Table 2.

The effect of increasing concentrations with immersion into a prefilled CO₂ chamber on the latency to behavioral indicators at 0, 3, and 6 D during CO₂ euthanasia of broiler chickens.

Indicators	Linear P value	Quadratic P value	Equation
Headshaking
0 D	0.19	0.51
3 D	0.63	0.17
6 D	0.20	0.39
Gasping
0 D	0.45	0.73
3 D	0.95	0.73
6 D	0.67	0.14
Loss of posture
0 D	<0.01	0.80	y = −0.10x + 21.18
3 D	0.77	0.78
6 D	0.93	0.99
Cessation of rhythmic breathing
0 D	<0.01	<0.01	y = 0.91x2 − 171.89x + 8069.71
3 D	<0.01	<0.01	y = 0.18x2 − 32.74x + 1533.19
6 D	0.02	0.41	y = −2.59x + 297.94
Cessation of movement
0 D	<0.01	<0.01	y = 0.93x2 − 173.58x + 8134.55
3 D	<0.01	<0.01	y = 0.17x2 − 31.37x + 1482.01
6 D	<0.01	0.59	y = −2.92x + 341.39