Which breed is most affected by the genetic defect pulmonary hypoplasia with anarsca (PHA)?

Which breed is most affected by the genetic defect pulmonary hypoplasia with anarsca (PHA)?

• A. Maine-Anjou
• B. Angus
• C. Charolais
• D. Holstein

Answer: (A)

Pulmonary hypoplasia with anasarca is a lethal congenital condition inherited as an autosomal recessive trait. This means calves are at risk when both parents carry the same defective allele, producing affected offspring that typically show underdeveloped lungs and severe fluid buildup at birth. The frequency of this defect varies by breed because the recessive allele is more common in some populations than others. In Maine-Anjou cattle, the allele for PHA is found at a higher frequency, so this breed shows the greatest number of affected calves. That higher prevalence is why this breed is most associated with the condition. To reduce risk, breeding programs test for the mutation and avoid mating two carriers, helping to eliminate the affected calves from the herd over time. Other breeds have lower allele frequencies, so they are less commonly affected.

Pulmonary hypoplasia with anasarca is a lethal congenital condition inherited as an autosomal recessive trait. This means calves are at risk when both parents carry the same defective allele, producing affected offspring that typically show underdeveloped lungs and severe fluid buildup at birth. The frequency of this defect varies by breed because the recessive allele is more common in some populations than others. In Maine-Anjou cattle, the allele for PHA is found at a higher frequency, so this breed shows the greatest number of affected calves. That higher prevalence is why this breed is most associated with the condition. To reduce risk, breeding programs test for the mutation and avoid mating two carriers, helping to eliminate the affected calves from the herd over time. Other breeds have lower allele frequencies, so they are less commonly affected.