Table 2. Comparison of major developmental parameters between Taiwan Country Chicken (TCC) and Brown Tsaiya Duck (BTD) embryos during the first 72 h post-incubation.

	Species
Morphological measurements or embryonic structures by hours of incubation	TCC	BTD	P value
Crown-to-tail length (ECTL) at first 72 h, mm	8.93a	6.23b	0.0014
Primitive streak length*
6–7 h post-incubation1	1.17a	0.00b	<0.0001
10–13 h post-incubation2	1.56a	0.68b	<0.0001
Intermediate primitive streak length*
12–13 h post-incubation1	1.72a	0.76b	0.0009
19–24 h post-incubation2	2.64a	1.07b	<0.0001
Full-length primitive streak*
18–19 h post-incubation1	2.55a	0.92b	<0.0001
25–27 h post-incubation2	1.66	1.46	0.2874
Regressing primitive streak*
23–39 h post-incubation1	1.15	0.99	0.1834
28–42 h post-incubation2	1.00a	0.55b	<0.0001
No. of somites formed during the first 72 h	40a	32b	0.0001

* Values of the measurements are adjusted proportionally by the egg weight of embryos.

¹ Hours of incubation are based on the emerging time of embryonic structures in TCC embryos.

² Hours of incubation are based on the emerging time of embryonic structures in BTD embryos.

^{a, b} Within the row, means without the same superscript differed (P < 0.05).