmortem, packaged, and then stored at 4°C until 1, 5, or 8 d postmortem. After the designated aging period, salt-soluble and water-soluble protein extractions were performed using buffers at 7 different pH levels (pH 5.4, 6.4, 6.9, 7.2, 7.5, 8.0, 9.0). Protein concentrations of the extracts were measured and SDS-PAGE analysis was performed. Salt-soluble protein concentration increased (P < 0.0001) as buffer pH increased from pH 5.4 to 6.9 and then remained unchanged from pH 6.9 to 9.0. Water-soluble protein concentration increased (P < 0.0001) as buffer pH increased from pH 5.4 to 7.2 and then remained unchanged from pH 7.2 to 9.0. There was not a significant extraction buffer pH by aging treatment interaction for the total protein concentration of either the salt-soluble or water-soluble protein extracts. The protein concentrations of salt-soluble extracts were similar at both 1 and 8 d postmortem but lower (P < 0.0001) at 5 d postmortem. The protein concentrations of water-soluble extracts were similar at both 1 and 5 d postmortem, but higher (P < 0.0001) at 8 d. Both extraction buffer pH and postmortem aging influenced the SDS-PAGE protein profiles of salt-soluble and water-soluble protein extracts from breast muscles. Data demonstrate that postmortem aging and extraction buffer pH influence both the total amount and the composition of the myofibrillar and sarcoplasmic proteins that can be extracted from broiler breast fillets.

Effect of the timing of posthatch feed restrictions on broiler breast muscle development and muscle transcriptional regulatory factor gene expression

The effect of the timing of an immediate posthatch feed restriction on broiler pectoralis major muscle development was studied by applying a 20% feed restriction either the first or second week after hatch. Pectoralis major muscle morphological structure and the expression of the myogenic transcriptional regulatory factors, myogenic determination factor 1 (MyoD), myogenic regulatory factor 4 (MRF4), and myogenin, were measured. Broiler chicks at hatch were divided into a full-fed (control) group and a 20% feed restriction treatment administered either the first or second week posthatch. At the end of the feed restriction, the chicks were placed on a full feed ad libitum diet with no further restrictions. Muscle fiber diameter and fiber bundle size of the pectoralis major muscle were smaller in the wk 1 restricted group than the control group by 7 d of age. By 15 d of age through the duration of the study, d 43, both endomysial and perimysial connective tissue spacing were diminished in the wk 1 feed-restricted group. The expression of MyoD, MRF4, and myogenin was affected by the wk 1 feed restriction. The expression of MyoD and MRF4 was significantly increased during the first week posthatch. Both of the genes have been shown to be expressed during proliferation especially MyoD, which is required for muscle cell proliferation. In contrast, myogenin expression was significantly decreased. Myogenin expression is required for differentiation to occur. The morphological changes and gene expression changes observed with the wk 1 feed restriction were eliminated by moving the 20% feed restriction to wk 2, which is after the period of maximal myogenic satellite cell mitotic activity. Taken together, these results demonstrate that the timing of early posthatch feed restrictions to chicks is critical for the morphological development of the pectoralis major muscle and the expression of genes required for muscle satellite cell proliferation and differentiation.

Comparative proteomic analysis of the breast muscle response to chronic corticosterone administration in broiler chickens showing long or short tonic immobility

Broilers of the same genetic origin were classified as short or long tonic immobility duration (STI and LTI, respectively) phenotypes and treated chronically with vehicle (control) or corticosterone (CORT) dissolved in drinking water between 27 and 42 d of age. Differential expression of proteins and mRNA was examined using 2-dimensional gel electrophoresis and real-time PCR to elucidate the mechanism behind the severe retardation of broiler breast muscle growth caused by LTI and CORT. The majority of the 13 proteins found to be differentially expressed in breast muscle of STI and LTI broilers are involved in either glycolysis (5 proteins) or myofilament formation (5 proteins). Of the 16 proteins differentially expressed in breast muscle following CORT treatment, 6 are structural proteins, 5 are categorized as cellular defense and stress proteins, and 3 (pyruvate kinase, l-lactate dehydrogenase, and creatine kinase) are involved in responses to stress and muscle damage. Real-time PCR results indicated that expression of these proteins is transcriptionally and posttranscriptionally regulated. Protein synthesis capacity, estimated by the RNA-to-protein ratio, was significantly lower in the breast muscle of CORT-treated broilers than in untreated control broilers. The level of Leu, Gly, and Ser in serum was significantly higher in CORT-treated broilers than in the control birds. Therefore, we conclude that CORT treatment retards the growth of skeletal muscle by suppressing protein synthesis and augmenting protein catabolism, paralleling the response to severe stress and muscle damage, and the negative effect of LTI on muscle growth is likely mediated through glucose metabolism. No interaction was observed between CORT and tonic immobility affecting growth performance or any parameter examined in the current study.

