Page 103 - The Welfare of Cattle

80 the WeLfare of CattLe

reactive to the nutritional aspects of the food, while the domestic rats were self-indulgent. A similar
phenomenon was seen in a study with domestic and jungle fowl, in which it was speculated that
domestication has produced an animal with diminished sensitivity to energy regulation (Kare &
Maller, 1967). Whereas these findings are not necessarily directly related to an animal’s taste abil-
ity, they do suggest a change in ingestive motivation, one of Spector and Glendinning’s (2009)
categories of taste processing.

taste and human–Cattle Interaction

Although a cow’s ability to taste does not play a direct role in animal handling, taste is con-
sidered one of the main determinants of food choice (Drewnowski & Rock, 1995; Leterme, Brun,
Dittmar, & Robin, 2008) and therefore is significant to other aspects of cattle management such as
health and nutrition. Taste perception of a species is linked to its diet type and environment. Bitter
taste, in part due to its significant role in identifying toxins in humans and other mammals, has been
studied more extensively than some of the other taste categories. In herbivores like cattle, the bitter
taste is complex; it is hypothesized that bitter-taste perception evolved in these animals to prevent
the consumption of plant toxins yet plants are also characteristically bitter and comprise the major-
ity of a herbivore’s diet (Garcia-Bailo, Toguri, Eny, & El-Sohemy, 2009). So how do cattle perceive
bitter tastes? Behavioral studies have indicated that carnivores and omnivores are more sensitive
than herbivores to certain bitter compounds (Glendinning, 1994). Glendinning (1994) predicts that
animals (like cattle) who are constantly exposed to bitter and potentially toxic compounds in their
diet have evolved to have a high threshold for bitter taste (or a reduction in bitter sensitivity) and a
higher tolerance for toxic substances. Cattle cannot reject bitter foods or they would risk compro-
mising their diet, whereas a carnivorous animal can more readily reject bitter food as bitter sub-
stances are not a large component of their diet so there is no malnutrition risk. Cattle sensitivity to
bitter compounds is directly related to their selectivity of the plants for consumption, their ruminal
fermentation, and their feeding behavior when they are identifying plants (i.e., they eat samples of
plants) (Freeland & Janzen, 1974; Li & Zhang, 2014). Neural communication between what a cow
tastes and smells and the subsequent reactions in the viscera enable ruminants, like cattle, to sense
the consequences of food ingestion (Provenza, 1995). Thus, the role of gustation in cattle feeding
and digestive behavior and subsequent nutritional status is significant.

eYe See YOU—the VISION SYSteM

As cattle are a prey species, their sense of vision has evolved to facilitate their need to continually
scan the environment around them for predators. As a naturally grazing animal, they need to have
the capacity to be able to survey the fields around them while grazing, capturing a panoramic view
of their environment. Although vision is also critical to survival for predatory species, they do not
use it in the same way that cattle and other ungulates do and this can be seen in some of the physical
differences in the vision systems between species. Visual cues are often used with other sensory
cues such as hearing and olfaction in many different aspects of cattle behavior, such as foraging,
communication, and reproductive behaviors.

Cow’s eye View

A cow’s eyes are on the side of its head as with many other grazing prey species. In nature, cattle
need to have the ability to see far off into the horizon to identify predators. The wide set eyes provide
cattle with approximately 330° of vision (Phillips, 2002). While cattle have extensive panoramic
monocular vision, they do not have significant binocular vision. A cow’s binocular range is only
25°–30° (Prince, 1956). In contrast, predatory species have eyes in the middle and front of their head