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Article| Volume 77, ISSUE 9, P2679-2686, September 1994

Factors Affecting Calculation and Use of Conversion Equations for Genetic Merit of Dairy Bulls

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      Abstract

      Factors affecting calculation and use of conversion equations were reviewed. Methods of expressing reliability of converted evaluations were surveyed. Of 16 countries responding, 6 did not calculate reliability for converted evaluations, 5 accepted reliability from the exporting country, and 5 assumed genetic correlations of .6 to 1.0 with the US. Genetic correlations between the US and 8 other countries were estimated and generally were ≥.9; estimated correlations between the US and Canada were 1.0. Estimated correlations averaged .93 for milk, .89 for fat, and .92 for protein yields. Correlation estimates were lowest for countries differing most from the US in management conditions (Australia, New Zealand) or trait definition (Germany), which suggests that correlation estimates <1.0 indicate differences in trait measurement as well as differences in biological expression. Conversion equations were computed from data of US and Canadian Holstein bulls with and against the gene flow. Equations against the gene flow generally had regression coefficients and intercepts lower than those calculated with the gene flow. Lower regression coefficients were explained by selection on the dependent variable. Lower intercepts were attributed to preferential treatment of daughters from imported semen, which would lower intercepts for equations against the gene flow and inflate intercepts with the gene flow.

      Key words

      Abbreviation key:

      DYD (daughter yield deviation), INTERBULL (International Bull Evaluation Service), rg (genetic correlation), rp (product-moment correlation), REL (reliability), RELC (REL of converted evaluation), RELe (REL in exporting country)

      References

      1. Banos, G. 1992. Report on COPA/INTERBULL joint project. Proc. INTERBULL Sem. on Sire Eval., Neustift, Austria, June 7–8, 1992. Int. Bull Eval. Serv. Bull. No. 7. Dep. Anim. Breed. Genet., SLU, Uppsala, Sweden.

        • Banos G.
        A theoretical comparison between direct and indirect conversions of dairy bull evaluations.
        J. Anim. Breed. Genet. 1993; 110: 57
        • Calo L.L.
        • McDowell R.E.
        • VanVleck L.D.
        • Miller P.D.
        Genetic aspects of beef production among Holstein-Friesians pedigree selected for milk production.
        J. Anim. Sci. 1973; 37: 676
      2. International Bull Evaluation Service. 1990. Recommended procedures for international use of sire proofs. Int. Bull Eval. Serv. Bull. No. 4. Dep. Anim. Breed. Genet., SLU, Uppsala, Sweden.

      3. International Bull Evaluation Service. 1992. Sire evaluation procedures for dairy production traits practiced in various countries 1992. Int. Bull Eval. Serv. Bull. No. 5. Dep. Anim. Breed. Genet., SLU, Uppsala, Sweden.

      4. Mattalia, S., and B. Bonaiti. 1993. Use of full sibs families to estimate the ‘a’ coefficients of conversion formulas between countries. Proc. Open Session IN- TERBULL Annu. Mtg., Aarhus, Denmark, Aug. 19–20, 1993. Int. Bull Eval. Serv. Bull. No. 8. Dep. Anim. Breed. Genet., SLU, Uppsala, Sweden.

        • Philipsson J.
        Standards and procedures for international genetic evaluations of dairy cattle.
        J. Dairy Sci. 1987; 70: 418
        • Powell R.L.
        • Sieber M.
        Direct and indirect conversion of bull evaluations for yield traits between countries.
        J. Dairy Sci. 1992; 75: 1138
        • Powell R.L.
        • Wiggans G.R.
        • Robinson J.A.B.
        Comparison of US and Canadian animal model evaluations of the same Ayrshire cows.
        J. Dairy Sci. 1991; 74 (Abstr.): 232
        • Robinson J.A.B.
        • Wiggans G.R.
        Comparison of Canadian and US animal model bull evaluations of Ayrshire and Jersey yield traits.
        J. Dairy Sci. 1991; 74 (Abstr.): 232
        • Schaeffer L.R.
        Model for international evaluation of dairy sires.
        Livest. Prod. Sci. 1985; 12: 105
      5. Schaeffer, L. R. 1993. Multi-trait, across country evaluation of dairy sires. Proc. Opening Session INTERBULL Annu. Mtg., Aarhus, Denmark, Aug. 19–20, 1993. Int. Bull Eval. Serv. Bull. No. 8. Dep. Anim. Breed. Genet., SLU, Uppsala, Sweden.

        • Wiggans G.R.
        • Misztal I.
        • Van L.D.
        • Vleck
        Implementation of an animal model for genetic evaluation of dairy cattle in the United States.
        J. Dairy Sci. 1988; 71: 54
        • Wiggans G.R.
        • VanRaden P.M.
        Method and effect of adjustment for heterogeneous variance.
        J. Dairy Sci. 1991; 74: 4350
        • Wiggans G.R.
        • VanRaden P.M.
        • Powell R.L.
        A method for combining United States and Canadian bull evaluations.
        J. Dairy Sci. 1992; 75: 2834