CONCENTRATIONS OF FOLATES IN RUMINAL CONTENT OF STEERS - RESPONSES TOA DIETARY-SUPPLEMENT OF FOLIC-ACID IN RELATION WITH THE NATURE OF THEDIET

In an attempt to evaluate the ruminal effects of dietary supplements o f folic acid, eight steers (352 +/- 27 kg BW) fitted with a ruminal ca nnula were randomly assigned to a replicated 4 x 4 Latin square design . The treatments were 70% rolled barley + 30% timothy hay (HC), HC + 2 mg of folic acid per kilogram of BW (HC + FA), 30% rolled barley + 70 % timothy hay (HF), and HF + 2 mg of folic acid per kilogram of BW (HF + FA). After 5 wk of adaptation to the dietary treatments, ruminal co ntents were sampled over three consecutive days, at 1, 2, 4, 8, 12, an d 23 h after feed distribution. Concentrations of folates in solid and liquid ruminal fractions were increased by the dietary supplement of folic acid (P = .0001) and by the ingestion of concentrate compared wi th hay-based diets (P < .05). Preprandial concentrations of serum fola tes were not affected by the nature of the diet when steers received n o folic acid but the increase of serum folates induced by the dietary supplement of folic acid was more important in steers fed concentrates than in those fed hay-based diets (diet x supplement of folic acid in teraction P = .002). Microbial protein (P = .004) and microbial mass ( P = .002) in ruminal fluid were increased with concentrate-based diets compared with hay-based diets; folic acid did not have any effect on these variables (P > .05). In conclusion, concentrations of folates in ruminal contents were affected by dietary supplements of folic acid a nd by the nature of the diet. Dietary folic acid did not have any mark ed effect on studied characteristics of ruminal microflora. However, t he intensity of the response of serum folates to dietary supplements o f folic acid given to steers was modified by the nature of the diet.