Page 99 - The Welfare of Cattle

76 the WeLfare of CattLe

The amygdala has been referred to as the “sensory gateway to the emotions” (Aggleton & Mishkin,
1986) and is critical for producing appropriate behavioral responses to sensory stimuli. Visual,
olfactory, gustatory, somatosensory, and auditory information is transmitted via mapped projec-
tions to the amygdala (McDonald, 1998). McDonald (1998) provides a detailed overview of the
cortical pathways projecting to the amygdala from the sensory cortices, highlighting the amygdala
as an essential link between the cerebral cortex, where sensory information is processed and other
brain regions that are integral in emotional (e.g., fear) and motivational responses of animals.

What’S that SMeLL?—the OLFaCtOrY SYSteM

Olfaction, the sense of smell, is a chemical sense utilized by cattle to gain information about
their environment. Smell is a primitive sense, emerging as a result of the evolutionary development
of land animals (Damask, 1981). Strict marine animals do not differentiate between gustation and
olfaction as all chemicals they are confronted with are in an aqueous solution. With the rise of
airborne creatures the need to be able to sense both chemicals in the air (smell) and chemicals in
solution (taste) became necessary and thus two different chemoreceptor systems evolved. Cattle
use their sense of smell to find food, identify individuals within their social network, find potential
mates, communicate, and be aware of danger. While humans use olfaction for similar purposes, it
is often accepted that other animals have a more highly developed olfactory system, being able to
differentiate and identify smells at a much farther range and concentration. Interestingly, sensory
system scientists have noted that studying olfactory perception in non-human species can some-
times be advantageous, despite the fact that animals can’t verbally share the things they smell,
because there are no outside lifestyle factor impacts such as smoking, eating, and sinus conditions
(Amoore, 1991).

Not all Noses are Created equal

Not only are noses and snouts morphologically different between species, different species also
have distinctive abilities to detect odors. Species can be categorized by their level of olfactory
function as microsmatic or macrosmatic, classification attributed to Turner (1890). Macrosmatic
species, such as carnivores and ungulates are “keen-scented” (Negus, 1958) as compared to other
species such as humans and other primates who have evolved to rely more heavily on other senses
(e.g., vision) and thus do not have as great a level of olfactory function. Primates, as representative
microsmatic animals, have proportionately smaller olfactory bulbs (area in the brain that receives
olfactory information) (Baron, Frahm, Bhatnagar, & Stephan, 1983) and less olfactory epithelia sur-
face area (area containing the odorant receptors) in the nasal cavity as compared with macrosmatic
mammals (Le Gros Clark, 1960), such as cattle.

Form and Function—What’s in a Nose?

A cow’s nose, technically called a muzzle, is its gateway into the olfactory world. Looking
closely, one will notice that the cow’s nose is covered in grooves and ridges; interestingly, these
muzzle dermatoglyphics can serve as a unique animal identifier, a cow’s nose print being like a
human’s finger print with no two animals having identical patterns (Noviyanto & Arymurthy, 2013;
Petersen, 1922). Inside the cow’s muzzle lies all the olfactory specific structures that capture the
chemical information being delivered to the cow, i.e., the main olfactory system. The gross anatomy
of the nasal passage differs greatly between species (Harkema, 1991).
Comparatively, humans have rather simple noses with the primary function being respiratory,
while other mammals have more complex systems due to the primary function being olfaction