Endothermic heart rate response in broiler and White Leghorn chicks (Gallus gallus domesticus) during the first two days of post-hatch life

The embryonic modal value of heart rate (MHR) differs between broiler and White Leghorn chickens, but the initial development of cholinergic chronotropic control of embryonic heart rate (HR) does not. Thus, we hypothesized that hatchling MHR should also differ between broiler and White Leghorn strains, while the development of a physiological regulation, such as the endothermic HR response, should not be different between hatchlings of the two strains. To test this, we measured the response of HR and cloaca temperature (Tb) to alteration of ambient temperature (Ta); i.e., 35 degrees C-25 degrees C-35 degrees C, in four groups of hatchlings on Days 0 and 1 post-hatch. Fertile eggs of both strains with similar mass were incubated simultaneously in the same incubator. Eggs of broiler chickens hatched approximately 7 h earlier than White Leghorn chicken eggs. Chick mass at hatching was identical in both strains, but diverged during 2 days after hatching. Tb measured at the initial Ta of 35 degrees C was identical in both strains. MHR at the same Ta was approximately 30 bpm lower in broiler chicks than in White Leghorn chicks, but the difference was reversed to that observed in the embryos. The endothermic HR response was advanced by approximately 1 day in broiler chicks compared with White Leghorn chicks. As a result, eggs of similar mass in both strains produced chicks with similar mass and Tb at hatching, but during 2 days of post-hatch life their masses diverged and regulation of the endothermic HR response developed earlier in broiler than in White Leghorn hatchlings. This physiological heterochrony between strains is most likely due to genetic selection for fast growth in broiler chickens.     

Effect of genetic background on the developmental expression of c-fos and c-myc in chicken

The developmental expression of the protooncogenes, c-fos and c-myc, in muscle and liver of 14-and 19-day embryos and 1-, 6-, 8-and 28-day-old chicks of Athens Canadian Random Bred (ACRB) Single Comb White Leghorn (SCWL) and Peterson X Arbor Acres commercial broiler (PXAA) was determined. For the three stocks of chicken, significant differences were found in c-fos and c-myc expression. For both muscle and liver, averaged across ages, abundance of c-fos RNA was highest in PXAA and lowest in ACRB with differences significant at the P<0.01 level. c-myc RNA levels were significantly higher (P<0.01) in PXAA than in ACRB or SCWL liver. Taken over the developmental period, expression of c-fos RNA in muscle increased at different rates between breeds from 14-day embryo levels to peak levels in 6- to 8-day-old chicks and declined in 28-day-old chicks. Levels of c-fos were much lower in liver and showed no consistent differences related to developmental stage. A steady decline in c-myc from 14-day embryo levels to 28-day-old chicks was found in both muscle and liver. This decline in c-myc levels generally parallels the decline in relative growth rates which occurs in all breeds over the developmental period. In liver, the fast growing PXAA had the highest levels of c-myc. c-fos, on the other hand, showed elevated levels in PXAA for both muscle and liver and distinctly different patterns between these two tissues over the developmental period, suggesting tissue-specific involvement in growth.     

Pathogenicity of Genetically Similar,H5N1 Highly Pathogenic Avian Influenza Virus Strains in Chicken and the Differences in Sensitivity among Different Chicken Breeds

Differences in the pathogenicity of genetically closely related H5N1 highly pathogenic avian influenza viruses (HPAIVs) were evaluated in White Leghorn chickens. These viruses varied in the clinical symptoms they induced, including lethality, virus shedding, and replication in host tissues. A comparison of the host responses in the lung, brain, and spleen suggested that the differences in viral replication efficiency were related to the host cytokine response at the early phase of infection, especially variations in the proinflammatory cytokine IL-6. Based on these findings, we inoculated the virus that showed the mildest pathogenicity among the five tested, A/pigeon/Thailand/VSMU-7-NPT/2004, into four breeds of Thai indigenous chicken, Phadu-Hung-Dang (PHD), Chee, Dang, and Luang-Hung-Khao (LHK), to explore effects of genetic background on host response. Among these breeds, Chee, Dang, and LHK showed significantly longer survival times than White Leghorns. Virus shedding from dead Thai indigenous chickens was significantly lower than that from White Leghorns. Although polymorphisms were observed in the Mx and MHC class I genes, there was no significant association between the polymorphisms in these loci and resistance to HPAIV.     

