Table 5. The concentrations of eggshell ion components of laying eggs at different hen ages.

Hen age	30 wk	60 wk	78 wk	p-value
	ppm (mg/kg)
P	1,093.40±195.76	1,031.16±175.92	1,080.19±187.42	0.8074
S	668.13±111.93a	555.19±121.35ab	510.67±38.49b	0.0211
K	403.93±48.45b	482.22±35.24a	491.96±30.42a	0.0008
Ca	443,450±6,437.6a	424,510±13,709.0b	426,776±13,291.0b	0.0134
Mg	3,468.2±355.41	3,824.1±257.82	3,452.0±457.29	0.1277
Ni	0.15±0.09b	0.24±0.04a	0.16±0.04ab	0.0178
Mn	0.06±0.10	0.06±0.05	0.07±0.12	0.9879
Co	0.19±0.11a	0.15±0.01b	0.15±0.02b	<.0001
Be	0.030±0.010	0.041±0.004	0.035±0.003	0.0839
V	0.38±0.05b	0.60±0.07a	0.65±0.09a	<.0001
Na	467.76±47.60b	570.33±49.32a	562.17±65.10a	0.004

^a,b Values (n=10) with different superscripts in the same row are significantly different (p<0.05).