Abstract: 【Objective】 The aim of this study was to analyze the molecular mechanisms related to the effects of perinatal nutritional supplementation and early weaning on yak’s maternal nutrient metabolism and reproduction through transcriptomics. 【Method】 18 healthy late-pregnant yaks with (233.9±18.3) kg weights,2-4 litters,and similar due dates were selected and randomly divided into three groups (n=6)：graze feeding group (GF),nutritional supplementation group (SF),and nutritional supplementation and early weaning group (SW).The yaks in GF,SF,and SW groups were naturally grazed from 30 days before delivery to 90 days after delivery,and after daily grazing,the yaks in SF and SW groups were supplemented with fully mixed feed (TMR).The calves in GF and SF groups were breastfed and naturally weaned after delivery,while calves in SW group were weaned early at 60 days postpartum.Whole blood samples were collected from the yaks in GF,SF,and SW groups at 15 days before(-15 d),30 and 90 days after parturition(30 and 60 d) for transcriptomic analysis. 【Result】 ① After data filtering，the whole blood cDNA library sequencing of yak showed,the average value of each group in Q20 ＞ 95%;the average value of each group in Q30 ＞ 90%,indicating high quality of transcriptome information.The reference gene comparison statistics showed that the average mapped ratio of each group was greater than 70% standard,indicating good comparison results.② Transcriptome sequencing revealed that a total of 884,443 and 354 significantly differentially expressed genes (DEGs) were identified in SF and GF groups at -15,30 and 90 d,respectively.Additionally,502 and 160 significantly DEGs were identified in SW group compared with the GF and SF groups at 90 d,respectively.③The GO analysis results showed that the three groups were enriched to 1 464-4 638,308-891 and 253-586 significantly different terms (P＜0.05) for biological process (BP),molecular function (MF),and cellular component (CC) in the two-by-two comparisons of -15,30 and 90 d,respectively.DEGs were mainly enriched in terms related to nutrient metabolism functions such as positive regulation of response to nutrient levels,sterol-transporting ATPase activity,chylomicron,and lipoprotein particle receptor activity.④ The KEGG enrichment analyses results showed that DEGs were significantly enriched in 16 pathways in SF group compared with GF group at -15 d.Pathways related to nutrient metabolism and reproduction included protein digestion and absorption,gastric acid secretion,salivary secretion,and regulation of lipolysis in adipocytes.At 30 d,23 pathways were significantly enriched in SF vs GF group.Pathways related to nutrient metabolism and reproduction included relaxin signaling pathway,arachidonic acid metabolism,ovarian steroidogenesis,protein digestion and absorption,regulation of lipolysis in adipocytes,and prolactin signaling pathway.At 90 d,17 significantly enriched pathways were found in SF vs GF group,included insulin secretion,arginine biosynthesis,C5-branched dibasic acid metabolism,and gastric acid secretion related to nutritional metabolism and reproduction.Additionally,10 significantly enriched pathways were found in SW vs GF group.Pathways related to nutritional metabolism and reproduction included arginine biosynthesis,nitrogen metabolism,and C5-branched dibasic acid metabolism.There was 4 significantly enriched pathways in SW vs SF group. 【Conclusion】 Nutritional supplementation treatment during the perinatal period promoted nutrient digestion and absorption,lipid metabolism,and attenuated the catabolism of protein-amino acids in body stores through the secretion of salivary and gastric acid in yak dams.It also enhanced the maintenance of pregnancy,lactation activity,and postpartum recovery through the synthesis,secretion,and action pathways of reproduction-related hormones,such as epinephrine,norepinephrine,prostaglandin E2,relaxin and prolactin.

Key words: perinatal; yak; nutritional metabolism; reproductive performance; transcriptomics