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Title: PARAMETER ESTIMATES FOR DIRECT, MATERNAL, AND GRANDMATERNAL GENETIC EFFECTS FOR WEANING WEIGHT

Author
item DODENHOFF, J. - UNIV. OF NEBRASKA-LINCOLN
item Van Vleck, Lloyd
item KOCH, ROBERT - UNIV. OF NEBRASKA-LINCOLN

Submitted to: American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/21/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Weaning weights preadjusted for age of dam from four lines of Hereford cattle were analyzed. Three selection lines were for 1) weaning weight, 2) yearling weight and 3) an index of yearling weight and muscle score. Line 4 was an unselected control. Observations ranged from 1699 to 2811. Estimates by REML of (co)variances were obtained using an average information (AI) method. The animal model included random direct, maternal and grandmaterna genetic, permanent maternal and grandmaternal environmental, and residual environmental effects and fixed sex by year effects. In line 3, variances due to grandmaternal genetic and grandmaternal permanent environmental effects were not estimable; in line 4, the latter variance was not estimable. Estimates for direct heritability were .17, .18, .14, and .16, respectively. Maternal heritability estimates were .34, .31, .13 and .34. Grandmaternal heritability estimates in lines 1, 2, and 4 were .05, .09, and .12 and estimates of correlations between direct and maternal genetic effects were -.13, -.44, -.11 and -.26. Estimates of correlations between direct and grandmaternal genetic effects were .21, .83, and .55, and those between maternal and grandmaternal genetic effects were -.97, -.84, and -.76. Compared to a model that did not include grandmaternal effects, estimates of direct heritability were not different. Estimates of maternal heritabilities in lines 1, 2, and 4 were reduced to .18, .20, and .20 when the model did not include grandmaternal effects. Results suggest grandmaternal effects may be important for weaning weight and that failure to include grandmaternal effects in the model may decrease estimates of maternal heritability.