Research Progress on Effects of Stocking Density on Performance, Health and Welfare of Duck

Stocking density is an important factor for animal production performance.It appears particularly urgent and important to research systematically on stocking density for the dual restriction of environmental protection and animal welfare.This review dealt with the influence of stocking density on ducks'productivity and health through production performance,animal behavior and animal welfare,and analyzed the possible mechanism of high stocking density reducing production performance,resulting in abnormal behavior and stress,causing welfare and health problems.We consider that it might be associated with heat stress,more spatial competition(to gather the food,drinking water,sports area,etc.),as well as the quality deterioration of litter and house air caused by high stocking density.Finally,we put forward some suggestions on the study of stocking density's effects on ducks,and proposed the future work that need to be studied and problems that need to be solved imminently.

Genetic and Breeding Progress Analysis on Five Pure Lines of Dahen Broiler

To timely modify breeding scheme and improve selection efficiency of Dahen broiler, genetic and breeding progress analysis on five pure lines was conducted. The results showed that the selection on breeding goal traits of each line was effective since 14 generations, especially the selection on growth traits did not cause adverse influence on reproductive performance. After the 6^ th generation, main performances of each line maintained in higher level, but the breeding progress obviously declined. It illustrated that current breeding means was effective for maintaining and consolidating breeding goal traits of Dahen broiler, and it should timely adjust breeding scheme to obtain more genetic progress.

miRNA sequencing analysis of healthy and atretic follicles of chickens revealed that miR-30a-5p inhibits granulosa cell death via targeting Beclin1

Background:The egg production performance of chickens is affected by many factors,including genetics,nutrition and environmental conditions.These factors all play a role in egg production by affecting the development of follicles.MicroRNAs(miRNAs)are important non-coding RNAs that regulate biological processes by targeting genes or other non-coding RNAs after transcription.In the animal reproduction process,miRNA is known to affect the development and atresia of follicles by regulating apoptosis and autophagy of granulosa cells(GCs).Results:In this study,we identified potential miRNAs in the atretic follicles of broody chickens and unatretic follicles of healthy chickens.We identified gga-miR-30a-5p in 50 differentially expressed miRNAs and found that gga-miR-30a-5p played a regulatory role in the development of chicken follicles.The function of miR-30a-5p was explored through the transfection test of miR-30a-5p inhibitor and miR-30a-5p mimics.In the study,we used qPCR,western blot and flow cytometry to detect granulosa cell apoptosis,autophagy and steroid hormone synthesis.Confocal microscopy and transmission electron microscopy are used for the observation of autophagolysosomes.The levels of estradiol(E2),progesterone(P4),malondialdehyde(MDA)and superoxide dismutase(SOD)were detected by ELISA.The results showed that miR-30a-5p showed a negative effect on autophagy and apoptosis of granulosa cells,and also contributed in steroid hormones and reactive oxygen species(ROS)production.In addition,the results obtained from the biosynthesis and dual luciferase experiments showed that Beclin1 was the target gene of miR-30a-5p.The rescue experiment conducted further confirmed that Beclin1 belongs to the miR-30a-5p regulatory pathway.Conclusions:In summary,after deep miRNA sequencing on healthy and atretic follicles,the results indicated that miR-30a-5p inhibits granulosa cell death by inhibiting Beclin1.

Establishment and Analysis of Growth Curve of Muchuan Black Chicken

To find out the growth and development regularity,the growth curves of Muchuan black chicken at the age of 0-21 weeks were established by Logistic,Bertalanffy and Gompertz models in this study.The results showed that all the three models can well fit the growth curve of Muchuan black chicken with a degree above 0.988,while the Gompertz model and the Bertalanffy model was the best for hens and cocks,respectively.Finally,the weight of hens and cocks were analyzed according to their corresponding high fitting models.Results showed that the inflexion age of Muchuan black chicken was 6.8-6.9 weeks old with an inflexion weight of 692.98 g in hens and 805.57 g in cocks.In conclusion,it was feasible to establish the growth curve of Muchuan black chicken with Logistic,Bertalanffy and Gompertz model.

Report on the Breeding of Dahen 799 Broilers

[Objectives]This study was conducted to improve the production efficiency of dark-shank partridge-like plumage high-quality broilers and ensure animal welfare,so as to meet the development needs of China’s yellow-feather broiler industry.[Methods]Sichuan Animal Science Academy and Sichuan Dahen Poultry Breeding Co.,Ltd.formed a joint breeding research team.The team bred Dahen 799 broiler complete set line with local chicken breeds as the main material and improving production efficiency,stabilizing meat quality and flavor and achieving autosexing of chicks as the main breeding goals by modern poultry breeding technologies,after 10 years and 8 generations.[Results]The Dahen 799 broiler complete set line was approved by National Commission of Livestock and Poultry Genetic Resources in December 2020.The 66-week-old egg production of the breed reached 189 eggs.For the commercial generation,cocks and hens showed 10-week-old weights of 2668 and 2269 g,respectively;the feed conversion ratio was 2.26-2.35;the survivability was 96.7%-97.2%;and the average intramuscular fat contents of cocks and hens were in the range of 1.8%-2.1%,and the inosinic acid contents were in the range of 2.3-3.2 mg/g.The production performance and meat flavor of Dahen 799 broilers were better than Dahen 699 broilers,Sichuan mountainous bone-black chickens and two other social breeds.Compared with Sichuan mountainous bone-black chickens,the egg production at the age of 66 weeks increased by 47 eggs;the average weight of cocks and hens of the commercial generation at 10 weeks increased by 45.21%;and the autosexing rate of chicks of the commercial generation reached 99.3%.[Conclusions]Dahen 799 broilers have the advantages of good production performance,high feed conversion ratio and excellent meat flavor and the characteristic of autosexing which other breeds do not have,and can fully meet the industrial development needs of dark shanks and partridge-like plumage broilers.

