Dwarf Chickens Research Articles

Differential responses to heat stress in normal and dwarf chickens: implications for meat quality and immune function

Abstract This study investigated the impact of heat stress (HS) on meat quality, antioxidant ability, and immunity in normal and dwarf-size chickens. A total of 144 chickens, with 72 from the normal yellow chicken (NYC) strain and 72 from the dwarf yellow chicken (DYC) strain, were equally divided into groups exposed to heat stress (35±1°C for 8 hours daily) and those kept at 28±1°C as the control group. After seven days of treatment, meat color parameters, including lightness (L*-value), redness (a*-value), and yellowness (b*-value), were assessed. Histopathological examination was conducted on spleen tissues to assess structural changes. Gene expression analysis determined the expression levels of interleukin-4 (IL-4), IL-6, and liver catalase (CAT) related to immune response and antioxidant capacity. HS significantly affected meat color parameters, with an increase in lightness (L*-value) (P<0.01) and a decrease in redness (a*-value) (P<0.01) observed in breast and thigh muscles. Furthermore, HS led to increased drip loss (P<0.05), cooking loss (P<0.05), and shear force (P<0.01) in breast muscles. Histopathological examination of spleen tissues revealed varying degrees of lymphoid depletion, necrosis, fibrosis, and inflammatory cell infiltration in response to HS. Gene expression analysis showed that HS upregulated the expression of interleukin-4 (IL-4) and IL-6 in the spleen of NYC (P<0.05) but not in DYC. Additionally, HS reduced the expression of liver catalase (CAT) in NYC (P<0.05) but had no significant effect on DYC. These findings indicate that HS adversely affects meat quality, immune response, and antioxidant capacity in broilers, with normal-sized chickens being more susceptible to these effects compared to dwarf chickens. The results provide valuable insights into the differential responses of chicken strains to HS and underscore the importance of considering genetic factors in mitigating the negative impacts of heat stress on poultry production.

Analysis of the mitochondrial genome and phylogenetic relationships of Mong chicken

In this study, the complete nucleotide sequence of the mitochondrial genome of the Mong chicken and an indigenous chicken breed of Vietnam, was determined by the Sanger sequencing method, structurally analysed and used to evaluate the phylogenetic relationship with different chicken breeds. The complete nucleotide sequence data of the Mong chicken’ mitochondrial genome was registered on GenBank with the accession number OR643716. The Mong chicken’ mitochondrial genome has a size of 16785 base pair (bp) and includes 22 transfer RNA genes, two ribosomal RNA genes, 13 protein-coding genes, and one non-coding control region (D-loop). A, T, G, and C nucleotide proportions were 30.28, 23.76, 13.48, and 32.48%, respectively. Results of the analysis of phylogenetic relationships based on 33 complete mitochondrial genome sequences showed that the Mong chicken has evolutional origin from the red junglefowl subspecies Gallus gallus spadiceus. The Mong chicken is in close relationship with the Dong Tao chicken and Cao Son dwarf chicken in Vietnam, Rugao yellow chicken and Xiaoxiang chicken in China.

Investigation of potential genetic factors for growth traits in yellow-feather broilers using weighted single-step genome-wide association study

Yellow-feather broilers take a large portion of poultry industry in China due to its meat characteristics. Improving the growth traits of yellow-feathered broilers will have great significance for the Chinese poultry market. The current study was designed to investigate the potential genetic factors using the weighted single-step genome-wide association study (wssGWAS) method, which takes consideration of more factors including pedigree, sex, environment and has more accuracy than traditional GWAS. The yellow-feather dwarf chickens from Wens Nanfang Poultry Breeding Co. Ltd. were revolved to recode 9 growth traits: Average daily gain (ADG), body weight (BW) at 45 d, 49 d, 56 d, 63 d, 70 d, 77 d, 84 d, 91 d for analysis. For the results, the region 4.63 to 5.03 Mb on chromosome 15, which was the QTL overlapped in BW45, BW49, BW56, BW63, BW84, might be the crucial genetic region for growth traits. Seven GO terms and 3 KEGG pathways, GO:0005200, GO:0005882, GO:0045111, GO:0099513, GO:0099081, GO:0099512, GO:0099080, KEGG:gga04020, KEGG:gga04540, KEGG:gga04210, were detected to relevant with growth traits. The genes enriched in these biological processes (NRAS, TUBB1, ADORA2B, NTRK3, NGF, TNNC2, F-KER, LOC429492, LOC431325, LOC431324, LOC396480) might have the function in growth of yellow-feather broilers.

