Lush: Inheritance in Swine 



6g 



A LITTER OF THE THIRD GENERATION ^BERKSHIRE X DUROC- JERSEY CROSS j 



Showing striped pigs with lighter colored bellies. This striping is a curious atavistic recurrence 

 of an ancestral trait present in the wild boar but not in the domestic breeds. The recurrence here is 

 doubtless due to a recombination of Mendelian factors. (Fig. 18.) 



black pigment patches in her skin, there 

 resulted an F3 litter of eleven pigs every 

 one oj which had a lighter belly than back 

 and was striped in a fashion similar to 

 that of the young of the wild boar but 

 differing from the latter in the shade of 

 the contrasting stripes. They were 

 not uniform in shade themselves. 

 This type of "reversion" in swine has 

 been reported frequently, but the re- 

 markable fact that so large a litter as 

 this should so uniformly show both 

 the lighter belly and the striping pat- 

 tern makes it seem certain that the 

 factorial basis for this "reversion" is 

 simple, and that both lighter belly and 

 striping are produced by almost identi- 

 cal factor complexes. Two individuals 

 of the Fo generation showed stripes 

 similar in pattern but very faint. 



DIFFERENCES IN GROWTH 



The economic importance of some 

 definite knowledge in regard to factors 

 for rapid growth may be surmised from 

 the extent of the practice of cross- 

 breeding hogs in order to secure the 



greater size and vigor of the Fi hogs 

 for market purposes. The Berkshire X 

 Duroc-Jersey cross was extensive 

 enough to furnish significant data upon 

 this point. Since they were not all born 

 at the same season nor in the same year 

 it is obvious that they were not all ex- 

 posed to identical weather conditions 

 nor fed rations as identical as would be 

 desirable in a nutrition experiment. 

 However it was the aim always to feed 

 the best possible ration to produce the 

 maximum practical gains and it is 

 believed that the data are, on the 

 whole, reasonably comparable. The 

 pigs were weighed at birth and at 

 monthly intervals afterward and the 

 coefficients of variation of the weights 

 of the Fi individuals for each month 

 were figured separately from those of 

 the F2 individuals. The resulting 

 curves are shown in the accompanying 

 figure. 



The outstanding fact of genetic im- 

 portance is that the variability of the 

 F2 generation is distinctly greater than 

 that of the Fi. That, to be sure, is 



