Breast Muscle Yield Research Articles

Messenger RNA sequencing and pathway analysis provide novel insights into the biological basis of chickens' feed efficiency.

BackgroundAdvanced selection technologies have been developed and continually optimized to improve traits of agricultural importance; however, these methods have been primarily applied without knowledge of underlying biological changes that may be induced by selection. This study aims to characterize the biological basis of differences between chickens with low and high feed efficiency (FE) with a long-term goal of improving the ability to select for FE.ResultsHigh-throughput RNA sequencing was performed on 23 breast muscle samples from commercial broiler chickens with extremely high (n = 10) and low (n = 13) FE. An average of 34 million paired-end reads (75 bp) were produced for each sample, 80% of which were properly mapped to the chicken reference genome (Ensembl Galgal4). Differential expression analysis identified 1,059 genes (FDR < 0.05) that significantly divergently expressed in breast muscle between the high- and low-FE chickens. Gene function analysis revealed that genes involved in muscle remodeling, inflammatory response and free radical scavenging were mostly up-regulated in the high-FE birds. Additionally, growth hormone and IGFs/PI3K/Akt signaling pathways were enriched in differentially expressed genes, which might contribute to the high breast muscle yield in high-FE birds and partly explain the FE advantage of high-FE chickens.ConclusionsThis study provides novel insights into transcriptional differences in breast muscle between high- and low-FE broiler chickens. Our results show that feed efficiency is associated with breast muscle growth in these birds; furthermore, some physiological changes, e.g., inflammatory response and oxidative stress, may occur in the breast muscle of the high-FE chickens, which may be of concern for continued selection for both of these traits together in modern broiler chickens.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1364-0) contains supplementary material, which is available to authorized users.

Polymorphisms in the Perilipin Gene May Affect Carcass Traits of Chinese Meat-type Chickens.

Improved meat quality and greater muscle yield are highly sought after in high-quality chicken breeding programs. Past studies indicated that polymorphisms of the Perilipin gene (PLIN1) are highly associated with adiposity in mammals and are potential molecular markers for improving meat quality and carcass traits in chickens. In the present study, we screened single nucleotide polymorphisms (SNPs) in all exons of the PLIN1 gene with a direct sequencing method in six populations with different genetic backgrounds (total 240 individuals). We evaluated the association between the polymorphisms and carcass and meat quality traits. We identified three SNPs, located on the 5′ flanking region and exon 1 of PLIN1 on chromosome 10 (rs315831750, rs313726543, and rs80724063, respectively). Eight main haplotypes were constructed based on these SNPs. We calculated the allelic and genotypic frequencies, and genetic diversity parameters of the three SNPs. The polymorphism information content (PIC) ranged from 0.2768 to 0.3750, which reflected an intermediate genetic diversity for all chickens. The CC, CT, and TT genotypes influenced the percentage of breast muscle (PBM), percentage of leg muscle (PLM) and percentage of abdominal fat at rs315831750 (p<0.05). Diplotypes (haplotype pairs) affected the percentage of eviscerated weight (PEW) and PBM (p<0.05). Compared with chickens carrying other diplotypes, H3H7 had the greatest PEW and H2H2 had the greatest PBM, and those with diplotype H7H7 had the smallest PEW and PBM. We conclude that PLIN1 gene polymorphisms may affect broiler carcass and breast muscle yields, and diplotypes H3H7 and H2H2 could be positive molecular markers to enhance PEW and PBM in chickens.

Effects of dietary pyrroloquinoline quinone disodium on growth, carcass characteristics, redox status, and mitochondria metabolism in broilers

