This bulletin is a sequel to Research Bulletin No. 30 published in 1916. It contains information and a discussion concerning the progeny from the original stock subsequent to that date.
The work of the previous investigators, their results and the conclusions drawn therefrom, are retabulated without details. Additional data are added showing that the recessive whites obtained from the F2 breed true.
The nature of the roan in the Shorthorn is considered. While it is recognized that Wright's criticism of the hypothesis used (Wentworth's) rendered it improbable, yet the fact that two whites when mated to self-colored bulls threw self-colored calves, seems to disprove the hypothesis that roan is the simple heterozygote between self-pigmented and white. Accordingly no conclusions are drawn with respect to roaning.
The relation of these whites with dark points to the similarly marked Wild White Park Cattle of Great Britain is discussed, and the conclusion is drawn that they are of a different genetic composition, the former being recessive and the latter dominant to most colors. It seems probable that the only coat color difference between these whites with dark points and the white Shorthorn lies in the degree of pigmentation in the points. The presence of pigment in the ears shows dominance over the almost complete lack of it.
A white with red points was obtained, as demanded by Lloyd Jones' and Evvard's theory.
Matings of the white with dark points to the almost white Ayrshire reveal that there is no genetic similarity between the two types of white. Data were obtained from these matings, but not in a quantity sufficient to advance or prove any hypothesis.
Detailed tables and descriptions of the new individuals are presented.
Evvard, John M.; Shearer, P. S.; Lindstrom, E. W.; and Smith, A. D. B.
"The inheritance of color and horns in Blue-gray cattle II,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 11
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol11/iss133/1