Gallus Gallus Research Articles

Keel bone fractures are more prevalent in White Leghorn hens than in Red Jungle fowl hens-A pilot study.

Fractures and deviations to the keel bone are common in commercial laying hens, with reported variations in occurrence across strains and breeds. The aetiology is not fully understood, however, modern genetics and selection for efficient egg production has been claimed to be important factors for the keel bone fractures. To explore this further, we investigated keel bones from two different breeds, representing different degrees of selection for egg production: Red jungle fowl (n = 82), and White Leghorn (n = 32), where the latter is a selected laying breed which is the origin for many modern laying hen hybrids. Keel bones from a total of 116 birds, 53 hens and 63 roosters, were examined by necropsy at 80 weeks of age. All birds were raised in modified aviaries in the same holding facility. Overall, 24.5% of the hens had one or more fractures to the keel, with a difference in the prevalence between hens from the two breeds (p<0.01): 10% (95% CI: 3.7–24%) in the Red Jungle fowl hens and 69% (95% CI: 37–90%) in the White Leghorn hens. No roosters, regardless of breed, had keel bone fractures. Mild to moderate keel bone deviations were present in 54% (95% CI: 25–80%) of the hens and 4.7% (95% CI: 0.5–30%) of the roosters, all White Leghorns.

Population Genetic Structure and Contribution of Philippine Chickens to the Pacific Chicken Diversity Inferred From Mitochondrial DNA.

The Philippines is considered one of the biodiversity hotspots for animal genetic resources. In spite of this, population genetic structure, genetic diversity, and past population history of Philippine chickens are not well studied. In this study, phylogeny reconstruction and estimation of population genetic structure were based on 107 newly generated mitochondrial DNA (mtDNA) complete D-loop sequences and 37 previously published sequences of Philippine chickens, consisting of 34 haplotypes. Philippine chickens showed high haplotypic diversity (Hd = 0.915 ± 0.011) across Southeast Asia and Oceania. The phylogenetic analysis and median-joining (MJ) network revealed predominant maternal lineage haplogroup D classified throughout the population, while support for Philippine–Pacific subclade was evident, suggesting a Philippine origin of Pacific chickens. Here, we observed Philippine red junglefowls (RJFs) at the basal position of the tree within haplogroup D indicating an earlier introduction into the Philippines potentially via mainland Southeast Asia (MSEA). Another observation was the significantly low genetic differentiation and high rate of gene flow of Philippine chickens into Pacific chicken population. The negative Tajima’s D and Fu’s Fs neutrality tests revealed that Philippine chickens exhibited an expansion signal. The analyses of mismatch distribution and neutrality tests were consistent with the presence of weak phylogeographic structuring and evident population growth of Philippine chickens (haplogroup D) in the islands of Southeast Asia (ISEA). Furthermore, the Bayesian skyline plot (BSP) analysis showed an increase in the effective population size of Philippine chickens, relating with human settlement, and expansion events. The high level of genetic variability of Philippine chickens demonstrates conservation significance, thus, must be explored in the future.

Fatty acid profile in the breast and thigh muscles of the slow- and fast-growing birds under the same management system.

The aim of the study was to assess the effect of feeding the same diet to different breeds of chickens and at different ages on fatty acid (FA) composition of the breast and thigh muscles. A total of 150 chickens comprising 50 each of red jungle fowl (RJ) and village chicken (VC), the slow-growing birds, and the commercial broiler (CB), fast-growing birds, were used for this study. Ten chickens from each breed were serially euthanized at days 1, 10, 20, 56, and 120 post hatch, and pectoralis major and bicep femoris were harvested to represent the breast and thigh muscles respectively. It was revealed that the breast muscle concentrations of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and total polyunsaturated fatty acids (PUFA) are significantly different (p<0.05) among the breeds. Also, the FA composition of breast and thigh muscles among RJ, VC, and CB at various ages studied varied significantly (p<0.05) but without a definite pattern. The composition of MUFA was lower, but that of PUFA was higher in the RJ and VC than in the CB breast muscles. Within the breeds, the composition of total MUFA decreased, while that of PUFA increased with age. The total MUFA and PUFA showed no significant difference (p>0.05) between the breast and thigh muscles at different ages evaluated. This study suggests that slow-growing birds (RJ and VC) might be better sources of desirable FA than the fast-growing birds, CB.

