DIFFERENT BIF ACCURACY OF EPD FOR INCLUDING RECORDS IN MARC ANALYSES TO ESTIMATE BREED OF SIRE DIFFERENCES

Authors: Van Vleck, Lloyd; Cundiff, Larry

Submitted to: Beef Improvement Federation Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/4/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Two sources of information are used in calculation of tables to adjust within-breed EPD of bulls so that comparisons can be made across-breeds of beef cattle. Records from the MARC are used to estimate breed of sire differences. The breed associations furnish EPD so that the MARC estimates can be adjusted for the difference in genetic values of bulls used at MARC and of bulls of the breed born in a current base year. Only progeny of bulls with reported EPD are used in the MARC analyses. Some bulls, however, have EPD with more or less accuracy than other bulls. This study showed that limiting the MARC analyses to progeny of bulls with greater than arbitrary specified accuracy can change across-breed adjustment factors. No evidence, however, was found from the regression of MARC progeny on sire EPD to suggest limits on accuracy are necessary. One conclusion is that the genetic prediction committee or a subcommittee of BIF should set the standards for BIF accuracy for including progeny of sires with EPD in the MARC analyses to estimate breed of sire or maternal grandsire differences. All breeds should attempt to submit similar information. Obviously, what information is submitted may influence the breed table factors, although what the effect would be is unknown until the analyses are done. There is, however, little evidence to suggest requiring anything more than a breed association EPD of a sire to allow progeny and grandprogeny into the analyses.

Technical Abstract: Weights of F1 progeny of 12 breeds of bulls mated to Hereford, Angus, and MARC III cows at MARC were used to determine the effect on estimates of breed of sire differences of limiting the data according to the accuracy of the EPD of the sire of the progeny. Analyses routinely done to create across-breed adjustments to convert within-breed to across-breed EPD were repeated with four subsets of the data file. A record was included if 1) the sire had an EPD, 2) if the BIF accuracy of the EPD of the sire was greater than .00, 3) if the BIF accuracy was equal to or greater than .10 and 4) if the BIF accuracy was equal to or greater than .15. Depending on the weight trait analyzed from 327 to 456 records were excluded out of nearly 5000 when accuracy of .15 was required. Not all breeds lost records or sires from the analyses. The largest effects on breed adjustments were for comparisons involving Angus which lost 6 of 68 sires and 123 of 619 progeny for birth weight when accuracy of .10 was required. Regressions of progeny weights on sire EPD did not indicate a need to exclude progeny of sires with low accuracy. Although what information is submitted by the breed associations may affect the breed table factors, what the effect will be is unknown until all steps in calculation of across-breed adjustment factors are completed. One conclusion is that the BIF genetic prediction committee should recommend uniform standards for all breeds for including progeny in the MARC analyses.