68 



DAIRY FARMING 



average the production of milk for the lactation period in- 

 creases each year until the cow is about five years old, after 

 which the production remains fairly constant until the 

 animal reaches at least 11 or 12 years. 



On the average a well-grown two-year-old may be expected 

 to produce 70 per cent, a three-year-old 80 per cent, and a four- 

 year-old 90 per cent of the milk and fat that she will pro- 



5 7500 



LU 



>- 



7000 



o_ 



M 



rd 6500 



i 



>- 5500 

 5000 



\ 



3 



11 12 



5.00 



t 



4.50 5 

 o 



5 



4.00 of 



56789 

 LACTATION PERIOD 



FIG. 24. Influence of age on yield of milk and percentage of fat, 

 averages for six Jersey cows for twelve years. 



duce when mature. The highest production for a year may 

 come anywhere between the 4th and llth year. Two-year- 

 olds that are not well grown may not give over half as much 

 as when mature. If a cow continues to breed, her milk 

 flow usually shows little decline until she is 12 years old and 

 sometimes even older. Probably the majority of dairy cattle 

 are rejected from the herd on account of failure to breed, 

 or from udder troubles before the effect of advancing years can 

 be observed to have had any effect upon the milk production. 



