152 DAIRY CATTLE AND MILK PRODUCTION 



The Yield of Milk. It will be seen from Table 7 that in 

 the University of Missouri herd the highest yield of milk was 

 in the fourth milking period, which corresponds closest to the 

 sixth year. The two-year-old heifers on the average yielded 

 71 pounds of fat for each 100 when mature ; the three-year- 

 olds 84 pounds, and the four-year-olds 93 pounds. 



From Table 9 we see that with the Ayrshires the two-year- 

 old cows produced 70 per cent, the Holsteins 65 per cent, 

 the Jerseys 68 per cent, and the Guernseys 77 per cent of the 

 average production for the mature cows. In each case it 

 might well be observed that the two-year-old animals produced 

 more in proportion to the mature cows than required by the 

 rules of the breed association under which the tests were 

 made. The chances are evidently better for a cow to enter 

 any of the Advanced Registries as a two-year-old than when 

 mature. 



The decline in milk production with age is difficult to rep- 

 resent, since it varies widely. In the table given from the 

 university herd up to the seventh period, the decline on the 

 average was slight. Many of the cows whose records are 

 used did their best year's work in the seventh period or 

 later. Since the number having more than seven periods in 

 our herd is limited, the figures are not given beyond that 

 point. 



Probably the majority of dairy cattle are rejected from the 

 herd on account of failure to breed, or from udder trouble, 

 before the effect of advancing years can be observed to any 

 marked extent. It is a fact often observed that a cow may 

 make her best record when 10 or 11 years old, although as 

 a rule she does her best rather earlier. If a dairy cow con- 

 tinues to breed, she usually shows no marked decline until 



