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

The study investigated the impacts of coated copper sulphate (CCS) and coated folic acid (CFA) on growth performance, nutrient digestibility and rumen fermentation in bulls. Fourty Holstein bulls were blocked by individual initial body weight and randomly allocated to one of four groups with a 2 × 2 factor design. The CCS at 0 (CCS-) or 8 mg Cu/kg (CCS+) was added to diets with CFA at 0 (CFA-) or 4 mg FA/kg (CFA+), respectively. In the rumen characteristics an interaction between CCS and CFA was observed. The decrease in rumen ammonia N and increase in xylanase activity, Ruminococcus albus population and urinary total purine derivatives were greater for supplementing CCS in CFA- diets than in CFA + diets. Dry matter intake increased with CFA inclusion and tended to be increased with CCS addition. Inclusion of CFA or CCS elevated average daily gain and apparent digestibility of dry matter, organic matter, crude protein, neutral detergent fibre and acid detergent fibre and decreased feed conversion ratio. Rumen pH was unaltered but total volatile fatty acids concentration and the ratio of acetate to propionate increased with addition of CFA or CCS. Dietary inclusion of CCS increased activities of cellulase and protease and copies of total bacteria, Butyrivibrio fibrisolvens and R. flavefaciens, but decreased α-amylase activity and copies of Prevotella ruminicola and Ruminobacter amylophilus. Rumen enzyme activity and bacteria population increased with CFA addition. The results showed that CFA and/or CCS had stimulatory impacts on growth and feed efficiency in bulls.