Preliminary Qualitative Evaluation of the Anatomical Structures for Vocalization in the Chicken (Gallus gallus domestica)

The anatomical structure of phonation in the domestic chicken Gallus gallus (red jungle fowl, forma domestica) of both sexes was studied to determine sex variations in structures. Ten (10) birds, involving 5 males and 5 females were obtained from a local market for student demonstrations and used for this study. Tracheal rings were observed to be made of circular cartilages numbering thirty and above with the distal most (1/5) tracheal rings narrowed, calcified and fused as the tympanum making part of the Syrinx. The rings become calcified and somewhat collapsed through the bronchial bifurcations. When squeezed, the trachea collapsed completely between fingers but could at releasing the fingers be raised up due to elastic components separating the rings from one another. Other structures involved in vocalization includes straps of muscles. Male structures involved in respiration and vocalization were well formed compared to those of the female. Both tracheobronchialis lateralis and ventralis muscles were thicker than those of the female. Male tracheobronchialis ventralis and dorsalis muscles were well formed and spindle shaped. However, the female tracheobronchialis muscles were seen to be wider compared to the male. The vocal organs (voice box) were seen to be arbitrarily triangular in structure at the bifurcation of the trachea in both sexes. The male Syringeal walls were thinner and were seen to have marked inter Pessula space. The Pessulus mark an abrupt change from the circular trachea to strongly elliptical entrances to the bronchi. It was concluded that the differences in the thinness of syringeal walls coupled with differences between the males and females in other tracheal muscles might be responsible for the stronger vocalization in the male.

Impulsivity is affected by cognitive enrichment and links to brain gene expression in red junglefowl chicks

Despite reported findings, explanations for within-species variation in behavioural performance on cognitive tests are still understudied. Cognitive processes are influenced by environmental and genetic differences, where cognitive stimulation and monoaminergic systems are predicted to be important. To explore explanations for individual variation in impulsivity (a behaviour that is negatively correlated with inhibitory control), we experimentally altered the environment of red junglefowl, Gallus gallus , by exposing chicks from newly hatched to 9 weeks old to either (1) both environmental and cognitive enrichment, (2) environmental enrichment without additional cognitive enrichment or (3) neither environmental nor cognitive enrichment. Subsequently, we measured variation in impulsivity and brain gene expression of genes from the dopaminergic system ( DRD1 and DRD2 ) and serotonergic system ( 5HT2A, 5HT1B, 5HT2B, 5HT2C and TPH ). We focused on two aspects of impulsivity, impulsive action and persistence, and their reduction over time. Cognitively enriched chicks tended to have higher initial impulsive action and had higher initial persistence, and our environmentally enriched chicks had slower reduction of impulsive action over time. DRD2 (a dopamine receptor gene) had lower expression in environmentally enriched chicks. Variation in impulsive action tended to correlate with expression of TPH (a gene involved in serotonin synthesis), whereas persistence correlated with both TPH and the dopamine receptor gene DRD1 , and tended to correlate with the dopaminergic gene DRD2 , regardless of rearing treatment. These results indicate that both environment and links to neurobiology could explain initial individual variation in, and reduction of, impulsivity. Further, distinct neurobiological pathways appear to govern impulsive action versus persistence, supporting the suggestion that impulsivity is a heterogenic behaviour. • We studied effects of experimentally altered rearing experiences on impulsivity. • We measured two aspects of impulsivity: impulsive action and persistence. • Cognitive enrichment affected impulsivity and rate of inhibiting impulsivity. • Brain monoaminergic gene expression linked to both aspects of impulsivity. • Thus, both environment and neurobiology contribute to variation in impulsivity.

Red Junglefowl Chicks Seek Contact With Humans During Foraging Task.