The potential benefits of supplementing pyrroloquinoline quinone disodium (PQQ·Na2) in the diet of broiler chicks were explored. We first examined the effect of different levels of dietary PQQ·Na2 on growth performance, carcass characteristics, and plasma biochemical parameters (trial 1). A total of 490 1-day-old male Arbor Acres (AA) broiler chicks were randomly divided into 5 dietary groups supplemented with 0, 0.05, 0.1, 0.2, or 0.4 mg PQQ·Na2/kg feed. As the 0.2 mg/kg PQQ·Na2 supplement gave the best performance, we then investigated whether this level of PQQ·Na2 influenced the redox status of plasma samples and mitochondrial-related metabolism (trial 2). A total of 120 1-day-old male AA chicks were randomly divided into 2 groups supplemented with 0 or 0.2 mg PQQ·Na2/kg diet. In trial 1, birds fed a diet containing 0.2 mg PQQ·Na2/kg showed lower feed conversion ratio compared with those fed the control diet in the overall study (d 1 to 42, P = 0.039). Breast muscle yield (d 42) increased quadratically in response to dietary PQQ·Na2 supplementation (P = 0.021). Analysis of plasma biochemical parameters revealed that feeding broiler chicks with ≤ 0.4 mg/kg PQQ·Na2 did not cause adverse health effects. In trial 2, birds fed 0.2 mg/kg PQQ·Na2 again showed improved feed efficiency than the control birds in the grower and overall phases (P = 0.038 and 0.016, respectively). In addition, dietary PQQ·Na2 supplementation resulted in a higher anti-oxidative capacity (P = 0.001), lower redox potential (P = 0.008), and higher hepatic citrate synthase activity (P = 0.002). In contrast, no difference in hepatic mitochondrial DNA copy number was observed between the 2 experimental groups (P > 0.1). These results indicate that PQQ·Na2 is a potentially effective feed additive for improving feed efficiency, stimulating breast muscle development, and maintaining redox status in broiler chicks. Enhancement of mitochondria efficiency, rather than modulating mitochondria numbers, may underlie the growth-promoting effect of PQQ·Na2.

Effect of Whole Inedible Date and Amino Acid Supplementation on Growth Performance of Ross 308 Broiler Chicks

This work aims to assess the potential of discarded date meal (DDM) as an alternative ingredient in broiler diets. The effect of substituting 5 or 10% of corn and soybean meal (SBM) with DDM on performance, carcass characteristics, serum constituents and nutrients retention of broilers from 12 to 35 d of age was evaluated. A total of 150 chicks were randomly distributed in a factorial arrangement (3x2) into six treatments. Three levels of DDM (0, 5 and 10%) and 2 levels of AAs (normal and high) were utilized. A significant interaction was detected for BWG (P<0.01) and FCR (P<0.001). Birds which had received 0% and 5% DDM and high AAs converted feed more efficiently when compared to those which had received low AAs. When examining the main effects for FCR, both DDM and AAs showed a significant effects on FCR (P<0.01 and 0.05, respectively). Birds received 5% DDM converted feed more efficiently as compared to 0 and 10%. Also, birds received the high AAs level converted feed more efficiently as compared to the normal level. On the other hand, breast muscle yield and abdominal fat were affected by DDM and AAs (P<0.01 and 0.05, respectively). Birds on the 0% DDM had higher breast muscle yield as compared to 5 or 10% DDM. Also, high AAs increased breast yield by 1.5% as compared to normal AAs. The results revealed that birds received 5% DDM performed better than the control or 10%. Also, supplementing diets with higher AAs level improved the performance. Based on presented evidences, it is recommended to substitute 5% of corn and SBM with DDM.

MSTN, mTOR and FoxO4 are involved in the enhancement of breast muscle growth by methionine in broilers with lower hatching weight.

Broilers with lower hatching weight (HW) present poorer performance than those with high HW, but there is limited research on the growth regulation of broilers with lower HW. The objective of this study was to investigate the effect of dietary methionine (Met) levels on the growth performance and breast muscle yield of broilers with different HW and underlying mechanisms. A total of 192 one-day-old Arbor Acres broiler chicks with different HW (heavy: 48.3±0.1 g, and light: 41.7±0.1 g) were allocated to a 2×2 factorial arrangement with 6 replicates of 8 chicks per replicate cage. Control starter (1–21 d) and finisher (22–42 d) diets were formulated to contain 0.50% and 0.43% Met, respectively. Corresponding values for a high Met treatment were 0.60% and 0.53%. Light chicks had lower body weight gain (BWG) and breast muscle yield than heavy chicks when the broilers were fed the control diets. High Met diets improved BWG, gain to feed ratio and breast muscle yield in light but not heavy chicks. Decreased DNA content and increased RNA/DNA and protein/DNA ratios in breast muscle were induced by high Met diets only in light chicks. MSTN mRNA level was decreased by high Met diets only in light chicks, and this decrease was accompanied by a significant increase in MSTN gene exon 1 methylation. In addition, high Met diets increased mTOR phosphorylation, but decreased FoxO4 phosphorylation in breast muscle of light chicks. In conclusion, the BWG and breast muscle yield of light chicks were improved by increasing dietary Met levels probably through alterations of MSTN transcription and phosphorylation of mTOR and FoxO4.

