Genetics and Animal Welfare - Genetics and the Behavior of Domestic Animals - page 446

markings were not present, or were very rare in their wild ancestors ( Guerts,
1977 ). Woolf (1990, 1991, 1995) suggests that white markings on the face or
legs provide less color protection from predators. However, flashy white
markings are favored by some breeders, and Forbis (1976) reports that
common white markings in the Arabian have been present since ancient
times. Attractive white markings on the legs and forehead of horses are often
deliberately selected for. In contrast, depigmentation in production livestock
and poultry is possibly a secondary effect of selection for production traits.
Many domestic animals are partially depigmented, especially high-producing
animals. A completely depigmented animal is albino with pink eyes. A good
example is white rats and mice. Several food-producing animals are partially
depigmented, and have either colored eyes or some areas of the body that
are not white. The highest-producing pigs, milk cows, and chickens are
either white or partially white. The maternal sow lines of commercial pigs
are mostly white. High-producing commercially bred turkeys and broiler
chickens have white feathers and white skin.
Depigmentation is both good and bad. Partial depigmentation in varying
degrees is highly correlated with production traits. Partial depigmentation is
also linked to behavior. The two calmest breeds of cattle, Herefords and
Holsteins, have depigmented white areas on their heads. However, large
areas of depigmentation often appear in conjunction with serious develop-
mental or neurological problems. Many veterinarians report that mostly
white Holstein dairy cows are more difficult to handle and more nervous
than Holsteins with larger pigmented areas of hair and skin. Also, a genetic
disorder called “white heifer disease” is commonly found in white heifers of
the Shorthorn breed, or in breeds related to them ( Rendel, 1952; Spriggs,
1946a,b ). White Shorthorn heifers are usually sterile ( Spriggs, 1946a,b ). The
ovaries and external genitalia are normal but the uterus and the vagina are
not completely developed.
Depigmentation, Behavior, and Defects
There is definitely a relationship between depigmentation and behavior.
When Belyaev (1979) selected foxes for tameness, the animals developed a
piebald coat pattern with areas of depigmented white fur. Depigmentation of
skin, hair, and eyes is related to the development of the nervous system.
Searle (1968) found a relationship between depigmentation and deafness in
several rodent species. In deer mice, Cowling et al. (1994) report a relation-
ship between deafness and the amount of depigmentation on the head. The
mice also had ataxia (staggering) and retinal problems. Mice with the most
extensive white areas were most likely to be deaf. Also in mice, the Variant-
Waddler is a neurological mutant strain where individuals are hyperactive,
deaf, and display an abnormal circling behavior. A remarkable relationship
was found between asymmetrical spotted areas of fur and the preferred