Production of somatic and germline chimeras in the chicken by transfer of early blastodermal cells

Cells were isolated from stage X embryos of a line of Barred Plymouth Rock chickens (that have black pigment in their feathers due to the recessive allele at the I locus) and injected into the subgerminal cavity of embryos from an inbred line of Dwarf White Leghorns (that have white feathers due to the dominant allele at the I locus). Of 53 Dwarf White Leghorn embryos that were injected with Barred Plymouth Rock blastodermal cells, 6 (11.3%) were phenotypically chimeric with respect to feather colour and one (a male) survived to hatching. The distribution of black feathers in the recipients was variable and not limited to a particular region although, in all but one case, the donor cell lineage was evident in the head. The male somatic chimera was mated to several Barred Plymouth Rock hens to determine the extent to which donor cells had been incorporated into his testes. Of 719 chicks hatched from these matings, 2 were phenotypically Barred Plymouth Rocks demonstrating that cells capable of incorporation into the germline had been transferred. Fingerprints of the blood and sperm DNA from the germline chimera indicated that both of these tissues were different from those of the inbred line of Dwarf White Leghorns. Bands that were present in fingerprints of blood DNA from the chimera and not present in those of the Dwarf White Leghorns were observed in those of the Barred Plymouth Rocks.(ABSTRACT TRUNCATED AT 250 WORDS)     

Different endogenous viral loci in Cornish and White Plymouth rock chickens

Summary Endogenous viral (ev) loci were studied in three broiler lines. In 5 birds of each of line cw1 and line cw2 (White Plymouth Rock lines) 19 and 14, respectively, different SstI ev-junction fragments were found, while in 8 R line birds (Cornish type) 15 different Sst I junction fragments were found. Further characterization of the line R loci with a second restriction enzyme, BamHI, revealed that these junction fragments represent 25 different loci, of which at least 21 have not been reported previously. SstI RFLP analysis of progeny from crosses between chickens of the three broiler lines and White Leghorns demonstrated that within line R and cw1 approximately 90% of the ev loci were hemizygous. In line cw2 at least 50% of the ev loci were hemizygous. There was no evidence for polymorphic loci, and only two ev loci were found to be linked genetically. Intertype crosses revealed that overall differences in the RFLP patterns observed between Cornish, White Plymouth Rock and White Leghorn chicken lines were due to the presence of different ev loci in each of the lines rather than to polymorphism. The few shared ev loci always contained similar allelic fragments.     

Induced liver tumour deaths by subgroup A Rous sarcoma virus in chicks inoculated via chorioallantoic membrane, a genetic marker

A study was made using two strains of light breed (White Leghorn strains, A and B) and four heavy beeds (Rhode Island Red, New Hampshire, Australorp, Columbian) to evaluate the breed difference in survival potential of chicks that were infected as 11-day-old embryos via chorioallantoic membranes (CAMs) with a subgroup A Rous sarcoma virus. Of the 1185 chicks hatched over multiple hatch-replicates, 845 chicks died rapidly of a fibrosarcomatous liver tumour (LT) with a peak mortality about 74% attained by the second week, post-hatch, in the heavy breeds and more than 90% by the second week in the light breed. The breeds did not differ in induced LT mortality when the chicks hatched from eggs that had at least 25 pock counts on CAMs, apparently genetically susceptible, i.e. 25 biologically active virus particles were enough to induce an unpreventable fatal LT. However, low pock-count on CAMs did not act as a pointer for predicting genetic resistance to infection because about 23% of chicks developed from eggs that had no pocks on CAMs, apparently genetically resistant, also died of LT, requiring further studies.     