Maternal zinc supplementation enhanced skeletal muscle development through increasing protein synthesis and inhibiting protein degradation of their offspring.

Previous studies proved that maternal zinc supplementation had no significant effect on body weight (BW) of the offspring, but the effects of maternal zinc supplementation on skeletal muscle development of the offspring are poorly defined. Here, broiler breeders at 46 weeks old were allocated into three treatments with six replicates of 40 hens each and fed with diets supplemented with zinc from ZnSO4 at 0 (group Zn/C), 50 mg/kg (group Zn/L), and 300 mg/kg (group Zn/H) respectively for 6 weeks. The male offspring from each dietary treatment were divided into seven cages of ten birds each and fed with a commercial diet with supplemental zinc from ZnSO4 at 20 mg/kg. Results indicated that with the increase of zinc supplementation in hen's diet, the zinc levels were significantly elevated (P < 0.05) in the egg yolk. Compared with the control group, the breast muscle yield and muscle fiber width were significantly (P < 0.05) higher and larger in the broilers from group Zn/H at 2 and 5 weeks post-hatch, the phosphorylation of AKT at serine 473 residue (Ser 473), mammalian target of rapamycin (mTOR) at serine 2448 residue (Ser 2448), and FOXO at serine 256 residue (Ser 256) in skeletal muscles of the birds from various dietary treatments at two different age post-hatch were significantly (P < 0.05) increased. The phosphorylation of mTOR and FOXO was usually related to protein synthesis and degradation. In conclusion, supplemental zinc into the breeders' diet could increase protein synthesis and decrease protein degradation, which, in turn, enhance breast muscle development of the offspring.

Dietary inclusion level and time effects of taurine on broiler performance, meat quality, oxidative status and muscle taurine content

1. Two experiments were conducted to investigate the effect of taurine on growth performance, meat quality, oxidative status and muscle taurine content in broilers. In Experiment 1, 50 one-day-old male Cobb chicks were given a diet supplemented with 0, 0.125, 0.50, 2.00 or 8.00 g/kg taurine from 1 to 42 d of age. In Experiment 2, 80 22-d-old male Cobb chicks were given a diet supplemented with 4.00 g/kg taurine for 0, 1, 2 or 3 weeks.2. Taurine contents of thigh and breast muscle increased linearly with increasing dietary taurine.3. Taurine supplementation for 1, 2 and 3 weeks significantly increased the taurine content of breast muscle. The taurine contents of liver and thigh meat were significantly increased by taurine supplementation for 3 weeks. The taurine contents of thigh and breast meat from broilers given a diet supplemented with 4 g/kg taurine for 3 weeks increased to 1.89 times the concentrations of the control group.4. There were no detrimental effects on growth performance, breast or thigh muscle yield, pH value or drip-water loss, and taurine supplementation did not affect the serum carbonyl content.5. Serum malondialdehyde concentration was significantly decreased by taurine supplementation for 1, 2 or 3 weeks.

