| Restricted feeding can improve the quality and nutritional value of ducks,reduce feed cost,improve breeding efficiency,and provide consumers with better quality poultry meat products.However,over-restricted feeding will affect bone calcification,which will affect the product quality of ducks.Therefore,the effects of different feeding restriction degrees on sternal calcification of meat ducks were explored to screen out the most suitable feeding restriction degree for raising high-quality meat ducks,and to provide corresponding data support and theoretical basis for the rational use of feeding restriction mode in the practice of meat duck breeding.In this study,the sternal bone of Tianfu Nonghua Ma ducks was used as the experimental material.The phenotypic traits,phenotypic indexes of sternal calcification and histological morphology of sternal cells of Tianfu Nonghua Ma ducks with different feeding restrictions were determined to analyze the effects of different feeding restrictions on sternal calcification of ducks.In addition,metabolome sequencing and transcriptome sequencing were conducted using male duck sternum tissues under free feeding and 60% restricted feeding conditions,and the key genes and key metabolic pathways affecting sternal calcification under restricted feeding conditions were analyzed.The results are as follows:(1)The length of complete calcification or white cartilage in the sternum of ducks in the 56-day-old AD libitum feeding group and each restricted feeding group,the 49-day-old AD libitum feeding group and the 80% restricted feeding group were within 1CM,which met the marketing requirements.With the aggravation of feeding restriction,the calcium and phosphorus contents of sternum decreased,while the chondrocytes and hypertrophic chondrocytes in bone tissue increased.The results indicated that the degree of sternal calcification decreased with the increase of dietary restriction in 49 and 56 days of age ducks.(2)A total of 332 annotated differential metabolites were identified from the differences of sternal metabolites between free-feeding group and 60% restricted feeding group at 49 and 56 days of age,mainly including amino acid,fatty acid and carbohydrate metabolites.This suggests that these three major nutrients have a greater impact on sternum development and sternum calcification.In addition,the relative contents of deoxyuridine and thymidine of pyrimidine metabolic pathway were significantly increased in the restricted feeding group at 49 days of age and 56 days of age.(3)A total of 838 differentially expressed genes were detected in sternal transcriptomic analysis of ducks at 49 and 56 days of age in free feeding group and 60%restricted feeding group,among which 81 differentially expressed genes were found at 49 and 56 days of age.The expression levels of CTSK,DMP1 and CHSY3 in the differentially expressed genes were higher in the restricted feeding group at 49 days of age than in the free feeding group,while the results were opposite at 56 days of age.The results indicated that compensatory growth occurred in the body and the expression of bone calcification related differential genes increased in the restricted feeding group.(4)An analysis of both transcriptome and metabolome revealed that the differential metabolites and genes expressed in pathways enriched by KEGG were mainly concentrated in 13 common pathways,such as pyrimidine metabolism,ABC transporter,amino sugar,and nucleotide sugar metabolism.In this study,we investigated the rules of sternum development,bone histomatous changes,and sternum calcification in Tianfu Nonghua ducks under different feeding restriction conditions,and screened the key metabolites and key genes that affected sternum calcification and sternum development.It can provide a theoretical basis and lay a certain foundation for further study on the effects of feeding methods on bone health of meat ducks and establishment of efficient matching technology of Tianfu Nonghua ducks. |
