PSIX-3 Rumen Bacteria Composition between pre-Weaning and Post-Weaning Dairy Calves

Abstract The purpose of this experiment was to study the changes of fecal bcteria of calves before and after weaning. Among 365 Holstein calves born in 2021, 8 Holstein calves with similar body weight were selected before weaning (60 ± 2 d) and after weaning (120 ± 6 d), and rectal manure was collected. Fecal samples for volatile fatty acids and fecal microorganisms. The results showed that: 1) Sobs index, Ace index, Chao1 index, Simpson index and Shannon index of pre-weaning calves and post-weaning calves were significantly different (P < 0.05); 2) At the phylum level, both pre-weaning calves and post-weaning calves were characterized by Bacteroidetes, Firmicutes, Actinomyces, the phylum is the dominant bacteria. Compared with pre-weaning calves, the composition of fecal bacteria of post-weaning calves at the phylum level, the relative abundance of Patescibacteria and Campilobacterota, decreased significantly (P < 0.05); 3) At the family level, the predominant bacteria of both pre-weaning and post-weaning calves are Lachnospiraceae, Vibriospira, and Prevotella. Compared with pre-weaning calves, the composition of fecal microbiota in post-weaning calves at the family level, the relative abundances of Oscillospiraceae, Muribaculaceae, Rikenellaceae, Erysipelotrichaceae, Christensenellaceae, Anaerovoracaceae, Clostridiaceae, norank_o__RF39, Monoglobaceae and UCG-010 were significantly increased (P < 0.05), while the relative abundances of Lactobacillaceae, Bacteroidaceae, Ruminococcaceae, Butyricicoccaceae and Coriobacteriaceae were significantly reduced (P < 0.05); 4) At the genus level, compared with pre-weaning calves, the relative abundance of UCG-005, norank_f__Muribaculaceae, unclassified_f__Lachnospiraceae, Rikenellaceae_RC9_gut_group, Prevotellaceae_UCG-003, Paeniclostridium, Christensenellaceae_R-7_group, Coprococcus, Clostridium_sensu_stricto_1, Agathobacter, norank_f__norank_o__RF39 decreased significantly (P < 0.05), Lactobacillus, Bacteroides, Blautia, Faecalibacterium were significantly increased (P < 0.05). In conclusion, in this experiment, there were significant differences in the fecal bacteria of Holstein calves before and after weaning in Tibet. This study provides reference information for the feeding and management of calves in high altitude areas.