INHERITANCE IN SWINE 



Jay L. Lush 

 Department of Genetics, University of Wisconsin, Madison 



ONE among the many casualties 

 of the Great War, which will not be 

 found listed in the files of the War 

 Department, was the stopping of a cer- 

 tain extensive experiment in swine 

 breeding which was conducted at the 

 Kansas Experiment Station under the 

 direction of Mr. E. N. Wentworth until 

 the spring of 1918 when the last of the 

 persons in immediate charge of the work 

 entered military ser\dce. That ended 

 the taking of detailed records and the 

 subjects of the experiment continued 

 their growth, matured, and were mar- 

 keted, so that it was impossible to 

 resume the experiment at the point at 

 which it stopped. 



SOME VALUABLE CONCLUSIONS 

 REACHED 



However the experiment was not a 

 complete casualty for the results al- 

 ready secured in four years of breed- 

 ing make a few conclusions almost 

 inescapable and point to others which 

 can perhaps be verified, one at a time, 

 by a few well-chosen crosses. This is 

 particularly fortunate because there 

 have been so few genetic experiments 

 on swine which have gone farther than 

 the production of a very few F2 litters, 

 and yet swine are very suitable for 

 studies in heredity, not only because 

 of their economic importance, but also 

 because of the rapidity of their multi- 

 plication and the wide diversity of 

 true-breeding forms and colors which 

 they offer to the investigators. 



The experiment was undertaken 

 with the idea of securing information 

 about the inheritance of a\l the well- 

 defined characters which differed in the 

 breeds used, but conclusions have been 

 reached only in regard to the shape of 

 face, set of ears, color, growth factors, 

 and litter size. The most of the work 

 was done on crosses of a registered 



1 Wentworth, E. N. and Aubel, C. E. Inheritance of Fertility in Swine. Journal of Agricul- 

 tural Research, Vol. 5, No. 25, pp. 1145-1160. 



^SiiiPSON, Q. I. 1912. Fecundity in Swine. Am. Breeders' Association, Vol. 7, pp. 261-275. 



57 



Berkshire boar on registered Duroc- 

 Jersey and Tamworth sows, but the 

 problem of litter size was separately 

 attacked by mating European wild 

 boars of the Schwarzwald type to 

 Tamworth and Berkshire sows. 



LITTER SIZE 



The use of the wild boar for investi- 

 gating this economically important 

 character was originally suggested by 

 an investigation by Wentworth and 

 Aubel* in which it appeared that the 

 distribution of the various litter sizes 

 among ordinary domestic swine did 

 not conform to the normal frequency 

 curve. Since the wild hog ordinarily 

 produces four pigs per litter, it was 

 decided to cross a boar of this kind 

 upon sows of one of the more prolific 

 of the domestic breeds, such as the 

 Tamworth which ordinarily produces 

 about eleven pigs per litter. There 

 were thirty-eight Fi pigs produced in 

 this cross, but only one of the females 

 among them had reproduced before 

 the experiment ended. The fact that 

 her litter consisted of but four pigs, 

 taken in connection with the fact that 

 Simpson^ reports litters of four, six, 

 and four, respectively, from three 

 sows of the same kind of breeding, 

 gives an indication that the wild litter 

 size is dominant, but tells us no more 

 about its inheritance. 



SET OF EARS 



The Berkshire, Tamworth and wild 

 hog all have erect ears of fine or 

 moderately fine texture, and since all 

 the pigs produced by crossing these 

 three breeds possessed a very similar 

 sort of ear, they throw no light upon 

 its inheritance. The Duroc-Jersey, 

 however, possesses a distinctly dif- 

 ferent sort of ear which is not so pointed , 

 is of medium size, and breaks over at 



