| Lueyang black-bone chicken is a special protected poultry in Shaanxi Province of china,and has high nutritional value and medicinal value.At present,there are three main rearing systerms for Lueyang black-bone chickens: cage rearing,grid flat rearing and free-range rearing in forests.The meat quality of Lueyang black-bone chickens is different under different rearing systems.Local farmers traditionally believe that the long rearing cycle of free-ranging chickens Long black chicken has more nutritional value and better meat quality.In order to quantitatively analyze the impact of the three rearing systems on meat quality,analyze the differences in the regulation of chicken traits,provide a theoretical basis for cultivating Lueyang black-bone chickens with more flavor and nutritional value,and at the same time provide the most suitable rearing systerms for Lueyang black-bone chickens and farmers’ opinions on The selection of rearing systerms provides a theoretical reference basis.In this study,90 Lueyang black-bone chickens with similar body weight at 10 weeks of age were selected and randomly divided into three groups: caged,grid flat and free-range,with 3replicates in each group.Raised to 17 weeks of age,6 males and 6 females were randomly selected from each group and slaughtered.The meat quality was measured,histomorphological analysis,and the nutritional and flavor substances in chicken were compared.Through transcriptomic analysis and RT-qPCR verification,differentially expressed genes and related regulatory pathways related to meat quality were screened.The results of this study are as follows:1.The effect of different rearing systems on the quality of Lueyang black chicken.The results showed that the pH value of chickens in free-range and grid flat rearing groups was significantly higher than that of cage group(P<0.05).There was no significant difference between free-range and online flat rearing groups(P>0.05).The shear force of free-range roosters was significantly higher than that of caged and grid flat roosters(P<0.05),and the shear force of flat roosters was no significantly different from that of caged roosters(P>0.05).There was no significant difference between free-rang and caged hens(P<0.05);In the free-range group,the shear force of roosters was significantly higher than that of hen(P<0.05),and the rest were not significant(P>0.05);The hydraulic,of Lueyang black-bone chicken was not significant under different rearing systems(P>0.05).2.The histological observation of breast muscle of Lueyang black-bone chicken showed that the muscle fiber diameter of free-range chicken was larger than that of caged group,and the difference in muscle fiber diameter was not significant(P>0.05).The muscle fiber density of free-rang group was higher than that in cage,but the difference was not significant(P>0.05).3.The results of the effects of different rearing systems on the nutrients and flavor substances in Lueyang black-bone chicken showed that the protein content of Lueyang black-bone chicken in caged group was significantly higher than that in free-range group(P<0.05),and the rest were not significant(P> 0.05),and there was no significant difference in protein content between roosters and hens under different rearing system(P>0.05).The fat content of chicken in both flat and free-range hens was significant lower than that of caged hens(P<0.05),while there was no significant difference between flat and free-rang group(P>0.05).The fat content of hen was significant higher than that of rooster in caged group(P<0.05).The content of inosinic acid in chickens in the free-range group was significantly higher than that in the caged group(P<0.05).The content of inosinic acid in flat group was significantly higher than that in caged group(P<0.05)..The content of unsaturated fatty acids in the roosters in flat rearing group was significantly higher than that in free-rang group(P<0.05),and the content in the chickens in the caged hens was significantly higher than that in free-rang hens(P<0.05).The saturated fatty acid content of free-rang group hens were significantly higher than that in caged group rooster(P<0.05).The content of free amino acids in rooster chickens in caged and flat group was significantly higher than that in free-range gruops(P<0.05);the amino acid content in roosters was significantly higher than that in hens under caged group,(P<0.05);the rest were not significant(P>0.05);the content of umami amino acids in the chickens in caged and flat groups were significant higher than those in free-range groups(P<0.05).The content of umami amino acids in caged group roosters was higher than that in flat rearing group,and the difference was not significant(P>0.05).In flat rearing group,the umami amino acid content of rooster was significantly higher than that of hen(P<0.05).4.Transcriptome analysis of Lueyang black-bone chicken with different rearing systems showed that there were 297 differentially expressed genes in the LY＿vs＿SY control group,of which 123 differentially expressed genes were up-regulated and 168 were down-regulated;there were 131 differentially expressed genes in the PY＿vs＿LY control group,of which 30 differentially expressed genes were up-regulated and 101 were down-regulated;there were 387 differentially expressed genes in the PY＿vs＿SY control group,including 71 up-regulated differential genes and 36 down-regulated differential genes.KEGG enrichment analysis was mainly enriched in pathways related to amino acid,fatty acid,carbohydrate lipid metabolism and nucleotide metabolism.According to the GO enrichment analysis,the function is mainly enriched in biological processes such as meat quality-related,muscle growth and development,and fatty acid precursor synthesis.PCK1,GLUL,GATM,ASNS,GSTA3,NMRK2,SLC7A5,COS2,SMTNL2,AMPD1,GADL1 were selected out which related to meat quality for RT-qPCR verification analysis,and the verification results were consistent with transcriptome sequencing results.To sum up: different rearing systems have a greater impact on the meat quality of Lueyang black-bone chickens.Compared with free-range chickens,flat and caged chickens tend to taste more tender and juicy.The flat group chickens rich in amino acids and fatty acids is a better choice,and free-range chicken is relatively poor in meat quality.Differentially expressed genes PCK1,GLUL,GATM,ASNS,GSTA3,NMRK2,SLC7A5,COS2,SMTNL2,AMPD1,GADL1 are related to the regulation of meat quality.The differentially expressed genes and regulatory pathways which affect chicken flavor and traits were studied in the molecular level.The research on the meat quality mechanism of Lueyang black-bone chicken lays a theoretical foundation. |
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