Table 3. Effect of dietary crude protein level and supplementation protease on nitrogen utilization in growing pigs

Items	HP			LP			SE	p-value
	PT 0	PT 150	PT 300	PT 0	PT 150	PT 300		CP	Protease	CP × protease
N intake (g/d)	39.77	39.65	39.53	35.16	35.03	34.69	0.54	<.001	0.934	0.992
Urine excretion (kg/d)	2.01	1.99	1.98	2.07	2.03	1.94	0.11	0.928	0.965	0.986
N concentration in urine (%)	0.157a	0.142ab	0.130b	0.135a	0.120ab	0.115b	0.004	0.010	0.034	0.905
N excretion in urine (g/d)	3.18	2.79	2.54	2.72	2.46	2.22	0.17	0.308	0.434	0.983
Feces excretion (g/d)	253	251	258	258	262	255	2	0.570	0.983	0.689
N concentration in feces (%)	3.73a	3.66a	3.46b	3.14a	3.08a	2.94b	0.05	<.001	<.001	0.649
N excretion in feces (g/d)	9.46	9.21	8.93	8.07	8.05	7.51	0.15	<.001	0.106	0.858
Total N excretion (g/d)	12.63	12.00	11.46	10.79	10.52	9.73	0.24	<.001	0.082	0.929
N retention (g/d)	27.14	27.65	28.07	24.38	24.52	24.96	0.42	<.001	0.689	0.971
N retention (% of N intake)	68.15	69.83	70.98	69.24	69.89	71.98	0.47	0.441	0.061	0.881
Biological value (%)1)	89.44	91.01	91.67	90.12	90.88	91.86	0.53	0.827	0.355	0.956

Each value is the mean value of 6 replicates (1 pig/cage; 6 × 6 latin square).
Means in the same row with different superscripts differ (p <0.05).
(N intake – urinary N excretion – fecal N excretion) / (N intake – fecal N excretion) × 100.
HP, high crude protein (17.3%); LP, low crude protein (15.1%); CP, crude protein; PT, protease (ppm); N, nitrogen.