J. Anim Sci.
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J. Anim Sci. 1983. 57:19-25.
© 1983 American Society of Animal Science
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Maternal Performance over Three Parities in Rats selected for Rate or Efficiency of Protein Gain1

Sara Melin Azzam2, M. K. Nielsen2 and G. E. Dickerson3

University of Nebraska and US Department of Agriculture, Lincoln, NE 68583-0908

Abstract

Direct, maternal and heterosis effects were estimated for preweaning traits over three parities, with unstandardized litters, in rats selected for 14 generations for rate (LG) or efficiency (LE) of postweaning protein gain. In generation 25, after 11 generations of relaxed selection, 60 males and females from each of the selected lines and the control (C) line were mated in a 3 x 3 diallel. Two more parities were produced by remating the females at each weaning. Loss of female breeders due to infertility and death was higher in the selected lines (LG 43%, LE 40%, C 27%). Rebreeding intervals in parities 2 and 3 were 3.1 (P<.01) and 3.0 (P<.10) d longer in LG compared with C, while LE was similar to C. Heterosis was significant only for litter size born and it was negative. Because the estimate included all line interactions, negative heterosis could arise from incompatibilities between sperm and ova or embryo and uterus. Both selected lines, but especially LE, had positive direct effects and negative maternal effects on litter size born and weaned. Maternal effects of LG on average pup weight were similar or slightly better than C, while lactational performance was lower in LE.

Footnotes

1 Published as Paper No. 6976 Journal Series, Nebraska Agr. Exp. Sta., Lincoln.

2 Anim. Sci. Dept., Univ. of Nebraska

3 Roman L. Hruska US Meat Animal Research Center, SEA, AR, Marvel Baker Hall, Univ. of Nebraska, Lincoln.






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Copyright © 1983 by the American Society of Animal Science.