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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Genetics and Animal Breeding » Research » Publications at this Location » Publication #146185
Title: EFFECTS OF GENETIC GROUPS TO ACCOUNT FOR SELECTION ON ESTIMATES OF GENETIC PARAMETERS FOR A LINE OF HEREFORD CATTLE

Author
item Van Vleck, Lloyd
item Hanford, Kathryn
item Macneil, Michael

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 4/2/2003
Publication Date: 6/22/2003
Citation: VAN VLECK, L.D., HANFORD, K.J., MACNEIL, M.D. EFFECTS OF GENETIC GROUPS TO ACCOUNT FOR SELECTION ON ESTIMATES OF GENETIC PARAMETERS FOR A LINE OF HEREFORD CATTLE. JOURNAL OF ANIMAL SCIENCE SUPPLEMENT. 2003. v. 81(1). p. 86.

Interpretive Summary:

Technical Abstract: Robin Thompson originated the idea of an accumulated groups model to account for prior selection. Robin Westell's rules made the coefficient matrix for group models as easy to compute as the A-inverse rules of Henderson and Quaas made use of the numerator relationship matrix for calculation of predicted breeding values given components of the phenotypic variance. The effects of groups in the model on estimates of variance components, however, seem to be unpredictable. Groups were assigned arbitrarily instead of sire identification for some or all of 3,884 weaning weight records of Line 1 Herefords. With usual sire identification, estimates of parameters were 0.20, -0.38, 0.16, 0.19, 0.52 for direct heritability, direct-maternal genetic correlation, maternal heritability, and proportions of variance due to maternal permanent environmental and residual environmental effects. With 22 groups (to replace about one sire for each intake of sires), estimates were 0.13, -0.23, 0.11, 0.20, and 0.58. With 49 groups (all sires of an intake group assigned to that group), estimates were 0.05, 0.41, 0.11, 0.20, and 0.61. With each sire (160) assigned as a group, estimates were 0.06, 1.00, 0.01, 0.24, and 0.67. As another extreme, all sires were coded as missing and were not grouped. Estimates were 0.30, -0.72, 0.08, 0.28, and 0.45. For birth weight, usual estimates were 0.36, -0.06, 0.14, 0.03, and 0.49. With arbitrary groups, estimates were affected but less extremely than for weaning weight. With a dam effect replacing maternal genetic and permanent environmental effects in the model, substitution of group effects for sires had little effect on estimates of heritability for birth weight but did affect estimates of heritability for weaning weight (although less extremely than for the direct-maternal genetic models). More extensive analytical or simulation studies of effects of genetic groups on estimates of genetic parameters seem warranted.