Anderson: Coat Color in Horses 



487 



There are some stallions that are 

 homozygous for their own colors and 

 are unable to produce even from chest- 

 nut mares any chestnut foals. The 

 two bay trotting stallions, Bingen and 

 Alcyo, we have found, do not produce 

 any chestnuts, although each one has 

 had numerous mares who to other 

 stallions do produce chestnut foals. 



Black is dominant to chestnut and 

 hypostatic to brown, bay, gray and 

 roan. The percentages are from a total 

 of 326 black x black matings : 90% 

 black, 3% chestnut, 5% brown, 2% bay. 

 The brown and bay from black matings 

 are very small, not enough to vitiate 

 the conclusion that black is hypostatic 

 to these two colors as well as to gray 

 and roan. Under the present methods 

 of registration there can be no sharp 

 line of demarcation between bay, black 

 and brown. I am confident that as the 

 records are now made up enough errors 

 have crept in, by registering bay or 

 brown, to account for the exceptions 

 above mentioned. In the opinion of 

 the writer, from true black horses 

 mated to true black, only black and 

 chestnut foals will be obtained. The 

 percentage of black colts from the cross 

 of black and brown and black and bay 

 are 36% and 22% respectively; just 

 about the figures that the Mendelian 

 law would require. 



In the tabulation given above the 

 stud book records are taken for brown. 

 As indicated elsewhere in this bulletin 

 mahogany bays are usually registered 

 as brown. All mahogany Vja^'S are 

 genetically bay and should be registered 

 as bay. 



The seal brown which characterizes 

 the larger nimiber of horses registered 

 as brown is just a light shade of black 

 horse and should be so registered. To 

 make all stud books conform to a 

 uniform standard the so-called brown 

 should be eliminated. The mahogany 

 browns should all be classed with bays. 

 The seal browns should be classed with 

 blacks. Should this be done the black 

 horse would have its variations in shade 

 as do the other recognized colors. 



In view of all the evidence the series 

 seems to be: chestnut recessive to all, 

 black dominant to chestnut and reces- 



sive to all others, bay dominant to 

 chestnut and black and recessive to the 

 three coordinate colors, gray, roah and 

 dun. 



The colors can be arranged in three 

 series : 



Gray Roan Dun 



Bay Bay Bay 



Black Black Black 



Chestnut Chestnut Chestnut 



The color at the top of the series is 

 dominant to all members of the series. 

 Chestnut comes last and is recessive to 

 all above. There is no question that 

 bay is recessive to gray, roan and dun, 

 and dominant to chestnut and black. 



when bay is dominant. 



Our records show 3712 bay matings, 

 and there is not a single gray, roan, or 

 dun horse thus produced. This is con- 

 vincing evidence that bay is hypostatic 

 to the three colors which head the 

 various series. 



The evidence of the dominant nature 

 of bay to black and chestnut is that 

 out of the 3712 bay matings 76% are 

 bay, 3% black, 13% chestnut and 8% 

 the so-called brown. 



That gray and roan are dominant to 

 bay there can be no doubt. Nine 

 hundred and sixty-seven foals from 

 matings gray x not-gray produced 46% 

 gray and 54% not-gray. It is known 

 that homozygous gray when mated 

 with any of the four popular colors will 

 always produce a gray. It is only from 

 a heterozygous gray that other than a 

 gray can be produced. We have no 

 records that would indicate the com- 

 parative strength of dun, roan and gray. 

 For the present we place them at the top 

 of the series as of coordinate strength. 



The factor for the roan pattern seems 

 to be independent of the factor for 

 color. There are the three factors, or 

 three causes, for the colors, chestnut, 

 black and bay. Intimately mingle 

 white hairs with chestnut and the result 

 is a chestnut roan. White hairs with 

 the black coat in sufficient numbers 

 give the blue or black roan. The bay, 

 or strawberry, roan is due to a mingling 

 of white with the bay coat-color. The 

 factor, or cause, for the roan condition 