Featherless and feathered broilers under control versus hot conditions. 2. Breast muscle development and growth in pre- and posthatch periods

Breast meat yield (% of BW) of featherless broilers (sc/sc) is higher than that of their feathered sibs (+/sc) and contemporary broilers (+/+) under hot temperature (32°C) conditions. This study tested the hypothesis that the advantage to the featherless broiler condition with respect to breast meat yield and quality is due to differences in muscle development during pre- and posthatch periods. Broilers from the 3 genetic groups were reared under normal (26°C) and hot (32°C) conditions and slaughtered on d 29 and 47. Evaluation of myofiber diameter (mean and distribution) and blood-vessel density in breast muscle sections sampled on these days revealed that the fluctuations in breast muscle yields of the different genetic groups under different temperature conditions and the better muscle growth of the featherless broilers are due to changes in muscle hypertrophy and vascularization. In addition, the featherless broilers presented continuous satellite cell proliferation and a slower rate of differentiation compared with the feathered broilers on immediate posthatch period, suggesting a higher reserve of myogenic progeny cells that will contribute to later muscle hypertrophy. In the embryos, breast muscle yield was higher for the featherless versus feathered counterparts between embryonic day (E) 15 and E20. This was manifested in a shift toward higher myofiber diameters in the featherless embryos on E18, and a higher number of myoblasts, which could be explained by higher insulin-like growth factor-I levels in the muscle tissue and lower triiodothyronine levels in the plasma on E17. Together, the data show the advantage of being featherless under hot conditions with regard to breast muscle growth and hypertrophy, and overall performance. Moreover, featherless embryos had increased breast muscle weight compared with their feathered counterparts, likely due to a higher proliferation rate of myoblasts and higher muscle hypertrophy.

Featherless and feathered broilers under control versus hot conditions. 1. Breast meat yield and quality

The improved genetic potential of contemporary commercial broilers cannot be fully expressed under hot conditions that depress growth rate, decrease breast meat yield, and reduce meat quality. The negative heat effects are attributed to the insulating feather coverage, which, under high ambient temperatures (AT), hinders dissipation of the excessive internally produced heat. Accordingly, featherless broilers (sc/sc), their feathered sibs (+/sc), and contemporary broilers (+/+) were subjected to control AT (26°C) and hot AT (32°C) to test the hypothesis that lack of feathers contributes to higher breast muscle yield and better meat quality, especially under hot conditions, and that differences related to lack of feathers are related to cardiovascular capacity. In 2 similar trials, the superior genetic background of the contemporary broilers was manifested under control conditions; their mean BW was about 15% higher than the means of the featherless broilers and their feathered sibs. The hot conditions depressed BW of the 2 feathered groups by approximately 25%, with hardly any effect on featherless broiler BW. Breast meat yield (% of BW) in the featherless broilers was higher than in those with feathers, especially under the hot AT. Furthermore, the featherless broilers were characterized by superior meat quality as indicated by lower drip loss, lower lightness, and higher redness. The superior meat quality of the featherless broilers could be explained by their larger hearts and higher hematocrit values, suggesting superior cardiovascular capacity to supply oxygen and nutrients to the breast muscles. On the practical side, the results clearly indicate that modern featherless broilers can reach normal BW, as well as yield and quality of breast meat, under hot conditions as well. It appears that broiler meat production in hot regions and climates can be substantially improved by introducing the featherless gene into contemporary commercial broiler stocks. This has become more feasible since the recent development of a simple DNA test to identify carriers of the recessive sc mutation.

Increasing dietary vitamin D3 improves the walking ability and welfare status of broiler chickens reared at high stocking densities

A study was conducted to evaluate the effects of varying dietary vitamin D3 and stocking density on growing performance, carcass characteristics, bone biomechanical properties, and welfare responses in Ross (308) broilers. Experimental diets, containing 1, 10, or 20 times the NRC recommended level of vitamin D3 (200 IU/kg), were formulated with low, medium, or high vitamin D3 levels for 3 growing phases. Two stocking densities were 10 and 16 birds/m2. One-day-old hatchlings (1,872 males) were randomly assigned to 6 pens in each treatment. Results showed that high stocking density decreased the feed intake, BW gain (P < 0.01), breast muscle yield (P = 0.010), and tibial development (P < 0.01), whereas increasing feed conversion ratio (P < 0.001), and the scores of gait, footpad and hock burn, and abdominal plumage damage (P < 0.01), particularly toward the age when birds attained their market size. Increasing dietary vitamin D3 improved the birds’ walking ability and tibial quality (P < 0.05), and reduced the development of footpad or hock dermatitis and abdominal plumage damage (P < 0.01), some aspects of which were age-dependent and appeared to vary with stocking density. These data indicate that increasing supplemental vitamin D3 has a favorable effect on walking ability and welfare status of high stocking density birds, but not on performance.

