218 BREEDING TRIAL OF CONGENITAL HYDROCEPHALUS OF JAPANESE BLACK CATTLE USING EMBRYO TRANSFER

Abstract

Hydrocephalus is a congenital defect of cattle. Births of Japanese Black calves with forehead doming were reported in Tohoku District from 1988 to 1989. The common finding on autopsy was the presence of excessive amounts of cerebrospinal fluid with expanding lateral ventricles without evidence of microbiologic infection. Breeding records for pedigree registration have been maintained by the Wagyu Registry Association in this area since 1960. A survey of the pedigrees suggested that an autosomal recessive gene might be responsible for the defect. The incidence of doming calves ceased by an advised mating system which excluded the suspected sires after 1990. Molecular genetics is useful for disclosing DNA sequences of a recessive gene and for detecting the carriers of the gene. This trial was conducted to produce congenital hydrocephalus calves for gene analysis using embryo transfer on a small number of the remaining cows that gave birth to affected calves over 10 years ago. One donor cow, 11 years old, was superovulated with 24 to 25 AU of FSH (Antrin; Kawasaki Mitaka K.K., Kawasaki, Japan) and inseminated with frozen semen of a suspected bull. Collected embryos were transferred on the day of the collection and the rest of them were frozen and transferred later. Superstimulation was repeated 4 times in this cow at an interval of 76-105 days during and 8-month period. A total of 4, 13, 17, and 18 embryos of good quality were collected. Eighteen fresh embryos were transferred into 7 (2 embryos each) and 4 (single embryo) recipients. Frozen embryos were transferred into 6 recipients (single embryo). Seven of 17 recipients became pregnant and gave birth to 8 calves. Three of 6 male calves born and one of 2 females showed symptoms of hydrocephalus. Clinically, 3 of the affected calves had a domed forehead and squint-eyes and were unable to stand. One calf underwent a fatal convulsion and ataxia 29 days after birth. Pathological findings of affected calves showed dilated bilateral ventricles with increased cerebrospinal fluid as typical lesions of hydrocephalus. Embryo transfer was demonstrated to be a useful tool for investigation of a potentially heritable disease. Gene scanning with microsatellite markers using the tissues from the calves and the related cattle was done. The suspected gene was found near the centromere of chromosome 3 (BTA3). It was possible to diagnose the mutant-carrier cattle using two DNA markers, INRA006 (17.0 cm) and BL41 (43.2 cm).