Evaluation of the selection of key individuals for genotype imputation in Chinese yellow-feathered chicken

Genotype imputation is a powerful technique employed by next-generation sequencing (NGS) and genotyping arrays, which can significantly enhance the cost-effectiveness and efficiency of genomic selection. The accuracy of imputation is largely determined by the choice of reference panel, with previous studies generally demonstrating that a closely related population as a reference panel leads to greater accuracy than a more distantly related population. Various strategies have been proposed for selecting desirable individuals via targeted resequencing, but their efficiencies need further improvement. In this study, we present a practical broiler selection methodology for a local Chinese chicken line that integrates established methods based on pedigree, genomics, and random sampling, and leverages genotype and pedigree information from the yellow-plumage dwarf chicken line. The efficacy of these selection strategies was assessed by evaluating their ability to accurately impute masked genotypes from data obtained using a 600K chip. Our findings reveal that the pedigree-based method yields superior accuracy in genotype imputation, whereas the haplotype-based method exhibits greater stability. Nonetheless, the impact of these targeted methods for selecting key individuals is slightly different when initiating a new sequencing project in a production context. Overall, this study highlights the advantages of using the pedigree-based approach as the preferred method for optimizing genotype imputation in broiler chickens.

Investigating the heat tolerance and production performance in local chicken breed having normal and dwarf size.

Heat stress significantly impairs the growth performance of broilers, which causes serious losses to the poultry industry every year. Thus, understanding the performance of indigenous chicken breeds under such environment is crucial to address heat stress problem. The purpose of this study was to investigate the effects of heat stress (HS) on production performance, tissue histology, heat shock response (HSP70, HSP90), and muscle growth-related genes (GHR, IGF-1, and IGF-1R) of Normal yellow chicken (NYC) and Dwarf yellow chicken (DYC). Seventy-two female birds from each strain were raised under normal environmental conditions up to 84days, with birds from each strain being divided into two groups (HS and control). In the HS group, birds were subjected to high temperature at 35±1°C for 8h daily and lasted for a week, while in the control group, birds were raised at 28±1°C. At 91days old, bird's liver, hypothalamus, and breast muscle tissues were collected to evaluate the gene expression, histological changes, and the production performance. The Feed intake, weight gain ratio, total protein intake and protein efficiency ratio showed a significant reduction in the treatments (P<0.01) and treatment×strain interaction (P<0.05) with breast muscle rate significantly reducing among the treatments (P<0.01) after 7days of HS. Correspondingly, total abdominal fat showed significant change among treatment and strain (P<0.01, P<0.05), respectively. Besides, HS markedly upregulated the mRNA expression of HSP70 and HSP90 in the pectoralis major of both chicken strains, but no significant increase (P<0.05) was found in mRNA expression of HSP90 in liver and hypothalamus tissues of both chicken strains. Moreover, HS significantly upregulated (P<0.05) the expression of lipogenic genes (FASN, ACC) in liver tissues of NYC, while mRNA expression of these genes showed no variation in DYC. Similarly, HS downregulated the mRNA expression of muscle growth-related genes (GHR, IGF-1, and IGF-1R). Consequently, the histopathological analysis showed that histological changes were accompanied by inflammatory cell infiltration in liver tissues of both chicken strains; however, histopathological changes were more severe in NYC than dwarf chicken strain. Conclusively, this study depicted that the production performance and growth rate varied significantly between treatment and control group of NYC. However, heat treatment in DYC has not shown significant damaging consequences as compared to the control group that signifies the vital role of the dwarf trait in thermal tolerance.

Genetic diversity and breed identification of Chinese and Vietnamese local chicken breeds based on microsatellite analysis.

