76 DUAL PURPOSE CATTLE 



VERMONT EXHAUSTIVE ANALYSIS 



VARIATIONS IN QUANTITY AND QUALITY OF MILK 



Some eighteen years ago the annual report of the Vermont Ex- 

 periment Station gave the result of an exhaustive analysis. A full 

 record had been kept, at the station, of the milk of each cow, year 

 after year, and many thousand analyses were mde. A study of the 

 records led to the following conclusions, which were given to the ag- 

 ricultural public by an American paper, present day folk having 

 recognized that farmers' "guess work" must give place to "facts 

 and figures," the statement is now reprinted as part of this essay 

 on milk inheritance. 



1. All cows shrink in quantity of milk as they get further from 

 calving. If they are farrow, this shrinkage in quantity is accom- 

 panied by almost no change in quality even until they go dry, pro- 

 vided they are still farrow. If they are in calf, the milk increases 

 in quality as it decreases in quantity. This increase is slight, about 

 one-twentieth during the first six months afer calving, but becomes 

 quite pronounced just before the cow goes dry. 



2. Cows that calve in the spring average giving more milk dur- 

 ing the first three months after calving than those that calve in the 

 fall. For the 7th, 8th, and 9th month this is reversed. Fall cows 

 show smaller variations in the quantity of milk than cows that calve 

 in the spring. 



3. The milk of a cow for the first few days or weeks after 

 calving is very variable in quality. On the average, it is thinnest 

 just after calving, becomes slightly richer during the next two weeks, 

 and then holds almost uniform in quality for four or five months. 



4. Cows vary in the quality of milk from one milking to the 

 next, and from day to day, the quality rising and falling without 

 apparent cause. Such changes are usually within one per cent, of 

 fat, though one cow was known to change 2.68 per cent in two days. 

 The least change of any cows in the station herd during an entire 

 period of lactation was 0.33 per cent fat, the average change 1.3 per 

 -cent., and the greatest change 2.78 per cent. The largest variation 

 in yield of butter was from milk that required 20 Ibs. to make a Ib. 

 of butter to a quality of milk which would require but 11.7 Ibs. It is 

 probably possible that cases may occur of a doubling of the richness 

 of the milk during different times in the same period of lactation. 



5. Just after calving the milk is poorer in fat and in solids not 

 fat than just before the cows goes dry. The average drop in fat 

 is 1.13 per cent., the greatest change being 2.35 per cent., the least 

 0.49 per cent. The average change in solids not fat is a fall of 0.47 

 per cent, with variations from a decrease of 1.95 to an increase of 

 0.42 per cent. 



6. Most cows give the same quality of milk year after year, 

 beginning with this quality at the first calving. There is no general 