Small RNA Sequencing Reveals Differentially Expressed piRNAs Related to Hypoxia in Tibetan Chickens

The relevance of genetic mechanism to the phenotype of hypoxic adaptation remains elusive.Tibetan chickens typically used to investigate the mechanism for the adaptation of hypoxia and the recognition of hypoxia-related piRNA remains an open issue.The purpose of this study was to illustrate whether the piRNAs were related to hypoxic adaptation.First of all,the differentially expressed piRNAs(DEpiRNAs)were identified through RNA sequencing between the Tibetan chickens and Daheng broilers.Subsequently,the target genes of DEpiRNAs were predicted and annotated by software.The network was constructed by Cytoscape.In our study,a total of 277 DEpiRNAs(33 down-regulated,244 up-regulated)were identified in the Tibetan chickens compared with the Daheng broilers.All of the 277 DEpiRNAs predicted 36658 targeted genes.Gene Ontology(GO)analysis showed that the target genes were significantly enriched in the biological process correlated with proliferation and apoptosis of cells,including cell cycle,mitochondrial outer membrane permeabilization,and positive regulation of stress-activated mitogen-activated protein kinase cascade.Kyoto Encyclopedia of Genes and Genomes(KEGG)analysis implicated that the DEpiRNAs were mainly involved in immune and metabolism,including natural killer cell-mediated cytotoxicity,toll-like receptor signaling pathway and fatty acid metabolism.Furthermore,a predicted network with four piRNAs acted on 11 pathways via interacting with 22 target genes,in which piR-gga-1368839 regulated metabolic pathways by acting on DHCR24.In conclusion,we determined the DEpiRNAs in the Tibetan chickens and found that these piRNAs were associated with metabolism,which may be favorable for researching the biological adaptation to hypoxic stress.

Differentiation of Expression Profiles of SREBF1 and SREBF2 Gene in Chicken

Sterol regulatory element-binding factor-1 and-2(SREBF1 and SREBF2)are important transcription factors involved in the regulating lipid homeostasis.Based on the essential role of SREBF1 and SREBF2,we measured the mRNA expression levels of the two genes in six various tissues at different growth points.Our results showed that the SREBF1 and SREBF2 were expressed in all six tissues examined in Erlang mountainous chicken(SD02)at 42 d,and were expressed abundantly in the uropygial gland and liver,with relatively lowest levels of expression in the abdominal fat,sebum cutaneum and leg muscle.The expression ratio of SREBF1 and SREBF2 in breast muscle,leg muscle,sebum cutaneum and uropygial gland exhibited a"decline-rise"trend.However,in liver,the expression ratio of these two genes exhibited a"decline-rise-decline"trend.Meanwhile,the expression level of SREBF1 gene of all tissues was lower than that of SREBF2 except for uropygial gland.The findings will provide important references for further function investigation of the two genes involved in fat deposition in chickens.

Production Performance of Different Generations of Muchuan Blackbone Chicken

In order to formulate feasible conservation measures and develop and utilize Muchuan black-bone chicken rationally,two generations of Muchuan black-bone chicken were bred,and their production performance and slaughter traits( at the age of 300 d) were compared. The results showed that the reproductive performance,slaughter performance and body size of the Muchuan black-bone chicken of Generation 1( G_1)were all improved compared with those of the Generation 0( G_0)( P <0. 05). At the age of 300 d,the live weight,carcass weight,and leg muscle weight of the G_1 were significantly higher than those of the G_0( P <0. 05); and the chest width of the cocks of the G_1 was significantly higher than that of the G_0( P <0. 05). It suggests that after rigorous selection and utilization of modern poultry breeding techniques,the reproductive performance,slaughter performance and survival rate of Muchuan black-bone chicken can be improved significantly.

Analyses of Chicken Tenderness Traits Based on Transcriptome Sequencing

The calpain system is ubiquitous in cells, mainly comprising calpains and calpain inhibitors, and is a widespread calcium-dependent cysteine protease in organisms that is involved in many cellular processes such as muscle degradation in vivo and affects the tenderness of meat after animal slaughter. The study found 128 DEGs that probably regulated tenderness traits were selected from 16 significantly enriched GO terms by transcriptome sequencing analysis, and found that the developmental changes in the expression levels of the CAPN1 gene in the pectoral and leg muscles were significantly positively correlated ( P <0.05) with the cumulative growth values of live weight and comb weight. The developmental changes in the expression levels of the CAST gene in the pectoral and leg muscles were not significantly correlated with the cumulative growth values of live weight and comb weight. Our results helped demonstrate the potential molecular mechanisms of tenderness in chickens and provide valuable information for chicken breeding.