Including Records of Daughters of Selected Bulls in Estimation of Sire Component of Variance

Vleck, L.D. Van

doi:10.3168/jds.s0022-0302(85)81115-2

Cited by 28 publications

(8 citation statements)

References 12 publications

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“…Regarding selected animals as fixed is equivalent to using only the proportion of variance among their progeny independent of the fixed parents to estimate the genetic variance, so only variance arising from Mendelian sampling in the progeny and subsequent generations is considered. This is logically appealing and has been employed in analyses of dairy data under a sire model when treating proven sires as fixed (Van Vleck, 1985), but the properties of this approach with an animal model analysis are not yet fully understood. Preliminary simulation results with the animal model suggest that, provided inbreeding is correctly taken into account, the estimate of the within-family variance is unbiased, whereas its partition into additive genetic and environmental variance may not be.…”

Section: Discussionmentioning

confidence: 98%

Mixed model analysis of a selection experiment for food intake in mice

Meyer

Hill

1991

Genet. Res.

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Data from 23 generations of mice selected for increased and reduced appetite were analysed by Restricted Maximum Likelihood fitting an animal model with litters as additional random effects. Traits considered were food intake between 4 and 6 weeks of age adjusted for 4-week body weight (AFI), the selection criterion, and body weight at 6 weeks (6WW). Selection was carried out within families. A high and a low selection line and a control were maintained in each of three replicates. Analyses were performed for each replicate separately taking subsets of the data spanning different numbers of generations. Overall estimates of heritabilities were 0-15 for AFI, which agreed well with realized heritability estimates, and 0-42 for 6WW. The litter variance, expressed as a proportion of the phenotypic variance, was 0-21 for both traits, yielding intraclass correlations of full-sibs of 0-29 and 0-42, respectively. Similar results were obtained for variances of each trait using univariate and multivariate analyses. From the latter, estimates of correlations between the two traits were 0-46 for additive genetic, -019 for litter and 0-31 for residual effects, resulting in a phenotypic correlation of 0-23. Analyses of data from generations 2-7, 8-13 and 14-23 separately showed a marked decrease in genetic variance and heritability in later generations for both traits. Heritabilities of AFI, for instance, were 0-24, 010 and 007, respectively. These changes could not be attributed to the effects of inbreeding or of selection in an infinitesimal model and suggested that some change in variance due to change in gene frequency had occurred during the course of the experiment.

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Section: Discussionmentioning

confidence: 98%

Mixed model analysis of a selection experiment for food intake in mice

Meyer

Hill

1991

Genet. Res.

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“…However, if only records of first crop daughters (those used to obtain first progeny proof) freshening in a single year are used, the number of degrees of freedom to estimate residual variance is reduced, and, in addition, absorption of herd-year-season effects may result in the effective loss of more records and perhaps even the loss of sires for analysis (22). Therefore, records of daughters of both sampling and proved bulls were included as suggested by Meyer (12) and Hill et al (7) after this study began.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, records of daughters of both sampling and proved bulls were included as suggested by Meyer (12) and Hill et al (7) after this study began. Sire and residual components of variance were estimated by Method 3 of Henderson (5) as described by Van Vleck (22) for the model:…”

Section: Methodsmentioning

confidence: 99%

Trends in Genetic and Phenotypic Variances for Milk Production

Mirande¹,

Vleck²

1985

Journal of Dairy Science

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Residual standard deviations estimated separately for each year of first freshening from first lactation milk records of artificially sired Holstein cows increased from 1960 to 1982, especially after 1976. The pattern on the square root scale was similar. On the logarithmic scale, residual standard deviations were smallest in the middle of the time period. Heritabilities estimated from paternal half-sib correlations were greater than .30 on all scales until about 1976 when estimates began to go below .20. Estimates were similar for untransformed and transformed records. When records were divided into four herd production groups within each year, the same patterns over time for residual standard deviations were observed as for the combined data for each year. On the untransformed scale, the largest standard deviations were associated with high herd production and the smallest with low herd production. On the square root scale, standard deviations were similar for all herd production groups. On the log scale, residual standard deviations were smallest with high production and largest with low productionthe reverse of the untransformed scale, although differences were smaller. Heritability was highest with middle-production groups and smallest with lowproduction groups. Data available for each year ranged from 1,400 and 2,849 to 6,821 and 58,082 records, respectively, of daughters of sampling and proved bulls with from 115 to 513 sampling bulls.

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“…Another approach to consider would be to include different sire effects for the same bull. The effect might be considered random for sampling daughters and fixed for daughters after the 1.00 bull is proved (12,14,15,18). Variations of this approach include: random for unregis-.9o tered daughters and fixed for registered daugh-.so ters; random for all records made before a .7o proof is established and fixed for all others .6o including later records of sampling daughters.…”

Section: Contemporariesmentioning

confidence: 99%