Table 2. Effect of different content on body weight, average daily gain, average daily feed intake, feed conversion ratio of male Pekin ducks for 21 days after hatching¹⁾

Item	Dietary protein content (%)						SEM	p-value
Item	15	17	19	21	23	25	SEM	p-value
Body weight (g/bird/day)
Day 7	268.1^e	280.6^d	290.1^c	297.4^bc	305.5^ab	308.0^a	2.30	0.001
Day 14	736.0^d	761.2^c	793.9^b	802.5^b	810.9^b	837.0^a	5.50	0.001
Day 21	1,329.2^c	1,383.4^b	1,430.7^a	1,465.1^a	1,454.9^a	1,429.6^a	8.90	0.001
Average daily gain (g/bird/day)
Day 7	30.32^e	32.11^d	33.44^c	34.50^bc	35.65^ab	36.02^a	0.331	0.001
Day 14	66.84^c	68.66^c	71.97^b	72.17^b	72.20^b	75.57^a	0.531	0.001
Day 21	84.73^c	88.89^bc	90.98^ab	94.66^a	92.00^ab	84.66^c	0.853	0.001
Day 1–21	60.63^c	63.22^b	65.46^a	67.11^a	66.62^a	65.42^a	0.424	0.001
Average daily feed intake (g/bird/day)
Day 7	36.99^c	38.16^bc	40.48^a	38.53^abc	39.31^ab	37.46^bc	0.308	0.008
Day 14	97.55^bc	96.11^bc	101.49^a	96.18^bc	94.91^c	99.32^ab	0.553	0.003
Day 21	148.63	151.17	152.17	147.43	148.89	143.07	1.074	0.188
Day 1–21	94.39	95.15	98.04	94.04	94.37	93.28	0.484	0.070
Feed conversion ratio (g/g)
Day 7	1.22^a	1.19^b	1.21^b	1.12^c	1.10^c	1.04^c	0.013	0.001
Day 14	1.46^a	1.40^ab	1.41^ab	1.33^c	1.32^bc	1.31^ab	0.009	0.001
Day 21	1.76^a	1.70^ab	1.67^ab	1.56^c	1.62^bc	1.70^ab	0.016	0.002
Day 1–21	1.48^a	1.43^b	1.43^b	1.34^c	1.35^c	1.35^c	0.010	0.001

Each value is the mean of 6 replicates (12 birds per cage).
Means in the same row with different superscripts differ in the level of crude protein content (p < 0.05).