Table 10. Effect of supplemental protease on nitrogen utilization with different CP levels in weaned pig at 14 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)	18.79	18.99	17.36	17.69	0.13	18.89	17.53	18.08	18.34	< 0.001	0.051	0.609
Urine excretion (g/day)	379.9	378.9	372.4	375.2	4.08	379.4	373.8	376.1	377.1	0.185	0.821	0.652
N concentration in urine (%)	0.18	0.16	0.16	0.16	0.01	0.17	0.16	0.17	0.16	0.195	0.075	0.296
N excretion in urine (g/day)	0.67	0.60	0.60	0.58	0.02	0.64	0.59	0.64	0.59	0.089	0.089	0.291
Feces excretion (g/day)	99.38	104.63	101.78	96.05	0.99	102.01	98.92	100.58	100.34	0.005	0.811	< 0.001
N concentration in feces (%)	4.43	3.92	3.91	3.91	0.04	4.18	3.91	4.17	3.92	< 0.001	< 0.001	< 0.001
N excretion in feces (g/day)	4.40	4.10	3.98	3.75	0.05	4.25	3.87	4.19	3.93	< 0.001	< 0.001	0.479
Total N excretion (g/day)	5.07	4.70	4.57	4.33	0.05	4.89	4.33	5.07	4.52	< 0.001	< 0.001	0.204
N retention (g/day)	13.73	14.29	12.79	13.36	0.14	14.01	13.08	13.26	13.83	< 0.001	< 0.001	0.089
N retention (% of N intake)	73.03	75.28	73.63	75.51	0.33	74.16	74.57	73.33	75.40	0.029	< 0.001	0.111

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.