Influences of amount of pedigree information on computing time and of model assumptions on restricted maximum-likelihood estimates of population parameters in Swiss black-brown mountain sheep.

Average daily gain between birth and 30 d of age of 42,644 lambs of Swiss Black-Brown Mountain Sheep were used in this analysis. The influence of amount of pedigree information on computing time and on REML estimates of population parameters was investigated on a subset of 7,848 lambs. If all available pedigree information was used, 89.4% of the lambs had at least four complete generations of known ancestors. For the reduced pedigree information, only parents and grandparents of a lamb were included. In the data set with complete pedigree information, 2,616 additional animals (without records) caused 19.4% more equations, 4.6 times the number of non-zero elements in the system of equations, and 21.2 times the computing time to reach convergence. The difference in amount of pedigree information had only a marginal influence on the estimates of direct heritability (h2), maternal heritability (m2), permanent environmental effects, and on the genetic correlation between direct and maternal effect (rAM). The complete data set of 42,644 recorded lambs was randomly split into four subsets to save computing time. In a fifth subset of 27,787 lambs (Set C) all combinations of recorded grandparents and grand-offspring were accumulated because they contain information on the covariance between direct and maternal effects (cov[AM]). Including cov(AM) in the model assumptions increased estimates of h2 and m2 in all subsets. Estimates from Set C were smallest but showed the same trend. The estimate of rAM was always strongly negative, < or = -.64.(ABSTRACT TRUNCATED AT 250 WORDS)