Interbull Routine Genetic Evaluation for Udder Health Traits

November 2003

Introduction
International genetic evaluations for milk somatic cell and clinical mastitis of bulls from Canada, Denmark, Estonia, Finland, France, Germany, the Netherlands, Norway, Sweden, Switzerland, The United Kingdom, The United States of America, Israel, Italy, Australia, Hungary, Belgium, Japan and Spain were computed in this evaluation. Ayrshire, Brown Swiss, Guernsey, Holstein and Jersey breed data were included.

New national data

• Spain participated in the Holstein evaluation for the first time.

Changes in national data

• Finland submitted milk somatic cell data based on a random regression test-day model and introduced a new data base system with changes in data extraction and handling of genetic evaluations.
   
• Australia updated their EDC computations to comply with multi-trait analysis (EDC's decreased).
   
• Belgium and Japan modified data edits.
   
• Identification of German bulls changed for the Holstein evaluation and all countries changed IDs accordingly.
   

Changes in Interbull procedures

• All countries are now expected to be identified with their appropriate ISO code. Thus, Czech Rep. is now identified as CZE and Slovenia as SVN.

Data and method of analysis

Data were national genetic evaluations of AI sampled bulls with daughters in at least 10 herds. For clinical mastitis information to be included, an additional requirement was that bulls had to have at least 50 daughters. Table 1 presents the amount of data included in this Interbull evaluation. Table 2 and Table 3 gives heritabilities and some additional information on national evaluations as provided by the participating countries.

Estimated genetic parameters are shown in APPENDIX I.

National proofs were first de-regressed within country and then analysed jointly with a linear model including the effects of evaluation country, genetic group of bull and bull merit. Heritability estimates used in both the de-regression and international evaluation were as in each country's national evaluation (Table 2 and Table 3).

Ancestor-bulls without own proofs were traced back two generations from the oldest bulls with proofs in order to increase across country connections and account for the effect of selection.

Genetic groups were defined according to unidentified parents by national origin, breed and birth year of the bull and path of selection (sire, maternal grand-sire, maternal grand-dam). Birth year grouping was by 1-5 year periods. Smaller groups (consisting of less than 30 bulls) were combined.

International genetic evaluations were computed using effective daughter contributions (EDC) as weighting factors.

For each breed, two separate international genetic evaluations were computed. The first included milk somatic cell de-regressed proofs from individual countries. The second included de-regressed proofs for clinical mastitis as a direct trait from countries that made this information available and milk somatic cell de-regressed proofs from all other countries. Note that the second evaluation was not carried out for BSW and GUE since none of the participating countries provided clinical mastitis information.

Genetic correlation estimation procedure

Genetic correlations among countries were estimated using a similar approach as for production traits:

Step 1:

Several subsets of countries were analysed and the highest estimate for a country pair was kept, as per Sigurdsson et al (1996) showing that genetic correlations are not likely to be over-estimated by the method used.

Step 2:

IIn some cases sufficient genetic links between countries may be missing, resulting in unreasonable genetic correlation estimates. If no reasonable correlations could be estimated one of the the following procedures was followed:

a) Estimates from another breed for the country pair were used, but bended towards the actual estimate

b) Estimates from the low end of the correlation distribution were assigned; for milk somatic cell information in different countries these would normally be around .80, for clinical mastitis information in different countries around .40, and between milk somatic cell information and clinical mastitis information in different countries around .35 (estimates between milk somatic cell and clinical mastitis above .80 were considered unrealistic and bended downward).

Step 3:

Since genetic correlation estimates were not derived simultaneously, the full covariance matrix needed to be bended in order to ensure it was positive definite.
 

Publication of Interbull evaluations

Test evaluation results are meant for review purposes only and should not be published.
 

Next routine international evaluation

The next routine international evaluation for dairy production, udder health and conformation traits is scheduled for February 2004. New data for that run should reach the Interbull Centre not later than January 27, 2004, 17:00 Central European Time (CET); in any case, the most recently received data will be considered. The target time for distribution of results for internal review to designated representatives, who have signed a confidentiality agreement with the Centre, is February 5, 2004. Official release date of the results is targeted to be February 9, 2004.

Next test international evaluation

The next test international evaluation for dairy production, conformation, and udder health traits is scheduled for March 2004. Countries wishing to enter the system for the first time or planning to submit new information (modified national evaluation procedure, new breeds etc) for following routine evaluations must have their data tested in this test-run.

Deadline for sending data to the Interbull Centre for the next test-run is March 1, 2004.

Means of result distribution from the Interbull Centre

Electronic exchange of data is probably more efficient than anything else. Currently most countries in the service have established internet connections and receive international evaluation results on the day of their release.  Subscribers to the service that do not already has this option are encouraged to consider it and establish an internet connection and ftp account. When such accounts are available, please provide their specifications to the Interbull Centre. Until then, data will be delivered on CD-ROM's.

For more information about the international genetic evaluation service please contact the Interbull Centre: address: SLU Box 7023, 750 07 Uppsala, Sweden; fax: +46-18-672648;