Technology

Light reception occurs in the eyes retina. Light inhibits an enzyme used in melatonin synthesis in the pineal gland. Therefore, as photoperiod increases, the duration of high levels of melatonin in the blood decreases. Melatonin concentration in the blood influences the concentration of some hormones in the blood, for example, insulin-like growth factor-1 (IGF-1). Scientists believe changes in the concentration of IGF-1 play a role in the effect of photoperiod on milk production, as IGF-1 has been shown to increase milk yield.  IGF-1 is basically growth hormone, which directly affects production of milk in the udder.

Cattle have a wide field of vision and they have well developed but un-pigmented eyes with a blue reflecting tapetum that improves vision in low light but causes poor sensitivity to colour variations in short to medium wavelengths, even in good light conditions. There is much better discrimination between short/medium wavelengths and long (orange/red) wavelengths. This probably reflects a common higher vertebrate arousal response to red colours recognizing the survival value of a vigorous response to the colour of blood. Cattle also have poor depth perception, which is why they are reluctant to enter dark or shaded areas. Cattle tend to move towards light, but are sensitive to harsh contrasts of light and dark within housing facilities.