J. Anim Sci.
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J. Anim Sci. 1986. 62:1509-1522.
© 1986 American Society of Animal Science
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Mass Selection in a Pig Population: Realized Heritabilities

H. T. Fredeen1,2, and Hitoshi Mikami3

University of Alberta, Edmonton, Alberta, Canada T6H 2H1

Abstract

Three lines of pigs selected over nine generations for maximum growth rate (G), minimum backfat (B) and a phenotypic index combining these two traits (I) diverged progressively from a contemporary control population (C) in both growth rate and fat. Although the cumulative selection for either trait in the I line was substantially less than was achieved in each of the single-trait lines, the I line at generation 9 was approximately equivalent to the G line in growth rate and to the B line in fatness. Realized heritabilities for the primary selection traits were .20 ± .03 for average daily gain (G line) and .28 ± .04 for fat (B line). As the experiment progressed, the G line became less fat relative to the control (realized rG = –.51) and the B line remained virtually equivalent to the control in growth rate (realized rG = .02). These line differences in correlated responses, and sex-line-generation differences in the relative selection intensity, accorded the secondary trait in each single-trait line (G and B), are discussed in the context of subgroup difference in performance evaluation procedures.

Footnotes

1 Research conducted by senior author at the Canada Agr. Res. Sta., Lacombe.

2 Mailing address: Box 1810, Lacombe, Alberta, Canada T0C 1S0.

3 Natl. Res. Council Post-Doctorate Fellow at Lacombe, 1975 to 1977. Present address: Natl. Inst. of Anim. Indu., Tsukuba Norindanchi, P. O. Box 5, Ibaraki 305, Japan.






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Copyright © 1986 by the American Society of Animal Science.