Cows not all black and white

8 December 2006 -- Research on colour vision in farm animals shows that they are dichromats with cones (colour sensitive retina cells) most sensitive to yellowish-green and blue purple light.

Humans are trichromats and see the full colour spectrum.

Dichromatic vision may make the animal more sensitive to seeing sudden movement. It may explain why grazing animals such as cattle balk at drain gates, shadows, and anything that has high contrast of light and dark. The brain’s fear centre which is called the amygdala is activated when an animal sees sudden movement.

One of the most common causes of balking in a handling facility is a small loose chain end that makes a rapid movement. Loose chain ends must be removed from races, chutes, and alleys. This is why people working with livestock should have slow deliberate movements. Grazing animals have a visual system that provides excellent distance vision but relatively weak eye muscles inhibit the ability to focus quickly on nearby objects.

This may explain the tendency of a horse to spook at nearby sudden movement. Grazing animals also have a split shaped pupil and a visual system that is designed to be most efficient at scanning at a distance while they are grazing. Animals will often refuse to enter a building that looks dark. This is most likely to be a problem on a bright sunny day. There are some handling facilities in buildings that work well at night or on a cloudy day, but not well on a sunny day.

Animals will enter a building more easily if they can see daylight in the building. Opening a door at the other end may help. Another option is to install skylights which will let in lots of shadow free light. The ideal illumination should resemble a bright cloudy day.