Journal of Dairy Science, Vol 75, Issue 10 2892-2901, Copyright
© 1992 by American Dairy Science Association
Use of reproductive technology to estimate variances and predict effects of
gene interactions
P. M. VanRaden, T. J. Lawlor, T. H. Short and I. Hoeschele
Animal Improvement Programs Laboratory, Agricultural
Research Service, Beltsville, MD 20705-2350.
Advanced reproductive techniques are creating the large numbers of close
relatives needed to study gene interactions. Identical triplets, a set
of 26 full sisters, a family of 4215 three-quarter sisters (same sire
and maternal grandsire), a family of 76,698 half sisters, and 1.6
million granddaughters of Round Oak Rag Apple Elevation now have
lactation records. Similarity of closest relatives might be explained
by similar nonadditive as well as additive genetic merit. The 23,015
families of full sisters with mean family size of 3 provide nearly as
much information about dominance variation as do the 55,779 families
of three-quarter sisters with mean family size of 13; the 79 families
of clones provide little information by comparison. Hypothetically,
REML analysis of all US Holstein data could provide estimates of
dominance and additive x additive variance with standard errors
approximately 1% of phenotypic variance, but estimates of any higher
order interactions would have standard errors greater than 10%. The
tilde-hat approximation proved to be incompatible with animal models
but was used for sire-maternal grandsire analysis of 765,868 first
lactation records. Dominance variance was estimated as 3.5% of
phenotypic variance for milk and 3.3% for fat with standard error of
4.2%. With constant data set size, variances are estimated most
precisely if family sizes equal 1 plus ratio of within-family to
between-family variance. An animal model evaluation including
dominance relationships for 581,670 animals was computed, but gene
interactions from distant ancestor pairs were ignored. Mating advice
and improved additive predictions, especially for clones, could be
obtained by including dominance in models.