South Asia and Southeast Asia are the origins of domestic chickens and are rich in poultry genetic resources, resulting in many unique local chicken breeds. However, with the rapid intensification of poultry farming worldwide, many local chicken breeds are threatened with extinction. In response to China's "One Belt, One Road" policy, it is imperative to strengthen the conservation and breeding of local chicken breeds in China and Vietnam. This study characterized 18 microsatellite molecular genetic markers to analyze the genetic diversity of 21 local chicken populations in southern China (Yunnan and Guangxi Provinces) and Vietnam, breed identification tags for microsatellite loci were constructed. The results showed that a total of 377 alleles were detected in all breeds, and the most alleles (44) and the highest polymorphic information content (0.7820) were detected at the LEI0094 locus. The average polymorphic information content (PIC) content of the whole population was 0.65, indicating moderate polymorphism. The genetic diversity of the whole population was rich, except for two loci MCW0111 and MCW0016, that showed heterozygote excess at microsatellite loci, and the population had high genetic differentiation. The Vietnamese breeds showed low pairwise fixation coefficient (FST) and Nei's standard genetic distance (DS) between them. According to the neighbor-joining dendrogram constructed by DS and the analysis of population genetic structure using the structure program, Longshengfeng chicken, Yunlong dwarf chicken, Tengchong white chicken, Xiayan chicken, and Daweishan mini chicken are similar, and Xishuangbanna game fowl, Wuding chicken, and Lanping silky chicken are similar to Yanjin black-bone chicken. In addition, excluding Dongtao chicken, other Vietnamese breeds are clustered together, indicating that the southern chicken breeds are closely related and have experienced better breeding. Overall, the whole population is rich in genetic resources, and the chicken breeds in the three regions are genetically close because of geographical factors and human activities. Dongtao chicken in Vietnamese, Chinese Yunnan local chicken breeds (Gallus gallus spadiceus), and red jungle fowl chickens (Gallus gallus) may have the same origin. We also constructed unique microsatellite molecular markers for 20 cultivars using 15 microsatellite loci. This study provides valuable insights to facilitate breed identification, improve cultivar protection, and new germplasm construction.

Penggunaan Sinbiotik Untuk Meningkatkan Pertumbuhan Ayam Pedaging Di Peternak Muara Selayar Desa Pijot Kabupaten Lombok Timur

Broiler cultivation is one of the largest MSMEs in East Lombok Regency, West Nusa Tenggara Province (NTB). The group of breeders carries out maintenance on a scale between 3,500 heads and 7,500 heads per cage. The Muara Selayar farmer group is one of the broiler farmer groups located in Pijot Village, Keruak District, East Lombok Regency. The main problem faced by the Muara Selayar Farmer Group at this time is that production performance is not optimal, which is characterized by sluggish chicken growth, many dwarf chickens, poor feed conversion, high mortality rate, which results in low profits obtained and even losses. The considerable number of dwarf chickens although it varies every period incurs losses due to poor ration conversion with low selling prices. The solution offered to bridge the problem of low broiler production performance in the Muara Selayar Broiler Farm Group is the use of symbiotic as a feed mixture for broilers of the starter period. Symbiotic are a mixture of prebiotics (feed ingredients that are difficult to digest in the digestive tract but benefit the host through selective stimulation of growth or activity of one or more microbes in the gut) and probiotics (live microbes that have benefits for the host). The results of this activity show that the use of symbiotic has succeeded in increasing the body's resistance and growth of slaughter chickens and laying hens.

Growth hormone receptor gene influences mitochondrial function and chicken lipid metabolism by AMPK-PGC1\u03b1-PPAR signaling pathway

BackgroundAdipose tissue is an important endocrine and energy-storage organ in organisms, and it plays a crucial role in the energy-metabolism balance. Previous studies have found that sex-linked dwarf (SLD) chickens generally have excessively high abdominal fat deposition during the growing period, which increases feeding costs. However, the underlying mechanism of this fat deposition during the growth of SLD chickens remains unknown.ResultsThe Oil Red O staining showed that the lipid-droplet area of SLD chickens was larger than that of normal chickens in E15 and 14d. Consistently, TG content in the livers of SLD chickens was higher than that of normal chickens in E15 and 14d. Further, lower ΔΨm and lower ATP levels and higher MDA levels were observed in SLD chickens than normal chickens in both E15 and 14d. We also found that overexpression of GHR reduced the expression of genes related to lipid metabolism (AMPK, PGC1α, PPARγ, FAS, C/EBP) and oxidative phosphorylation (CYTB, CYTC, COX1, ATP), as well as reducing ΔΨm and ATP levels and increasing MDA levels. In addition, overexpression of GHR inhibited fat deposition in CPPAs, as measured by Oil Red O staining. On the contrary, knockdown of GHR had the opposite effects in vitro.ConclusionsIn summary, we demonstrate that GHR promotes mitochondrial function and inhibits lipid peroxidation as well as fat deposition in vivo and in vitro. Therefore, GHR is essential for maintaining the stability of lipid metabolism and regulating mitochondrial function in chicken.

