Genetics and Behavior During Handling, Restraint, and Herding - Genetics and the Behavior of Domestic Animals - page 131

with the novel surroundings of an auction market or slaughter plant
( Grandin, 1994 ). Problems with highly reactive animals are most evident in
cattle breeds imported from Europe and crosses of these breeds.
Observations in feedlots and slaughter plants by the first author indicate that
crossbred animals are more likely to become agitated compared to purebred
European Continental cattle. These cattle were introduced to extensive ranch-
ing operations in the United States during the late 1960s and early 1970s,
and came into favor when the drive for lean beef motivated producers to
select for lean rapidly growing cattle.
An example of genetic selection for leanness which causes handling pro-
blems in a slaughter plant was observed by both authors. Three hundred
highly excitable fine-boned heifers of Saler and British genetics were impos-
sible to handle calmly. Some engaged in self-destructive behavior. One
heifer tore off her front leg, and two others had ripped off pieces of a hoof.
This occurred after they stepped in a crack between the loading ramp and
the truck which caused them to react with instant panic. Cattle with a calmer
temperament are more likely to stop and withdraw their foot from the crack.
One heifer fell down and became so fearful that she thrashed around on the
floor and was unable to make coordinated movements to get up. Another
pounded her head against the side of the chute after she fell down. The hei-
fers constantly bellowed and if touched they kicked with both back feet.
When a plant employee leaned over the side of the race to encourage one to
move, she responded by kicking with both back feet to a height of about
7 feet (2 m), narrowly missing his head. One hind foot caught the brim of
his hard hat with such force that the hat flew high in the air. This type of
extremely agitated behavior has a strong genetic basis. Cattle with calmer
temperaments do not display such frenzied behavior, even when they origi-
nate from a remote ranch and have minimal previous contact with people.
The first author has observed thousands of cattle move through this particular
facility. In several years she had never observed such berserk behavior. This
type of behavior is similar to that of a high-strung horse. Compared to cattle,
horses are more likely to became extremely fearful and injure themselves.
ANIMAL SIZE, BODY SHAPE, COAT COLOR,
AND TEMPERAMENT
A phenotype is the composite of an animal's observable characteristics or
traits: such as its morphology (body shape and size), biochemical or physio-
logical properties, coat color, phenology (biological phenomenon correlated
with climatic conditions), behavior, and temperament. Phenotypes result
from the expression of an organism's genes as well as the influence of envi-
ronmental factors and the interactions between the two. Phenotypic variation
(due to underlying heritable genetic variation) is a fundamental prerequisite
for evolution by natural selection. Within any given population, there are