Management and Breeding Data on a Dairy Herd in which Bang's Disease (Infectious Abortion) was Eradicated by Segregation

Abstract

Summary Initial division of the herd was made on May 10, 1926, according to the results of the agglutination test for Bang's disease (infectious abortion). The abortion-negative group consisted of 65 females of breeding age and the abortion-positive group 82 females of breeding age. The 82 reactors were moved to new buildings, about one-half mile from the home buildings, where the 65 nonreactors were held. From May 21,1926, to June 18, 1932, 80 cows from the abortion-negative group were added to the abortion-positive group. The abortion-positive group was terminated October 4, 1935. Mere division of the herd was not effective in preventing the spread of the disease. Strict supervision of all communication between the two groups stopped the spread of the disease. Different crews cared for the different groups of animals. The milk from the two groups was handled in the same room at the home buildings. Calves born in the abortion-positive group were fed milk from that group until they were 50 to 60 days old, then changed to milk from the abortion-negative group for 10 days, after which they were taken to the home buildings and isolated for 10 days before being placed with the other calves in the abortion-negative group. The same bulls were bred to abortion-negative and abortion-positive cows without evidence of their spreading the disease. The group of 80 cows added to the abortion-positive group from time to time required more services for a conception than any other group, and the percentage of conceptions resulting from the first four services was smaller in this group than in any other. The percentage of pregnancies terminating in live calves was also smaller in this group than in any other group. This group was also less efficient than the other groups, as judged by the average number of live calves per cow-year. The less favorable showing of these 80 cows was probably due to the fact that they became positive and went through the most serious phase of the disease during the period covered by these data, while many of the animals in the original positive group had already passed through the most serious phases of the disease prior to segregation and were not so seriously affected during the period covered by these data. The abortion-positive cows required more services for a conception when bred after an abortion than when bred after a normal calving. The sex of calves and fetuses is given for the time the abortion-positive group was maintained.