Regulation of feed intake in chickens represents a complex homeostatic mechanism involving multiple levels of control. Understanding the regulation of feeding behavior can be a very important theme in animal production. Recently, a close evolutionary relationship between the peripheral and hypothalamic neuropeptides has become apparent. In the infundibular nucleus (the avian equivalent of the mammalian arcuate nucleus), the melanocortin system, which contains neuroendocrine neurons that regulate endocrine secretions by releasing substances, is an essential site in the brain for signals about the status of peripheral energy balance. The structure and function of many hypothalamic neuropeptides, melanocortins, neuropeptide-Y (NPY) and agouti-related protein (AGRP) have been characterized. This review provides as overview of the various effects and interrelationship of these central and peripheral neuropeptides, and summarizes the role of the melanocortin system on feeding regulation in chicks.

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Introduction of genes into blastodermal cells is one of the procedures for chicken genetic modification in combination with construction of germline chimera. Currently, in vitro cultures of chicken blastodermal cells require feeder cells. In the present study, we employed a simple culture method of chicken blastodermal cells for their germline transmission without using feeder cells. The present study was undertaken to determine whether cultured blastodermal cells of Barred Plymouth Rock (i/i) contained periodic acid-schiff (PAS)-positive materials, alkaline phophatase (ALP), SSEA-1, and EMA-1, which are the markers of pluripotent cells including chicken embryonic stem cells (cESCs). The examination revealed that not all but a large portion of cultured cells contained those markers. Then, the cultured cells (i/i) were injected into White Leghorn recipients (I/I) to generate chimeric chickens. The chimeric chickens thus obtained were crossed with Barred Plymouth Rock, and the cross produced chicks with black feathers (i/i). This observation demonstrated that cultured blastodermal cells were transmitted to germ cells in a chimera. In conclusion, the present culture system provided a tool for genetic modification of chicken.

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The present study was conducted to investigate the effects of dietary cereals such as corn, sorghum, wheat, hulled barley and naked barley on amino acid digestibility using fistulized chickens. Chickens were fistulized to either the distal end of the jejunum, the middle part of the ileum, the distal end of the ileum or the distal end of the rectum. The cereals were supplemented as the sole source of protein in each experimental diet. Intestinal digesta were collected from each site of the intestines, and the contents of amino acids were measured. There was no significant difference in the true digestibilities of all measured amino acids between the sites of chicken intestines. However, the true digestibilities of 13 amino acids (Asp, Thr, Ser, Gly, Ala, Val, Met, Ile, Leu, Tyr, Phe, His and Arg) in the hulled barley group, 10 amino acids (Asp, Thr, Ser, Gly, Ala, Val, Met, Ile, Leu and Tyr) in the naked barley group, nine amino acids (Asp, Thr, Gly, Ala, Met, Ile, Leu, Tyr and Arg) in the wheat group and five amino acids (Gly, Met, Lys, His and Arg) in the sorghum group were lower than those in the corn group. These results clearly demonstrate that corn shows the highest amino acid digestibility among cereals used in this study and that there is no significant effect of sampling site on the amino acid digestibility of the dietary cereals.

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The effects of non-saponified lutein from marigold flower meal (MFM) and saponified lutein from marigold flower extract (MFE) on chicken egg yolk coloration was evaluated. A total of 90 laying hens were randomly divided into 9 groups: the basal diet (0mg/kg lutein; control) was supplemented with 10, 20, 30, and 40mg/kg lutein from MFM or MFE. During the three-week feeding experiment period, birds had free access to feed and water, and feed consumption and egg production were recorded weekly. Five eggs per group were evaluated weekly for egg quality such as shell-breaking strength, shell thickness, shell ratio, albumen ratio, yolk ratio, yolk color, and Haugh units. The egg yolk color was visually examined using the Roche Yolk Color Fan. The egg yolk color was further examined for yolk color, yellow index, lightness (L*), redness (a*), yellowness (b*), ratio of redness to yellowness (a/b), chroma, and spectrum wavelength reflectance using a spectrophotometer, an objective method. Feed consumption, body weight, egg production, egg mass, and egg quality with the exception of egg yolk color were not affected significantly by the dietary treatments. Compared with the yolk color parameters of the control, those of the dietary treatment groups tended to be higher; and the 40mg/kg lutein from MFM group and the 20, 30, and 40mg/kg lutein from MFE groups were significantly increased (P<0.001). In two-way ANOVA, the visual and objective egg yolk colors, a* and a/b were improved by both the dietary lutein treatment (P<0.05) and the lutein supplementation levels (P<0.001).
It was concluded that dietary lutein enhances egg yolk color at levels of approximately 30 to 40mg/kg, and that saponified lutein from MFE appears to be more effective in egg yolk color than non-saponified lutein from MFM.

