Five ruminally cannulated steers (initial BW=464±26kg) consuming low-quality forage (5% CP; 78% NDF; DM basis) were used in an incomplete 5×4 Latin square with four 18-d periods to determine the influence of supplemental N source and supplementation frequency (SF) on ruminal fermentation dynamics. Treatments, arranged as a 2×2 factorial with a negative control, consisted of urea or soybean meal (SBM) supplements offered daily (D) or alternate days (2D) plus an unsupplemented treatment (CON). Urea supplements were provided to meet 100% of the degradable intake protein requirement while SBM supplements were provided on an isonitrogenous basis. All supplemented treatments received an equal quantity of supplemental N over a 2-d period. Ruminal indigestible acid detergent fiber (IADF) passage rate was increased with supplementation (P≤0.03) on the days when D and 2D supplements were provided, as well as when only D supplements were provided. In contrast, ruminal liquid fill and dilution rate were not affected by supplementation, N source, or SF on the days when D and 2D supplements were provided (P≥0.24). However, when only D supplements were offered, ruminal liquid dilution rate was greater (P=0.03) for SBM supplemented steers compared with cohorts receiving supplemental urea, whereas ruminal liquid fill was greater (P=0.03) for steers fed urea supplements. Nitrogen supplementation increased (P<0.01) ruminal NH3-N by 122% and 70%, compared with the CON, on the days when both D and 2D supplements were provided and when only D supplements were provided, respectively. We noted a N source×SF interaction for ruminal NH3-N on the days when D and 2D supplements were provided (P=0.02), as well as when only D supplements were provided (P<0.01). On the days when D and 2D supplements were provided, urea increased NH3-N by 61% (2.93 vs. 4.73mM for D and 2D, respectively), whereas the increase in NH3-N with SBM was only 15% (2.23 vs. 2.58mM for D and 2D, respectively). However, when only D supplements were provided, NH3-N was almost 36% less for the 2D compared with the D urea treatment (2.76 vs. 1.81mM, respectively), whereas an 11% increase was noted for SBM 2D compared with SBM D (1.99 vs. 1.79mM, respectively). Total concentration of VFA was increased on the days when both D and 2D supplements were provided (P=0.03), but not influenced by treatments on the days when only D supplements were provided (P≥0.50). In summary, providing a urea-based supplement, as infrequently as every-other-day, was an effective alternative to a SBM-based supplement in maintaining acceptable ruminal fermentation of steers consuming low-quality, cool-season forage.
|Number of pages||9|
|State||Published - Aug 2013|
Bibliographical noteFunding Information:
The Eastern Oregon Agricultural Research Center, including the Burns and Union Stations, is jointly funded by the Oregon Agricultural Experiment Station and USDA-Agricultural Research Service. The authors would like to thank Alma D. True for conducting VFA analyses.
Copyright 2013 Elsevier B.V., All rights reserved.
- Non-protein N
- Soybean meal
- Supplementation frequency
ASJC Scopus subject areas
- Animal Science and Zoology
- Veterinary (all)