Contact seeking with humans is documented in some domestic animals, mainly dogs, which have advanced communication skills. Domestication as a companion animal is thought to underlie this ability. However, also domesticated horses and goats display similar human-directed behaviors. This suggests either a broader effect of domestication on contact-seeking behavior, or alternatively, that social interactions with humans can result in the development of human contact seeking. As part of another study, we observed contact-seeking behavior in juvenile red junglefowl (Gallus gallus) chicks exposed to behavioral training since hatching, during a foraging task, where chicks were singly required to collect food rewards in a familiar arena using odor cues. If chicks left the arena, we recorded if they approached and looked up at the experimenter, or if they approached other objects (including another human). Chicks approached the experimenter significantly more often than they approached other objects. This behavior was not linked to a fast performance in the test arena, which gave some birds more time to explore the surroundings, or to learning ability measured in a cognitive task. Yet, the preference for the experimenter was lower for chicks that were handled more prior to the experiment. Also, approach probability was positively correlated with escape attempts in a novel arena test. The observed variation in approach behavior suggests a link to aspects of personality, and exposure to human interactions and experimental procedures. Our observations suggest that, although neither domesticated nor selectively bred, red junglefowl that are socialized with humans can potentially develop behavior used to describe contact seeking. Together with evidence from cognitive and behavioral studies, our results suggest that social experiences, not only domestication, can affect human-animal interactions. We propose how interactions between behavior, cognition and handling could be studied further in controlled settings to validate the preliminary findings of our study and uncover the underlying mechanisms.

Large-scale genomic analysis reveals the genetic cost of chicken domestication

BackgroundSpecies domestication is generally characterized by the exploitation of high-impact mutations through processes that involve complex shifting demographics of domesticated species. These include not only inbreeding and artificial selection that may lead to the emergence of evolutionary bottlenecks, but also post-divergence gene flow and introgression. Although domestication potentially affects the occurrence of both desired and undesired mutations, the way wild relatives of domesticated species evolve and how expensive the genetic cost underlying domestication is remain poorly understood. Here, we investigated the demographic history and genetic load of chicken domestication.ResultsWe analyzed a dataset comprising over 800 whole genomes from both indigenous chickens and wild jungle fowls. We show that despite having a higher genetic diversity than their wild counterparts (average π, 0.00326 vs. 0.00316), the red jungle fowls, the present-day domestic chickens experienced a dramatic population size decline during their early domestication. Our analyses suggest that the concomitant bottleneck induced 2.95% more deleterious mutations across chicken genomes compared with red jungle fowls, supporting the “cost of domestication” hypothesis. Particularly, we find that 62.4% of deleterious SNPs in domestic chickens are maintained in heterozygous states and masked as recessive alleles, challenging the power of modern breeding programs to effectively eliminate these genetic loads. Finally, we suggest that positive selection decreases the incidence but increases the frequency of deleterious SNPs in domestic chicken genomes.ConclusionThis study reveals a new landscape of demographic history and genomic changes associated with chicken domestication and provides insight into the evolutionary genomic profiles of domesticated animals managed under modern human selection.

Shifts in growth, but not differentiation, foreshadow the formation of exaggerated forms under chicken domestication.

Domestication provides an outstanding opportunity for biologists to explore the underpinnings of organismal diversification. In domesticated animals, selective breeding for exaggerated traits is expected to override genetic correlations that normally modulate phenotypic variation in nature. Whether this strong directional selection affects the sequence of tightly synchronized events by which organisms arise (ontogeny) is often overlooked. To address this concern, we compared the ontogeny of the red junglefowl (RJF) (Gallus gallus) to four conspecific lineages that underwent selection for traits of economic or ornamental value to humans. Trait differentiation sequences in embryos of these chicken breeds generally resembled the representative ancestral condition in the RJF, thus revealing that early ontogeny remains highly canalized even during evolution under domestication. This key finding substantiates that the genetic cost of domestication does not necessarily compromise early ontogenetic steps that ensure the production of viable offspring. Instead, disproportionate beak and limb growth (allometry) towards the end of ontogeny better explained phenotypes linked to intense selection for industrial-scale production over the last 100 years. Illuminating the spatial and temporal specificity of development is foundational to the enhancement of chicken breeds, as well as to ongoing research on the origins of phenotypic variation in wild avian species.

