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Title: COMPARISON OF DYSTOCIA EVALUATIONS FROM SIRE AND SIRE-MATERNAL GRANDSIRE THRESHOLD MODELS

Author
item Wiggans, George
item Van Tassell, Curtis - Curt
item Lake, Jill
item MISZTAL, I - UNIV OF GEORGIA

Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: 8/19/2002
Publication Date: 8/19/2002
Citation: Wiggans, G.R., Van Tassell, C.P., Philpot, J.C., Misztal, I. Comparison of dystocia evaluations from sire and sire-maternal grandsire threshold models. World Congress of Genetics Applied in Livestock Production.

Interpretive Summary: Over 5 million USA calving ease records where both sire and sire-maternal grandsire (MGS) were reported were analyzed with both a sire and a sire- MGS threshold model. Variance components were based on a heritability of .16 for the direct effect, .06 for the maternal effect and a correlation between them of -.3. There were 45,567 bulls represented as either a sire or MGS. Correlations between sire and sire-MGS evaluations were .930 for all bulls and rose to .991 for the 181 bulls with >5000 records. The sire- MGS model will give more accurate evaluations than the sire model because it partially accounts for merit of the mates of the bull and the maternal ability of the dam.

Technical Abstract: Over 5 million USA calving ease records where both sire and sire-maternal grandsire (MGS) were reported were analyzed with both a sire and a sire- MGS threshold model. Variance components were based on a heritability of .16 for the direct effect, .06 for the maternal effect and a correlation between them of -.3. These values gave a slightly positive covariance between the sire and MGS effects. The model included herd-year, sex, parity of dam, year-season of birth, birth year group of sire, birth year group of MGS, sire, and MGS. Herd-year was assumed random with a variance of 10 percent of the error variance. There were 45,567 bulls represented as either a sire or MGS. Correlations between sire and sire-MGS evaluations were .930 for all bulls and rose to .991 for the 181 bulls with >5000 records.