Estimating Transmitting Abilities of Artificial Insemination Dairy Sires

First available DHIA production records ot7 40,501 Wisconsin Holstein eows were used to compare several methods of estimating the transmitting abilities of A.I. sires.These methods involved the use of different contemporary averages to adjust A.I. daughter records for herd-year-season effects.The different types of adjusted daughter records were compared to each other and to unadjusted records on the basis of variance components for herd effects, sire effects and herd-by-sire interaction effects.Correlation and regress]oil eoeflicieuts for the average performance of a large number of later daughters on the average performance of different ureahers of early daughters also were comouted.Variance eomponent analyses indicated that the adjustment of daughter records by use of contemporary averages substantially reduced the influence of herd variation.However, no type of daughter reeord appeared to be superior in terms of the percentage of variance due to sire effects or in terms of the degree of relationship between later and early daughters.Use of deviations ()f daughter recm'ds frmn some kind of contemporary average has been widely accepted as a fairly reliable method of proving dairy sires.However, there have been some differences of opinion c,meerning the exact form these contemporary comparisons or herdmate comparisons shouM take.The general plan followed by the progeny-testing programs of northwestern Europe is to compare the actual 1)roduction of first-lactati<m daughters to the a(~tual production of their first-productlon herdmates (13,15,17,18), but for sire proving in the United States individual records are ,tenorally corrected to a mature-a~'e basis and all records of daughters and herd-mates are used