Effect of glutathione on pre and post-freezing sperm quality of Indian red jungle fowl (Gallus gallus murghi)

During cryopreservation sperm encounter oxidative stress due to higher production of ROS molecules and insufficient natural antioxidant defence system. Therefore, present study was designed to identify the effects of various glutathione (GSH) concentrations on Indian red jungle fowl (Gallus gallus murghi) sperm quality and fertility pre-freezing and post-thaw incubation hours. Semen was collected from eight cocks and qualified semen ejaculates having motility >65% were pooled after initial evaluation. Semen was divided in four aliquots, diluted with red fowl extender (1:5) at 37 °C having GSH 0 mM (control), 0.1 mM, 0.5 mM and 1.0 mM, cryopreserved and stored at (−196 °C) in liquid nitrogen. Semen quality was assessed at post dilution, cooling, equilibration, and freeze-thawing at 0, 2 and 4 h of incubation at 37 °C. Sperm motility, plasma membrane integrity, viability, acrosome integrity and mitochondrial function were recorded highest (P < 0.05) with 0.5 mM GSH in extender at post-dilution, cooling, equilibration, freeze-thawing and 0, 2 and 4 h of incubation. Lipid peroxidation in sperm and seminal plasma were recorded lowest (P < 0.05) with 0.5 mM GSH during cryopreservation stages and post-thawing incubation. Moreover, antioxidant activities (total antioxidant potential and free radical scavenging capacity) were recorded highest (P < 0.05) in extender having 0.5 mM GSH. Fertility rates were recorded higher (P < 0.05) with 0.5 mM GSH compared to control. It is concluded that 0.5 mM GSH in extender improves sperm structural (sperm viability, plasma membrane integrity and acrosome integrity), functional integrity (motility, mitochondrial function) and fertility parameters of Indian red jungle fowl through enriching antioxidant potential and ameliorating the oxidative stress.

Early nutrition programing - an approach for improving production performance of Indonesian Native Chicken – Kampung Chicken

Indonesia is considered as one the major chicken domestication centers in the world due to distinctive characteristics of chickens in this country compared to those in Asia and other countries in the world. Based on molecular studies, Red Junglefowl (Gallus gallus) is strongly presumed as the ancestor of the of Indonesian native chicken (INC). Through domestication processes, now, there are at least 30 different clumps of INC, which can be grouped into identifiable clumps with specific characteristics (colour, sound, etc, such as Pelung, Kedu, etc), and the non-identifiable clump with no specific characteristic, and usually called Kampung chicken. Kampung chicken clump represent the highest population among local chickens, and most of them are raised under an extensive traditional system. They are having very high genetic variation and diverse physical appearances (body size, colour, sound), and the most of them has not been modified gentically. Compared with exotic commercial breed, both broiler or layer, Kampung chicken has lower in production and reproduction, very slower growth rate and poorer feed efficiency. However, from market point of view, Kampung chicken products have better prices and consumer preferences. This market condition is certainly an opportunity to fill and to develop market of Kampung chicken. Additionally, this condition also motivates the farmers improving Kampung chicken production as their livelihood. As an approach, Early Nutrition Programming (ENP) may be a complementary of various previous efforts carried out to improve the performance of Kampung chicken. The program is a mean to provide specific additional nutrients earlier to the developing embryo in the incubation period (in ovo feeding – IOF program), which then continued after hatching (Post-hatch feeding - PHF program) with neonate nutrition in the perinatal period (a week before to a week after hatching). In the modern broiler industry, the application of ENP has been widely implemented and reported that the program resulted in achieving market weight quicker than before. However, information about application of ENP in Kampung chicken is still scarce. The early nutrition programing (ENP) can be implemented for improving the performance of INC – Kampung chicken with some considerations. From scientific point of view, ENP can be fully conducted.The ENP has much potential to yield several advantages, among them reduced post-hatch mortality and morbidity; greater efficiency of feed nutrient utilization at an early age; improved immune response to enteric antigens, and increasing production performance as a whole. From technical point of view, consideration should be done during embryonal period, particularly for the treatment of IOF (injected solution : diluted nutrient, osmotic pressure, time, site); During perinatal period, earlier acces to external feed will help the new hatched chicken to improve the overall performance of Kampung chicken.

Sustainable intensification of indigenous village chicken production system: matching the genotype with the environment.

