Days-Open Adjusted, Annualized, and Fat-Corrected Yields as Alternatives to Mature-Equivalent Records

Open Access
Publisher Website
Google Scholar
Abstract
Models for developing adjustment factors for days open, effects of alternative methods to evaluate lactation yields and effects of alternative methods of measuring yield on sire evaluation were investigated. Effects of days open on production were reduced by including summit production (average of 2 highest of first 3 test days) in models; adjustment of records by factors from models including summit production were not satisfactory for records with > 180 days open. Annualized yield [total lactation production divided by days between calvings (365)] overcompensated for days open > 180. Days open adjusted, annualized yield and fat-corrected yield were closely correlated. Mature-equivalent production in 1st parity was most predictive for yield in 2nd parity, but yield adjusted for days open was more predictive of total cumulative yield at 26, 39 and 52 mo. Rank correlations among sire transmitting abilities computed from alternative measures were > 0.86. Evaluations by yield adjusted for days open were most similar and fat-corrected yield least similar to evaluation by mature equivalent production. Changes in culling decisions and sire evaluation from use of annualized yield or yield adjusted for days open vs. mature equivalent were small, and yield adjusted for days open is preferred over annualized yield.