. 2020 Jan 24;99(2):812–819. doi: 10.1016/j.psj.2019.12.027

Table 5.

Effects of age at photostimulation on eggshell quality at sexual maturity, peak of laying, and 43 wk of age of White Leghorn breeder hens.

Period	Item	Age at photostimulation (wk)				SEM	P-value
Period	Item	16	18	20	22	SEM	P-value
Sexual maturity¹	Egg weight, g	37.04	37.76	37.37	40.03	0.70	0.52
	Eggshell weight, g	3.63	4.00	4.14	4.24	0.11	0.19
	Eggshell, % of egg weight	9.82^b	10.48^a	11.14^a	10.57^a	0.19	0.01
	Eggshell thickness, mm	0.34	0.37	0.39	0.37	0.01	0.13
	Eggshell strength, kg • cm⁻²	2.61	3.06	3.22	3.25	0.11	0.10
Peak of laying²	Egg weight, g	48.22	50.40	49.09	50.68	0.50	0.28
	Eggshell weight, g	5.09	5.41	5.20	5.40	0.07	0.26
	Eggshell, % of egg weight	10.58	10.75	10.62	10.63	0.08	0.93
	Eggshell thickness, mm	0.39	0.40	0.39	0.40	<0.01	0.72
	Eggshell strength, kg • cm⁻²	3.77	4.04	3.99	3.94	0.06	0.53
43 wk of age	Egg weight, g	57.21	59.16	56.68	58.44	0.48	0.27
	Eggshell weight, g	5.75	6.21	5.91	5.98	0.08	0.26
	Eggshell, % of egg weight	10.30	10.49	10.48	10.23	0.07	0.50
	Eggshell thickness, mm	0.39	0.42	0.41	0.40	<0.01	0.20
	Eggshell strength, kg • cm⁻²	3.59	3.91	3.70	3.73	0.08	0.62

Data are the mean of 2 replicates.

^a,b

Values within a row with different superscripts differ significantly at P < 0.05.

Age at sexual maturity was defined as age at 5% egg production.

Peak of laying was defined as 32 wk of age.