Table 3.

Egg quality of duck breeders from 38 to 77 wk of age^{c, d}

Vitamin level	CX + 25-OH-D₃	Egg shape index (long:short)	Yolk pigmentation	Shell thickness, mm	Shell strength, kg/cm²	Shell ratio, %	Albumen height, mm	Haugh units
REGULAR	-	1.349	1.9	0.334^ab	4.00	9.9	8.2	80.6
REGULAR	+	1.341	12.6	0.325^b	3.97	9.8	8.6	83.0
HIGH	-	1.347	2.1	0.324^b	4.10	9.9	8.3	81.2
HIGH	+	1.344	12.5	0.342^a	4.24	10.0	8.7	83.2
SEM		0.004	0.4	0.002	0.07	0.1	0.1	0.8
P-value
Vitamin		0.934	0.914	0.779	0.128	0.436	0.668	0.732
CX + 25-OH-D₃		0.477	<0.001	0.189	0.758	0.866	0.233	0.264
Vitamin × (CX + 25-OH-D₃)		0.761	0.382	0.011	0.688	0.412	0.833	0.897

^{a, b} Different superscripts in a row indicate differ significantly (P ≤ 0.05)

^c Mean of 5 times of sample analysis at wk 8, 16, 24, 32 and 40 of the trial

^d CX canthaxanthin, 25-OH-D ₃ 25-hydroxycholecalciferol