Table 9. Effect of supplemental protease on nitrogen utilization with different CP levels in weaned pig at 7 days

Variables	Basal1)		Low		SE	CP		PT2)		p-value
	0%	0.1%	0%	0.1%		HP	LP	0	10	CP	PT	CP × PT
N intake (g/day)	18.29	18.32	16.38	16.71	0.14	18.31	16.55	17.34	17.52	< 0.001	0.209	0.291
Urine excretion (g/day)	368.7	372.4	366.8	367.7	4.25	370.5	367.3	367.7	370.1	0.451	0.589	0.745
N concentration in urine (%)	0.15	0.14	0.14	0.13	0.01	0.15	0.14	0.15	0.14	0.062	0.154	0.627
N excretion in urine (mL/day)	0.53	0.53	0.52	0.49	0.01	0.53	0.51	0.53	0.51	0.057	0.367	0.673
Feces excretion (g/day)	99.16	99.18	93.82	101.34	3.72	99.17	97.58	96.49	100.26	0.673	0.323	0.325
N concentration in feces (%)	4.06	3.98	3.84	3.77	0.01	4.02	3.81	3.95	3.88	< 0.001	<.001	0.904
N excretion in feces (g/day)	4.03	3.95	3.61	3.82	0.14	3.99	3.72	3.82	3.89	0.067	0.654	0.322
Total N excretion (g/day)	4.56	4.48	4.12	4.31	0.15	4.52	4.22	4.34	4.40	0.051	0.739	0.367
N retention (g/day)	13.73	13.84	12.26	12.41	0.26	13.79	12.34	13.00	13.13	< 0.001	0.624	0.944
N retention (% of N intake)	75.04	75.55	74.76	74.22	1.05	75.30	74.49	74.90	74.89	0.452	0.986	0.620

Basal, diet containing 18.78% CP; Low, diet containing 16.92% CP.
PT0, non-supplementation of protease; PT10, supplementation of 0.1% protease.
CP, crude protein; PT, protease; HP, high protein; LP, low crude protein; N, nitrogen.