Effects Of Different Vitamin D₃ Levels Of Sows During Pregnancy On Muscle Development And Meat Quality Traits Of Offspring

The growth and development of muscle tissue is one of the important indicators of pork quality.In order to explore the molecular mechanism of the effects of different vitamin D₃horizontal pairs of sows in the sow pregnancy,this study was for feeding different vitamin D₃levels of 27-headed pregnant sows（41 days of pregnancy;Normal group（ND）:800IU;Test Group（LD,HD）:200 IU,3,200 IU;9 heads per group）a total of 36 offspring pigs（sex balance）were weighed and slaughtered to analyse the muscle developmental and meat quality characteristics of sow.At the same time,the C2C12 cells were studied and the body-formed muscle differentiation model was established.We set up a control group（2%horse serum,0n M vitamin D₃）and 5 test groups（add 50,100,200,400,800 n M vitamin D₃）.Through the identification of MyoD1 and MYH10 proteins and expression analysis of the key myoblast genes during myoblast induction of C2C12 cells,we screened the optimal concentration of vitamin D₃ in myoblast induction of C2C12 cells,and combined analysis verified the function and mechanism of vitamin D₃ in the process of muscle growth and development of offspring pigs.The major findings of this study are as follows:1.Molecular mechanism studies of vitamin D₃ on mouse C2C12 cells have shown.Morphological and immunofluorescence identification results showed that compared with the control group and other experimental groups,C2C12 cells after 6 and 12 days of induction had more clear and parallel distribution of multinucleated muscle tubes at 400 n M vitamin D₃ level,and showed positive expression of MyoD1 and MYH10,respectively.RT-PCR results show that 400 n M Vitamin D₃ treatment group C2C12 cells MyoG,MyoD1,Myf5,Myh6,Myh7,Myh8,IGF-I,IGF-IR,IGF-II,IGF-IIR,CAST mRNA expression levels were significantly higher than that of the control group and other test groups（P<0.05）.Compared with the control group,50,100,200,800 n M vitamin D₃ test group C2C12 cells Myh7,IGF-II,IGF-IIR,CAST mRNA expression levels were significantly increased（P<0.05）,but the expression level of MSTN mRNA was significantly reduced（P<0.05）.It was suggested that the vitamin D₃ concentration increased to 400 n M,which could stimulate the expression of the muscle-related gene,reduced the expression of myostatin.However,the effect of vitamin D₃ was weakened when the concentration of vitamin D₃was increased to 800 n M,indicating that the expression of myogenic genes in mouse C2C12 cells had a concentration-dependent change of vitamin D₃.2.Effects of different vitamin D₃ levels on key genes of longissimus dorsi muscle development in offspring:compared with the ND group,the HD group MyoD1,CAST,IGF-I,IGF-II,IGF-IIR,My HCI,My HCIIx mRNA expression levels were significantly increased（P<0.05）,but the LD group was significantly reduced（P<0.05）,The expression levels of MSTN,IGF-IR,My HCIIb mRNA in the HD group and the LD group were significantly reduced（P<0.05）.Compared to the LD group,the proportion of Type I in the ND group and the HD group was significantly reduced（P<0.05）,while the Type II was significantly enhanced（P<0.05）.These results suggested that maternal high-dose vitamin D₃ levels influenced the expression of muscle development-related genes and proteins,and thus improved the meat quality of offspring pigs.3.Effects of different vitamin D₃ levels on pork quality of offspring shown:HD group had higher p H,a*value,hardness,cohesiveness,springiness,chewiness,and storage modulus（G’）values,while had lower shear force,cooking loss,L*value,T₂₁ and T₂₂ relaxation time compared with LD group during postmortem cold storage period（P<0.05）.In addition,cold storage time increased cooking loss and b*values of LD and ND groups,TPA parameters,T₂₂relaxation time and G’values of all experimental groups,while decreased a*and L*values of LD and ND groups（P<0.05）.The results revealed that maternal high-dose vitamin D₃ levels influenced these indicators of chilled pork batters in offspring pigs,which improved the quality attributes during postmortem cold storage.In conclusion,this study suggested that maternal high-dose vitamin D₃ levels during pregnancy could improve meat quality characteristics by regulating the expression of genes and proteins related to muscle development of offspring,thus providing a scientific basis and production implementation plan for improving the quality characteristics of offspring pork by regulating early porcine nutrition（vitamin D₃）.