Thiamine ameliorates subacute ruminal acidosis-induced mastitis in goats and is associated with modulation of the NF-κB/NLRP3/CLOCK axis and rumen microbial homeostasis.

Subacute ruminal acidosis, induced by high-concentrate diets, can trigger systemic inflammation and mastitis, a pathology linked to ruminal dysbiosis and disruption of the host's circadian rhythm. In this study, 32 mid-lactating Saanen goats (41.5 ± 1.79 kg BW) were randomly allocated to 4 treatment groups (n = 8/group): a low-concentrate diet (LC; 30:70 concentrate:forage ratio), a high-concentrate diet (HC; 70:30), and their respective counterparts supplemented with 200 mg/kg of DM thiamine (LCT and HCT). Results demonstrated that the HC diet decreased ruminal pH, induced microbial dysbiosis, and increased plasma LPS concentrations. This resulted in systemic and mammary inflammation, characterized by elevated cytokine expression and a significant decline in milk yield and quality. Thiamine supplementation in the high-concentrate diet (HCT group) effectively reversed these changes. It stabilized ruminal pH, modulated the microbiota by enriching beneficial taxa such as f_Ruminococcaceae, reduced inflammatory cytokine levels, and restored milk production. At the molecular level, goats receiving thiamine supplementation exhibited reduced activation of the NF-κB and NLRP3 inflammasome pathways and higher expression of core clock proteins (CLOCK, BMAL1) in the mammary tissue. In conclusion, thiamine alleviates SARA-induced mastitis by stabilizing the rumen microbiota and mitigating inflammation, and these protective effects are associated with concurrent changes in the NF-κB/NLRP3/CLOCK signaling axis in the mammary gland.