Studies in Milk Secretion. 551 



General Summary and Conclusions. 



A good grade herd can be bred up from a herd of ordinary 

 cows by the use of first -class thoroughbred sires and a careful 

 selection of the best heifers. 



By breeding in this way the University herd has increased in 

 milk production from an average of 3,000 pounds per cow in 1874 

 to an average of 7,575 pounds in 1898. 



It pays to select heifers from the best cows as well as to use 

 only well bred bulls. Milk such heifers at least one year and 

 then retain only those which give promise of being profitable 

 producers. 



The greatest production for one lactation period was by Ruby 

 in 64 weeks, 16089.5 pounds of milk, and 531.32 pounds of fat, 

 equivalent to 625 pounds of butter containing 85 per cent fat. 



The average production for seven years was 7330 pounds of 

 milk, 275 pounds of fat and 3.76 per cent fat. The average for 

 each 3^ear varied from 6,875 pounds of milk in 1892-3, and 266 

 pounds of fat in 1895-96 to 7,575 pounds of milk in 1897-8, 

 and 292 pounds of fat in 1893-94. 



The average gain in production of milk as the cows increased 

 in age was 5 per cent from two to three-year-olds, 18 per cent 

 from three to four-year-olds, and 15.3 per cent from four-year- 

 olds to full aged cow^s. 



The average gain in production of butter fat was 5.5 per cent 

 from two to three-year-olds, 17 per cent from three to four-year- 

 olds, and 13.6 from four-year-olds to full aged cows. 



Beginning with the third week after calving and dividing the 

 remainder of the lactation into periods of four weeks, and then 

 considering the average daily yield of milk of all the cows for 

 the first period as loo there was a gradual decrease in milk flow 

 to 55 during the eleventh period. 



Calculating the average per cent of fat in like manner, there 

 was a decrease to 96 in the second period and then a gradual 

 increase to 106 during the eleventh period. 



Speaking in other terms there was an average decrease in yield 

 of milk as lactation advanced, of about five per cent from each 

 period of four weeks to the next. In per cent of fat there was 



