High lignan- and flavonoid-based polyherbal mixtures improve performance in Holstein calves via modulating diarrhea frequency, rumen volatile fatty acid levels, and serum health parameters.

This study aimed to determine the effects of a polyherbal mixture (PM) containing 42.3% lignans and 21.2% flavonoids on the performance, ruminal fermentation, and serum biomarkers in preweaning Holstein calves. Sixty-four neonatal calves (40.6 ± 4.3 kg BW; 48 females and 16 males) were allocated to a randomized complete block design stratified by birth weight, birth date, and sex. Starter feed was provided ad libitum from d 4 until weaning. Treatments included a control (no PM supplementation in milk) and milk combined with PM supplement at 10, 20, or 40 g/d. The results revealed that feed efficiency, body length, or heart girth did not significantly differ among treatments. However, BW, DMI, ADG, wither height, and shank circumference increased linearly with increasing PM supplementation, while diarrhea frequency decreased linearly from d 4 to 15. Ruminal ammonia-nitrogen and molar proportions of individual VFA were not significantly affected by PM supplementation, while ruminal pH and total VFA showed a linear decrease and increase with increasing PM, respectively. Similarly, serum glucose, BUN, total protein, albumin, globulin, aspartate aminotransferase, alanine aminotransferase, IL-6, and IgM were not significantly affected by PM supplementation, while triglyceride concentrations showed quadratic and cubic decreases with increasing PM. The IGF-1 concentration, total antioxidant capacity, and IL-10 concentration increased linearly, while tumor necrosis factor-α concentrations increased quadratically with increasing PM supplementation. In conclusion, PM additions improved the growth performance of preweaning Holstein calves and reduced diarrhea frequency, with PM supplementation of 40 g/d exerting the most significant effect.