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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Genomics and Improvement Laboratory » Research » Publications at this Location » Publication #382425

Research Project: Improving Dairy Animals by Increasing Accuracy of Genomic Prediction, Evaluating New Traits, and Redefining Selection Goals

Location: Animal Genomics and Improvement Laboratory

Title: Use of international clinical mastitis data as independent trait in the US evaluation system

item MOTA, RODRIGO - Council On Dairy Cattle Breeding
item NICOLAZZI, EZEQUIEL - Council On Dairy Cattle Breeding
item MEGONIGAL, JR, JOEL - Council On Dairy Cattle Breeding
item PARKER GADDIS, KRISTEN - Council On Dairy Cattle Breeding
item DURR, JOAO - Council On Dairy Cattle Breeding
item Vanraden, Paul

Submitted to: Interbull Annual Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Since its first publication in Holsteins (HOL) in April 2018, and later inclusion of Jerseys (JER) in April 2020, USA bull evaluations for mastitis resistance (MAS) have been exchanged with Interbull participating countries. Foreign phenotypes for MAS have been used since then to enhance the domestic reference population. Prior to next routine run in April 2021, countries had the choice of exchanging pure clinical mastitis (as the case in the USA), somatic cell score (SCS) for countries without a health evaluation, or a combination of methodologies where clinical/subclinical mastitis or a multi-trait approach using multiple sources of information are used. Hence, only ID s of bulls coming from certain countries with similar trait definitions, e.g., CAN, DFS, FRA, BEL, CHE, and NLD, and only if the country of most daughters does not send only SCS, e.g., USA bulls with daughters only in JPN are not considered, were being used in the US evaluations. To be effective in the April 2021 routine run, Interbull will introduce a new trait named SNP training for clinical mastitis (STCM) to better estimate SNP effects specifically for clinical mastitis. The new edits in the USA were validated in January 2021 in a full test run. Therefore, in the April evaluation, genotyped bulls with an international evaluation from the other participating countries (CAN, CHE, DEU, DFS, FRA, GBR and NLD) will be using STCM results, whereas the STCM or the previous trait (called hereafter as the MAS trait), that combines mastitis from some countries and correlated SCS from others, will be used for non genotyped animals depending upon PTA availability and/or reliability (REL). Most of the participating countries to the new trait have been already accounted for, thus, only a minor impact to the USA evaluations is expected. To confirm this hypothesis, this study aimed to compare PTA and REL values from 2012 routine run and from 2101 test run, for both HOL and JER breeds, but now taking into account the aforementioned criteria for the use of STCM PTA/REL values. A total of 81,691 bulls having values from both runs (2012 and 2101) were investigated. The investigation was conducted in four different scenarios: s1- all animals (n=81,691) having values from both runs; s2- animals changing from MAS to a STCM (n=27,665; ~34%); s3- High REL animals changing from MAS to STCM (n=501; ~0.6%); s4- animals keeping the previous combined MAS trait (n=54,026; ~66%). Descriptive statistics, Pearson and Spearman correlations as well as regression coefficients (b1) by predicting MAS on STCM to measure potential biases, were calculated. The PTA and REL values for both data sets (2012 vs. 2101) were similar for both breeds. Pearson and Spearman correlations were high for all scenarios, always higher than 0.96 for both breeds. The b1 values were, in general, close to 1 (range 0.98-1.07), with the highest bias (1.07) observed in JER on s4, where animals kept their combined MAS value. Our results suggest that minor impact is expected, and genetic progress improvement is enabled by the implementation of international STCM in the next routine run (April 2021). On the other hand, identifying which countries or individual bulls had direct MAS or only correlated SCS was previously difficult to automate correctly at the national level. Therefore, it is of most importance that Interbull continues to keep track of STCM countries, so several benefits such as gains in REL for bulls with many STCM daughters, would be achieved.