Developmental Anomalies in Farm Animals: II. Defining Etiology.

Anomalous development is a function of the genetic make-up of the fetus and the environment in which it develops. The cause of anomalous development may occasionally be obvious but more often is obscure, because of its multifactorial nature. Therefore a methodological approach is often required to define the etiology. In this paper we describe a methodological approach that first defines the incident, the genotype of the individuals involved, and the environment in which the fetus has developed. This procedure can be undertaken in a stepwise fashion and need not be followed through to the end if the etiology becomes obvious. This approach highlights the necessity to characterize the defects, to use ancillary tests, and to apply basic epidemiological methods.