GMACE pilot #4: Adjusting the national reliability input data

Abstract

International standards do not exist for the approximation of national genomic reliabilities, which are used as input data for the GMACE international genomic evaluation system.  The focuses of the present study were to develop a method of reducing differences among the national reliabilities approximated by different countries, to apply GMACE using modified national reliabilities, and to use cross-validations tests to determine if GMACE results could be measurably improved.  A non-linear international regression model was applied to the average national reliabilities provided by countries for use in GMACE.  Residuals of prediction for the average national reliabilities were smaller, indicating greater consistency among the approximations of different countries, for protein and stature relative to traits more difficult to evaluate, such as mastitis, stillbirths and cow conception rate.  GMACE input reliabilities were modified by subtracting either some or all of the average prediction error for each combination of  trait by country.  The impacts of modifying the national reliabilities on GMACE results were relatively small.  Predictability of national genomic evaluations by GMACE with only foreign genomic data as input, was essentially the same using either modified or unmodified national reliabilities.  However, the international reliabilities produced by GMACE were more consistent if national reliabilities were modified as input and then the modifications were reversed for the GMACE reliability output.  The approach was to essentially apply an international standardization of reliability on the way into GMACE and then a de-standardization back to each of the original national scales of expression on the way out.