Thermal manipulation of the embryo modifies the physiology and body composition of broiler chickens reared in floor pens without affecting breast meat processing quality1

Selection in broiler chickens has increased muscle mass without similar development of the cardiovascular and respiratory systems, resulting in limited ability to sustain high ambient temperatures. The aim of this study was to determine the long-lasting effects of heat manipulation of the embryo on the physiology, body temperature (Tb), growth rate and meat processing quality of broiler chickens reared in floor pens. Broiler chicken eggs were incubated in control conditions (37.8°C, 56% relative humidity; RH) or exposed to thermal manipulation (TM; 12 h/d, 39.5°C, 65% RH) from d 7 to 16 of embryogenesis. This study was planned in a pedigree design to identify possible heritable characters for further selection of broiler chickens to improve thermotolerance. Thermal manipulation did not affect hatchability but resulted in lower Tb at hatching and until d 28 post-hatch, with associated changes in plasma thyroid hormone concentrations. At d 34, chickens were exposed to a moderate heat challenge (5 h, 32°C). Greater O2 saturation and reduced CO2 partial pressure were observed (P < 0.05) in the venous blood of TM than in that of control chickens, suggesting long-term respiratory adaptation. At slaughter age, TM chickens were 1.4% lighter and exhibited 8% less relative abdominal fat pad than controls. Breast muscle yield was enhanced by TM, especially in females, but without significant change in breast meat characteristics (pH, color, drip loss). Plasma glucose/insulin balance was affected (P < 0.05) by thermal treatments. The heat challenge increased the heterophil/lymphocyte ratio in controls (P < 0.05) but not in TM birds, possibly reflecting a lower stress status in TM chickens. Interestingly, broiler chickens had moderate heritability estimates for the plasma triiodothyronine/thyroxine concentration ratio at d 28 and comb temperature during the heat challenge on d 34 (h(2) > 0.17). In conclusion, TM of the embryo modified the physiology of broilers in the long term as a possible adaptation for heat tolerance, without affecting breast meat quality. This study highlights the value of 2 new heritable characters involved in thermoregulation for further broiler selection.

Thermal manipulations during broiler incubation alter performance of broilers to 70 days of age

Recent decades have seen significant progress in the genetic selection of fast-growing broiler chickens. Whereas in many countries the average marketing age is 5 to 6 wk, the US, French, and other markets demand heavier broilers (~4 kg) that require a longer posthatching growing period. With greater age and greater BW, the ability to cope with hot weather conditions deteriorates, which can result in increased economic losses during periods of hot weather. Recent studies have demonstrated a long-lasting effect of intermittent thermal manipulation (TM) during embryogenesis, when it was applied for 12 h/d between embryonic (E) days E7 and E16, which was shown by improved thermotolerance during acute posthatching heat stress as well as improved feed conversion ratio (FCR) and breast muscle yield. The present study was designed to elucidate the effect of TM during embryogenesis on Cobb 500 broiler performance up to 70 d of age. Hatchability and male BW were not affected by TM, but TM females demonstrated a lower (P = 0.024) BW during the entire 70-d posthatching study. However, following embryonic TM, both sexes exhibited lower (P = 0.028 and P = 0.018 for males and females, respectively) feed intake and body temperature accompanied by improved FCR and greater breast muscle weight. In light of the present and previous studies, it was concluded that intermittent TM during broiler embryonic development had a long-lasting effect on energy balance that led to improved FCR and breast muscle yield.

