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Minnesota Agricultural Experiment Station
Abstract
The amount of selection as measured by the average deviation of selected parents from their generation averages in number of pigs farrowed alive and number of pigs weaned was determined in two inbred lines of swine (Minnesota No. 1 and Minnesota No. 2) in the Minnesota swine breeding project. The average annual selection differentials for the Minnesota No. 1 and No. 2, respectively, in number of pigs per litter farrowed alive was .73 pig and .48 pig; for number of pigs weaned per litter the selection differentials were .81 pig and 1.14 pig. Theoretical rates of change in each trait were computed, using the selection differentials, the heritabilities of the traits, and estimates of the effect of inbreeding. The theoretical rate was compared with the estimate of the "actual" rate determined by the regression of the trait on a time scale in years. In the Minnesota No. 1, actual and predicted rates were in rather close agreement; in the No. 2 there was only agreement as to direction of change. Selection appeared to accomplish most in the line where most selection was practiced.
1 Paper No. 2764, Scientific Journal Series of the Minnesota Agricultural Experiment Station in cooperation with the Regional Swine Breeding Laboratory, Ames, Iowa, Bureau of Animal Industry, U.S.D.A. This paper is condensed from a portion of a thesis submitted to the Graduate Faculty of the University of Minnesota in partial fulfillment of the requirements for the degree of doctor of philosophy.
2 Formerly graduate student at the University of Minnesota, now Assistant Dean of Agriculture and Professor of Animal Husbandry at Texas Technological College.
3 Professor of Animal Husbandry at the University of Minnesota.
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