This study was conducted to evaluate the effects of dietary supplementation of endotoxins binders (Saccharomyces cerevisiae cell wall (SCW) and bentonite (BEN)) on blood urea nitrogen (BUN), triglyceride, alkaline phosphates (ALP), and calcium (Ca) in high-producing dairy cows during the transition period. Twenty-four Holstein dairy cows (n = 6, average milk production = 35.8 ± 1.6 kg/day, body weight (BW) = 567.5 ± 40.3 kg, body condition score (BCS) = 3.5 ± 0.26 out of 5) were assigned in a completely randomized design, to the following treatments: (1) basal diet (BD), (2) BD + SCW, (3) BD + BEN, and (4) BD + SCW + BEN. Blood samples were taken 4, 3, and 1 weeks before and 1and 3 weeks after parturition. Serum concentrations of BUN, triglyceride, ALP, and Ca were measured. It was observed that, BUN concentration was lower in SCW + BEN group, probably because of the better utilization of NH3-N and better stimulation for ruminal microbial protein synthesis. Triglyceride plasma concentration was lower in the control group, which might be due to decreased lipolysis and a lower pH. The treatment groups showed no effect for Ca at any time point. Serum ALP concentration was within references range. In conclusion, lower BUN concentration could be a result of better stimulation of ruminal microbial protein synthesis in the treatment groups and also due to lower triglyceride in control group, which might be result of lower pH in the rumen, we suggest that endotoxins binders (especially combined feeding of endotoxin binders) can modulate rumen function by optimizing the rumen pH.

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