The records of the herds studied show clearly that the 

 quality of the milk depends on the dam as well as the sire. 

 It is impossible as yet to determine the Mendelian factors 

 concerned, but by selection according to milk records, and 

 by mating the highest, animals are produced with all the 

 factors, whatever they may be, necessary for the produc- 

 tion of high quality milk. 



Breeding for Milk Production. 



Few records have as yet been published regarding the 

 inheritance of quantity in milk, but these seem to show that 

 quantity and quality are inherited separately. It must be 

 borne in mind that milk yields fluctuate with food, weather, 

 comfort, shelter, health, age and lactation period. 



Professor Wilson of Dublin suggests a method of cal- 

 culating the milk yield which is free from many of the un- 

 certainties referred to. He says that about half the cow's 

 total yield for a normal lactation is given by about the end 

 of three months. This part is freer from variation than the 

 remaining part ,and may be used to determine the grade of 

 the cow. He computes that a cow giving 5| gals, a day at 

 her maximum will give over 1000 gallons during a normal 

 lactation; a 4-gallon cow will give 800 gallons, and a 2|- 

 gallon cow about 500 gallons. That is, the maximum when 

 multiplied by 200 gives the total yield approximately. ^ To 

 breed up a milking herd, first secure a high grade bull, i.e. a 

 bull which has produced all high grade daughters from high 

 grade cows, or half his daughters high grade by medium 

 grade cows, or all his daughters medium from low grade 

 cows. By continuing the application of this principle it is 

 possible to grade up a herd in time so that all its members 

 will be high grade. 



(g) — Atavism and Reversion 



When a form arises which resembles a grandparent in 

 some characters rather than a parent, the term atavism 

 has been given to designate the occurrence. When a form 

 possesses a character which does not appear in any near 

 generation the case is one of reversion. 



Atavism is often readily explained by Mendelian laws. 

 For example, a blue-eyed child of heterozygous brown-eyed 

 parents has two blue-eyed grandparents. This is a case of 



(1) — Canadian and American authorities are of the opinion that this 

 method of computing the milk yield is not sufficiently accurate 

 for scientific purposes. They prefer to trust to the systematic 

 weighing of the milk and to reckon the total milk yield from 

 the daily or weekly records. 



12o 



