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The Development of an Inbred Line of Swine (Minn. No. 1) from a Crossbred Foundation¹

University of Minnesota

Abstract

A cross was made between the Landrace and Tamworth breeds of swine. New breeding stock was then introduced and the second crop of pigs consisted of F₁, F₂, Landrace backcross, and Tamworth backcross individuals. From that time on the herd was bred from within.

The herd was founded with 14 animals derived from 4 different herds. Only 6 of the 14 have contributed to the ancestry of the stock now on hand, and of those 6 only 3 have made major contributions.

Rigorous selection for performance has been followed throughout the conduct of this experiment. The advance in inbreeding has not been rapid but in six years from the time of the first matings the coefficient of inbreeding has been raised to .24 which, with the exception of Shorthorn cattle, is about 2 to 6 times as high as that of the breeds reported on by Lush (1937).

The wide segregation and general deterioration in performance generally believed to accompany the subsequent inbreeding of an F₁ population did not occur.

¹ Paper No. 2048, 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. Department of Agriculture.

² The authors acknowledge contributions made during the first years of this experiment by R. L. Donovan and C. L. Cole, formerly Superintendent and Assistant Professor of Animal Husbandry, respectively, of the North Central Experiment Station. The authors also express their appreciation to Dr. W. A. Craft, Director of the Regional Swine Breeding Laboratory, Bureau of Animal Industry, for his interest, encouragement, and many helpful suggestions. The authors are Professor of Animal Husbandry, Assistant Professor of Animal Husbandry, and Superintendent of the North Central Central Experiment Station, respectively.