Fig 1.
LED fixtures placed on each side of the head of every cow.
Fig 2.
Spectral composition of the light used during daytime in the Light lab.
(A) Red light treatments, (B) Blue light treatments, and (C) White light treatments.
Table 1.
Light intensity levels used in the experiments, expressed as photon flux density (μmol s-1 m-2), illuminance (lux), and luminance (candela/m2).
Fig 3.
Photograph illustration for the calculation of relative area of the pupil (RAP).
The yellow marks in the right photograph indicate the pupil area and the iris area. RAP was calculated by dividing the area covered by the pupil with the area area circumscribed by the peripheral iris at the limbus cornea.
Fig 4.
Schematic illustration of the light treatments during 24 hours.
Daylight was provided during 16 hours and dim night light during eight hours. Symbols indicate times of feeding, milking, and blood sampling.
Table 2.
Chemical composition of silage and concentrate.
Fig 5.
Relative area of the pupil (RAP) of cows exposed to Red, Blue, and White light intensity.
There was no difference in relative pupil area for cows under red light. Under blue and white light, the relative pupil area decreased by almost half (***p <0.001).
Fig 6.
Relative number of photons reaching the retina when different light-emitting diode (LED) lights were employed.
Grey area indicates dim night light treatment and daylight treatment in Experiment II.
Fig 7.
Treatment least squares means (LSM) for activity.
Standing proportion per treatmeant, and in daytime (16 h) and night-time (8 h).
Table 3.
Least squares mean (LSM) ± standard error of: Milk yield, energy-corrected milk (ECM), milk composition, dry matter intake (DMI), and energy balance for cows exposed to the Blue, Red, White and White-Blue light treatments.
Fig 8.
Treatment least squares mean (LSM) of plasma melatonin within 24 hours.
Cows exposed to the Blue and Red light treatments had higher plasma melatonin than cows exposed to White light (*p <0.1) and White-blue light (** p<0.05).
Fig 9.
Treatment least squares mean (LSM) of plasma IGF-1 within 24 hours.
Cows exposed to the Blue light treatment had higher plasma IGF-1 concentration at 2230 h than at 0830 h (*** p < 0.001).