Introduction

• Cause: congenital autosomal recessive or sex-linked condition.
• Signs: less than the ‘normal’ amount of hair may be present at birth or develops within the first 1-6 months of life. The condition may be associated with other congenital conditions such as anodontia.
• Diagnosis: provisional diagnosis can be made based on the history and clinical presentation.
• Treatment: provision of shelter and/or coats to protect the affected animals from the elements.
• Prognosis: the prognosis is good for most affected calves. If the affected calf has concurrent congenital condition this may affect the prognosis.

Pathogenesis

Etiology

• Congenital autosomal recessive condition (some forms may be sex-linked):
  • In Herefords Hereford it is attributed to the gene mutation, c.334_343del of the KRT71.
  • In Holsteins Holstein a hypotrichosis condition has been attributed to a mutation in the EDA gene (R244X).

Predisposing factors

Specific

• Either the calf’s dam or sire is carrying the genetic condition.

Pathophysiology

• Some affected calves are born with the condition, whereas others develop the condition within the first few months of life.
• The poor structural integrity of the epithelial cells and inner root sheath of the hair follicles results in the loss of the hair fiber.

Timecourse

• Calf may be affected at birth or the condition may develop in the first few months (1-6 months) of life.

Epidemiology

• If two individuals in a herd carry the autosomal recessive traits and are mated, then the progeny will be in the proportion of ¼ expressing the disease, ½ clinically normal heterozygous (carriers) and ¼ clinically normal homozygous (non-carriers).
• Due to the mode of inheritance, it is possible to have a number of off-spring born with the condition if a single sire carrying the condition is used in the herd with high proportion of heterozygous carrier females.

Diagnosis

Treatment

Prevention

Outcomes