Table 3. Dietary effects of varying levels of vitamin premix (VP) on egg and eggshell qualities in laying hens

	Treatments			SEM	p-value
	Control 0.1% VP	T1 0.05% VP	T2 0% VP		Linear	Quadratic	ANOVA
Eggshell strength (kg/cm2)	3.9a	3.8a	2.8b	0.263	0.006	0.134	0.011
Eggshell thickness (mm)	0.45a	0.46a	0.41b	0.008	< 0.001	0.010	< 0.001
Haugh unit	89.6	90.1	89.7	1.350	0.944	0.773	0.956
Yolk color	8.5	8.1	7.9	0.154	0.046	0.579	0.118

Mean values with different superscripts within the same row differ significantly at p < 0.05.