Effect of β-hydroxy-β-methylbutyrate calcium on growth, blood parameters, and carcass qualities of broiler chickens

Beta-hydroxy-β-methylbutyrate (HMB), the metabolite of leucine, plays an important role in muscle protein metabolism. To investigate the effect of dietary HMB calcium (HMB-Ca) on growth performance, breast muscle development, and serum parameters in broiler chickens, a total of two hundred seventy 1-d-old Arbor Acres male broiler chicks were randomly allotted into 3 dietary treatments supplemented with 0, 0.05%, or 0.1% HMB-Ca during the starter (1 to 21 d) and grower (22 to 42 d) period. The results showed that broilers fed 0.1% HMB-Ca diet had higher ADG during the starter or the whole period, and gain 148 g more BW than the chicks fed the control diet at 42 d of age (P < 0.05). At 21 d of age, birds receiving 0.1% HMB-Ca had more breast muscle yield, less abdominal fat than the control, and more dressing percentage than birds fed the control or 0.05% HMB-Ca diet (P < 0.05). At 42 d of age, 0.1% HMB-Ca increased breast muscle yield than the control and decreased abdominal fat compared with the control or 0.05% HMB-Ca group (P < 0.05). In comparison with the control, feeding 0.1% HMB-Ca increased the triiodothyronine, thyroxine, triiodothyronine/thyroxine ratio and decreased the serum uric acid level at d 21 (P < 0.05). At 42 d of age, serum thyroxine level was elevated in the 0.05% HMB-Ca treatment, and the uric acid concentration was significantly decreased by the 0.1% HMB-Ca-supplemented diet (P < 0.05). Dietary HMB-Ca did not affect the growth hormone or insulin content. This study suggested that dietary supplementation of HMB-Ca improved growth performance, stimulated the breast muscle development, and decreased the abdominal fat deposition in broiler chickens, and the favorable effects were more pronounced in the starter phase. The growth promotion effect of HMB-Ca may be partly related to the increased serum thyroid hormones in broiler chickens.

Nutritional Value of Green Seaweed (Ulva Lactuca) for Broiler Chickens

The current work aimed to assess the potential of the green seaweed Ulva lactuca (U. lactuca) as an alternative ingredient in broiler chicken diets. The effect of substituting 1.0 or 3.0% of corn with U. lactuca on performance, carcass characteristics and serum constituents of broilers from 12 to 33 d of age was evaluated. Three treatments were distributed in a RCBD design: T1, control diet (0% U. lactuca); T2, 1.0 % U. lactuca; T3, 3.0 % U. lactuca. A total of 45 chicks were assigned to three treatments (5 replicates per treatment) used in this experiment. Cumulative feed intake (FI), body weight gain (BWG), feed conversion ratio (FCR) and nutrients retention from 12 to 33 d of age were not affected by treatment (P>0.05). Birds which had received T3 had a higher dressing percentage and breast muscle yield compared to those which had received T1 or T2. Serum total lipid, cholesterol and uric acid concentrations were significantly lower in birds which had received T2 and T3 (P<0.05). Serum enzymes and electrolytes were not influenced by any dietary treatment except for alanine transaminase (ALT) which was significantly lower for the treated groups. Based on presented evidences, it is recommended to substitute 3.0% of corn with green seaweed (U. lactuca).

Dietary arginine from 15 to 35 days of age affects feed intake and carcass yield in White Pekin ducks

An experiment was conducted to investigate the effect of dietary arginine (ARG) provided from 15 to 35 days of age on the feed intake and carcass yield of White Pekin ducks. Sixty 14-day-old White Pekin ducks were allotted to one of three dietary treatments, with 10 males and 10 females per treatment. Birds were kept individually and fed diets containing 0.60, 0.85 or 1.70% ARG for 3 weeks. Ducks that were fed the diet containing 1.70% ARG had greater bodyweight gain (P &lt; 0.05), higher feed intake (P &lt; 0.05), and a lower feed conversion ratio (P &lt; 0.05) than those fed the diet containing 0.60% ARG. The hypothalamic contents of neuropeptide Y and leptin at 35 days of age were not affected by dietary ARG levels. Breast muscle yield increased with each increment of dietary ARG content (P &lt; 0.05), and birds fed the diet containing 1.70% ARG had highest leg muscle yield (P &lt; 0.05) and total muscle yield (P &lt; 0.05); in contrast, the abdominal fat yield was not affected (P &gt; 0.05) by dietary ARG. No interaction between dietary ARG level and sex was observed for the above mentioned indices (P &gt; 0.05). In conclusion, dietary ARG supplementation promoted appetite without changing the concentrations of neuropeptide Y or leptin in hypothalamus, and ARG supplementation stimulated muscle growth, especially breast muscle growth, in growing White Pekin ducks of both sexes.

