Serological Studies on Bovine Infectious Abortion

Abstract

Reacting cows may be divided into three main groups by testing their sera and milk at monthly intervals and titering to the end point. One of these groups comprises animals whose udder secretions constantly exhibit reacting bodies of both classes. The second is made up of cows in the milk of which the so-called immune bodies are present only during the colostral and drying off periods; while in the third group the complement fixing bodies are never present in the milk. Animals classified in the second group constituted 50 per cent of the cows under observation. All calves, regardless of the reaction of the dam, are born non-reactors to both the agglutination and complement fixation tests. If they are permitted to suck positive dams within the first twenty-four hours of life, they become reactors in a remarkably short time, but again become negative almost invariably before the sixth month of age. On the other hand, if they ingest the colostrum of negative dams, they remain negative unless they become infected from without during or after sexual maturity.