Table 4. Changes in eggshell strength of eggs laid from laying hens fed vitamin D3 enriched diets¹

Farms	Normal diet (IU/kg feed)	Enriched diet (IU/kg feed)	Eggshell strength (kgf/cm2)				P-value
			Before		After
			Mean	S.D.	Mean	S.D.
A	4,000 IU	16,500 IU	5.2	0.34	5.22	1.00	0.950
B	4,000 IU	16,500 IU	4.57	1.08	4.91	0.87	0.278
C	4,000 IU	29,000 IU	5.07	0.66	5.01	0.91	0.862
D	4,000 IU	29,900 IU	4.78	0.74	4.57	0.51	0.332

Value are least squares means.
S.D.: standard deviation.