J. Anim Sci.
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J. Anim Sci. 1986. 63:54-58.
© 1986 American Society of Animal Science
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Selection for Postweaning Gain in Rats: III. Correlated Response in Maternal Performance1

Jose G. Rios2, M. K. Nielsen3 and G. E. Dickerson4

University of Nebraska and U.S. Department of Agriculture, Lincoln 68583-0908

Abstract

Effects from 34 generations of selection, either up (U) or down (D), for 3- to 9-wk weight gain on genetic direct and postnatal maternal effects, dam size and maternal efficiency were evaluated in 25 cross-fostered sets of rats. Direct genetic effects on 12-d pup weight were 14 and 9% above controls (C) for U and D lines, respectively (P<.01). Postnatal maternal effects on 12-d pup weight were also 11% higher for the U line (P<.01), but not different from C for the D line. Females of the U line were heavier (P<.01) by 13% at mating, 12% at parturition and 15% at 12 d of lactation, relative to controls. They also produced 11% greater total litter weight at 12 d and consumed 9% more feed, but were only nonsignificantly lower in feed per unit of pup 12-d litter weight. Females of D line were –8, –7 and –3% relative to controls in the three weights, but did not differ from controls in 12-d litter weight, feed consumed or in feed efficiency during lactation.

Footnotes

1 Published as Paper No. 7880, Journal Ser., Nebraska Agr. Exp. Sta., Lincoln. Appreciation is expressed to A. B. Chapman and J. J. Rutledge, Univ. of Wisconsin, Madison, for providing the genetic stocks used in this study.

2 Present address: Facultad de Zootecnia, Univ. of Chihuahua, Chihuahua, Mexico.

3 Anim. Sci. Dept., Univ. of Nebraska, Lincoln, 68583-0908.

4 Roman L. Hruska U.S. Meat Anim. Res. Center, ARS, USDA, 225 Baker Hall, Univ. of Nebraska, Lincoln 68583-0908.






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Copyright © 1986 by the American Society of Animal Science.