Effects Of Dietary Energy And Protein On Productive Performance,Intestinal Microflora,and Expression Of Lipid Metabolic Genes In Jingdian Pekin Duck

To investigate the appropriate metabolizable energy（ME）and crude protein（CP）requirements of Jingdian Pekin ducks during the rearing period,the effects of ME and CP on production performance,serum biochemical indexes,expression of lipid metabolism-related gene and cecum microflora of Jiangdian Pekin ducks were investigated.In this experiment,the two factors（ME and CP）trial design was adopted,480 18-day-old Jingdian Pekin ducks were randomly divided into 6 groups with 8 replicates,10 ducks per replicate,respectively.The crude protein levels were 16.5% and 17.5%,and three metabolizable energy levels were11.92 MJ/kg,12.34 MJ/kg and 12.80 MJ/kg.The results showed that dietary crude protein level had a significant effect（P < 0.05）on the sebum rate and the percentage of half-eviscerated yield of male Jingdian Pekin ducks,and the interaction between dietary energy and protein level had a significant effect（P < 0.05）on the sebum rate of male Pekin ducks.The sebum rate of male ducks was the highest at the dietary energy level was 12.34 MJ/kg and the protein level was 16.5%,and the percentage of eviscerated yield was highest at the protein level 17.5%.The dietary energy level had a significant effect（P < 0.05）on the liver weight of male Pekin ducks,and the dietary energy was directly proportional to the liver weight.The interaction of dietary energy and protein had no significant effect on organ index（P > 0.05）.Dietary energy level had a significant effect on total protein and albumin in serum of male ducks（P < 0.05）.Its content was directly proportional to dietary energy level,and had a highly significant effect on low density lipoprotein cholesterol（P < 0.01）,the energy content of 12.8 MJ/kg was significantly higher than that of 11.92 MJ/kg and 12.34 MJ/kg.Energy level had a significant effect on serum total protein and albumin of female ducks（P < 0.01）,which content was directly proportional to dietary energy level.Dietary protein level had a significant effect on high density lipoprotein cholesterol in male ducks（P < 0.05）.The content of high density lipoprotein cholesterol was significantly higher in 17.5% protein level than16.5% protein level.Dietary protein level had a highly significant effect on serum total protein,albumin,low density lipoprotein cholesterol and uric acid in female ducks（P < 0.01）,which was directly proportional to protein level,and had a significant effect on serum high density lipoprotein cholesterol（P < 0.05）.The interaction of energy and protein had significant effects on the serum total protein,albumin,high density lipoprotein cholesterol and total cholesterol of male ducks（P < 0.05）,extremely significant effects on the levels of serum uric acid and triglyceride（P < 0.01）,and had no significant effects on the serum biochemical indexes of female ducks（P < 0.05）.The dietary protein level had a significant effect on the SCD gene expression of male ducks（P < 0.05）,which showed that the expression of 17.5% protein group was significantly lower than that of 16.5% protein group.Dietary energy had a significant effect on the expression of CPT1 A and ACSL1 genes in male ducks（P < 0.05）.The expression of 11.92MJ/kg and 12.34 MJ/kg energy levels were significantly higher than that of 12.8 MJ/kg energy levels.The interaction of energy and protein had a significant effect on the expression of DGTA2 and FAS genes in male ducks（P < 0.05）,and FAS genes in female ducks（P <0.05）.At the phyla level,the dominant species of cecum microflora in each group were Firmicutes and Bacteroidetes,but the abundance of dominant species in phyla was different.The relative abundance of microorganisms in the 17.5% protein group was greater than 1%,and there were two more phyla,Proteobacteria and Spirochetes,than in the 16.5% protein group..Dietary protein level had a significant effect on the abundance of microflora at genus level（P < 0.05）.The abundance of beneficial bacteria such as Colidextribacter and Butyricimonas was directly proportional to the energy level of the dietIn summary,different energy or protein levels had effects on production performance,slaughter performance,serum biochemical indexes,the expression of genes related to lipid metabolism and cecum microflora of Jingdian Pekin ducks.The appropriate metabolizable energy and crude protein levels in this experiment were 12.34 MJ/kg and 16.5%,respectively.