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JOBRNAL OF AGRICUITIIRAL RESEARCH 



Vol. XX Washington, D. C, January 15, 1921 No. 8 



INHERITANCE OF SYNDACTYLISM, BLACK, AND 

 DILUTION IN SWINE 1 



By J. A. DETLEFSEN, Professor and Chief in Genetics, and W. J. Carmichael, 2 Asso- 

 ciate in Animal Husbandry, Illinois Agricultural Experi?nent Station 



Our present point of view in animal and plant breeding is being shaped 

 to a large extent by experiments in the field of genetics. Probably the 

 plant breeders have profited more by these experiments than the animal 

 breeders; for there are relatively few precise observations on inheritance 

 in domestic mammals, for obvious reasons. While the animal breeder 

 can not afford to neglect the conclusions obtained with pedigreed cul- 

 tures of laboratory material, nevertheless the data accumulated directly 

 from domestic mammals will more quickly stimulate clear thinking and 

 intelligent practice. For these reasons, among others, the following 

 observations are presented and put on record. 



The data in this study are derived from an original cross between a single 

 pure-bred registered mule-foot boar and a number of pure-bred Duroc- 

 Jersey sows, eligible to registration. Both boar and sows were owned 

 by Mr. J. H. Percival, of Champaign, 111. The results of the cross were 

 so striking and uniform that we were invited to examine the progeny 

 born in the fall litters of 1915 and in the spring litters of 1916. All 

 the F x offspring, about 250 in number, 3 were self-colored black and mule- 

 footed. Furthermore, the progeny resembled the mule-foot boar in 

 general conformation (in which, as a matter of fact, both the sire and 

 the Duroc- Jersey sows were much alike). The case is a good illustra- 

 tion of one type of prepotency, where the sire is homozygous in a number 

 of conspicuous dominant characters, such as black and mule-foot in this 

 particular instance. But the progeny inherited as much from their dams 

 as they did from the sire, as the next generation showed. The vigorous 

 hybrids were raised for the market and not for further breeding purposes, 

 as is the case generally with such hybrids. Since the material seemed 



1 Paper No. 9 from the Laboratory of Genetics, Illinois Agricultural Experiment Station. 



2 Resigned May 31. 1918, to become Extension Animal Husbandman, United States Department of Agri- 

 culture; at present Secretary of the National Swine Growers' Association. The writers are indebted to 

 Mr. J. B. Rice, Associate in Animal Husbandry, for much assistance after the resignation of the junior 

 writer. 



3 The number of Fi young in this paper is conservatively estimated at about 250. The exact number 

 can not be given because the animals were kept in a large pasture, which made an exact count difficult. 

 There is no doubt, however, that all Fi individuals were black and mule-footed. 



Journal of Agricultural Research, Vol. XX No. 8 



Washington, D. C Jan. 15, 1921 



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