Effect of corticosterone on growth and welfare of broiler chickens showing long or short tonic immobility

Tonic immobility (TI) test is commonly used to assess fear. Animals showing different TI durations demonstrate distinct behavior and biochemical responses to stress. However, less is known about how TI phenotype affects growth and welfare of domestic fowl. In this study, broiler chickens (Gallus gallus) were classified into short and long TI duration (STI and LTI) phenotypes and treated chronically with vehicle (CON) or corticosterone (CORT). STI broilers demonstrated significantly higher growth rate with higher breast muscle yield (P<0.05) and liver weight relative to BW tended to be lower (P=0.053), which was accompanied by higher serum concentration of CORT (P<0.05) and uric acid (P<0.01), but lower serum level of T4 (P=0.01). CORT severely reduced body weight, as well as the relative weight of muscle, bursa of Fabricius and spleen (P<0.001), but relative liver weight was increased (P<0.001). CORT-treated chickens had reduced serum CORT, elevated heterophile/lymphocyte ratio, and increased serum levels of total and free T3. STI broilers displayed more preening behavior (P<0.05), yet CORT elicited more walking behavior (P<0.05). No difference was observed in the welfare assessment scores between STI and LTI phenotypes under basal situation, while LTI chickens showed significantly increased incidence of pad dermatitis compared to STI under CORT exposure. The results suggest that STI broilers demonstrate better growth performance and higher adaptability to stress compared to LTI chickens.

Analysis of a slow-growing line reveals wide genetic variability of carcass and meat quality-related traits

BackgroundSlow-growing lines are widely used in France for the production of high quality free-range chickens. While such production is mainly dedicated to the whole carcass market, new prospects are opening up for the development of cuts and processed products. Whether the body composition and meat quality of slow-growing birds can be improved by selection has thus become an important issue. The genetic parameters of growth, body composition and breast meat quality traits were evaluated in relation to behaviour at slaughter in a large pedigree population including 1022 male and female slow-growing birds.ResultsThe heritability coefficients (h2) of body weight and body composition traits varied from 0.3 to 0.5. Abdominal fat percentage was genetically positively correlated with body weight but negatively correlated with breast muscle yield. The characteristics of the breast meat (i.e., post-mortem fall in pH, colour, drip loss, shear-force and lipid content) were all heritable, with h2 estimates ranging from 0.18 to 0.48. The rate and extent of the fall in pH were under different genetic control. Strong negative genetic correlations were found between the ultimate pH and the lightness, yellowness and drip loss of the meat. Wing flapping on the shackle line was significantly heritable and exhibited marked genetic correlations with the pH at 15 min post-slaughter and the redness of the meat. The genetic relationships between meat quality traits, body weight and body composition appeared slightly different between males and females.ConclusionThis study suggested that there are a number of important criteria for selection on carcass and breast meat quality in slow-growing birds. Selection for reduced abdominal fatness and increased breast muscle yield should be effective as both traits were found to be highly heritable and favourably correlated. Substantial improvement in meat quality could be achieved by selection on ultimate pH which was highly heritable and strongly correlated with the colour and water-holding capacity of the meat. Moreover, this study revealed for the first time that the behaviour at slaughter is partly genetically determined in the chicken.

