January, 1938] Dairy Herd Replacements 21 



Table 13. Results of tuberculin test, according ta period within which the 



test tvas conducted. 



Seventy-three per cent of the cows in herds which were predomi- 

 nantly purebred were raised on the respective farms where tested, com- 

 pared with 55 per cent of the cows in herds which were predominantly 

 grade. Reactors were proportionately fewer among the purebred herds, 

 especially for cows purchased. Undoubtedly many breeders of pure- 

 bred cattle purchased cows which had already been tested previous to 

 their owji official test. A larger percentage of the cows raised in pure- 

 bred herds reacted than in the case of grades. 



Abortion. None of the farmers included in this survey had tested 

 their herds for Bang's disease or infectious abortion. It was not until 

 1934 that the Federal Government in cooperation with the states made 

 payments available to voluntary participants as indemnity for cattle 

 that reacted to this disease. An attempt was made in this survey to 

 observe how seriously this disease prevails as a menace to dairymen, 

 and to observe its relation to replacement methods. 



Tlie number of untimely births on these 200 farms amounted to 5.2 

 per cent of the 3366 cows inventoried at the beginning of the year 

 (Table 14). Those which had to be bred more than once amounted to 

 19.8 per cent and those which failed to breed 3.6 per cent. The preva- 

 lence of this disease, as with tuberculosis, is associated with replace- 

 ment methods. Herds which consisted of only cows raised had com- 

 paratively little trouble with premature births and with cows which 

 failed to breed. In general, abortion and breeding troubles were much 

 more serious in herds which depended entirely or in part on purchasing 

 cows for replacements. In the 20 herds which consisted only of pur- 

 chased cows, the abortion cases amounted to 14.4 per cent of the cows 

 on hand at the beginning of the year, but the difficulty encountered in 

 getting cows bred was slightly less serious than in herds which were 

 only partly replaced by purchase. Undoubtedly many cows in the 

 former group were bred before purchased. 



Application and Conclusions 



The decision as to whether or not any individual farmer should raise 

 his own replacements should be based on that organization of his en- 



