Table 3. Gene expression values of collagen type I (col1α2), collagen type II (col2α1), collagen type X (col10α1), osteopontin (spp1), osteonectin (sparc), osteocalcin (bglap), and alkaline phosphatase (alpl) relative to ß-actin on embryonic day (E)13, ED17, and at hatching for broiler embryos and chickens incubated under continuous light (24L), 16h of light, followed by 8h of darkness (16L:8D), or continuous darkness (24D).

	n1	col1A2	col2A1	col10a1	spp1	sparc	bglap	alpl
Treatment
24L	18	1.73	1.61	1.58	1.09	1.25	1.01	1.42
16L:8D	18	1.29	1.16	1.42	1.05	1.32	1.31	1.25
24D	18	1.10	1.08	1.24	1.14	1.07	1.15	1.15
SEM		0.259	0.171	0.190	0.17	0.151	0.142	0.237
Day
ED13	18	1.62	1.33	0.94b	1.40	1.39	1.12	1.43
ED17	18	1.36	1.33	1.33b	0.95	1.16	1.34	1.13
Hatching	18	1.14	1.19	1.97a	0.92	1.08	1.01	1.25
SEM		0.259	0.171	0.190	0.17	0.151	0.142	0.237
Treatment x day
24L - ED13	6	2.34	2.10	0.95	1.45	1.82	0.84	2.08
24L - ED17	6	1.78	1.66	1.54	0.99	0.99	1.39	1.15
24L –Hatching	6	1.06	1.07	2.27	0.82	0.93	0.81	1.02
16L:8D - ED13	6	1.34	0.81	0.56	1.44	1.33	1.25	0.98
16L:8D - ED17	6	1.29	1.30	1.41	0.85	1.45	1.60	1.22
16L:8D - Hatching	6	1.25	1.36	2.29	0.85	1.19	1.08	1.57
24D - ED13	6	1.18	1.08	1.32	1.30	1.03	1.27	1.23
24D - ED17	6	1.01	1.03	1.05	1.03	1.05	1.04	1.03
24D –Hatching	6	1.11	1.15	1.35	1.09	1.13	1.13	1.18
SEM		0.449	0.297	0.330	0.294	0.262	0.245	0.410
P-values
Treatment		0.22	0.072	0.45	0.93	0.47	0.34	0.72
Day		0.43	0.81	0.002	0.10	0.33	0.25	0.67
Treatment x Day		0.65	0.12	0.13	0.95	0.26	0.50	0.38

¹ Embryo was the experimental unit.

^a,b Values within a factor, within a column with different superscripts differ significantly at P≤0.05.