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Long-term selection for protein amount over 70 generations in mice

Published online by Cambridge University Press:  01 October 1998

LUTZ BÜNGER
Affiliation:
Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland
ULLA RENNE
Affiliation:
Research Institute for Biology of Farm Animals, Dummerstorf-Rostock, Wilhelm-Stahl-Allee, 18196 Dummerstorf, Germany
GERHARD DIETL
Affiliation:
Research Institute for Biology of Farm Animals, Dummerstorf-Rostock, Wilhelm-Stahl-Allee, 18196 Dummerstorf, Germany
SIEGFRIED KUHLA
Affiliation:
Research Institute for Biology of Farm Animals, Dummerstorf-Rostock, Wilhelm-Stahl-Allee, 18196 Dummerstorf, Germany

Abstract

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Based on the outbred mouse strain Fzt: Du, which has been obtained by systematic crossing of four inbred and four outbred lines, a long-term selection experiment was carried out for total protein amount (PA) in the carcass, starting in 1975. An unselected control line (CO) was kept under the same management but without continuous protein analysis. The protein amount of male carcasses at 42 days of age (P42) increased from 2·9 g in generation 0 to 5·2 g at generation 70, representing 97% of a theoretical selection limit. The total selection response amounts to 2·3 g, which is about 80% above the initial value and corresponds to 9σp or 12σA . The estimated realized heritability of protein amount decreased from 0·56 to 0·03 at generation 70, which was due to an increase in phenotypic variance from 0·065 to 0·24 g2 and a reduction in genetic variance from 0·04 to 0·01 g2. Half the selection response was obtained after about 18 to 23 generations, a half-life of 0·25 to 0·3 Ne. The maximum selection response was 0·094 g/generation and the response was 0·01 g/generation at generation 70. The measurements of body weights at 0, 10, 21, 42 and 63 days throughout the experiment showed a strong correlated effect for all weights. The PA mice are one of the heaviest lines of mice ever reported, and do not differ significantly in their body composition from control mice at 42 days. The direct selection response was due primarily to increased general growth. Body weight and protein amount are phenotypically and genetically highly correlated (rp=0·82, rA≈1); however, selection for body weight led to fatter animals, whereas selection for protein opposed increased fatness (at least until selection age). This may be of general importance in animal breeding. The comparatively high selection response in this experiment seems due to the heterogeneity of the base population, the relatively high effective population size, and the duration of the experiment.

Type
Research Article
Copyright
© 1998 Cambridge University Press