Table 5.

Rumen pH, volatile fatty acids (VFA), and ammonia nitrogen (NH₃–N) concentration from beef heifers (n = 8) fed a high forage diets containing finely chopped grass hay (45%) and barley silage (45%) supplemented without 3-nitrooxypropanol (3-NOP, control) and with 3-NOP (150 mg/kg DM, 3-NOP). Animals were fed at 1000 hours with small top-up at 1300 hours

Item	Control	3-NOP	SEM	P-value2
				Treatment (treat)	Sampling time (St)	Treat × St
Rumen pH1
Minimum	5.84	5.97	0.040	<0.01	0.01	0.65
Mean	6.43	6.64	0.037	<0.001	<0.001	0.82
Maximum	6.86	7.01	0.030	<0.001	<0.01	0.92
Range	1.05	1.00	0.036	0.16	0.10	0.63
Total VFA, mM	112	104	2.5	<0.01	<0.001	0.80
VFA molar percentage, mol/100 mol
Acetate	68.6	63.2	0.32	<0.001	<0.001	0.21
Propionate	17.0	19.3	0.21	<0.001	<0.001	0.25
Butyrate	10.7	12.5	0.27	<0.001	<0.001	<0.001
Valerate	1.10	1.48	0.020	<0.001	<0.001	<0.001
Isobutyrate	0.81	0.88	0.019	<0.01	<0.001	0.16
Isovalerate	1.20	1.77	0.066	<0.001	<0.001	<0.001
Caproate	0.55	0.96	0.044	<0.001	<0.001	<0.001
Ac:Pr ratio	4.07	3.30	0.055	<0.001	<0.001	0.10
NH3–N, mM	3.15	2.95	0.190	0.31	<0.001	0.18

¹Rumen pH was measured at 1 min intervals over 7 d using continuous pH loggers. Range = maximum rumen pH—minimum rumen pH.

²Significance was declared at P ≤ 0.05 and a tendency to significance was declared at 0.05 < P ≤ 0.10.