Growth Hormone Receptor Controls Adipogenic Differentiation of Chicken Bone Marrow Mesenchymal Stem Cells by Affecting Mitochondrial Biogenesis and Mitochondrial Function.

Growth hormone receptor (GHR) can activate several signaling pathways after binding to growth hormone (GH) to regulate cell growth and development. Sex-linked dwarf (SLD) chickens, normal protein functions are prevented because of exon mutations in the GHR gene, have more severe fat deposition. However, the specific molecular mechanisms responsible for this phenotype remains unclear. We therefore investigated the effect of the GHR gene on adipogenic differentiation of chicken bone marrow mesenchymal stem cells (BMSCs). We found that bone marrow fat deposition was more severe in SLD chickens compared to normal chickens, and the expression of genes related to adipogenic differentiation was enhanced in SLD chicken BMSCs. We also detected enhanced mitochondrial function of BMSCs in SLD chickens. In vitro, overexpression of GHR in chicken BMSCs increased mitochondrial membrane potential but decreased reactive oxygen and ATP contents, oxidative phosphorylation complex enzyme activity, and mitochondrial number. Expression of genes associated with mitochondrial biogenesis and function was repressed during adipogenic differentiation in chicken BMSCs, the adipogenic differentiation capacity of chicken BMSCs was also repressed. With knockdown of GHR, opposite results were observed. We concluded that GHR inhibited adipogenic differentiation of chicken BMSCs by suppressing mitochondrial biogenesis and mitochondrial function.

Effects of lipoproteins on yolk microstructure in duck, quail, goose, pigeon, and chicken eggs

Poultry eggs are among the most important protein and nutrient sources in human diets. There are considerable differences in the evolutionary processes of different species. Therefore, we evaluated the differences and correlations among the microstructure, low-density lipoprotein (LDL) level, and high-density lipoprotein (HDL) level in duck, quail, goose, pigeon, dwarf chicken, ShanDong chicken, Rhode Island Red, and HeTian DaHei chicken eggs. The egg microstructures were polygonal, compact, and granular and showed no evidence of cross-linking. There was a significant variation among the eight poultry egg types in terms of yolk particle size (3829.34-10373.25 μm2), LDL level (0.023-0.048 mmol/l), and HDL level (3.39-7.98 mg/g). There were also significant differences among the chicken species in terms of yolk particle size (4070.87-8139.48 μm2), LDL level (0.028-0.047 mmol/l), and HDL level (3.57-7.98 mg/g). The yolk granules of local chicken breeds were smaller than those of typical egg-laying chickens. The LDL level weakly correlated with the size of egg yolk (r = 0.24)l there was a very weak correlation between HDL level and yolk particle size (r = 0.008). This study provides a theoretical basis for variations in the taste of eggs from different poultry species and sub-species.

Meat yield characteristics of different upgraded dwarf chicken under intensive management condition

