Table 5.

Effect of dietary protein levels on nitrogen metabolism balance of female mink during gestation.

Item, g/d	Group A	Group B	Group C	Group D
N intake	3.12 ± 0.13C	3.70 ± 0.15B	3.97 ± 0.18AB	4.25 ± 0.15A
Fecal N	0.77 ± 0.05	0.86 ± 0.07	0.87 ± 0.07	0.79 ± 0.05
Urine N	1.54 ± 0.12	1.53 ± 0.12	1.68 ± 0.14	1.72 ± 0.16
N retention	0.81 ± 0.08Bb	1.30 ± 0.08ABab	1.41 ± 0.11ABa	1.74 ± 0.13Aa

Groups A to D denoted dietary protein levels, 32, 36, 40 and 44%, respectively.

N = nitrogen.

^{a, b}Means in the same row with different lowercase of superscripts were significantly different at P < 0.05.

^{A, B}Means in the same row with different capital letters of superscripts were greatly and significantly different at P < 0.01.