The multi-purpose indigenous village chickens (IVCs) are kept in low- and middle-income countries. IVCs are hardy and are resilient to disease, hostile environment, global warming, and climate change. The IVCs are a little impacted by anthropogenic effects; consequently, they possess high genetic and phenotypic diversity. Likewise, the genetic structure of IVCs is principally shaped by natural selection, which enables them to accumulate high genetic polymorphism and to adaptively radiate. Regardless of this, the genetic wealth of IVCs has been eroded by indiscriminate crossbreeding. Emerging infectious and non-infectious diseases, flawed assumptions, predation, inadequate nutrition, poorly maintained night enclosures, and underdeveloped market infrastructure, and the overlooked multiple-use values and unique attributes of IVCs have threatened their mere survival. The IVCs lay a few eggs and produce less meat, which cannot meet the growing (existing) demand. However, the demand for IVC products is growing attributable to the flavor and texture of eggs and meat, and they are well-aligned with the subsistence farming system. The several use values and ecosystem services provided by IVCs have been increasingly realized. Enhanced production can be attained through sustainable use of local (genetic) resources and by scaling up and out best practices. Genetic improvement needs to mainly rely upon IVC genetic resources and should have to match the genotype with the environment. Moreover, it has to maintain the genetic polymorphism that has been accumulated for time immemorial to respond to unanticipated changes in the production system and consumers' demand. In this review, enhanced management, selection strategies, and genetic crosses including the crossing of commercial chickens with red junglefowl have been proposed to sustainably intensify the IVC production system.

Genetic diversity among two native Indian chicken populations using cytochrome c oxidase subunit I and cytochrome b DNA barcodes.

Background and Aim:India has large varieties (recognized, unrecognized) of native chickens (Desi) scattered throughout the country, managed under scavenging system different from commercial chicken breeds. However, they are less investigated for genetic diversity they harbor. The present study was planned to evaluate genetic diversity among two native chicken populations of North Gujarat (proposed Aravali breed) and South Gujarat (Ankleshwar breed). Aravali chicken, a distinct population with unique characters different from the registered chicken breeds of India is under process to be registered as a new chicken breed of Gujarat, India.Materials and Methods:Two mitochondrial markers, namely, cytochrome oxidase c subunit I (COX I) and cytochrome b (Cyt b) genes were studied across 10 birds from each population. Methodology included sample collection (blood), DNA isolation (manual), polymerase chain reaction amplification of mitochondrial genes, Sanger sequencing, and purification followed by data analysis using various softwares.Results:Haplotype analysis of the COX I gene unveiled a total eight and three haplotypes from the Aravali and Ankleshwar populations, respectively, with haplotype diversity (Hd) of 92.70 % for the Aravali and 34.50% for the Ankleshwar breed. Haplotype analysis of the Cyt b gene revealed a total of four haplotypes from the Aravali population with 60% Hd and no polymorphism in Ankleshwar breed. The phylogenetic analysis uncovered Red Jungle Fowl and Gray Jungle Fowl as prime roots for both populations and all domestic chicken breeds.Conclusion:Study findings indicated high genetic variability in Aravali chicken populations with COX I mitochondrial marker being more informative for evaluating genetic diversity in chickens.

Exploring the Relationship Between Boldness, Activity, Exploration and Monoaminergic Gene Expression in Red Junglefowl Chicks

Why individuals differ in behavioral responses has received intense research attention (particularly in the context of animal personality), and has typically focused on describing variation in boldness, activity, and exploration. Nevertheless, the mechanisms underlying this behavioral variation remain largely unknown. Variation in these behaviors is likely influenced by genetic differences between individuals, with genes in the monoaminergic systems commonly implicated. When examining the link between variation in boldness, activity and exploration and genes, studies have focused on different monoaminergic systems (mainly serotonergic and dopaminergic), and predominantly on mammals and passerine birds. Therefore, to replicate this general approach and examine if genes from these systems are linked to boldness, activity, and exploration, we exposed red junglefowl chicks (Gallus gallus) to behavioral assays (measuring boldness, activity, exploration) before analyzing prefrontal cortex gene expression of several dopaminergic (DRD1, DRD2) and serotonergic genes (TPH, 5HT2A, 5HT2B, 5HT2C, 5HT1B). We observed no relationships between our measured behaviors and gene expression. Together with previous studies, our results suggest that a clear link between boldness, activity and exploration and monoaminergic gene variation is lacking. We, therefore, suggest that this is due to differences among studies (e.g., methodological differences), or that the nature of the relationship between these behaviors and monoaminergic systems is more species-specific, and/or more complex than so far assumed.

