The Primary Analysis About Mechanism Underlying Duck Meat Quality Difference Between Feed Modes Of Floor-Raising And Net-Raising

Floor-raising or net-raising mode has become a major development trend of meat duck industry.Although there are many researches on the effects of meat duck production and meat quality in different feeding ways,the specific molecular mechanism affects meat quality differences in ducks remains to be studied.High quality Nong Hua hemp duck were used to compare the differences in meat quality and molecular mechanism between the ground group and the net group at 4,8 and 13 weeks of age and RNA-Seq technology was used to explore the reasons for the differences in meat quality indicators,and thus provide theoretical basis for the selection of production and feeding methods of meat ducks.The main results are as follows:1.There are significant differences in muscle p H value,muscle fiber diameter and density,and fat deposition between floor-raising or net-raising mode.The muscle p H values in the net group are significantly higher than the ground group at 4 and 8 weeks of age（P<0.05）,while that show the adverse result in p H₁ value in pectorals at 13 weeks old（P<0.05,p H₁ and p H₂ are opposite）.At 4 weeks old,the diameter of muscle fibers is significantly higher in crureus of the ground group than that in the net group（P<0.05）,while that is significantly higher in net ground than that in the ground group（P<0.05）.In addition,the fat content of crureus in the net group is significantly lower than that in the net group at 13 weeks old（P<0.05）.Ground and net farming also have effects on meat color,shear force and cooking loss,but there was no significant difference between them.2.RNA-Seq technique was used to sequence the transcriptomes of breast and leg muscles of 4,8 and 13-week-old ducks raised on the ground and on the net.And the Clean Data of each sample was above 6.GB,and the ratio of Clean Read to reference genome was between 70.16%and 76.60%.Differential gene analysis showed that the number of differentially expressed genes（DEGs）decreased first and then increased with the increase of week-old meat ducks.Among them,the number of DEGs was the least at 8 weeks of age,the most in breast muscle at 4 weeks of age,and the most in leg muscle at 13 weeks of age.3.The analysis of GO and KEGG shows that the DEGs are mainly involved in biological processes such as muscle activity,carbohydrate metabolism and lipid metabolism,and are mainly enriched in the pathways including m TOR signaling pathway,PPAR signaling pathway,regulation of actin cytoskeleton,apoptosis,adrenergic signal transduction in cardiac myocytes,adipocytokines and other signaling pathways.4.Functional interaction analysis of DEGs in duck muscle of ground and net-raised ducks showed that the up-regulated genes in ground-raised ducks were CASQ2,KRAS,CACNG1,PLN.These genes were involved in regulating the biological processes of sarcomere,adrenergic signal transduction,cell homeostasis of muscle cells,and were related to muscle activity;LDHA,PGK1,PGM1,GPI,PDK4,ALDOB genes were involved in muscle activity.It is involved in starch and sucrose metabolism,pentose phosphate pathway,glycolysis/gluconeogenesis,and is related to carbohydrate metabolism.On the other hand,PDK4 is up-regulated in the expression of online nutrition,which participates in active oxygen metabolism and glucose homeostasis;PNPLA2,STAT3,MTOR,IRS2,LPL,AGPAT2 are mainly involved in glyceride metabolism,glycerophospholipid metabolism,glyceride metabolism and other biological processes,which are related to lipid metabolism..Above all,the meat quality difference of meat ducks was mainly reflected in the p H value of muscle,the diameter and density of muscle fibers and the deposition of fat content under the condition of flat farming on the ground and on the net.The transcriptome revealed that differentially expressed genes were mainly involved in muscle activity,carbohydrate metabolism and lipid metabolism,suggesting that the two feeding methods may affect meat quality by affecting the above metabolic processes.This study provides a theoretical basis for the mechanism of meat quality regulation by feeding methods.