The study was conducted with attempts to determine the effects of autosomal dwarf (adw) gene introgression from Indigenous dwarf chicken (IDC) to White Leghorn (WLH) and Fayoumi (Fay) on growth and meat yield characteristics. Experiment was carried out at the Poultry Farm of Bangladesh Agricultural University (BAU), Mymensingh for a period of 28 months from March 2013 to June 2015 under intensive management condition. In this study, the di-allele crossing between WLH, Fay and IDC produced 4 up-graded chickens viz. IDC♂ × WLH♀, WLH♂ × IDC♀, IDC♂ × Fay♀ and Fay♂ × IDC♀. The up-graded F1 generations were mated intersex to access their productivity. The up-graded F1 generations were mated intersex to access their productivity. Pre-slaughter live weight of birds significantly (P&lt;0.001) varied by genotype, sex and genotype × sex interaction. Percentage of thigh meat, drumstick meat, dark and total meat weights was significantly influenced by genotype. Although meat yield parameters of male birds in relation to live weight were found higher than their female birds, some parameters like breast meat, liver, giblet and total meat yield were found higher in female birds than that of male birds of all genotypes. However, meat yield parameters like percentage of thigh, drumstick and total meat yield were the highest in IDC♂ × Fay♀ and Fay♂ × IDC♀ and the lowest in IDC♂ × WLH♀. From the above findings, Fayoumi mediated dwarf genotypes showed better meat yield characteristics than Leghorn mediated dwarf genotypes.

TMEM263: a novel candidate gene implicated in human autosomal recessive severe lethal skeletal dysplasia

IntroductionSkeletal dysplasia is a common, clinically and genetically heterogeneous disorder in the human population. An increasing number of different genes are being identified causing this disorder. We used whole exome sequencing (WES) for detection of skeletal dysplasia causing mutation in a fetus affected to severe lethal skeletal dysplasia.PatientFetus was assessed by ultrasonography in second trimester of pregnancy. He suffers from severe rhizomelic dysplasia and also pathologic shortening of ribs. WES was applied to finding of causal mutation. Furthermore, bioinformatics analysis was performed to predict mutation impact.ResultsWhole exome sequencing (WES) identified a homozygous frameshift mutation in the TMEM263 gene in a fetus with severe lethal skeletal dysplasia. Mutations of this gene have been previously identified in dwarf chickens, but this is the first report of involvement of this gene in human skeletal dysplasia. This gene plays a key role in the growth hormone signaling pathway.ConclusionTMEM263 can be considered as a new gene responsible for skeletal dysplasia. Given the complications observed in the affected fetus, the mutation of this gene appears to produce much more intense complications than that found in chickens and is likely to play a more important role in bone development in human.

Genomic Regions Related to White/Black Tail Feather Color in Dwarf Chickens Identified Using a Genome-Wide Association Study.

Although the genetic foundation of chicken body feather color has been extensively explored, that of tail feather color remains poorly understood. In the present study, we used a synthetic chicken dwarf line (DW), derived from hybrids bred between a black tail chicken breed, Rhode Island Red (RIR), and a white tail breed, dwarf layer (DL), to investigate the genetic rules associated white/black tail color. Even though the body feathers are predominantly red, the DW line still comprises individuals with black or white tails after more than 10 generations of self-crossing and selection for the body feather color. We first performed four crosses using the DW chickens, including black-tailed males to females, reciprocal crosses between the black and white, and white males to females to elucidate the inheritance pattern of the white/black tail. We also performed a genome-wide association (GWA) analysis to determine the candidate genomic regions underlying the tail feather color using black tail chickens from the RIR and DW lines and white individuals from the DW line. In the crossing experiment, we found that (i) the white/black tail feather color is independent of body feather color; (ii) the phenotype is a simple autosomal trait; and (iii) the white is dominant to the black in the DW line. The GWA results showed that seven single-nucleotide polymorphisms (SNPs) on chromosome 24 were significantly correlated with tail feather color. The significant region (3.97–4.26 Mb) comprises nine known genes (NECTIN1, THY1, gga-mir-1466, USP2, C1QTNF5, RNF26, MCAM, CBL, and CCDC153) and five anonymous genes. This study revealed that the white/black tail feather trait is autosome-linked in DW chickens. Fourteen genes were found in the significant ~0.29 Mb genomic region, and some, especially MCAM, are suggested to play critical roles in the determination of white/black tail feather color. Our research is the first study on the genetics underlying tail feather color and could help further the understanding of feather pigmentation in chickens.

