Quantifying Dairy Breeding Goals. 1. A Technique to Elicit Decisions and Define Equations for Goals

Abstract A decision, obtained by forced choice technique, was used to quantify a perceived difference in total merit between cows taken pairwise. Information on milk, fat percent, and 15 type traits was used. The study consisted of 9,240 decisions by 91 respondents who compared pairs of hypothetical cows using simulated phenotypic scores displayed on two or three traits. Each decision resulted in the assignment of a perceived difference in total merit arising from only knowledge of the displayed phenotypic scores. Differences were fitted simultaneously to a function consisting of the sum of quadratic equations, each defined in terms of the single traits. Within respondent, the estimated quadratic equation for the traits milk, fat percent, rear udder height, fore udder attachment, angularity, rear udder width, body depth, strength, rump width, and rump length continually increased as phenotypic scores increased. Functions for rump angle and rear legs side showed a peak in merit values near the midpoint of the scale, whereas merit values for stature, teat placement rear, udder support, udder depth, and foot angle each reached an effective plateau. Pooled relative merits reported are probably greater than if perceived total merit comparisons had been made between real cows.