PRINCIPLES OF LIVESTOCK BREEDING. 31 
Another interesting pair of factors is found in the red and white of 
the Shorthorns. In this case neither is dominant. The heterozygous 
animals have a mixture of red and white, the familiar roan pattern. 
The roan is thus an unfixable color. Roan by roan produces only 
about 50 per cent roan calves, the rest being equally divided between 
red and white. Practically 100 per cent roan can be obtained by 
breeding a white bull with red cows, or the reverse. The iactor 
which removes the color from the hair of roans and whites is inherited 
independently of the kind of color. Thus, when a white Shorthorn 
bull is bred with black Aberdeen- Angus or Galloway cattle, the black 
of the latter is dominant over the red factor which is present in white 
Shorthorns as well as red ones, while the white factor of the Shorthorn 
is imperfectly dominant over the solid color of the Aberdeen Angus or 
Galloway. The result is a blue roan. When such blue roans are 
crossed together, blacks, blue roans, whites with black ears, reds, red 
roans, and whites with red ears, are all produced if enough calves 
are born. All but the last class were found among 21 calves pro- 
duced in such an experiment at the Iowa agricultural experiment 
station. 
Other colors in cattle have not been worked out so satisfactorily. 
There appears, however, to be an imperfectly dominant dilution 
factor which reduces black to dun color and red to fawn. The white 
patterns of many breeds are inherited independently of their colors 
and are, at least to some extent, dominant. The white face of the 
Hereford is thus transmitted to nearly all the calves in the first 
generation of a cross whether the rest of the coat is black or red, and 
is a useful " trade-mark " for the recognition of Hereford grades in the 
market. Grades of the dairy breeds are usually recognized by show- 
ing traces of the dilute color of Jerseys or Guernseys or the large, 
irregular, white areas of Ayrshires, Holstein-Friesian, and many 
Guernseys. 
COLORS OF HORSES. 
The colors of horses have been worked out in much detail. The 
power to develop black (factor H) seen in bays, blacks, duns, etc., is 
dominant over its absence, as seen in chestnuts (factor h). Bays (B) 
differ from blacks (b) by an independent factor which may or may not 
be transmitted by chestnuts. The dilute colored duns, creams, and 
mouse-colored horses differ from bays, chestnuts, and blacks, respec- 
tively, by a third dominant factor (factor D and d). Three other 
independent pairs of factors determine between the roan (R), gray 
(G), and piebald (S) patterns and their absence (r, g, and s). Since 
a chestnut horse is recessive in all essential factors Qihddrrggss) , he or 
she can produce only one kind of reproductive cell Qidrgs), and two 
chestnuts, whatever their ancestry, can produce only chestnut 
foals. 
