IN SITU DEGRADABILITY OF CORN SILAGE BY DAIRY CATTLE SUPPLEMENTED WITH STAREAS WITH DIFFERENT CONCENTRATIONS OF UREA.

Abstract

The soluble, potentially degradable and undegradable fractions, the fermentation rate and the potential and effective degradabilities, at the passage rates of 2, 5 and 8%/h, of the dry matter (DM), nitrogen (N), neutral detergent fiber (NDF) and acid detergent fiber (ADF) of the corn silage supplemented with isoproteic concentrate (17% of crude protein in the dry matter basis) composed by starea 25 or 30 (extruded corn with 25 or 30% of urea, respectively) were studied. The degradabilities were determined by in situ method, with four dairy crossbred animals with 375 kg of live weight. The potential degradabilities were: 64.2 and 61.1% for DM; 81.5 and 82.8% for N; 41.6 and 36.6% for NDF; 39.5 and 38.3% for ADF for the corn silage in the diets with stareas 25 and 30, respectively. It was concluded that the degradability parameters of the corn silage were not affected by N concentration above 12% (25% of urea) in starea. The presence of nitrogen compounds with high solubility in the corn silage suggest that more attention must be gave to the study of the effects of the starea on the ruminal fiber utilization. KEY-WORDS: Acid detergent fiber. Dry matter. Neutral detergent fiber. Nitrogen.