Table 2.

Effects of different dietary CP levels on the productive performance of laying ducks (50–61 wk).

Variables	CP levels (%)1					SEM	P-values
	17.5	16.5	15.5	14.5	13.5		ANOVA	Linear	Quadratic
Egg production (%)
1 to 3 wk	77.8	83.7	83.1	78.4	80.0	1.27	0.560	0.905	0.059
4 to 6 wk	78.8	82.1	83.2	81.3	78.9	1.09	0.648	0.923	0.218
7 to 12 wk	77.8a	74.6a	74.2a	75.8a	65.5b	1.28	0.017	0.006	0.198
1 to 12 wk	79.4a	80.0a	78.9a,b	78.0a,b	72.3b	0.94	0.044	0.013	0.010
Average egg weight (g)
1 to 3 wk	69.3	68.8	68.1	68.7	68.2	0.242	0.530	0.180	0.336
4 to 6 wk	69.7	69.3	69.7	68.4	68.1	0.263	0.155	0.028	0.067
7 to 12 wk	71.8	71.5	70.3	69.4	69.4	0.389	0.135	0.013	0.738
1 to 12 wk	69.8	69.1	69.0	68.6	68.3	0.243	0.428	0.049	0.145
Egg mass (g)
1 to 3 wk	53.7	57.2	58.1	53.7	53.1	0.861	0.218	0.434	0.124
4 to 6 wk	54.7	56.3	57.7	55.4	53.5	0.678	0.381	0.500	0.136
7 to 12 wk	54.2a	51.3a,b	49.0a,b	52.0a	44.4b	0.998	0.013	0.004	0.559
1 to 12 wk	55.2a	54.9a	54.0a	53.4a,b	48.8b	0.699	0.018	0.003	0.003
Average daily feed intake (g/per duck)
1 to 3 wk	151	152	154	153	149	0.61	0.254	0.503	0.119
4 to 6 wk	145	145	143	144	141	0.76	0.457	0.082	0.204
7 to 12 wk	139a	135a	131a,b	135a	124b	1.13	<0.001	<0.001	0.431
1 to 12 wk	144a	141a	140a,b	142a	136b	0.75	0.024	0.006	0.022
FCR (g:g)
1 to 3 wk	2.81	2.66	2.66	2.83	2.81	0.041	0.540	0.813	0.248
4 to 6 wk	2.67	2.59	2.49	2.59	2.64	0.027	0.358	0.632	0.114
7 to 12 wk	2.58	2.63	2.65	2.59	2.80	0.035	0.150	0.078	0.274
1 to 12 wk	2.62	2.58	2.60	2.65	2.77	0.026	0.070	0.039	0.036

^a,bMeans within a row with differing superscripts differ significantly (P < 0.05). Abbreviation: FCR, feed conversion ratio.

¹Mean of 6 replicates (24 ducks per replicate) per treatment.