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Bovine Infectious Abortion

Increased Productivity of an Abortion-Free Dairy Herd

Storrs Agricultural Experiment Station, Storrs, Connecticut

ABSTRACT

In looking forward, in 1923, to the establishing of an abortion-free herd at the Connecticut Agricultural College, the practice was instituted of protecting maturing heifers by removing calves at six months of age, whether they were from abortion reacting or non-reacting dams, to separate premises a half mile distant from the main herd.

In order to stabilize the infection in the main herd the policy was adopted in 1924 of disposing of all aborting (premature calving) cows.

In February and March of 1925 the fifteen remaining reactors were removed from the herd and segregated. In July, 1925, one of the supposedly clean young cows reacted. She was promptly removed, and aborted two months later. Since that time not a single animal has reacted to the blood tests except young calves from the segregated reacting cows. This outstanding success in so completely removing the foci of infection in the initial separation was undoubtedly promoted by the process of stabilization or delimitation of the disease through the preliminary measures employed.

The abortion rate (premature calvings prior to the 265th day of gestation) which had varied in intensity during the years from 1904 to 1924, averaging 19.5 for each 100 calvings during this time, dropped to 2.9 per cent in 1925. It was 6.1 per cent in 1926, and 0.0 in 1927. The average premature calving rate during the past three years was 3.1 per cent, this figure being substantially the same as that previously reported by us from over 500 calvings of non-reacting cows.

The number of cows calving in each calendar year, which averaged 80.5 for each 100 cows from 1904 to 1924, was 87.4 in 1925, 100 in 1926, and 91.8 in 1927, the last three years being the period in which the herd has been free from abortion reactors.The live stock sales reached a high peak in 1927, due not only to a larger number of surplus animals but also to the larger proportion of more valuable breeding and producing animals available from the non-reacting herd.

The milk yield of the non-reacting herd has averaged 1505 pounds more of milk testing 4 per cent per cow per twelve-month year than the previous herd which contained both reacting and non-reacting cows. During the last four years the average yield of the herd has been 10,530 pounds of four per cent milk, while for nine years prior to that the average was 9025 pounds.

Finally, the appearance of the herd unquestionably shows an improvement as a result of the increased opportunity for culling that is afforded in an abortion-free herd.

In conclusion, the writers wish to express their appreciation to Dr. Charles A. Slanetz, Mr. George Brigham and Mr. Charles Oliver for their valuable assistance and cooperation.