Effect Of Glucosamine Supplementation During Pregnancy On Reproductive Performance Of Fixed-time Artificial Insemination Sows

In this paper,fixed-time artificial insemination（FTAI）sows were used as the research object to explore the effects of adding glucosamine（GlcN）during pregnancy to delivery on the reproductive performance,intestinal microorganisms,serum metabolites and steroid hormone synthesis of FTAI sows.Three experiments were designed:Experiment 1:The aim of this study was to evaluate the effect of GlcN supplementation during pregnancy to parturition on the reproductive performance of FTAI sows.A total of 170 Landrace-Yorkshire sows with 3-5 parities and similar body weight were selected in the experiment.After weaning at the same time,they were bred by FTAI and randomly divided into 2 groups.The control group was fed with basal diet,and the GlcN group was fed with basal diet+10 g/d GlcN.The feeding period was from sow breeding to delivery.On the day of delivery,the litter size and live litter size of sows in each group were counted,the birth weight and placental weight of piglets were weighed,and the live litter rate was calculated.The results showed that GlcN could improve the reproductive performance of FTAI sows,that is,it increased the number of live births of FTAI sows by 0.86（P=0.02）and the rate of live births by 6.52%（P<0.001）,increased the birth litter weight by 1.79 kg（P=0.08）and placental weight by 25.5 g（P=0.07）,and reduced the coefficient of variation of birth weight by 1.9%（P=0.04）and placental weight by 2.07%（P=0.05）.Experiment 2:The aim of this study was to investigate the effects of dietary GlcN supplementation during pregnancy on gut microbiota and serum metabolites in FTAI sows.On the basis of experiment 1,fecal and blood samples of sows in each group were randomly collected at 30 d,70 d,110 d of gestation and after delivery for microbial diversity and serum metabolomics analysis.The results showed that compared with the control group,the addition of GlcN increased the diversity of gut microbiota in late pregnancy,but the effects of GlcN on the abundance of gut microbiota in sows at different pregnancy stages were different.At the genus level,GlcN supplementation during pregnancy significantly increased the abundance of Streptococcus at 30 and 70 days of pregnancy（P<0.05）,while the relative abundance of Prevotellaceae＿UCG＿001 decreased at 30 days of pregnancy and increased at 70days after GlcN supplementation（P<0.05）.In addition,the addition of GlcN can increase the levels of serum metabolites such as anti-inflammatory and antioxidant（sinapic acid,etc.）and promote placental and fetal development（glutamine methionine,etc.）.After analyzing the gut microbiota and serum metabolites of sows at different pregnancy stages,it was found that 30 d and 70 d of pregnancy,sinapic acid and glutamine methionine were positively correlated with Streptococcus（all P<0.05）,while at 110 d of pregnancy,sinapic acid and glutamine methionine were positively correlated with Oscillatoria（all P<0.05）.Experiment 3:The aim of this study was to evaluate the effect of GlcN on the synthesis of P4 in placenta of FTAI sows and the effect of P4 on steroid hormone production in porcine placental trophoblast cell（pTr）and related mechanisms.P4 is the most active progesterone and the precursor of estrogen and androgen,which is essential for maintaining normal pregnancy.On the basis of experiment 1,the placentas of the fetus in the control group and the GlcN group were collected,and the concentration of P4 in the GlcN group was significantly higher than that in the control group（P<0.05）.pTr cells were treated with different concentrations of P4 for 48 h in serum-free medium in vitro.Cell number,steroidogenesis,and relevant gene and protein expression levels were detected.A high dose of P4（10.0μM）significantly increased P4（P<0.01）,androstenedione（P<0.05）,testosterone（P<0.05）,and estradiol（P<0.05）production in porcine placental trophoblast compared to that in control cells,while a low dose of P4(1×10^-3μΜ)had no significant effect on steroid production.The m RNA expression of apoptosis-related genes（CASP3,CASP8,and Bax）（P<0.05）and steroidogenesis-related genes（CYP11A1,CYP19A1,and StAR）（P<0.01）was upregulated,and the expression of HSD3B and HSD17B4 was inhibited（P<0.05）in porcine placental trophoblast treated with high doses of P4.Low doses of P4 had a lighter effect on gene expression than high doses.The expression of apoptosis-related proteins CASP3（P<0.05）,and Bax（P<0.01）and steroidogenesis-related proteins CYP19A1（P<0.05）and StAR（P<0.01）was upregulated,but proliferation-related protein CCND2（P<0.01）was downregulated in pTr cells treated with high dose of P4.While a low dose of P4 had inhibited the expression of Bax,CYP11A1（all P<0.01）,and CCND2（P<0.05）,but the expression of CASP3（P<0.05）,and StAR（P<0.01）was upregulated.Conclusion:GlcN supplementation during pregnancy can improve the reproductive performance of FTAI sows,and affect the intestinal microbiota and serum metabolites of sows,as well as placental steroid hormone synthesis;high levels of P4 in vitro can affect pTr cell proliferation and steroid hormone secretion disorders,affecting placental function.