1 7 6 



The Journal of Heredity 



record above thirty pounds of butter 

 in a week and most of those that 

 have done so are here considered. This 

 error, then, is in all probability very 

 small. 



The group averages and the class 

 average all show that the best records 

 of the animals herein considered were 

 made at an average age of about six 

 years. Of course many were much 

 older than this and many were younger, 

 but it is well known that animals vary 

 greatly in rapidity of development. 

 It would seem that the numbers con- 

 sidered are large enough to make the 

 average significant even though it is 

 recognized that most cows do not have 

 a chance to make a record every year. 

 The cow is most likely to be tested at 

 the time she shows greatest promise. 

 Since these high producers made their 

 best records at six years of age, it 

 seems only fair to assume that they 

 were at the height of their productive 

 capacity at this time. It would also 

 indicate that cows generally reach the 



limit of their possibilities for high 

 production at about this age. This 

 contention is supported from other 

 sources, 1 although one investigator, 2 

 who attacked the problem in an 

 entirely different manner, maintains 

 that the highest production is not 

 reached until much later in life. 



SUMMARY 



The parentage of superior or high 

 producing dairy cows is no older than 

 the parentage of comparatively inferior 

 or low producing cows and thus the old 

 animal is no more valuable as a parent 

 than the young animal. 



As far as the age of either parent is 

 concerned, the young born at one time 

 in life seem to be just as valuable as 

 the young born at any other time. 



A very large percentage of our cows 

 are born of immature parents but the 

 proven animal at any age is much more 

 valuable for breeding purposes. 



On the average, cows make their 

 best records at about six years of age. 



1 PEARL RAYMOND, The Change of Milk Flow with Age. 

 Station Bulletin, No. 262. 1917. 



2 GOWAN, J. W., Studies in Milk Secretion VIII. 

 Bulletin, No. 293. 1920. 



Maine Agricultural Experiment 



Maine Agricultural Expiriment Station 