High expression of BCL6 inhibits the differentiation and development of hematopoietic stem cells and affects the growth and development of chickens

BackgroundB-cell CLL/lymphoma 6 (BCL6) is a transcriptional master regulator that represses more than 1200 potential target genes. Our previous study showed that a decline in blood production in runting and stunting syndrome (RSS) affected sex-linked dwarf (SLD) chickens compared to SLD chickens. However, the association between BCL6 gene and hematopoietic function remains unknown in chickens.MethodsIn this study, we used RSS affected SLD (RSS-SLD) chickens, SLD chickens and normal chickens as research object and overexpression of BCL6 in hematopoietic stem cells (HSCs), to investigate the effect of the BCL6 on differentiation and development of HSCs.ResultsThe results showed that comparison of RSS-SLD chickens with SLD chickens, the BCL6 was highly expressed in RSS-SLD chickens bone marrow. The bone marrow of RSS-SLD chickens was exhausted and red bone marrow was largely replaced by yellow bone marrow, bone density was reduced, and the levels of immature erythrocytes in peripheral blood were increased. At the same time, the hematopoietic function of HSCs decreased in RSS-SLD chickens, which was manifested by a decrease in the hematopoietic growth factors (HGFs) EPO, SCF, TPO, and IL-3, as well as hemoglobin α1 and hemoglobin β expression. Moreover, mitochondrial function in the HSCs of RSS-SLD chickens was damaged, including an increase in ROS production, decrease in ATP concentration, and decrease in mitochondrial membrane potential (ΔΨm). The same results were also observed in SLD chickens compared with normal chickens; however, the symptoms were more serious in RSS-SLD chickens. Additionally, after overexpression of the BCL6 in primary HSCs, the secretion of HGFs (EPO, SCF, TPO and IL-3) was inhibited and the expression of hemoglobin α1 and hemoglobin β was decreased. However, cell proliferation was accelerated, apoptosis was inhibited, and the HSCs entered a cancerous state. The function of mitochondria was also abnormal, ROS production was decreased, and ATP concentration and ΔΨm were increased, which was related to the inhibition of apoptosis of stem cells.ConclusionsTaken together, we conclude that the high expression of BCL6 inhibits the differentiation and development of HSCs by affecting mitochondrial function, resulting in impaired growth and development of chickens. Moreover, the abnormal expression of BCL6 might be a cause of the clinical manifestations of chicken comb, pale skin, stunted growth and development, and the tendency to appear RSS in SLD chickens.

Integrative Analyses of mRNA Expression Profile Reveal SOCS2 and CISH Play Important Roles in GHR Mutation-Induced Excessive Abdominal Fat Deposition in the Sex-Linked Dwarf Chicken.

Sex-linked dwarf (SLD) chicken, which is caused by a recessive mutation of the growth hormone receptor (GHR), has been widely used in the Chinese broiler industry. However, it has been found that the SLD chicken has more abdominal fat deposition than normal chicken. Excessive fat deposition not only reduced the carcass quality of the broilers but also reduced the immunity of broilers to diseases. To find out the key genes and the precise regulatory pathways that were involved in the GHR mutation-induced excessive fat deposition, we used high-fat diet (HFD) and normal diet to feed the SLD chicken and normal chicken and analyzed the differentially expressed genes (DEGs) among the four groups. Results showed that the SLD chicken had more abdominal fat deposition and larger adipocytes size than normal chicken and HFD can promote abdominal fat deposition and induce adipocyte hypertrophy. RNA sequencing results of the livers and abdominal fats from the above chickens revealed that many DEGs between the SLD and normal chickens were enriched in fat metabolic pathways, such as peroxisome proliferator-activated receptor (PPAR) signaling, extracellular matrix (ECM)-receptor pathway, and fatty acid metabolism. Importantly, by constructing and analyzing the GHR-downstream regulatory network, we found that suppressor of cytokine signaling 2 (SOCS2) and cytokine-inducible SH2-containing protein (CISH) may involve in the GHR mutation-induced abdominal fat deposition in chicken. The ectopic expression of SOCS2 and CISH in liver-related cell line leghorn strain M chicken hepatoma (LMH) cell and immortalized chicken preadipocytes (ICP) revealed that these two genes can regulate fatty acid metabolism, adipocyte differentiation, and lipid droplet accumulation. Notably, overexpression of SOCS2 and CISH can rescue the hyperactive lipid metabolism and excessive lipid droplet accumulation of primary liver cell and preadipocytes that were isolated from the SLD chicken. This study found some genes and pathways involved in abdominal fat deposition of the SLD chicken and reveals that SOCS2 and CISH are two key genes involved in the GHR mutation-induced excessive fat deposition of the SLD chicken.

