5. Method of international evaluation

5.1. Multiple-trait across country (MACE) evaluation

5.1.1. International evaluations will be computed by a linear multiple-trait across country (MACE) model analysis of national evaluation results from the participating countries.

• The model to be used is: Y = c + g + s + e

• Where: Y = De-regressed national genetic evaluations c = Country of evaluation effect g = Genetic group of bull effect, defined by the bull’s population of origin and year of birth s = Bull genetic effect including genetic relationships among bulls in all participating countries e = Residual effectThe international predicted genetic merits will be formed by the sum of the solution for the bull, the genetic group and country effects.

5.1.2. International evaluations will be computed for one trait at a time, and within breed. For breed definition, see item 7.1.7.

5.1.3. Data on all bulls evaluated in each country will be considered in the international genetic evaluation, subject to the following editing criteria:

1. only artificial insemination (AI) bulls are included; "other" bulls (status of bull = 20) are considered only if the predicted genetic merit is identified as based on second crop daughters only (type of genetic merit = 21) or imported daughters/embryos (type of genetic merit = 22; see file formats for definitions of status of bull and type of predicted genetic merit),
2. only bulls with daughters recorded in at least 10 herds are included,
3. only bulls born since 1986 and 1981 for Holstein and other breeds, respectively, are included,
4. bulls with second country evaluations (type of predicted genetic merit = 21) are included only when the predicted genetic merit meets national standards for official publication in the country sending the information (official publication of predicted genetic merit = Y) or if the predicted genetic merit is based on minimum 150/30/80 daughters in 50/10/20 herds (Holstein/Guernsey/other breeds), and first country evaluation (type of predicted genetic merit = 11 or 12) is included in the data. Second country data may be excluded in view of scientific evidence of bias, examined by the Interbull Centre
5. bulls with second country evaluations based on more than 50% imported daughters/embryos (type of genetic merit = 22) are included only when the predicted genetic merit meets national standards for official publication in the country sending the information (official publication of predicted genetic merit = Y), and first country evaluation (type of predicted genetic merit = 11 or 12) is included in the data.

Exceptions from these requirements may be accepted if part of Interbull standard procedures for a trait-group and specified in the appropriate section of Chapter 6 “Traits and breeds”.

5.1.4. Data on all bulls evaluated in each country will be considered in estimation of genetic correlations between countries, subject to the following editing criteria:

1. only artificial insemination (AI) bulls are included; “other” bulls (status of bull = 20) are considered only if the predicted genetic merit is identified as based on second country evaluation (type of predicted genetic merit = 21; see file formats for definitions of status of bull and type of predicted genetic merit).

Exceptions from these requirements may be accepted if part of Interbull standard procedures for a trait-group and specified in the appropriate section of Chapter 6 “Traits and breeds”.

5.1.5. Dependent variables in the evaluation model are de-regressed national genetic evaluations.

5.1.6. Variation in the precision of the national predicted genetic merits is accounted for in the linear model by applying a weighting factor (effective daughter contribution, EDC) that considers amount of information, contemporary group structure, correlations of repeated observations within the same animal, and the reliability of daughters’ female ancestors. The calculation of EDC’s has to be implemented separately by each individual organisation participating in Interbull evaluations, following the procedure in Appendix IV and V.

5.1.7. Within‑country sire variances are to be estimated during each evaluation run; correlations between countries every time a new country enters the scheme, major changes have occurred in the national evaluations in participating countries, or when new ties have been developed.

5.1.8. Conversion coefficients among all participating countries and for all traits are computed based on international predicted genetic merits of bull’s that are progeny tested only in one country (country of origin), with minimum birth year 1993 and 1992 for Holstein and other breeds, respectively in year 2004 (to be updated by 1 year at each January evaluation), and a predicted genetic merit based on a minimum 20 herds and with 75% international reliability/repeatability. A minimum of 20 bulls is required to compute such conversions. For country combinations not fulfilling these requirements conversion equations are computed based on theoretical b-values and empirical a-values. The theoretical b-value is computed as rG(i,j)×std(i)/std(j), where rG(i,j) is the genetic correlation between country i and j, and std(j) is the sire standard deviation for country j. The a-value is estimated as m(i)-b×m(j) where m(i) is the mean international proof for country i based on all bulls progeny tested only in one country born since 1996 (Holstein; 1995 for other breeds).

Exceptions from these requirements may be accepted if part of Interbull standard procedures for a trait-group and specified in the appropriate section of Chapter 6 “Traits and breeds”.

5.1.9. Some details on the genetic evaluation procedure are provided in the service documentation made available at http://www.interbull.org and together with each distribution of results from the international evaluations

5.1.10. The international genetic evaluation procedure is based on international work described in the following scientific publications:

1. International genetic evaluation computation:
   1. Schaeffer, 1994. J. Dairy Sci. 77:2671-2678
   2. Klei, 1998. Interbull Bulletin 17:3-7
2. Weighting factors:
   1. Fikse and Banos, 2001. J. Dairy Sci. 84:1759-1767
3. De-regression:
   1. Sigurdsson and Banos, 1995. Acta Agric. Scand. 45:207-219
   2. Jairath et al., 1998. J. Dairy Sci. Vol. 81:550-562
4. Genetic parameter estimation:
   1. Sigurdsson et al., 1996. Acta Agric. Scand. 46:129-136
   2. Klei and Weigel, 1998. Interbull Bulletin 17: 8-14
   3. Sullivan, 1999. Interbull Bulletin 22:146-148
   4. Jorjani et al., 2003. J. Dairy Sci. 86:677-679
5. Time edits:
   1. Weigel and Banos, 1997. J. Dairy Sci. 80:3425-3430 5.11
6. International reliability estimation:
   1. Harris and Johnson, 1998. Interbull Bulletin 17:31-36

5.1.11. Newer developments regarding international evaluation methodology will be applied whenever research efforts are completed and considered appropriate, and approved by the Interbull Steering Committee.