Figure 1.
Figure 1.

Ammonia-N (NH3–N) as affected by hours after feed delivery in cattle fed diets without urea added (negative control [CON]), or added at 0.6% of dietary DM, in the form of conventional urea (positive control [UREA]) or 1 of 2 slow-release urea sources (Optigen II [OPTI; 89% urea; Alltech Inc., Nicholasville, KY] or NitroShure [NITRO; 89% urea; Balchem, New Hampton, NY]). a,b,cMeans with uncommon superscripts differ within hour after feed delivery at α = 0.08 (treatment × time, P = 0.06); SED at each time point averaged 1.7 mg/dL.

 


Figure 2.
Figure 2.

Nitrogen (N) disappearance from polyester bags for conventional urea (CU) and 2 slow-release urea sources (Optigen II [Alltech Inc., Nicholasville, KY] and NitroShure [Balchem, New Hampton, NY]), as affected by hours after incubation in the rumen (Exp. 2). a,bMeans with uncommon superscripts differ within hour after incubation at α = 0.05 (urea source × time, P < 0.01); SED at each time point averaged 4.8%.

 


Figure 3.
Figure 3.

Ruminal pH and total VFA concentration as affected (P < 0.01) by hours after feed delivery; SEM at each time point averaged 0.08 for ruminal pH and 10.6 mM for total VFA concentration.

 


Figure 4.
Figure 4.

Acetate and propionate molar proportions and acetate-to-propionate ratio (A:P) as affected (P < 0.01) by hours after feed delivery; SEM at each time point averaged 0.8 and 2.1 mol/100 mol for acetate and propionate molar proportions, respectively, and 0.1 for A:P.