Studiks in Milk Secretion. 543 



change on the quality of milk is not so well understood. Prob- 

 ably it is the general belief that the early summer pasture tends 

 to produce a milk less rich in fat than the barn feed. The records 

 of the University herd throw some light on the effect of this 

 change in feed both on the quantity and quality of the milk. In 

 considering these records, however, it should be borne in mind 

 that nearl}^ all the cows are fresh in milk in the early fall and are 

 therefore so near to the end of the lactation period that most of 

 them are dried off within six weeks to two months after they are 

 turned to pasture. Under these conditions it is not to be expected 

 they would show so much variation on a radical change of food 

 as though they were fresh j ust before the change. Up to the time of 

 going to pasture the cows receive an abundant ration of corn silage, 

 mixed or clover hay, grain and roots, usually mangel wurtzels. 

 On going to pasture, this ration is discontinued entirely except 

 for some grain and what little hay the cows will eat at milking 

 time. About one third or one fourth as much grain is given as 

 when on full stall feed except to such of the cows as are fresh in 

 the spring which receive about as much as the}' will eat. If the 

 pasture continues good the grain is taken entirely away from all 

 except the fresh cows. 



To compare the quantity of milk given under the two condi- 

 tions above named, the daily average yield for each cow was 

 determined for four separate periods, viz : the last three weeks 

 before going to pasture ; the first week at pasture ; the first two 

 weeks at pasture ; and the three weeks following the first two at 

 pasture. From these averages was found the daily increase or 

 decrease per head for each of the three periods at pasture as com- 

 pared with the period on bam feed. The per cent of fat for 

 each cow was averaged for the same periods and the increase or 

 decrease determined. 



In the following table (V) are given the individual records of .he 

 variation in milk and per cent of fat for one year (1898) in order 

 to show the method of comparison and how some cows increase 

 while others decrease under seemingly the same conditions. There 

 are also given the averages for all the cows for each year and for 

 the six years during which this study is carried. 



Some interesting data on this same point has been published 



