60 



Report of the Chemist of the 



of May represents on an average the first month of lactation of 

 factory cows — at least this is sufficiently close for the purpose 

 of comparison. We have averaged the yield of milk by lacta- 

 tion months from our Station herd covering a period of five years. 

 Now, taking the yield of the first month of lactation as 100, we 

 give below the comparative yield, on this basis, for the first six 

 months of lactation. It has been necessary to make some correc- 

 tion in case of the factory herds, as the yield in September and 

 October was to some slight extent affected by the discontinu- 

 ance of some herds. 



Assuming that the data furnished by the Station herd repre- 

 sent averages near the truth, w^e see that in the second month 

 of lactation there was a marked increase of milk yield and this 

 was followed by a fairly uniform decrease from month to month. 

 Tn the case of the factory herds, we observe an increase of milk 

 yield in the second month of lactation and then a decrease, ir- 

 regular and rapid. In the fifth month (September) there was an 

 increase of yield due to improved pastures, supplemented by 

 green corn fodder. In the factory herds the marked decrease 

 of milk yield, compared with what we may call the normal condi- 

 tions, as seen in our Station herd, can be explained satisfactorily 

 only on the ground of an insuflflcient supply of nutritious food, 

 due to dry pastures. 



We have reason to believe, therefore, that the observed 

 changes in composition and yield of milk during July and August 

 in case of the factory herds were due to abnormal conditions 

 unfavorable to the production of milk, and the main cause of the 

 effects observed was the lack of nutritious food. 



