Effects of coated copper sulphate and coated folic acid supplementation on growth, rumen fermentation and urinary excretion of purine derivatives in Holstein bulls

•Coated copper sulphate (CCS) or coated folic acid (CFA) addition improved growth performance and feed efficiency in bulls.•Addition of CCS or CFA increased total tract nutrient digestibility and rumen total volatile fatty acids concentration.•The CCS and CFA had the potential to stimulate rumen microbial growth and enzyme activity.•In growth performance and nutrient digestibility the interaction between CCS and CFA was not observed.