Effects of folic acid and sodium selenite on growth performance, nutrient digestion, ruminal fermentation and urinary excretion of purine derivatives in Holstein dairy calves

•The higher DM and nutrient intake and average daily gain were observed for folic acid (FA) addition.•Nutrient digestibility, total VFA and microbial population increased with FA and sodium selenite (SS) addition.•Urinary purine derivatives (UPD) increased with FAand SS supplementation.•Digestibility, cellulolytic bacteria and UPD induced by SS addition was greater in diet added without FA than with FA.