Study On The Differences In Lipid Metabolism And Liver Transcriptomics Between Muscovy And Peking Duck

The study aimed to compare the differences in lipid metabolism between lean type Muscovy duck and fatty type Peking duck,explore the correlation between serum biochemical parameters and carcass fatty deposition,moreover to screen candidate genes and metabolic pathways that affect lipid metabolism in duck by transcriptomics analysis.A total of 320 newborn ducklings were allotted to two groups according of breeds.Each group has 8 replicates with 20 ducks.Muscovy duck and Peking duck were reared for 70 days in the same conditions.Eight ducks(sex balance)of each breed were randomly selected and slaughtered to measure fatty deposition parameters and serum biochemical parameters,at ages of I,3,7,14,28,42,70 d respactively.Four male ducks were selected from each group at 42 d,and their livers were collected for transcriptomics analysis.The results showed that:(1)The change curves of Muscovy duck and Peking duck weight were "S" shape.Except for 1d and 70 d,Muscovy duck body weight(BW)was significantly lower than Peking duck(P<0.05).Muscovy duck had lower liver weight(LW)than Peking duck at 1～14 d(P<0.05).The LW of Muscovy duck increased rapidly after 28 d and surpassed Peking duck(P<0.05).The hepatic body ratio(HBR)of the two breeds increased to the maximum at 7d and then decreased(P<0.05).Compared with Peking duck,HBR and liver Triglyceride(TG)contents of Muscovy duck were significantly higher at 7～28 d and 14～28 d,respectively(P<0.05).Muscovy duck livers had more obvious steatosis at 42～70 d and were observed large lipid droplet vacuoles compared with Peking duck.The abdominal fat weight(AFW)and abdominal fat rate(AFR)of the two breeds increased with age.In addition,AFW and AFR of Muscovy duck were lower than Peking duck at each ages.Compared with Peking duck leg muscles,the intramuscular fat(IMF)in Muscovy duck leg and breast muscles were lower(P<0.05).(2)Breed had a significant effect on serum Glucose(Glu)and lipid contents(P<0.01).Except for low-density lipoprotein,the other serum components were significantly affected by the age(P<0.05).The interaction between breed and age significantly affected serum high-density lipoprotein and total cholesterol content(P<0.05).Muscovy duck had lower serum lipid components than Peking duck.Serum TG and very low-density lipoprotein(VLDL)had the similar trend in two breeds.Compared with Peking duck,Muscovy duck had lower TG at 28 d(P<0.05)and lower VLDL at 28～42 d(P<0.05).However,Serum Glu at 28～70 d in Muscovy duck was higher than Peking duck significantly.TG and VLDL in Serum were positively correlated with HBR and AFR(P<0.05)and negatively correlated with liver TG content(P<0.05).Serum TG also positively correlated with LW and BW(P<0.05).(3)Transcriptomics revealed 4954 different express genes(DEG)between the two breeds.Compared with Peking duck,there were 2513 up-regulated genes and 2441 down-regulated genes in Muscovy duck.The GO results indicated that there were 159 significantly enriched entries.Organic acid metabolism was significantly enriched.Analysis of the KEGG pathway indicated that fatty acid metabolism pathway and fatty acid degradation pathway were significantly enriched.By analyzing the DEGs in these two pathway,we focused on the downstream genes in the PPAR signaling pathway.Compared with Peking duck,the expression of FABP3 and ACBP were significantly rised to 4.19 and 3.10 times,and the expression of ACOX1,ACOX2,ACSL1 and CPT1A were significantly decreased to 0.20,0.35,0.17 and 0.45 times in Muscovy duck.The results suggest that:Muscovy duck have more fatty deposition of liver,while Peking duck has more peripheral fatty deposition.Muscovy duck have lower serum lipids level and higher serum Glu level than Peking duck.Serum VLDL and TG may serve as indirect parameters for regulating lipid metabolisim in meat duck breeding selection.Transcriptomics analysis suggest that the differences in the expression of downstream target genes(FABP3,ACBP,ACSLI,CPT1A,ACOX1,ACOX2)in the PPAR signaling pathway may explain the differences in liver lipid metabolism between Muscovy duck and Peking duck.