429 



The line for the specific gravity runs parallel to that for solids-not- 

 fat. In general the yield of milk decreased after the middle of the 

 period. From time to time temporary variations from this rule were 

 noticed, and at such times the percentage of fat in the total solids 

 showed an increase in the case of 8 cows and a decrease in the case of 

 6 cows. In the case of the majority, therefore, the temporary increase 

 in yield was accompanied by an increase in the relative per cent of fat, 

 that is the milk became relatively richer in fat. These temporary 

 increases in yield, therefore, affected more especially the secretion 

 of fat. 



Calculations are made of the milk and butter (with 83.33 per cent 

 fat) yielded by each cow per 500 kg. live weight, and during a period 

 of 300 days. The butter yield varied with the different cows from 

 82 to 148 kg. The author alludes to the unavoidable effect on the profit 

 of dairying which such differences in cows must have, when with the 

 same food and the same live weight, during a like period of lacta- 

 tion, one cow yields 82 and another 148 kg. of butter, a relation of 100 

 to 180. For further comparison the cows are arranged in groups of 

 four each with reference first to age and second to live weight, the 

 yield of butter and milk per 500 kg. live weight during a like period 

 of lactation being given in each case. The average results with each 

 group are given in the following statement : 



Relation ietween yield of milk and hutter and age and iceight of cow. 



Kelation between age of cow 

 and yield per 500 kg. live 

 weight. 



Number 

 of lac- 

 tation. 



Yield during 

 period of lactation. 



MilV. 



Butter. 



Kelation between weight of 

 cow and yield per 500 kg. 

 live weiglit. 



Live 

 weiglit. 



Yield during 

 period of lactation. 



Milk. Butter. 



Group 1 

 Groii]) 2 

 Group 3 

 Group 4 



Ito 2 

 3 

 5 



5 to 11 



39.57 

 30.24 

 33.08 

 28.22 



Kg. 



118 

 126 

 126 

 96 



Kg. 



581 

 560 

 524 

 489 



Kg. 

 28.74 

 29.80 

 31.22 

 33.35 



Kg. 



113 

 111 

 113 

 129 



The above statement indicates that in this case the oldest cows 

 yielded the smallest and those cows in the fifth lactation, in general, 

 the largest amounts; and that the yield of milk per 500 kg. of live 

 weight increased as the live weight of the animal decreased, that is 

 within this breed the lighter cows gave a larger amount of milk in pro- 

 portion to their weight than the heavier animals. With regard to the 

 butter, while thehghtest cows yielded the largest amount, the difference 

 between the heaviest cows and those of medium weight was not marked. 

 If further investigation should show that under otherwise correspond- 

 ing circumstances lighter cows require proportionally more food for the 

 production of a given quantity of mQk than heavy cows, the lighter 

 cows would still possess the advantage that per unit of weight they 

 produce more milk and butter than the heavier animals. 



