10 MASS. EXPERIMENT STATION BULLETIN 291 



allowance. The problem is concerned only in a minor sense with the amount of 

 milk produced, the more important question being the relative economy of pro- 

 duction, which is discussed later. """ .. 



Table 6. — Data Respecting Milk Production. 



High Roughage Low Roughage 



Average daily milk yield per cow* pounds 



Total milk yield of each group* pounds 



Dry matter required to produce 100 pounds of 



milk pounds 114 106 



Digestible nutrients required to produce 100 

 pounds of milk pounds 



Average length of lactation period days 



Average length of dry period days 



Average length of time calf was carried during 



the lactation days 182 200 



Average number of productive days per calen- 

 dar year days 285 290 



♦Corrected to a 305-day basis. 



The high roughage group was slightly more persistent in milk flow as evidenced 

 by an average lactation period two weeks longer than the average for the low rough- 

 age group. This can be attributed almost entirely to a shorter calf-carrying period 

 during the lactation, the difference being eighteen days. The possible significance 

 of the later breeding and resultant shorter calf-carrying period is discussed in the 

 section dealing with reproduction. It may be noted at this point that both groups 

 remained non-pregnant after calving somewhat longer than is usual and hence had 

 somewhat shorter calf-carrying periods during the lactations. The slightly greater 

 persistency in milk yield shown by the high roughage group is completely offset 

 by a longer average dry period, the average number of productive days per calendar 

 year being slightly higher for the low roughage group. 



The low roughage group made slightly better use of their feed, eight pounds 

 (7 per cent) less dry matter and two pounds (2.7 per cent) less digestible nutrients 

 being required to produce one hundred pounds of milk. 



Feed Cost of Milk Production 



The next question that naturally arises relates to the feed cost of production of 

 the milk. This will vary with local conditions and relative costs of roughage and 

 grain, and for any given time and place must of necessity be determined by the 

 individual farmer. During the time this investigation was in progress the relation 

 between grain prices and roughage prices was such that the feed cost of production 

 was practically the same for both systems of feeding. With grain prices as low as 

 they are at present (December, 1932), the low roughage system has an apparent 

 advantage in immediate economy of production. It should be remembered, how- 

 ever, that where roughage is largely home-grown the high roughage system in- 

 volves a considerably smaller cash outlay. Also, a farmer may be able to raise 

 hay and silage for less than average prices. If so, the difference represents a profit 

 on his labor which should be taken into consideration in calculating costs. 



Costs should be figured not on the basis of actual cash outlay but on the cost of 



