40 DAIRYING 



a decline with a slight change in the per cent of fat in the milk 

 from 3.37 in the first to 3.19 in the sixth lactation period. 



The evidence indicates that cows as a rule begin to decline in 

 milk production after the sixth to the eighth lactation period. 



S. Abortion. 



197. The statement is sometimes made that abortion ruins 

 a cow as a milk producer, and she should be fattened and sold. 

 This is a mistake, as abortion can be cured ; and after recovery a 

 cow may produce a satisfactory yield of milk. Several observa- 

 tions have been made which show the effect of abortion on the 

 milk yield. Hills* gives the average per cow of six that aborted 

 as follows: 



Normal Calving Abortion Period 



Milk, pounds 6115 3902 



Fat per cent 4.93 5.43 



Fat pounds 351 247 



Beach** reports the records of 10 cows under normal calving 

 and through an abortion period to the following normal calving 

 period. The average milk production per cow per year before 

 abortion was 5,892 pounds milk and 283 pounds butter fat. "These 

 cows aborted seven months (average 211 days) after conception" 

 and the average time per cow before another normal calving took 

 place was 2.1 years. During this time or the abortion period, the 

 the average per cow was 5,196 pounds of milk and 268 pounds of 

 butter fat per year. The milk was 696 pounds, or 12% less per 

 year during the abortion period. The satisfactory yields are at- 

 tributed in part to the complete removal of the after birth, and the 

 thorough disinfection of the animal after abortion." No trouble 

 arose from failure to breed -after abortion when time (about six 

 months) is given to recuperate from the effects of abortion. 



T. The Use of Tuberculin. 



198. When cows are tested for tuberculosis by injecting a 

 small quantity of tuberculin into the circulation an increase in the 

 temperature is noticed in the reacting cows. This treatment does 



*Vt. Expt. Sta. Report 1895. 

 **Storrs Conn. Expt. Sta. Report 1907. 



