60 Milk and Its Products 



If we concede that it is not an entirely safe practice to 

 base this selection upon the producing capacity of the 

 dams, we must look for some other basis of selection. 



It is a generally accepted principle of heredity that 

 an animal which shows a tendency toward variation 

 is one that is not likely to be prepotent. We desire 

 to raise calves from cows that are not prepotent, in 

 order that the prepotent qualities of the bull may 

 have full scope. Cows, then, that show tendency 

 toward variation, particularly toward improvement, 

 are logically the ones over which the male is most 

 likely to be prepotent, and at the same time the calves 

 show the greatest tendency toward improvement. It 

 is comparatively easy to determine in any herd of 

 cows those which show the greatest tendency toward 

 variation, and more particularly those which show 

 the greatest tendency toward improvement when their 

 conditions are made more favorable. We can then 

 determine the cows from which we are likely to get 

 the best half-blood heifer calves by giving the herd 

 more and better feed, and selecting calves from those 

 animals which show the' greatest improvement under 

 such a change of treatment. 



Experience has shown that where the principles 

 stated above have been carefully carried out a very 

 satisfactory improvement has been secured in the first 

 generation. It is not uncommon to find an increase 

 of fully 50 per cent in the average production of half- 

 blood cows over their common mothers. Experience 

 has also shown that in the second generation the 

 three -quarter -bloods are not nearly so uniform as 



