Table 5. Melatonin and cortisol concentrations in milk of dairy cows milked with automatic milking system according to the milking time per 24-h

Milking time (MT)	Control	T1	T2	T3	SEM	p-value
Milking time (MT)	Control	T1	T2	T3	SEM	Treat	MT	Treat × MT
Melatonin (pg/mL)
00:01–04:00	17.17^y	18.82^yz	25.63^xy	27.58^xyz	0.70	< 0.001
04:01–08:00	19.18^y	17.85^z	24.73^y	28.78^xy	0.68	< 0.001
08:01–12:00	25.64^x	20.38^xy	21.79^z	26.35^yz	0.62	< 0.001
12:01–16:00	19.48^y	20.42^xy	22.55^z	25.22^z	0.40	< 0.001
16:01–20:00	19.28^y	22.11^x	26.95^x	29.60^wx	0.71	< 0.001
20:01–24:00	19.01^y	20.51^xy	26.00^xy	31.86^w	0.80	< 0.001
Mean	19.36^c	19.78^c	24.62^b	28.20^a	0.28	< 0.001	0.007	< 0.001
Cortisol (pg/mL)
00:01–04:00	1,016.25^y	777.78^xy	906.81^x	787.47^y	15.51	< 0.001
04:01–08:00	1,041.33^xy	798.62^xy	886.40^xyz	760.71^y	14.85	< 0.001
08:01–12:00	1,091.50^x	807.69^xy	845.80^yz	903.67^x	20.90	< 0.001
12:01–16:00	975.07^y	764.29^y	834.59^z	935.34^x	12.96	< 0.001
16:01–20:00	1,004.45^y	752.09^y	889.90^xy	884.99^x	14.37	< 0.001
20:01–24:00	998.78^y	831.69^x	858.52^xyz	780.69^y	14.71	< 0.001
Mean	1,011.14^a	790.65^c	870.75^b	840.63^bc	6.29	< 0.001	0.049	< 0.001

Control, natural photoperiod; T1, LDPP (day : night = 16 : 8 h) with 50 Lux of the light intensity; T2, LDPP with 100 Lux; T3, LDPP with 200 Lux.
Denote comparison made within row.
Denote comparison made within column.