Abstract
A landrace boar being heterozygous for a translocation has been used in 43 matings to 30 sows. Compared to a normal boar which also served part of the same sow group the defect boar had a by 30 % reduced fertility. Five different types of unbalanced karyotypes were detected in fetuses sired by the translocation heterozygote. Since no unbalanced karyotype was to be found postnatally in 111 offspring, all defect karyotypes seem to be lethal at the embryonic stage. Forty-one % of the postnatally investigated cases had the same translocation as the father.