Effects of a probiotic on the growth performance, intestinal flora, and immune function of chicks infected with Salmonella pullorum

This study investigated the effects of a Lactobacillus paracasei KL1 and Lactobacillus plantarum subsp. plantarum Zhang-LL mixed probiotic on Salmonella-caused pullorosis in chicks. A total of 120 1-day-old Nongda no.3 dwarf chicks were randomly assigned to 4 treatments, with 6 replicates of 5 birds each. The treatments were blank group, Salmonella pullorum–infected group, probiotic treatment group, and probiotic prevention (PP) group. All birds (n = 90) except those in the blank group were infected with S. pullorum on day 4. On day 14, the BW, ADG, mortality, pathology of tissue, cecum colony count, immune organ indices, cecal mucosa secretory IgA, and cytokines were investigated. The results showed that the chicks infected with S. pullorum were depressed and their BW reduced. The PP group had the highest ADG and lowest mortality rate (0%), whereas the S. pullorum–infected group had 37.50% mortality rate and lowest ADG. Pathologic sections showed that the probiotic treatment group had minor lesions but the PP group had no lesions in the ileum, cecum, and liver. Cecal Lactobacillus counts was the highest (P < 0.05) and Salmonella and Escherichia coli counts were the lowest (P < 0.05) in the PP group; Compared with the S. pullorum–infected group, the thymus and spleen indexes of the probiotic treatment group increased (P < 0.05), but they were unaffected (P > 0.05) in the bursa of Fabricius, whereas in the PP group, all the immune organs were increased (P < 0.05).Cecal mucosa secretory IgA and IL-4 were the highest (P < 0.05) and tumor necrosis factor α and interferon gamma were the lowest (P < 0.05) in the PP group; In summary, the Lactobacillus KL1 and L. plantarum Zhang-LL mixed probiotic effectively reduced the mortality of pullorosis in chicks, promoted the growth performance, regulated the balance of the intestinal flora, improved the immune function, resisted pullorosis disease, completely prevented chicks from pullorosis after infection, and reduced economy loss in the poultry industry.

Mutation of TWNK Gene Is One of the Reasons of Runting and Stunting Syndrome Characterized by mtDNA Depletion in Sex-Linked Dwarf Chicken.

Runting and stunting syndrome (RSS), which is characterized by low body weight, generally occurs early in life and leads to considerable economic losses in the commercial broiler industry. Our previous study has suggested that RSS is associated with mitochondria dysfunction in sex-linked dwarf (SLD) chickens. However, the molecular mechanism of RSS remains unknown. Based on the molecular diagnostics of mitochondrial diseases, we identified a recessive mutation c. 409G > A (p. Ala137Thr) of Twinkle mitochondrial DNA helicase (TWNK) gene and mitochondrial DNA (mtDNA) depletion in RSS chickens’ livers from strain N301. Bioinformatics investigations supported the pathogenicity of the TWNK mutation that is located on the extended peptide linker of Twinkle primase domain and might further lead to mtDNA depletion in chicken. Furthermore, overexpression of wild-type TWNK increases mtDNA copy number, whereas overexpression of TWNK A137T causes mtDNA depletion in vitro. Additionally, the TWNK c. 409G > A mutation showed significant associations with body weight, daily gain, pectoralis weight, crureus weight, and abdominal fat weight. Taken together, we corroborated that the recessive TWNK c. 409G > A (p. Ala137Thr) mutation is associated with RSS characterized by mtDNA depletion in SLD chicken.

Recombinant infectious bronchitis coronavirus H120 with the spike protein S1 gene of the nephropathogenic IBYZ strain remains attenuated but induces protective immunity

