Postnatal bacterial succession and functional establishment of hindgut in supplemental feeding and grazing goats

The objectives of this study were 1) to investigate the age-related changes in functional achievement (establishment of fermentation capacity and enzyme activities) and bacterial succession (selected functional bacterial species) in the cecum and colon and 2) to assess the effect of feeding system (supplemental vs. grazing, Sup vs. G) on hindgut development in small ruminants. A total of 44 Liuyang black goat kids were randomly slaughtered at 0, 7, and 14 d of age (nonrumination period), 28 and 42 d of age (transition period), and 56 and 70 d of age (rumination period). Intestinal contents were sampled to determine VFA, activities of amylase, carboxymethylcellulase (CMCase), and xylanase, as well as abundances of total bacteria and selected functional bacterial species (genus Prevotella, cellulolytic and amylolytic bacteria) with quantitative PCR targeting the 16S rRNA subunit genes. Total VFA concentration (P < 0.01) and enzyme activities (P < 0.05) in hindgut contents were greater and total bacterial 16S rRNA gene copy numbers (P = 0.003) in the cecum were lower for Sup vs. G. Furthermore, irrespective of feeding system, hindgut total VFA concentrations and total bacterial 16S rRNA gene copy numbers increased with age (P < 0.01), with the greatest increase rate observed from 14 to 28 d. Amylase fluctuated with age, whereas CMCase and xylanase activities in Sup kids increased (P < 0.05) as age increased. The proportions of 16S rRNA copy numbers associated with the genus Prevotella and P. ruminicola increased (P < 0.05) with age, but those of cellulolytic bacteria and Ruminobacter amylophilus were detected only after 28 d of birth. The bacterial succession, fermentation capacity, and starch-degrading capacity in the hindgut of both groups were achieved at 1 mo, whereas fiberdegrading capacity in Sup kids was established at 2 mo of age; and supplemental feeding surpassed the grazing system in shaping hindgut development.