Effect of Humic/Fulvic Acid in Beef Cattle Finishing Diets on Animal Performance, Ruminal Ammonia and Serum Urea Nitrogen Concentration

This study was designed to investigate the effects of a humate supplement on rumen ammonia N (RAN), serum urea N (SUN) and live performance in beef cattle finishing diets. Twenty-four English cross steers (BW 432±5 kg) were stratified by weight, randomly assigned to individual pens and fed one of the four diets, containing 0 (control), 0.5, 1.0 or 1.5% humic/fulvic acid, for 56 d. Control diets contained 33.3 mg/kg monensin. Steers were weighed at d 0, 28 and 56. Blood (jugular veni-puncture) samples and rumen (esophageal tube) samples were taken prior to feeding on d 0 and there after prior to and 4 h post feeding on d 28 and 56. Rumen fluid pH was determined immediately, acidified with HCl and stored (−20C) for subsequent RAN analysis. Serum was also stored (−20C) for analysis of SUN. During the 56 d period there was no difference in DMI (P>0.58), ADG (P>0.24) or G:F (P>0.28) between treatments. There were no two or three way interactions for SUN (P>0.95), RAN (P>0.87) or rumen pH (P>0.15). There was a tendency for a cubic response (P<0.10) for RAN and SUN, however, no biological significance could be determined. These results suggest that humic/fulvic acid does not affect DMI, ADG, G:F, SUN, RAN and pH in finishing steers when compared to those fed monensin.