The objectives of the study were to characterize
the effects of CP concentration and ruminal
degradability of barley-based backgrounding diets on
route and chemical form of N excretion, ruminal fermentation,
microbial protein synthesis, and nutrient
digestion in beef cattle. Four Angus heifers (479 ± 14.6
kg average BW) with ruminal and duodenal cannulas
were used in an experiment designed as a 4 × 4 Latin
square. The basal diet consisted of 54% barley silage
and 46% barley grain-based concentrate (DM basis).
Dietary treatments included the basal diet with no added
protein (12% CP) or diets formulated to contain 14% CP
by supplementation with urea (UREA), urea and canola
meal (UREA+CM), or urea, corn gluten meal, and
xylose-treated soybean meal (UREA+CGM+xSBM).
The amount of feed offered was restricted to 95% of
ad libitum intake. There was no effect of the diets on
DMI (P = 0.38), and therefore, N intake was less (P <
0.05) in heifers fed the 12% CP diets than the 14% CP
diets. Fecal N output was not affected by the diet (P =
0.15), but urine N (P < 0.10) and urea N output were
greater (P < 0.05) in heifers fed the 14% CP than the
12% CP diets. There was no effect of CP degradability