Study of the inheritance of the SME seminal defect in the boar.

The characteristic SME-defect was demonstrated in the spermiogram of two boars in Denmark, one of the Danish Iandrace, and one of Yorkshire breed (imported from England). Recently a similar case has been reported from Norway in a Norwegian Iandrace boar. In order to ascertain whether or not the SME-defect is due to heredity, an inbreeding experiment was performed during the years 1974--76 based on two sons (with normal spermiograms) and two daughters of the Yorkshire boar. In the F2 generation 13 boars were studied. Ten had normal semen, while two were affected with the SME-defect to about the same extent as the grandfather. The last one showed a somewhat lower percentage of affected sperm heads. Assuming simple, recessive inheritance, the observed ratio of affected (2 + 1) to nonaffected boars (10) is, generally speaking, identical with the expected ratio. Thus the results support the theory of simple, recessive inheritance.