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This work aimed at examining the interactive effect of maternal intake of astaxanthin (AX) and storage conditions (temperature and period) on the hatchability of fertilized eggs. Single comb White Leghorn laying hens were allocated to 4 groups with cocks. Experimental diets with 4 levels of AX were prepared by supplementing AX to a basal diet. AX levels were 0, 5, 10 and 20ppm. Eggs from each treatment group were stored for 0, 4, 7, 14 and 21 days at either 10 or 21°C of storage temperature with 70% of relative humidity. The number of hatched chicks was counted and un-hatched eggs were used to check the age of embryo death. When fertilized eggs were stored at 10°C, the hatchability was kept at high level regardless of storage period. At 10°C of storage temperature, maternal intake of AX had no effect on the hatchability of fertilized eggs. On the other hand, the hatchability of eggs stored at 21°C was significantly lower than that at 10°C, and lowered hatchability was restored by maternal intake of AX. Elevated levels of dietary AX from 5 to 20ppm gradually restrained the decrease in hatchability at 21°C. On the mortality of embryos from 0 to 7 days of incubation, the interaction between dietary AX levels and storage temperature was significant. However, after 7 days of incubation, there was no significant interaction between dietary AX levels and storage temperature, and the effect of AX was not significant. These results suggest that the lowered hatchability of eggs stored at high temperature was restored by maternal feeding of dietary AX, and the beneficial effect of AX may be effective at early stage of embryo development.

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In order to test whether exogenous coenzyme Q₁₀ (CoQ₁₀) can improve growth performance and heart mitochondrial function of broilers grown at high altitude, a study was conducted on a farm in Xining City of Qinghai Province of China at an altitude of 2,200m with a 78% of partial pressure of atmospheric oxygen (O₂) as compared to that at sea level. Three hundred, 1-d-old male, broilers (Arbor Acres) were divided into three groups and fed diets supplemented with 0mg (control, C), 20mg (Q1) or 40mg (Q2) CoQ₁₀ per kg feed. CoQ₁₀ supplementation increased body weight (BW) of broilers at 21d of age. BWs of Q1 (551.6±9.8g) and Q2 (509.4±10.7g) were higher than that of C (465.7±10.3g) at 21d of age (P<0.05). At 42d of age, BW of Q1 (2047.5±40.8g) was higher than that of C (1895.9±39.0g; P<0.05). Supplementation with CoQ₁₀ decreased heart weight as a percentage of total BW (P<0.05) and improved yield (% BW) of breast muscle (P<0.05) as compared to C. Supplementation with CoQ₁₀ at 40mg/kg feed decreased drip loss of breast muscle (P<0.05). Oxygen consumption of state III respiration and succinate-CoQ oxidoreductase (complex II) activity of heart mitochondria were increased by supplementation of CoQ₁₀ (P<0.05). Supplemental CoQ₁₀ at 40mg/kg feed increased state IV respiration rate (P<0.05). There was no significant difference in respiration control rate of heart mitochondria among the three treatment groups. Supplementation with CoQ₁₀ at 20mg/kg increased glutathione peroxidase activity (P<0.05), and concomitantly decreased (P<0.05) the content of malondialdehyde in serum of 35-d old broilers. These findings suggest that CoQ₁₀ can be used as a growth promoter in broilers at high altitude.

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An experiment was conducted to evaluate the effects of two commercial phytases on performance and bone mineralization of male broilers from two commercial strains when included into a diet marginal in both calcium (Ca) and non-phytate phosphorus (npP). Male chicks from two broiler strains (Strains 1 and 2; 320 of each) were placed on fresh bedding across 64 pens (10 birds/pen with 8 replicates/treatment). All birds were fed a corn-soybean meal diet (22% CP, 3,086kcal/kg) adequate in all nutrients except Ca and npP. Dietary treatments were arranged as a 2×4 factorial using 2npP/Ca combinations and four dietary treatments: 1) standard (0.45% npP, 1.0% Ca), 2) marginal (0.35% npP, 0.87% Ca), 3) marginal+500 FTU Phytase A, and 4) marginal+500FTU Phytase B. All diets were pelleted at 79°C, crumbled and provided from 0 to 21 days of age. Individual body weights and feed consumption were recorded at 21d of age and 24 birds per treatment were sacrificed for tibia breaking strength.
Chicks of Strain 2 were 1.7g heavier (P<0.05) than Strain 1 chicks at hatch, however there were no significant differences (P>0.05) in body weight at 21d of age. Body weight, body weight gain, feed consumption and bone strength were significantly decreased (P<0.05) in the marginal diet-fed birds in comparison with the standard diet-fed birds. However, all these parameters were completely reversed with supplementation of either Phytase A or B. Overall, live performance, bone breaking strength, and response to phytase supplementation were not affected by genetic strain or type of phytase utilized in the diet. These findings suggest that reducing dietary npP requires phytase supplementation to obtain normal growth performance and skeletal growth, regardless of commercial broiler strain.