Differences in the structure of the rete ophthalmicum among three breeds of domestic fowls,Gallus gallus f. domesticus (Aves)

Summary The morphology of the rete ophthalmicum, which functions as a brain cooling system, was studied in the desert-origin Bedouin fowl in comparison with two commercial breeds: the White Leghorn and the White Plymouth Rock.Cross-sections of the rete ophthalmicum revealed a significantly higher degree of arteriovenous contact in the Bedouin fowl than in the commercial breeds (P<0.01). Based on the allometric relationship between the heat exchange area in the rete and body weight, the Bedouin fowl has a significantly higher heat exchange area than non-Bedouin fowls of similar body weights (P<0.02).These findings suggest that the higher heat exchange area and the high degree of arteriovenous contact in the rete ophthalmicum of the Bedouin fowl is an adaptation to desert conditions, and contributes functionally to the apparently superior heat resistance in this desert breed.     

Phylogenetic analysis in chicken breeds inferred from complete cytochrome b gene information

Complete cytochrome b (cyt b) gene (1140 bp) nucleotide sequences were used to investigate characteristics of the genetic constitution of Chunky broiler chickens, and these were compared with the Hy-Line and WL-GM (Garber) line of White Leghorn, the GSP line of Fayoumi, the BM-C line of Black Minorca (egg-chickens), and an outgroup of wild-origin Japanese quail. A high genetic difference (five haplotypes) was observed at the cytochrome b region in the Chunky broiler in contrast to the high homologies observed among the other chicken breeds (egg-purpose). Chunky broilers can be distinguished from the other breeds (White Leghorn, Fayoumi, and Black Minorca) at positions 552 and 779. The molecular phylogenetic tree exhibited genetic differences within Chunky broilers, and between Chunky broilers and the other three chicken breeds. As a result, some chicken strains or breeds apparently different from the other egg-chickens may have contributed to the Chunky broiler formation. Artificial selection may be one of the biggest factors causing nucleotide diversity in the chicken breeds.     

Genetic characterization of biodiversity in highly inbred chicken lines by microsatellite markers

Forty-two microsatellite loci were analysed in 23 highly inbred chicken lines derived from Leghorn, Jungle Fowl, Fayoumi and Spanish breeds. Line-specific alleles among breeds and lines were detected. The band-sharing (BS) values were calculated and the proportion of shared alleles distances (Dps) were estimated. The BS values and Dps between sets of MHC-congenic lines ranged from 0.74 to 0.96, and 0.05-0.35, respectively. The BS values between each pair of noncongenic Leghorn lines were 0.32-0.97, and between Leghorn and exotic (Jungle Fowl, Fayoumi and Spanish) breeds were 0.03-0.55. The Dps between Fayoumi lines and other lines were much larger (0.66-1.34) than within Leghorns, and the Jungle Fowl breed had the largest distances with other lines (1.12-5.38). The phylogenetic consensus tree that was constructed grouped these 23 inbred chicken lines into four different clusters. These results are in accordance with the origin and breeding history of these inbred lines, which indicates that the use of microsatellites for the study of genetic biodiversity is accurate and reliable. In addition, the significance and value of inbred chicken lines in molecular genetic research is discussed.     

Genome‐wide association study reveals novel variants for growth and egg traits in Dongxiang blue‐shelled and White Leghorn chickens

This study was designed to investigate the genetic basis of growth and egg traits in Dongxiang blue‐shelled chickens and White Leghorn chickens. In this study, we employed a reduced representation sequencing approach called genotyping by genome reducing and sequencing to detect genome‐wide SNPs in 252 Dongxiang blue‐shelled chickens and 252 White Leghorn chickens. The Dongxiang blue‐shelled chicken breed has many specific traits and is characterized by blue‐shelled eggs, black plumage, black skin, black bone and black organs. The White Leghorn chicken is an egg‐type breed with high productivity. As multibreed genome‐wide association studies (GWASs) can improve precision due to less linkage disequilibrium across breeds, a multibreed GWAS was performed with 156 575 SNPs to identify the associated variants underlying growth and egg traits within the two chicken breeds. The analysis revealed 32 SNPs exhibiting a significant genome‐wide association with growth and egg traits. Some of the significant SNPs are located in genes that are known to impact growth and egg traits, but nearly half of the significant SNPs are located in genes with unclear functions in chickens. To our knowledge, this is the first multibreed genome‐wide report for the genetics of growth and egg traits in the Dongxiang blue‐shelled and White Leghorn chickens.     

