RESUMO
BACKGROUND: Considering the insufficient ruminal synthesis of folic acid (FA), the higher degradability of FA, and the reduction of sodium selenite (SS) by ruminal microbes into non-absorbable elemental Se, this study evaluated the effects of rumen-protected FA (RPFA) and rumen-protected SS (RPSS) on lactation performance, nutrient digestion and blood metabolites in dairy cows. RESULTS: Dry matter (DM) intake and milk composition were unaltered, milk and milk fat yields were higher for both supplements, and milk protein yield was higher for RPFA addition. Digestibility of DM, neutral detergent fibre and acid detergent fibre was higher for both supplements, whereas that of organic matter and crude protein was higher for RPFA addition. Ruminal pH and ammonia N were lower, and concentration of total volatile fatty acids was higher for both supplements. Activity of cellobiase and xylanase was higher for RPFA addition, whereas that of pectinase and protease was higher for both supplements. The populations of total ruminal fungi, protozoa, Ruminococcus flavefaciens and Butyrivibrio fibrisolvens were higher for both supplements. The RPFA × RPSS interaction was significant for α-amylase activity, total ruminal bacteria and R. albus populations; these three variables were increased by RPSS but the increase was greater when cows were also fed RPFA. CONCLUSION: The results indicated that addition of RPFA or RPSS improved lactation performance, nutrient digestibility and ruminal fermentation in dairy cows by stimulating ruminal microbial growth and enzyme activity. © 2019 Society of Chemical Industry.
