**8.1 Genetic counseling**

The basic recommendation in the case of genetic diseases in animals is that affected individuals should not breed and that normal couples with affected descendents should not breed again. However, owners of normal animals that have had affected descendents are not usually willing to follow this advice. With this in mind, when there is a correct diagnosis and the genetic nature of the defect is known, other decisions are possible, but the risk of recurrence should be taken into consideration. To avoid autosomal recessive phenotypes, an important strategy is never to mate individuals who are known to be heterozygotes one with another, such as those who have already had an affected descendent. For recessive Xlinked phenotypes, daughters of affected individuals are all carriers (heterozygotes) and should not be mated, even when the males are normal. When there is a family history of a recessive defect and the zygosity of an individual is unknown, consanguineous unions should be avoided.

#### **8.2 Screening**

When breeding small or large animals, identifying heterozygotes (recessive phenotypes and dominant phenotypes with reduced penetrance) can be an economically advantageous procedure and allows people to make appropriate preventive decisions concerning the mating of such individuals. For several recessive heredopathies commercial DNA tests are now available, significantly reducing costs. For instance, there is a test for arthrogryposis multiplex in cattle; for pulmonary hypoplasia with anasarca (PHA) in Dexter cattle; for polycystic kidney disease in cats, for Sly disease (mucopolysaccharidosis VII) in dogs; for hereditary microphthalmia in sheep. In abnormalities in which there is incomplete dominance between the mutant and normal allele, the heterozygotes can be identified visually because they have an abnormal phenotype, although it is less serious than that of homozygotes for the mutant allele. For example, there is a type of chondrodysplasia in cattle, common in the Dexter breed, in which the heterozygotes have shorter than normal limbs. If two chondrodysplasic individuals breed, there is a 50% risk of recurrence of the parents' phenotype (heterozygotes) and a 25% risk of a very serious and lethal chondrodysplasia, popularly known as a "bulldog calf", when the affected animals have very short limbs and spine, and their heads somewhat resemble that of a bulldog.

#### **8.3 Monitoring during pregnancy**

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examinations should be conducted in the later stages of the pregnancy; 4) Examinations that use radioactive contrast (scintigraphy) should not be conducted; 5) Care should be taken concerning the quality and conservations of animal food. Feed that is exposed to dampness could lead to contamination by mycotoxins; 6) Food should be supplemented with folic acid13; 7) Pregnant animals that suffer from diabetes should be monitored. In humans, diabetes mellitus is a significant risk factor when it comes to congenital defects. This may also be the case in animals.
