Dunn, Schneider and \Ve]:)b: Spotting- in Cattle 



239 



OFFSPRING OF KING PIETERTJE 



Figure 21. Notice how closely the calves resemble their sire, not onh- in 

 amount of black and white, but in its distribution. A certain amount of non-genetic 

 variation certainly occurs, but just how much is diificult to determine. Photograph 

 courtesv the Holstein-Fresian World. 



could be determined. Because of the 

 tendenc}^ of originally separate chorions 

 to fuse, the evidence from the condi- 

 tions of the membranes at birth is 

 not reliable, so that this method which 

 would seem to offer a mode of attack 

 on the problem of spottiiig inheritance, 

 appears actually to be of no value. 

 Gowen (loc. lit.) collected 1132 cases 

 of twins in Jersey cattle and from 

 the degree of resemblance in body 

 markings between monosexual as com- 

 ])ared with bi-sexual twins and sisters 

 of separate l)irths concluded (p. 5), 

 "These facts all point to not more than 

 a low percentage of identical twins in 

 cattle if they exist at all." 



Of the two pairs of monosexual 



twins in our series, one pair is alike 



in coat pattern, one member having 



250 units of black left 



150 units of black right 



and the other 



150 left 



150 right 

 The members of the other pair are 

 dissimilar, one being 



200 left 



100 right 



the other 



650 left 

 650 right 



The second pair is from a cross oi 

 light by dark and shows segregation 

 of light and medium ; while the first 

 pair is from medium by light and 

 shows segregation of light from me- 

 dium. In view of the facts cited 

 above, the resemblances and differences 

 of these twins are only such as might 

 be expected to arise from segregation 

 of spotting factors in individuals of 

 separate birth. 



Discussion and Conclusion 



The results obtained from this study 

 are chiefly of value in pointing out an 

 interesting problem for which a greater 

 amount of material is available than 

 for any other problem of coat color 

 or spotting inheritance knowii to us. 

 and in indicating some of the methods 

 by which it may be attacked. 



The preliminary evidence is suffi- 

 cient to indicate that : 



(1) Differences in amounts of spot- 



ting in Holstein cattle are in- 

 herited, and amenable to se- 

 lection even when this is prac- 

 tised on the male side only 

 as in the present case. 



(2) That the darker grades are 



probably partially dominant 

 over the lighter grades. 



