LOOKING FOR THE RIGHT WAY TO CONVERT TO U.S. PTA?

Authors: Powell, Rex; SIEBER, MARTIN - NAAB; Hubbard, Suzanne

Submitted to: Nuestro Holando
Publication Type: Trade Journal
Publication Acceptance Date: 1/21/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The preferred way to compare the genetic merit of bulls from different countries is to have the evaluations all expressed on the same scale. However, evaluations on the desired scale may not always be conveniently available. The main purpose of conversion equations is to convert from one scale to another for bulls without international evaluations for milk, fat, and protein yields. They also can be used to get an approximate idea of what a bull's evaluation might be on a U.S. scale as a check on marketing practices. Conversion tables were developed as a convenient reference for estimating the genetic merit for milk, fat, and protein yields of Holstein bulls from Canada, France, Germany, Italy, Spain, and The Netherlands that would be equivalent to certain U.S. estimates of genetic merit. Although the conversion is only approximate and an international genetic evaluation would be different, typically the difference is less than 100 pounds. The reference tables are based on equations that were developed from November 1998 evaluations that were calculated by the International Bull Evaluation Service and will need to be updated after subsequent international evaluations. The best option for comparing genetic merit of bulls from different countries always is to use the national or international evaluations on a single scale if available. However, when such evaluations are not available, the reference values in the conversion tables can assist breeders in assessing information on the genetic merit of bulls provided by semen sellers from different countries and in making more informed breeding decisions.

Technical Abstract: The preferred way to compare the genetic merit of bulls from different countries is to have the evaluations all expressed on the same scale. However, evaluations on the desired scale may not always be conveniently available. The main purpose of conversion equations is to convert from one scale to another for bulls without International Bull Evaluation Service (Interbull) evaluations for milk, fat, and protein yields. They also can be used to get an approximate idea of what a bull's evaluation might be on a U.S. scale as a check on marketing practices. Conversion tables were developed as a convenient reference for approximating the estimated breeding values (EBV's) in kilograms for milk, fat, and protein yields of Holstein bulls from Canada, France, Germany, Italy, Spain, and The Netherlands that would be equivalent to certain U.S. predicted transmitting ability (PTA) in pounds. Actual PTA milk from Interbull would be different. Typically, however, the difference is less than 100 pounds. A U.S. PTA can be approximated from an EBV from one of the countries, but the tables are not valid for estimating EBV's of other countries from a U.S. PTA or from EBV from other countries. The reference tables are based on equations that were developed from November 1998 Interbull evaluations and will need to be updated after subsequent Interbull evaluations. The best option for comparing genetic merit of bulls from different countries always is to use the national or Interbull evaluations on a single scale if available.