Effect of Dietary Phosphorus and Calcium on Performance of Broilers from 3 to 7 Weeks of Age

In this experiment the effects of total dietary phosphorus (TP) and calcium (Ca) on growth, feed conversion ratio, breast muscle yield, serum phosphorus (P), and bone measurements were examined. From 3 to 6 weeks, four levels of TP (4.5, 5.0, 5.5, and 6.0g kg−1) and two levels of Ca (7.0 and 9.0g kg−1) provided eight treatments. From 6 to 7 weeks, diets with two levels of TP (4.5 and 5.5g kg−1) and three levels of Ca (6.0, 7.0, and 8.0g kg−1) were used. Diets with 4.5g kg−1 TP did not contain a source of inorganic P. Interactions were detected for feed intake, weight gain, and serum P at 6 weeks. Birds fed 5.0, 5.5, and 6.0g kg−1 TP with 9.0g kg−1 Ca consumed more feed and gained more weight as compared to the other groups. Feed conversion of birds fed the 9.0g kg−1 Ca diet was lower than those fed diets with 7.0g kg−1 Ca. Serum P was increased (P &lt; 0.05) at the lowest level of TP when dietary Ca was lowered. Lowering the Ca level, in general, raised (P &lt; 0.05) serum P. Ash was a function of the amounts of TP and Ca in the diets; Ca and P contents of the bones were not affected by the dietary treatments (P &gt; 0.05). Interactions or main effects for TP and Ca were not detected for body weight gain, feed consumption, feed conversion, breast muscle yield, serum P and bone measurements at 7 weeks of age. Our findings demonstrate that from 3 to 6 weeks of age, dietary total P can be lowered to 5.0-5.5 g kg−1 while the inorganic P source can be removed in the finisher diets without loss in performance or bone integrity.

Nutritional value of breast and thigh muscle of chukar partridge (Alectoris chukar) under intensive fattening conditions

The aim of our study was to evaluate the nutritional value of the breast and thigh muscle of chukar partridge (Alectoris chukar) under intensive fattening conditions. Commercial feeding mixtures for broilers were used. Live weight of 60 partridges (birds were not sexed) was controlled during 90 days of fattening. After the fattening was finished, 30 birds were selected to monitor the carcass yield. Breast and thigh muscle were used for chemical analysis of crude protein (Kjeldahl method), total lipids (fat analyser ANKOMXT10), ash (Muffle furnace - 550° C) and gross energy (calorimetry). Average values ​​of live weight were increasing in the course of fattening; at the end of fattening the live weight reached 0.452 kg. The carcass yield, breast muscle yield and thigh yield were evaluated (73.72%, 18.09%, 20.80%, respectively). Chemical analysis showed a highly significant difference (P ≤ 0.01) between the breast and thigh muscle for crude protein, fat, ash and gross energy. The ash content demonstrated a significant difference (P ≤ 0.05) between the breast and thigh muscle. This study brings new data on the nutritional value of the meat of chukar partridge that can be used for reccomendation of a suitable feeding mixture.

Influence of Excess Lysine and Methionine on Cholesterol, Fat and Performance of Broiler Chicks

This study was carried out to determine the effects of excess dietary Lysine (Lys) and Methionine (Met) on some blood parameters, cholesterol and fat content of carcass and the performance of broiler chicks. In a completely randomized design three hundred male Ross 308 broilers were allotted to five group, each of which included four replicates (15 birds per replicate). The groups received the same basal diet supplemented with Lys and Met(as TSAA) in 0, 10, 20, 30 or 40% more than NRC (1994) recommendation. The collected data were analyzed by SPSS software and Duncan’s test was used to compare the means on a value of P< 0.05. The results indicated that the two highest levels of Lys and Met treatments (30 and 40% more than NRC recommendation) led to significant increase in carcass efficiency, breast muscle yield, heart and liver weight and also plasma cholesterol (P< 0.05), whereas feed conversion ratio (FCR), crude fat contents of breast and thigh muscles and plasma triglyceride were the least in these two treatment groups (P< 0.05). Addition Lys and Met 40% more than NRC tend to significant decrease in body weight gain but there was no significant effect of treatment on cholesterol content of the breast and thigh muscle and also thigh and leg yield. The finding of this experiment showed that increasing Lys and Met to diets of today’s broiler in excess of NRC recommendations can improve FCR, abdominal fat deposition, breast meat yield, fat content of the breast and thigh muscles and carcass efficiency and also results reported here support the hypothesis that it is possible to produce poultry meat with different fat content by supplementation excess Lys and Met to diet.