Early-life Clostridium butyricum supplementation improved rumen development and immune by promoting the maturation of intestinal microbiota

This study evaluated the effects of Clostridium butyricum supplementation on rumen fermentation, serum immunoglobulins, and fecal microbiota in dairy calves. Seventy-five 3-days-age calves were divided into five groups ( n = 15 per group) receiving 0, 0.2, 0.4, 0.8, and 1.6 g/day of C. butyricum freeze-dried powder (10^10 CFU/g) in milk replacer. Rumen fluid and blood samples were collected at various intervals, and fecal samples from eight calves per group were collected at 3, 28, and 42 days. C. butyricum supplementation showed a negative correlation with rumen pH ( P = 0.032) and positive correlations with acetate/propionate ( P = 0.007) and acetate + butyrate/propionate ( P = 0.022). It had quadratic effects on rumen acetate ( P = 0.029) and isobutyrate ( P = 0.021). IgA concentration increased with dose ( P = 0.002), and dose-time interactions affected serum IgM ( P = 0.013) and IgG ( P < 0.001). C. butyricum did not influence fecal microbiota diversity but increased the abundance of Helicobacter japonicus , Weissella viridescens , Leuconostoc mesenteroides , Leuconostoc citreum , while negatively correlating with Streptococcus hyointestinalis ( P < 0.05). Microbiota functions related to galactose metabolism, and fatty acid degradation decreased with age ( P < 0.05), while fatty acid biosynthesis and glycolysis/gluconeogenesis increased ( P < 0.05). L. mesenteroides, and L. citreum , and negatively correlated with galactose metabolism and fatty acid degradation but positively with fatty acid biosynthesis ( P < 0.01). C. butyricum supplementation variably impacted rumen pH, acetate/propionate, and acetate + butyrate/propionate, particularly on day 42 versus day 60, affecting acetate, butyrate, and isovalerate differently over time. Our findings suggest that early-life C. butyricum supplementation may promote the maturation of immunity and intestinal microbiota of pre-weaning dairy calves, the optimal dose was 0.8–1.6 x 10^10 CFU/d. • Clostridium butyricum did not increase ruminal butyrate but the acetate/propionate ratio in early-life dairy calves. • Clostridium butyricum supplements increase serum IgA and IgG in the first four weeks of life in dairy calves. • Clostridium butyricum supplements promote the development of fecal microbiota during the weaning process.