The earliest evidence of chicken in Italy

The chicken (Gallus domesticus) originates from the red jungle fowl (Gallus gallus), a bird found in south and south-east Asia. The timing of the initial domestication, as well as its spread to western Asia and Europe, are still unclear. In Italy, the species was likely to have been introduced in the early Iron Age, though the precise chronology of this event is hitherto unconfirmed. By the 6th – 5th century BC, chicken remains occur at several Italian sites. Probably, the bird was originally raised for its symbolic value rather than for food, as its presence in early and mid-Iron Age cultic archaeological contexts suggests.We have re-analysed remains identified as ‘chicken’ from a cinerary hut urn found at Montecucco in central Italy during a 19th century archaeological investigation, to verify identification and establish an ante quem date for the introduction of the chicken in Italy. The analysis of these remains, combined with a review of additional zooarchaeological and iconographic evidence, has allowed us to push back the date of the earliest presence of this bird in Italy to at least the first half of the 9th century BC. This has also relevance for our understanding of the dynamics of chicken diffusion in the rest of Europe.

The International Society for Biological and Environmental Repositories Presents Abstracts from Its 2021 Annual Meeting Connect and Collaborate through Biobanking: Powering Innovation and Discovery May 10–14, 2021

The International Society for Biological and Environmental Repositories Presents Abstracts from Its 2021 Annual Meeting Connect and Collaborate through Biobanking: Powering Innovation and Discovery May 10–14, 2021

Sexual selection and personality: Individual and group-level effects on mating behaviour in red junglefowl.

Despite increasing evidence of the importance of repeatable among-individual differences in behaviour (animal personality) in ecology and evolution, little remains known about the role of animal personalities in sexual selection. Here, we present an investigation of the hypothesis that the personalities of individuals and their sexual partners play a role in different episodes of sexual selection, and the extent to which these effects are modulated by the social environment. We first examined how two repeatable behaviours-exploration and boldness-are associated with pre- and postcopulatory sexual selection in male red junglefowl Gallus gallus, using replicate groups across three experimental sex ratio treatments. We further explored how the social environment modulates relationships between male personality and mating performance, and whether mating is assortative or disassortative with respect to exploration or boldness. Finally, we examined behavioural mechanisms linking personality with mating performance. Across all sex ratios, the fastest and slowest exploring males courted females proportionally less, and faster exploring males associated with females more and received more sexual solicitations. In female-biased groups, the fastest and slowest exploring males experienced the highest mating success and lowest sperm competition intensity. Faster exploring males also obtained more mates in female-biased groups when their competitors were, on average, slower exploring, and the proportion of matings obtained by fast-exploring males decreased with the proportion of fast-exploring males in a group, consistent with negative frequency-dependent sexual selection. While boldness did not predict mating performance, there was a tendency for individuals to mate disassortatively with respect to boldness. Collectively, our results suggest that male exploration can play a role in sexual selection, and that sexual selection on personality is complex and contingent on the social environment.

Primordial germ cells isolated from individual embryos of red junglefowl and indigenous pheasants of Thailand

