Duck : Short-Horn Color Inheritance 



73 



1)ecause it would seem unlikely that 

 (Rree) and (RrEe) would occur in 

 €qual ratio. In fact, the preponderance 

 of data shows that whenever possible 

 (RrEe) individuals are registered as 

 roans because of the greater popularity 

 of this color over red-and-white. 

 Practical Aspects 



1. The crossing of red on white 

 will both theoretically and actually give 

 the highest percentage of roans. Cross- 

 ing roan on white will give the next 

 highest percentage of roans. Red on 

 roan, red-and-white on roan, roan on 

 white, and roan on roan will all give 

 about the same percentage of roan 

 calves, approximately forty per cent. 



2. To produce a strain of roan 

 Short-Horns which will breed true for 

 roan seems impossible from both a 

 practical and theoretical standpoint. 



3. A few isolated cases should not 

 be used as a guide or to draw conclu- 

 sions from. Several hundred cases 

 should be traced to come to any definite 

 conclusion. 



4. Color pattern seems in no way 



to be correlated with sex in Short- 

 Horns. A red bull crossed on white 

 cows will produce as many roans as a 

 white bull on red cows. Sufficient in- 

 dividuals to establish a fair average 

 must be used. 



5. Genetically there are three kinds 

 of red and three kinds of white Short- 

 Horns. This will account for many 

 of the apparent contradictions in Short- 

 Horn color mating. 



6. Pure red on pure red will pro- 

 duce only red. Pure white on pure 

 white will produce only white. 



7. White in Short-Horns is due to 

 the total absence of any color factor. 



8. Red is the only real basic color 

 in Short-Horns. 



9. Red-and-white is due to a dilu- 

 tion of the red color factor, in the ab- 

 sence of the roan extension factor. 



10. Roan is not a separate color, 

 but is a blending of red and white due 

 to the presence of an extension factor 

 in the germ cells of one or both parent 

 types.^ 



Table I. The relative proportions of the various recoyni.ced colors of Short-Horn cattle 

 in the United States at three different periods. 

 Data for the years 1895-1914, inclusive, is taken from Plumb's Types and Breeds of 

 Farm Animals, by permission of Professor C. S. Plumb. That for 1921 was compiled by 



the author. 



1895-1903 1910-1914 1921 



Color Number Percent Num ber Percent Number Percent 



Rid I Z^I^ 40.4.'^ II 1.S.085 62.85 II 4,959 AqTq 



Red and White 

 Roan 



White 



tl 



Table II. Percentage of Color Segregation in the Zygote. 



Red 



Red and 

 White 



Roan 



White 



I. Red X Red = 



2. Red X R- and W. 



RREE 

 RREe X 

 RRee 



RREE 

 RREe = 

 RRee 



fRREE 

 J RREe 

 [RRee 



X Rree 



50 



25 



' The author wishes to acknowledge the assistance and co-operation given by the Ameri- 

 can Short-Horn Breeder's Association through their secretary, P. K. Groves. Also to the 

 assistance given by Mr. A. W. Lathrop and Mr. Herbert Comstock, of Syracuse University. 

 To the many breeders and herdsmen consulted the author wishes to express his appreciation 

 and thanks. 



