Effect Of 1α,25（OH）₂VD₃ On Mammary Gland Development And Colostrum Composition Of First-born Sows During Pregnancy

1α,25（OH）₂VD₃ is the most important active form of VD₃ in animals,and is responsible for performing most of its biologically active functions.As an important growth and lactation organ of female mammals,the mammary gland is directly related to the level of reproductive traits.The mammary gland development of the first-born sow,especially during pregnancy,determines its lifetime lactation performance.This study contains two parts:cell experiment and animal experiment.The sampling site of breast tissue was determined by cell culture experiment and provided a reference for the addition amount of animal experiment part;In order to explore the effect of 1α,25（OH）₂VD₃ on mammary gland development and lactation of first-born sows,we selected 140 ternary sows with similar body weight,age and condition,and randomly divided them into 4 groups.From about two weeks before estrus and mating until the sows farrowing,and the sows were fed basal diets containing 0,1,2 and4μg·kg^-1 1α,25（OH）₂VD_3-glycoside,which provided in the form of1α,25（OH）₂VD_3-glycoside.After the experiment,the production data of each group of sows were recorded and the colostrum was collected for analysis.The mammary gland tissues of sows were sampled at two stages of 65th day and 114th day of pregnancy.The proteomics TMT/i TRAQ labeling technology was used to analyze the mammary tissues of each group.The results showed that the addition of1α,25（OH）₂VD_3-glycoside in the diet had no effect on litter size（P>0.05）;the addition of 2μg·kg^-1 showed an upward-regulating trend on the main components of colostrum;4μg·kg^-1 addition amount can significantly increase the new born piglet weight of first-born sows,the content of milk fat,milk protein and non-fat milk solids in colostrum（P<0.05）,and significantly increase the total solids content in colostrum（P<0.01）.The results of proteomic analysis of the mammary glands of sows in the stage of 65th and 114th day of pregnancy showed that of the 13995/53118 peptides identified,13019/48868 were unique peptides.A total of 3286/5029 proteins were identified,of which 2815/4292 proteins contained quantitative information.Differentially abundant proteins（DAPs）related to fatty acid metabolism and fatty acid biosynthesis,regulation of lipolysis in fat cells,peroxisomes,and PPAR signaling pathways were screened out,such as:FASN,ACACA,HADH,SCD,CSN2,CSN3,CSN1S1,CSN1S2,ACSL3,ACSL6,LALBA,FABP3,PLIN2,TRAF1,LTF.And these signaling pathways and DAPs in them are closely related to the mammary gland development,lactation and the regulation of milk quality.In summary,plant-derived 1α,25（OH）₂VD_3-glycoside as a nutritional additive may have a positive regulatory effect on the mammary gland development and colostrum of first-born sows during pregnancy.This study determined the optimal dose of 1α,25（OH）₂VD_3-glycoside in the diet to regulate the mammary gland development of first-born sows.Our reaserch identified DAPs and potential signaling pathways associated with mammary gland development and lactation in first-born sows,providing valuable information on the proteins involved in regulation and contributing to a better understanding of the mechanisms by which 1α,25（OH）₂VD₃regulate mammary gland development and lactation in sows.