Primary sex ratio in fertilized chicken eggs (Gallus gallus domesticus) depends on reproductive age and selection

Recent studies of several avian species have shown that the primary sex ratio can change as a result of prevailing conditions, especially in the female bird's first reproductive season. In this study, we sought to determine the primary sex ratio of the first 15 eggs produced in chickens. The study compared chickens which had been commercially selected over many generations for egg-laying performance (Leghorns) with "fancy-bred" chickens selected for feather coloration. These fancy-bred chickens are known to reach reproductive maturity 4 weeks later than Leghorns. A group of precociously matured Leghorn chickens was produced by modification of diet and day length to investigate the effect of age at reproductive maturity on sex ratio. Sex diagnosis was performed on embryos which had died on or before embryonic day 10 by polymerase chain reaction (PCR). Living embryos were allowed to hatch before sex diagnosis. The group of precociously matured White Leghorns reached egg-laying age 3 weeks earlier than normal. In this group, the sex ratio of hatched chicks was in tendency skewed to females. In the White Leghorns maintained under normal conditions for commercial layers, sex ratio was balanced with a tendency to more males only in the first five eggs. In the group of fancy-bred chickens, the primary sex ratio was significantly biased toward more males and dependent on the laying sequence. Our data suggested a sex ratio bias toward males in the very first eggs at onset of reproduction in chickens depending on genetic background.     

Oxygen affinity of red cells hemolysates of different hen breeds

Summary Oxygen affinity and number of -SH groups of hemoglobins have rather constant values for hens belonging to Leghorn, Whiterock, Rhode Island Red, Sussex and Cornish breeds, and for hybrids between Rhode Island Red and Leghorn, irrespective of the breed. Number of -SH groups in red cell hemolysates amounts to 8 per mole Hb (7,88 – 8,48) , logp₅₀=1,04–0,94; value of n for Leghorns is 1,70, for Whiterocks 2,80.This work was performed within the project 09.3.1 of Polish Academy of Sciences.     

Genetic polymorphisms of proteins in different breeds and different populations of chickens

Six polymorphic protein systems in 15 chicken breeds have been investigated. In the Silkie breed another variant of G3 proteins (G₃ A^F Silkie) has been observed characterized by higher electrophoretic mobility than G₃ A. The frequencies of individual alleles in various lines and different generations have been determined in two breeds (White Leghorn and White Cornish).     

Assessment of functional gametes in chickens after transfer of primordial germ cells

The ability of primordial germ cells (PGCs) transferred from donor to recipient embryos to form functional gametes was assessed using feather colour as a phenotypic marker. Donor primordial germ cells were obtained in blood samples taken from Dwarf White Leghorn embryos, homozygous for the dominant allele at the locus for 'dominant white' plumage (I), which had been incubated for 52 h. Blood samples containing PGCs were transferred by intravascular injection to Barred Plymouth Rock embryos (ii) incubated for 53, 72 and 96 h. Of the embryos which hatched, 28 were male and 31 were female. All chicks were raised to sexual maturity and test mated with Barred Plymouth Rock fowl. All of the 3117 offspring exhibited the typical Barred Plymouth Rock phenotype; no Barred Plymouth Rock x Dwarf White Leghorn chicks were obtained. The results of this study suggest that the frequency of transmission of the donor line genotype after PGC transfer must be improved for this technique to be useful for the routine development of transgenic poultry.     

Short Copy Number Variations Potentially Associated with Tonic Immobility Responses in Newly Hatched Chicks

Introduction

Tonic immobility (TI) is fear-induced freezing that animals may undergo when confronted by a threat. It is principally observed in prey species as defence mechanisms. In our preliminary research, we detected large inter-individual variations in the frequency and duration of freezing behavior among newly hatched domestic chicks (Gallus gallus). In this study we aim to identify the copy number variations (CNVs) in the genome of chicks as genetic candidates that underlie the behavioral plasticity to fearful stimuli.

Methods

A total of 110 domestic chicks were used for an association study between TI responses and copy number polymorphisms. Array comparative genomic hybridization (aCGH) was conducted between chicks with high and low TI scores using an Agilent 4×180 custom microarray. We specifically focused on 3 genomic regions (>60 Mb) of chromosome 1 where previous quantitative trait loci (QTL) analysis showed significant F-values for fearful responses.

