Am. Soc. Anim. Prod.
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Am. Soc. Anim. Prod. 1935:215-217
© 1935 American Society of Animal Science
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The Relationship of Degree of Inbreeding to Size of Litter in Poland China Pigs1

James H. Bywaters, C. C. Culbertson and W. E. Hammond

Iowa State College

Abstract

Conclusions: Because this experiment has been in operation but a short time, the present paper should be considered as a report of progress and the following conclusions are presented on that basis.

  1. In the data herein reported, the boars have had no significant influence on the size of the litters sired by them. This agrees, in general, with our knowledge of the physiology of reproduction.
  2. In the litters farrowed in this experiment, there has been no important relationship between the degree of inbreeding of the litters and the number of pigs in the litter. Nor has there been any difference in this relationship between or within the several sires.
  3. While considerable effort has been made to select for large litter size, no apparent progress has been made. Neither has there been any significant decrease in size of litter. This lack of progress has probably been due, in part at least, to the fact that the force of selection for any one character is decreased as the number of characters selected for is increased. In this experiment a few of these other factors have been breed type and general conformation, pounds of pig farrowed, pounds of pig weaned and general health and vigor. Other factors less apparent have been selected for or against during the progress of the work.

Footnotes

1 Journal Paper No. J203 of the Iowa Agricultural Experiment Station, Ames, Iowa. Project No. 32.






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Copyright © 1935 by the American Society of Animal Science.