EFFECT OF DIET AND FOLIC-ACID ADDITION ON DIGESTIBILITY AND RUMINAL FERMENTATION IN GROWING STEERS

Eight ruminally fistulated steers (352 +/- 27 kg BW) were used in a re plicated 4 x 4 Latin square design. Treatments were 1) 70% rolled barl ey + 30% timothy hay (HC), 2) HC + folic acid (2 mg/kg BW; HC + F), 3) 30% rolled barley + 70% timothy hay (HF), and 4) HF + F. Total tract apparent digestibility of DM and CP were greater (P less-than-or-equal -to .05) in steers fed the HC diet, whereas that of ADF and NDF was gr eater ( P < . 00 1) in steers fed the HF diet. Supplemental dietary fo lic acid had no effect on either of the forementioned variables, regar dless of whether the animal received the HC or the HF diet. To compare ruminal DM disappearance, nylon bags containing either hay or barley were incubated in the rumen of each steer for 4, 8, 12, 24, and 48 h. Ruminal DM disappearance of hay and barley was affected (P < .05) by t he type of diet fed but not by the addition of folic acid to either di et. Ruminal fluid was sampled on three consecutive days, at the follow ing postprandial hours: 1, 2, 4, 8, 12, and 23. Differences in ruminal pH and individual VFA among treatments were attributable to the type of diet fed. Changes in ruminal VFA concentrations at various times af ter feeding were altered with folic acid addition; however, these modi fications were not sufficient to affect in a significant way either ru minal or total tract digestibility.