Abstract: 【Objective】 The objective of this experiment was to study the effects of gastric and intraperitoneal injection of Lactobacillus rhamnosus (LGG) on the diversity of fecal flora in mice during pregnancy, and provide a theoretical basis for the physiological and intestinal health of animals during pregnancy.【Method】 45 SPF-grade pregnant Kunming mice with similar body weight (23.33 g±1.55 g) and the same breeding date were randomly divided into 3 groups, namely control group, test groups Ⅰ and Ⅱ, 15 in each group.Under the same feeding management and dietary nutrition level, starting from the second day of pregnancy, the control group was fed with basic diet, the test group Ⅰ was intraperitoneally injected 0.5 mL sterilized normal saline containing 0.125 g of LGG (continuous 14 days), and the test group Ⅱ was gavaged with 0.5 mL sterilized normal saline containing 0.125 g of LGG (continuous 18 days).The experiment lasted for 21 days. All mice were dissected 1 day before delivery, and large intestinal stool samples were collected.Genomic DNA was extracted from fecal samples of each group and amplified by PCR for library construction, the qualified libraries were sequenced using NovaSeq 6000 sequencing platform, Uparse software (v 7.0.1001) was used to cluster the sequences into operational taxa (OTUs) with 97% consistency and screen representative sequences.Species annotation analysis was performed using the Mothur method with the SSUrRNA database of SILVA 132, and community composition was counted at phylum, family and genus levels.QIQME 1.7.0 software was used for alpha diversity analysis, Chao1, ACE, Shannon, Simpson indexes were calculated, LEfSe analysis was performed, and FAPROTAX was used to predict the function of intestinal flora.【Result】 Compared with control group, Chao1 and ACE indexes in test group Ⅱ were significantly increased (P<0.05), the Simpson index of mice in test groups Ⅰ and Ⅱ was decreased (P>0.05).Compared with control group, at the phylum level, Firmicutes in test groups Ⅰ and Ⅱ were increased, Proteobacteria in test group Ⅰ was increased, and Proteobacteria in test group Ⅱ was decreased;At the family level, the levels of Lachnospiraceae, Lactate bacteria, Erysipelotrichaceae and Desulfovibrionaceae in test groups Ⅰ and Ⅱ were increased;At the genus level, Lactobacillus and undetermined Trichospiraceae were increased in test groups Ⅰ and Ⅱ. LEfSe analysis showed that there were two significant bacteria in control group.FAPROTAX predicted 35 functions for gut microbiota.【Conclusion】 Under the conditions of this study, LGG gavage could significantly improve Chao1 and ACE indexes, and the number of OTUs in LGG gavage group was higher than that in intraperitoneal injection group.The ratio of Firmicutes/Bacteroidetes, Proteobacteria, Desulvibriaceae and Lactobacillus in the gavage group were lower than those in the intraperitoneal injection group, while the undetermined Trichospiraceae were higher.A comprehensive comparison of the two supplementary feeding methods showed that gavage of LGG to pregnant mice could promote their health during pregnancy.

Key words: gavage; intraperitoneal injection; Lactobacillus rhamnosus (LGG); pregnancy mice; fecal bacteria