ABSTRACT:Birth and weaning weights adjusted for age of dam from four lines of Hereford cattle were analyzed to determine the relationships among grandmaternal, maternal, and direct genetic effects. Three lines were selected for 1 ) weaning weight (WWL), 2 ) yearling weight (YWL), and 3 ) an index of yearling weight and muscle score (IXL). The fourth line was an unselected control line (CTL). Numbers of observations ranged from 1,699 (CTL) to 2,811 (WWL), and number of animals in the pedigree file ranged from 2,266 to 3,192. Two animal models were used to obtain estimates by REML using an average information method. Model 1 included random direct and maternal genetic, permanent maternal environmental, and residual environmental effects, and fixed sex × year effects. Model 2 additionally included random grandmaternal genetic and permanent grandmaternal environmental effects. For birth weight, Models 1 and 2 gave almost identical estimates for direct and maternal heritability, and for the fraction of variance that was due to maternal permanent environmental effects. Estimates for grandmaternal heritability could be obtained only for IXL (.03) and CTL (.01). For weaning weight, estimates for direct heritability were similar from both models. Estimates for maternal heritability from Model 1 were .18, .20, .13, and .20, and corresponding estimates from Model 2 were .34, .31, .13, and .34 for WWL, YWL, IXL, and CTL, respectively. For IXL, estimates for variances that were due to grandmaternal genetic and grandmaternal permanent environmental variances could not be obtained and were set to zero. Grandmaternal heritability estimates for WWL, YWL, and CTL were .05, .09, and .12. Estimates of correlations between direct and maternal genetic effects were −.13, −.44, −.11, and −.26 for WWL, YWL, IXL, and CTL. Estimates of correlations between direct and grandmaternal genetic effects were .21, .83, and .55, and those between maternal and grandmaternal genetic effects were −.99, −.84, and −.76 for WWL, YWL, and CTL, respectively. These results indicate that grandmaternal effects may be important for weaning weight and that maternal heritability may be underestimated if grandmaternal effects are not included in the model.

Weaning weights from nine parental breeds and three composites were analyzed to estimate variance due to grandmaternal genetic effects and to compare estimates for variance due to maternal genetic effects from two different models. Number of observations ranged from 794 to 3,465 per population. Number of animals in the pedigree file ranged from 1,244 to 4,326 per population. Two single-trait animal models were used to obtain estimates of covariance components by REML using an average information method. Model 1 included random direct and maternal genetic, permanent maternal environmental, and residual environmental effects as well as fixed sex x year and age of dam effects. Model 2 in addition included random grandmaternal genetic and permanent grandmaternal environmental effects to account for maternal effects of a cow on her daughter's maternal ability. Non-zero estimates of proportion of variance due to grandmaternal effects were obtained for 7 of the 12 populations and ranged from .03 to .06. Direct heritability estimates in these populations were similar with both models. Existence of variance due to grandmaternal effects did not affect the estimates of maternal heritability (m2) or the correlation between direct and maternal genetic effects (r(am)) for Angus and Gelbvieh. For the other five populations, magnitude of estimates increased for both m2 and r(am) when estimates of variance due to grandmaternal effects were not zero. Estimates of the correlation between maternal and grandmaternal genetic effects were large and negative. These results suggest that grand-maternal effects exist in some populations, that when such effects are ignored in analyses maternal heritability may be underestimated, and that the correlation between direct and maternal genetic effects may be biased downward if grandmaternal effects are not included in the model for weaning weight of beef cattle.

ABSTRACT:Weaning weights from nine sets of Angus field data from three regions of the United States were analyzed. Six animal models were used to compare two approaches to account for an environmental damoffspring covariance and to investigate the effects of sire × herd-year interaction on the genetic parameters. Model 1 included random direct and maternal genetic, maternal permanent environmental, and residual effects. Age at weaning was a covariate. Other fixed effects were age of dam and a herd-year-management-sex combination. Possible influence of a dam's phenotype on her daughter's maternal ability was modeled by including a regression on maternal phenotype (f m ) (Model 3) or by fitting grandmaternal genetic and grandmaternal permanent environmental effects (Model 5). Models 2, 4, and 6 were based on Models 1, 3, and 5, respectively,

Test-day records for average flow rate (AFR) from the routine dairy recording from Bavarian Fleckvieh cows were analysed. Two data sets with observations on approximately 20 000 cows each were sampled from the total data set. For the estimation of variance parameters, a two-step approach was applied. In a first step multiple-trait restricted maximum likelihood (REML) analyses were carried out. For each of the first three lactations, six time periods with up to 33 days were defined. An algorithm for iterative summing of expanded part matrices was applied in order to combine the estimates. In a second step covariance functions (CF) for additive-genetic variances and non-genetic animal variances were derived using second-order Legendre polynomials plus an exponential term. Estimates of test-day heritability for AFR ranged from 0.21 to 0.40, and were largest in lactation 1. For lactations 1 and 3, heritabilities decreased considerably towards the end of lactation. Genetic correlation estimates within lactation decreased as the distance between days in milk (DIM) increased. Genetic correlations between corresponding DIM in the three lactations were generally large, ranging from 0.80 to 0.99. The largest estimates were found between DIM from lactations 2 and 3. Results from this study suggest that including AFR data from second and third lactations in genetic evaluation systems could the improve accuracy of genetic selection.

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