Cholesterol and total lipid content in raw and heat processed commercially produced meat from two farms

The present study was conducted to present information about the cholesterol and total lipid content in fresh and roasted chicken meat with skin (breast and drumstick meat), most commonly consumed in Serbia. In addition, to assess the possible effects of carcass weight and nutrition on total lipid and cholesterol content in examined meat cuts. A total number of 48 samples of breast and drumstick muscle of broilers from two farms (Farm I and II), fed ad libitum by commercial diets for growing broilers, were taken in summer, 2012 and autumn, 2013. Total lipid and cholesterol content were determined in raw and heat-processed breast and drumstick muscle with skin. Total lipid content was determined by extraction of fat by petrol ether (Soxhlet) after acid hydrolysis of samples (SRPS ISO 1443/1992).Cholesterol determination was performed after direct saponification (without prior lipid extraction) by using HPLC/PDA system. Generally, all parameters measured were influenced by interaction of care and management and broiler performance at the 5% level or less. The total lipid content in samples of raw breast muscle of chicken from Farm I were the highest in summer (5.53%), (4.2%, in autumn), compared to samples of chickens from Farm II (3.05% in summer and 2.61% in autumn). The total lipid content in samples of raw drumstick were significantly differ (p < 0.001) between Farm I (9.63%) and Farm II (5.19%), only in summer. Cholesterol content (mg/100 g) in the raw breast muscle from Farm I was 53.9 (autumn) and 62.1 (summer), while in samples from Farm II was 46.97 (autumn) and 49.53 (summer). There was significant difference (p < 0.001) in cholesterol content in raw breast muscle of chickens in summer from two farms. In raw drumstick from Farm I the average cholesterol content (mg/100 g) was 70.24 (autumn) and 83.95 (summer), while in samples of chickens from Farm II was 65.05 (autumn) and 60.92 (summer). These differences were significant for cholesterol levels in drumstic between farms in summer (p < 0.001). In heat-processed meat belonging to chickens from Farm I, breast and drumstick contained higher quantities of total lipids compared to samples from Farm II. These differences was significant (p < 0.01) in drumstick between Farm I and II (autumn) and were 13.37%, and 11.10%, respectively. The average cholesterol content (mg/100 g) in samples of heat-processed meat of chicken from Farm I varied between 70.32 (autumn) and 87.37 (summer) and from 75.23 (autumn) to 78.92 (summer) in drumstick, versus 64.33 (summer) and 66.24 (autumn) in breast muscle and from 81.31(summer) to 91.6 (autumn) in drumstick samples of chickens from Farm II. We conclude that factors, such as feed composition, genotype (breed) and gender, influence the total lipid and cholesterol content in the meat. There were no obviously effects of slaughter traits on cholesterol and total lipid content. The results presented here, also shows that further investigations have to be conducted on greater number of samples.

Comparison of carcass yields and meat quality between Baicheng-You chickens and Arbor Acres broilers

This study examined carcass yields and meat quality traits between Baicheng-You (BCY) chickens and Arbor Acres (AA) broilers. Thirty birds for each strain were selected and slaughtered at market ages of 49 d for AA broilers and 120 d for BCY. The results showed that BCY chickens had lower dressing (2.99%), semi-evisceration (5.10%), breast muscle (5.80%), and abdominal fat (1.55%) than those for AA broilers (P < 0.05). However, the leg muscle (%) of BCY chickens was greater (3.14%) than that of AA broilers (P < 0.05). The meat pH45min and pH24h value variations of these 2 breeds were within the normal range (5.53-6.70). The meat color density (optical density, OD) of thigh muscle was darker than breast muscles in both strains (P < 0.05). The cooking loss (%) of breast and thigh muscles of BCY chickens (18.81 and 20.20%, respectively) was also significantly lower (P < 0.05) than that of same muscles of AA broilers (26.41 and 27.33%, respectively). The shear force of breast meat in both breeds was lower (P < 0.05) than that of their thigh meat. The moisture of breast muscle of BCY chickens (72.93%) was lower (P < 0.05) than breast muscles of AA broilers (74.43%). The CP content of breast muscles was greater (P < 0.05) than its thigh muscles of same strain, but it had no significant (P > 0.05) difference of CP content in the same muscles of the 2 strains. The intramuscular fat (IMF) content was greater (P < 0.05) in thigh muscles of BCY chickens (6.80%) than those of AA broilers (4.28%), and inosine-5'-monophosphate (IMP) content was greater (P < 0.05) in breast and thigh muscles of BCY chickens (IMP: 3.79 and 1.47 mg/g) than same muscles in AA broilers (1.42 and 0.47 mg/g). In this study, muscle from 120-d-old BCY chickens was judged to have better quality traits with regard to cooking loss, drip loss, contents of IMF, and IMP compared with meat from 42-d-old AA broilers. At the same time, greater carcass yields, greater thigh pH24, and lower IMF content were observed in AA broilers compared with the BCY chickens.

Water-holding capacity of broiler breast muscle during the first 24 h postmortem

Water-holding capacity of broiler breast muscle during the first 24 h postmortem