Interspecific germline chimerism mediated by transplantation of primordial germ cells (PGCs) of wild species to domestic hosts promises the conservation of wild birds. Cryopreservation of avian eggs and embryos is impracticable, and currently only frozen PGCs enable conservation of both the male and female descendants. Purebred offspring have been obtained from germline chimeras of wild avian species, proving the feasibility of such technology. In vitro propagation has been optimized for avian PGCs of domestic species; however, evidence is rather limited for successful isolation as well as long-term culture from a single embryo of wild species. With accelerating biodiversity loss, we have committed to preserving current genetic resources by freezing PGCs isolated from individual embryos in addition to their genetic material. We have devised a reliable protocol for the isolation and proliferation of PGCs from wild fowls in the family Phasianidae that are conserved in captive breeding (red junglefowl, bar-tailed pheasant, kalij pheasant, Siamese fireback pheasant, and silver pheasant). We obtained individual isolates of cultured circulating PGCs (49.7%, 79/155) as well as tissue PGCs (92.9%, 144/155). The specific co-culture conditions of autologous embryonic cells, without additional growth factors, facilitated the proliferation of so-called tissue PGCs (the remaining PGCs in embryonic tissue following blood aspiration). Only circulating PGCs left in blood vessels and of PGCs migrating to developing gonads have been previously reported. However, the present study is the first to report on the harvest of ectopic PGCs. The defined conditions sustained continuous proliferation of tissue PGCs for at least six months and maintained PGC identity following cryopreservation. Cultured tissue PGCs of these wild species were extensively characterized for their expression of the germ cell-specific proteins, chicken vasa homolog (CVH) and deleted in azoospermia-like (DAZL), as well as the ability to colonize chicken embryonic gonads. The novel protocol is practical for generating enough PGCs for cryopreservation, transplantation, and additionally, it enables isolation of PGCs from both blood circulation and embryonic tissue simultaneously. For conservation purposes, this approach is potentially applicable more widely to other non-domestic birds than those in the family Phasianidae that were investigated in the present study.

Cerebellum size is related to fear memory and domestication of chickens.

Red Junglefowl (Gallus gallus) were selected for divergent levels of fear of humans during eight generations, causing the selection lines to differ in fear levels as well as in the proportional brain and cerebellum masses. Birds from the two lines were then crossed to obtain an F3 intercross in order to study the correlations between brain mass and fear learning. We exposed 105 F3-animals individually to a fear habituation and memory test at 8 days of age, where the reactions to repeated light flashes were assessed on 2 consecutive days. After culling, the absolute and relative sizes of each of four brain regions were measured. Stepwise regression was used to analyse the effects of the size of each brain region on habituation and memory. There were no effects of any brain region on the habituation on day one. However, birds with a larger absolute size of cerebellum had significantly reduced reactions to the fearful stimuli on day two, indicating a better memory of the stimuli. No other regions had significant effects. We conclude that increased cerebellum size may have been important in facilitating chicken domestication, allowing them to adapt to a life with humans.

Novel mutation of avian leukosis virus subgroup J from Tibetan chickens

Tibetan chickens are descendants of the ancestral red jungle fowl Gallus gallus. Very little is known about pathogens in Tibetan chickens living in the high-altitude environment. Here, we report for the first time the detection and isolation of avian leukosis virus from Tibetan chickens, with all the avian leukosis virus–positive samples belonging to subgroup J. Phylogenetic analysis of the sequence revealed these viruses were in a new branch compared with previous reports. The 3′-end of the pol gene in the new strains showed 8-amino acid deletion, with 2 strains displaying a large-scale deletion in the hr2 region of gp85 protein. Among all the strains, several mutations in the primer binding site leader sequence and untranslated region, which came from Rous-associated virus, were identified. It is interesting that some of these mutations may have contributed to the competitive advantages to these isolates as observed from their increased replication in vitro. These results indicated that the virus isolates from Tibetan chickens can have competitive advantage over the other strains circulating in the poultry population in future.

Origin and evolutionary history of domestic chickens inferred from a large population study of Thai red junglefowl and indigenous chickens

In this study, we aimed to elucidate the origin of domestic chickens and their evolutionary history over the course of their domestication. We conducted a large-scale genetic study using mitochondrial DNA D-loop sequences and 28 microsatellite DNA markers to investigate the diversity of 298 wild progenitor red junglefowl (Gallus gallus) across two subspecies (G. g. gallus and G. g. spadiceus) from 12 populations and 138 chickens from 10 chicken breeds indigenous to Thailand. Twenty-nine D-loop sequence haplotypes were newly identified: 14 and 17 for Thai indigenous chickens and red junglefowl, respectively. Bayesian clustering analysis with microsatellite markers also revealed high genetic diversity in the red junglefowl populations. These results suggest that the ancestral populations of Thai indigenous chickens were large, and that a part of the red junglefowl population gene pool was not involved in the domestication process. In addition, some haplogroups that are distributed in other countries of Southeast Asia were not observed in either the red junglefowls or the indigenous chickens examined in the present study, suggesting that chicken domestication occurred independently across multiple regions in Southeast Asia.