ATRESIA-COLI INHERITED IN HOLSTEIN CATTLE

A mating plan was designed to test the gentic hypothesis that atresia coli is inherited as an autosomal recessive at a single locus with two alleles. Matings between 8 putative carrier sires and 56 putative car rier dams resulted in 59 normal and 8 atresia coli calves, which was n ot different from the expected number of 8.1 affected calves. One case of atresia coli was observed among 628 calves born concurrently in th e herd. All of the affected calves born from planned and contemporary matings were inbred, and their dominance relationships with each other were greater than zero, which is complementary evidence of pairs of a lleles in common among affected calves. In planned matings, 7 of the 3 9 pregnancies diagnosed during the first 40 d of gestation of putative carriers produced affected calves. In contemporary matings, for pregn ancies diagnosed before d 41 of gestation, there were 1 affected and 2 95 normal calves. Atresia coli in Holstein calves was associated with putative carrier parents. Retrospective analysis of early pregnancy di agnosis in dams was inconclusive in evaluating the role of palpation o n atresia coli in genetically predisposed calves.