Dietary supplementation of Clostridium butyricum and rumen protected fat alters immune responses, rumen fermentation, and bacterial communities of goats

The objective of this investigation was to explore the impact of supplementing goats’ diets with Clostridium butyricum (CB) and rumen protected fat (RPF) on rumen fermentation characteristics, bacterial communities, and immune responses. Thirty-two male Saanen goats (initial body weight of 20.5 ± 0.82kg) were used in a study with a 2 × 2 factorial arrangement of treatment. The 4 treatments were the combination of 2 RPF dosages (0 vs. 30g/d) and 2 CB levels (0 vs. 1.0g/d) with a 14-d adaptation and 70-d experimental period. The goats were individually housed in pens (1.2 × 1.2m) with free access to water and fed ad libitum with a total mixed ration (TMR) at 08:00 and 18:00. The TMR consisted of 400g/kg roughage and 600g/kg concentrate (dry matter basis). The blood was collected via jugular vein from each goat before the morning feeding on d 69 of experimental period. The rumen and cecum fluid samples were collected after slaughter. Supplementation of CB decreased concentrations of aspartate aminotransferase (P = 0.048), lowered density lipoprotein (P = 0.050) and aspartate aminotransferase/alanine aminotransferase (P = 0.015), but increased concentrations of superoxide dismutase (P < 0.001), catalase (P = 0.006), immunoglobulin A (P = 0.032), and immunoglobulin G (P = 0.013). The RPF supplementation also elevated the blood glucose concentration (P < 0.001). The rumen pH was not changed by CB, whereas it was decreased (P < 0.001) by RPF. Feeding CB did not change the total volatile fatty acid (VFA) concentration or VFA profiles, whereas RPF supplementation tended (P = 0.051) to increase the total VFA concentration. The supplementation of CB increased (P = 0.048) rumen NH3-N concentration. No interaction between CB and RPF was noticed for alpha diversity indexes or bacterial communities in the rumen or cecum. The gastrointestinal alpha diversity indexes remained unaffected by CB, whereas they increased (P < 0.05) with RPF supplementation except for indexes of amplicon sequence variants, Simpson and Chao1 in the rumen. Unweighted uniFrac analysis indicated that the groups supplemented with or without RPF clustered separately from each other either in the content of rumen or cecum. At the phylum level, the relative abundance of Spirochaetota increased with supplementation of CB either in the rumen (P = 0.019) or cecum (P = 0.008). Additionally, relative abundance of Firmicutes increased (P < 0.05), and the relative abundances of Bacteroidota and Desulfobacterota decreased (P < 0.05) with supplementation of RPF both in the rumen and cecum. At the genus level, the Prevotella abundance increased and the abundances of Christensenellaceae_R-7_group and NK4A214_group decreased both in the rumen and cecum (P < 0.10) by adding CB. Furthermore, RPF supplementation increased (P < 0.05) the abundances of Christensenellaceae_R-7_group, [Eubacterium]_coprostanoligenes_group_unclassified, Lachnospiraceae_unclassified and Ruminococcaceae_unclassified. In conclusion, supplementation of CB enhanced the immune responses of goats, and RPF supplementation demonstrated beneficial effects on rumen fermentation by modulating the gastrointestinal bacterial community composition in goats.