Genetics and Animal Welfare - Genetics and the Behavior of Domestic Animals - page 447

direction of circling ( Cools, 1972a,b ). This author postulated that asymmetry
in the fur pattern and laterality in circling are expressions of the same basic
neurological disturbance.
It is well known that white cats with blue eyes are often deaf ( Bergsma and
Brown, 1971; Schaible and Brumbaugh, 1976 ). In both dogs and cats, a white or
piebald coat color is also related to an increased incidence of deafness ( Schaible
and Brumbaugh, 1976; Sorsby and Davey, 1954 ). Bergsma and Brown's (1971)
review of the literature discussed a continuum in the relationship between the
depigmentation and deafness. White cats with dark eyes or dark-pigmented
areas of hair and skin on the head are less likely to be deaf, in comparison to
white cats with blue eyes. Hudson and Rubin (1962) and Schaible and
Brumbaugh (1976) both discuss deafness in Dalmatians, a heavily depigmented
breed. Thirty per cent of Dalmatians are deaf ( Strain et al., 2009 ). Dalmations
with the most extensive white areas are most likely to be deaf. In addition to
Dalmations, other extensively depigmented dog breeds, such as pale colored
Australian shepherds have a high incidence of brain, ear, and eye abnormalities
( Schaible and Brumbaugh, 1976; Sponenberg and Lamoreaux, 1985; Strain
et al., 2009; Strain, 2011 ). A higher incidence of depigmentation and deafness
is also found in albino cattle ( Leipold and Hutson, 1962 ). Paint horses can
also have neurological abnormalities ( Figure 12.2 ). The authors speculate that
selection for a moderate amount of depigmentation appears to provide produc-
tion advantages, but excessive selection will cause serious welfare problems.
Depigmentation is also related to abnormalities in the visual system.
Guillery (1974) reports that many albino mammals have visual pathways
with crossed connections to the brain. Siamese cats, which are partially
albino, have crossed visual pathways ( Guillery et al., 1971 ). The crossed
FIGURE 12.2 A paint horse with blue eyes has a nervous switch that resembles Tourettes (the dis-
order) in humans. Overselection for appearance traits is sometimes linked to neurological problems.