Infectious bronchitis (IB) is a highly infectious viral disease responsible for major economic losses in the poultry industry. A reverse genetic vaccine is a safe, rapid, and effective method of achieving IB prevention and control. In this study, we constructed the recombinant strain, rH120-S1/YZ, using a reverse genetic system, based on the backbone of the H120 vaccine strain, with the S1 gene replaced with that of the QX-like nephropathogenic strain, ck/CH/IBYZ/2011, isolated in China. The results of dwarf chicken embryos, growth kinetics, and viral titration in the embryos demonstrated that the biological characteristics of the recombinant virus remained unchanged. Like the rH120-infected group and in contrast to the rIBYZ-infected group, no mortality, clinical signs, or lesions were observed in the lungs or kidneys of young chickens inoculated with rH120-S1/YZ. The viral loads in various tissues, cloacal, and oral swabs was lower in most types of samples, indicating that the rH120-S1/YZ strain was highly safe in chicks. Compared to rH120 vaccination group, when the efficacy of this strain was evaluated against the QX-like IBV strain, better protection, with 100% survival rate and no disease symptom or gross lesion was observed in the chickens vaccinated with rH120-S1/YZ. Increased levels of IBV-specific antibodies were detected in the serum of the rH120-S1/YZ-vaccinated animals 14 days post-vaccination. Collectively, our results suggest that the recombinant strain, rH120-S1/YZ, may represent a promising vaccine candidate against QX-like IBVs.

Runting and Stunting Syndrome Is Associated With Mitochondrial Dysfunction in Sex-Linked Dwarf Chicken.

Runting and stunting syndrome (RSS) in chicken are commonly known as “frozen chicken.” The disease is characterized by lower body weight and slow growth and the incidence rate is widely 5%–20% in sex-linked dwarf (SLD) chickens. However, the etiology of RSS in chickens has plagued researchers for several decades. In this study, histopathology studies demonstrated that the hepatocytes of the RSS chickens contain many mitochondria with damaged and outer and inner membrane along with vacuolar hydropic degeneration. No mtDNA mutation was detected, but our microarray data showed that RSS chickens exhibited abnormal expression of genes, many of which are involved in oxidative phosphorylation (OXPHOS) and fatty acid metabolism. In particular, nuclear gene IGF2BP3 was upregulated in RSS chickens' liver cells. The abnormal expression of these genes is likely to impair the OXPHOS, resulting in reduced ATP synthesis in the hepatocytes of the RSS chickens, which may in turn leads to poor weight gain and retarded growth or stunting of chicks. Our findings suggest that mitochondria dysfunction rather than chronic inflammation is responsible for the reduced growth and RSS in SLD chickens. Mutations in GHR have been shown to compromise mitochondrial function in SLD chickens. Since the mitochondrial damage in the RSS chicken is more severe, we suggest that extra genes are likely to be affected to exacerbate the phenotype.

Body Conformation, Morphometry Indices and Inheritance Pattern of Indigenous Dwarf Chickens of Bangladesh

The study was conducted to investigate the body dimension, morphometric features and inheritance pattern of indigenous dwarf chicken (IDC) of Bangladesh under intensive management condition. The experiment was conducted at Bangladesh Agricultural University (BAU) poultry farm for a period of 28 months from March 2013 to June 2015 including a total of 979 birds. Body weight, shank length and circumference, chest girth, length of trunk, wing, keel and body, and body conformation indices were recorded at 8, 24 and 52 weeks of age. The average shank length, shank circumference and live weight at 24th week in adult dwarf males and females were 7.38 and 4.37 cm, 6.20 and 3.63 cm, and 1650 and 1067 g, respectively. The reduction of live weight for dwarf male and female chickens relative to their normal shank counterpart (NSC) at same age was 14.06 and 16.05%, respectively. Length of body, trunk, wing, shank and keel of IDC were also significantly shorter than NSC at all ages. The indices of shape, massiveness and long leggedness of NSC were significantly greater than IDC almost all ages. Shank lengths of day old chicks were measured within 1.4-1.6 cm. The ratio of non-dwarf and dwarf in indigenous chicken populations was found 9:7 for 1st generation where significant deviation observed in subsequent generations. Among the dwarf progeny, the male and female ratio was close to 1:1. Current hypothesis is in favor of autosomal dwarfism control by at least 2 pairs of genes where duplicate recessive gene interaction also known as complementary gene effect has probably been exerted between two pairs of genes. In conclusion, the present estimates give some insight information on morphometry and body conformational aspects between normal shanked and dwarf chickens which relate with lowered motoric activity, reduced metabolic rate and their body surface-mass makes the dwarf birds suitable for hot-humid climate like Bangladesh.