Comparison of Urea and Biuret as Nitrogen Supplements to Low-Quality Forage: Daily and Alternate Day Supplementation

Site of Digestion and Microbial Efficiency in Steers

Five steers (491 ± 21 kg BW) were used in an incomplete 5 × 4 Latin square with four 24-d periods to determine the influence of supplemental non-protein N (NPN) source and supplementation frequency (SF) on nutrient intake and site of digestion in steers consuming low-quality grass straw (4% CP).  Treatments (TRT) included an unsupplemented control and a urea- or biuret-containing supplement placed directly into the rumen daily (D) or every-other-day (2D) at 0700.  The NPN treatments were formulated to provide 90% of the estimated degradable intake protein requirement.  Daily TRT were supplemented CP at 0.04% of BW/d while the 2D TRT were supplemented at 0.08% of BW every-other-day.  Therefore, all supplemented TRT received the same quantity of supplemental CP over a 2-d period.  Forage OM intake was not affected (P > 0.05) by NPN supplementation, NPN source, or SF.  However, total OM and N intake were increased (P < 0.01)

with CP supplementation.  Duodenal flow of N was greater (P = 0.04) with CP supplementation compared with the control.  In addition, duodenal bacterial N flow was increased with CP supplementation (P = 0.04) and for biuret compared with urea (P < 0.01).  Bacterial efficiency (g bacterial N/kg OM truly digested in the rumen) was greater (P = 0.05) for biuret compared with urea.  Apparent total tract N digestibility was increased with NPN supplementation (P < 0.01) and not affected by NPN source or SF.  These results suggest that urea or biuret can be used effectively as a supplemental N source by steers consuming low-quality forage.

 

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Currier, T.A., D.W. Bohnert, S.J. Falck, C.S. Schauer, and S.J. Bartle. 2004.  Daily and alternate-day supplementation of urea or biuret to ruminnts consuming low-quality forage: II  Effects on site of digestion and microbial efficiency in steers. J. Anim. Sci.82:1518-1527.  (DWB PDF#3)