Results

ACGH successfully detected short CNVs within the regions overlapping 3 QTL peaks. Eleven of these identified loci were validated by real-time quantitative polymerase chain reaction (qPCR) as copy number polymorphisms. Although there wkas no significant p value in the correlation analysis between TI scores and the relative copy number within each breed, several CNV loci showed significant differences in the relative copy number between 2 breeds of chicken (White Leghorn and Nagoya) which had different quantitative characteristics of fear-induced responses.

Conclusion

Our data shows the potential CNVs that may be responsible for innate fear response in domestic chicks.     

Effects of breeds and dietary protein levels on the growth performance, energy expenditure and expression of avUCP mRNA in chickens

The physiological mechanisms of thermogenesis, energy balance and energy expenditure are poorly understood in poultry. The aim of this study was designed to investigate the physiological roles of avian uncoupling protein (avUCP) regulating in energy balance and thermogenesis by using three chicken breeds of existence striking genetic difference and feeding with different dietary protein levels. Three chicken breeds including broilers, hybrid chickens, and non-selection Wuding chickens were used in this study. Total 150 chicks of 1 day of age, with 50 from each breed were reared under standard conditions on starter diets to 30 days. At 30 days of age, forty chicks from each breed chicks were divided into two groups. One group was fed low protein diet (LP, 17.0 %), and the other group was fed high protein diet (HP, 19.5 %) for 60 days. Wuding chickens showed the lowest feed conversion efficiency (FCE) and the highest expressions of avUCP mRNA association with high plasma T3 and insulin concentrations. Hybrid chickens showed the lowest expressions of avUCP mRNA association with high FCE and energy efficiency. Expressions of avUCP mRNA association with diet-induced thermogenesis (DIT) were only observed in broiler and hybrid chickens. The expressions of avUCP mRNA were positive association with plasma insulin, T3 and NEFA concentrations. Age influence on the expression of avUCP mRNA were observed only for hybrid and broiler chickens. It seems that both roles of avUCP regulation thermogenesis and lipid utilisation as fuel were observed in the present study response to variation in dietary protein and breeds.     

The refractive development of the eye of the American kestrel (Falco sparverius): a new avian model

Summary Most measures of avian visual performance are carried out on commonly available domestic species such as the chicken, and most of the data on avian induced refractive error deals with chickens. Raptors are predatory birds in which good visual resolving ability is particularly important. Behavioral studies indicate that the eyes of raptors have two to three times the resolving ability of the human eye. The domestic chicken is precocial at hatching whereas most raptors are semi-altricial. This study was an effort to determine if the effect of early visual deprivation on the refractive development of the chicken eye can be reproduced in the American kestrel, a species which is not domesticated and in which the need for acute vision is particularly important.Visual deprivation was achieved by unilaterally applying translucent plastic goggles over the eyes of kestrels two days after hatching. Refractive error was measured using a retinoscope and trial lenses. Ocular growth was monitored by A-scan ultrasonography, and frozen ocular sections of sacrificed birds. The effect of the experimental manipulation on the contralateral control eye and body weight was evaluated each day over a 42-day period. The goggles did not significantly affect the normal changes in body weight or the normal pattern of ocular growth and refractive development in the untreated eyes. An analysis of the refractive state changes as a result of form deprivation was made each week for 6 weeks after hatching on both the treated and untreated eyes in a separate group of experimental birds. Visual form deprivation caused a significant myopic shift in refractive error and a significant increase in the vitreous chamber depth in the treated eyes at 3 and 6 weeks of age. However, the amount of myopia produced is much less than that induced in chicks, and in certain cases hyperopia is produced. The kestrels recover from myopia and hyperopia within 10 days of goggle removal, after 3 to 4 weeks of deprivation.This study is the first indication that chickens may not be a representative bird model for studying form deprivation myopia. First, myopia is not always produced in kestrels in response to form deprivation. Second, kestrels are severely myopic at hatching and therefore, the direction of emmetropization is opposite to that found in hatchling chicks.