Page 105 - The Welfare of Cattle

82 the WeLfare of CattLe

potentially be impacted by light absorption of the lens and/or light reflection by the tapetum (a tape-
tum lucidum is a feature in the eyes of some vertebrates that enhances visual sensitivity at low-light
levels) (Jacobs, Deegan, & Neitz, 1998). It is clear in the literature that to make conclusions about
what colors cattle can actually perceive, behavioral studies must be designed to measure a cow’s
ability to discriminate between different colors. Several studies have been conducted to determine
which colors cattle can discriminate and although the studies are successful in identifying that
cattle have some ability to discriminate between colors there have been some issues in research
design that have limited the application of results (Gilbert & Arave, 1986; Phillips & Lomas, 2001;
Riol, Sanchez, Eguren, & Gaudioso, 1989). It is difficult to assess a cow’s ability to discriminate
colors as researchers have a limited perspective of what cattle actually are seeing but this is an
area of potential research. Interestingly, in dichromatic vision, when a certain wavelength (color)
stimulates both cone types equally there are varying theories as to what the cow actually perceives.
Some theories suggest the cow will not be able to distinguish what color the object is at the neutral
point and thus the object will appear achromatic (i.e., white or gray) others suggest the cow sees
a continuum of colors and the object is a desaturated version of the two colors (Carroll, Murphy,
Neitz, Ver Hoeve, & Neitz, 2001; Roth, Balkenius, & Kelber, 2007).
Although there are some limitations associated with dichromacy, it is thought that dichromatic
animals are better adapted to identifying things that are camouflaged (Morgan, Adam, & Mollon,
1992); they use cues other than color to differentiate. Additionally, dichromats, like cattle, are more
effective than trichromats at grazing in the shade (Caine, Osorio, & Mundy, 2009). It has also been
suggested that dichromats outperform trichromats in low-light situations (Verhulst & Maes, 1998).
This is a characteristic of arrhythmic species, like cattle, that are active during the day but can
successfully navigate difficult terrain in the evening as well.

Vision and the human–Cattle Interaction

Understanding the visual perception of cattle is a critical component to working with and raising
cattle. They “see” the world from a different perspective than humans. Cattle are prey animals and
humans are not and therefore cattle and their human caretakers do not approach and/or perceive
situations in the same manner. The differences in cattle vision can aid in cattle handling but the
differences can also hinder cattle handling if not managed properly. As noted, cattle have a wide
angle of vision and therefore see and respond to animal handlers entering their field of vision, likely
differently that a predatory species would. A cow’s lack of depth perception can impact how they
are handled. As discussed extensively by Dr. Temple Grandin, shadows and sharp contrasts in light
make it difficult to move cattle due to their limited ability to determine depth. When confronted
with shadows on the ground cattle will often refuse to move forward or will walk around the dark
shadow contrast if they are able. It is essential to understand and consider visual perception of cattle
when designing yards and various types of cattle handling facilities (Grandin, 1978).
Due to cattle’s large number of rod photoreceptors they are better equipped than humans are
to see in low-light scenarios but this limits their acuity. Objects are often blurry and not as well
defined. Fast moving objects that come into their field of vision are sometimes not easily identifiable
and therefore can often scare cattle. It is important to move calmly and deliberately when moving
into a cow’s field of vision.

DO YOU hear What I hear?—the aUDItOrY SYSteM

For cattle, hearing and locating a sound are critically important to survival. In a natural habitat,
a sound is often made by another animal and therefore an animal’s ability to hear and localize that
sound enables the animal to approach or avoid it. Young calves can recognize their mothers from