Allen: Effect of Parents' Age on Quality of Dairy Cows 173 



whole, even here, the 

 curves run nearly 

 parallel. There is, 

 however, a distinctly 

 larger percentage of 

 high producers born 

 of very young dams 

 than there is of low 

 prod ucers. 1 1 is hard 

 to account for this 

 unless the Superior 

 Class have received 

 better care and are 

 bred younger on the 

 average than the In- 

 ferior Class. 



It will be noted in 

 connection with Table 

 III that a slightly 

 larger percentage of 

 the Superior Class 

 were born from dams 

 under five years of 

 age than there were 

 of the Inferior Class. 

 In later life, the two 

 classes are very near- 

 ly alike and almost 

 exactly as many of 

 the Superior Class 

 were born from dams 

 over eight years of 

 age as were born in 

 the Inferior Class 

 from dams of a 

 like age. The per- 

 centage having dams 

 over twelve years is 

 exactly alike for both 

 classes. 



VALUE OF OFFSPRING 



OF VERY YOUNG 



AND VERY OLD 



PARENTS 



From a study of 

 the frequency curves 

 and Tables II and 

 III, it is evident that 

 the young born from 

 very young parents or 

 from very old parents 

 are as valuable as 

 any for productive 



18. Or 

 17.5 



17.0 



15.5 



15.0 



I4.0t 



I3.5F 



13.0 



SUPERIOR CLASS 

 INFERIOR CLASS 



y\ 



24 30 36 42 48 54 60 66 72 78 84 90 96 102 108 114 120 126 132 138 144 



AGE OF ^SH IN MONTHS 

 FREQUENCY CURVE FOR SIRES 



FIGURE 14. The co-ordinates are the same as in the preceding 

 chart. The same conclusions apply even more strikingly in this 

 case, as the sires are not used for breeding purposes as long as the 

 dams. A sire cannot be considered a proven sire until his first 

 crop of daughters have been in milk at least a year, which means 

 that he must be five years of age. These figures are for a selected 

 class of sires and show that even the breeders who are making 

 records use tried sires for only a small percentage of their cows. 

 (See text, p. 170.) 