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Changes in expression of proteolytic-related genes in chick myoblasts during myogenesis were investigated. Expression of MyoD and myogenin, as an index of differentiation, was regulated in chick myoblasts during myogenesis. Expression of PAX7, as an index of myoblast proliferation, was decreased during myogenesis. Expression of ubiquitin, atrogin-1/MAFbx, proteasome C2 subunit, m-calpain large subunit, cathepsin B, and caspase-3 mRNA of chick myoblasts was also decreased during myogenesis. These results show that the expression of proteolytic-related genes of myoblasts was decreased during myogenesis, resulting in an increase in differentiation of chick myoblasts.

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The purpose of this study is to clarify the effects of freeze-thaw treatment on viability and functionality of primordial germ cells (PGCs) in chickens. PGCs were collected separately from embryonic blood of White Leghorn, Barred Plymouth Rock and Fayoumi breeds. Some PGCs were labeled with the fluorescent lipophilic carbocyanine dye to analyze functionality by transfer assay. 100 PGCs were used for each experiment to ensure accuracy of the test results. In the experimental group, PGCs were slow-frozen, then stored in liquid nitrogen for 1 month. In the unfrozen control group, PGCs were utilized immediately. The recovery rate of PGCs after freeze-thaw was 54.3%. The viability of PGCs in the frozen group was significantly lower than that of the control group (P<0.05) (85.7% vs. 99.2%) with no significant difference between the three breeds. Thirty fluorescent-labeled PGCs were randomly chosen from each set of recovered PGCs after freeze-thaw in the frozen group, and from each set of 100 PGCs in the control group, for transfer into the bloodstream. Gonadal migration of transferred PGCs was observed in all embryos in both test and control groups. The number of PGCs settled in the gonads of embryos at stage 27 was 52.8% lower in the frozen group than in the unfrozen control group (P<0.05). In the control group, significant difference in establishment of PGCs in stage 27 gonads was observed between the three breeds, with White Leghorn chickens harboring the most PGCs, and Barred Plymouth Rock chickens the fewest. We conclude that freeze-thaw treatment causes a decrease in functionality of PGCs in chicken, with only an estimated 46.5% of frozen PGCs being viable after thawing.

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Chickens are an ideal animal model study tool for developmental biology, and a farm animal with excellent productivity. Researchers have therefore long sought to establish chicken embryonic stem cells (cESCs) to enable the creation of genetically modified chickens. Here, we derived novel cESCs from chicken blastodermal cells (CBCs) cultured with chicken leukemia inhibitory factor (chLIF). These cESCs have the capacity for long-term (100 days or more) successive subculture and express both chicken Nanog (chNanog) and chicken vasa homolog (Cvh) mRNAs and proteins. The cESCs showed a capacity for chimeric formation during a transplant experiment that used a fertilized egg. Transfer of the enhanced green fluorescent protein (EGFP) gene to cESCs enabled green fluorescence to be observed among primordial germ cells (PGCs). These results indicate that novel cESCs should have the capacity to differentiate into germ cells.

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The aim of this study was to examine the changes in the density of immunoreactive avian β-defensins (ir-avβDs) -3 and -11 in response to lipopolysaccharide (LPS). Healthy laying hens were intravenously injected with LPS (1mg/kg of body weight) at 0, 3, 6 and 12h (n=4) before tissue collection, which was uniformly 6h after oviposition. Their uterus tissues were fixed in formalin-PBS and processed for paraffin sections. Immunohistochemistry was then performed using polyclonal antibodies for avβD-3 and -11. Immunoreactive avβD-3 was localized in the supranuclear cytoplasm of the surface epithelial cells, whereas ir-avβD-11 was observed in the apical cytoplasm of those cells. The density of the immunoreaction products of avβD-3 showed a significant decrease at 3h after LPS injection compared to 0h group, and then returned to the original level by 6h. On the other hand, the density of the immunoreaction products of avβD-11 was significantly higher at 3h and 12h after LPS injection compared to the 0h group. These results suggest that avβD-3 protein was secreted, and avβD-11 was synthesized and stored in the mucosal epithelial cells in response to LPS injection. These two types of avβDs may play a significant role in the innate host defense in the hen uterus.

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