Use of linear semen quality score for classification and decision making in evaluation of individual ejaculates of Holstein bulls.

Four hundred seven ejaculates from 15 Holstein bulls collected from December 1984 to June 1985 were evaluated postthaw for viability characteristics (percent progressive motility at 0 h and after 3 h at 37 degrees C incubation, percent intact acrosomal membrane after 3 h at 37 degrees C incubation) and abnormal morphological characteristics [percent head (primary), midpiece, and tail (secondary) abnormalities]. Weighting coefficients for combining viability and abnormality characteristics were generated from between-bull and within-bull variance and covariance matrices. Two hundred ninety-eight additional ejaculates collected from July 1985 to February 1986 were added. Linear quality scores for 705 ejaculates (24 bulls) were the sum of the product of each quality characteristic and weighting coefficients. Univariate analysis yielded significant bull effects for viability and abnormality characteristics and linear quality score. Significant correlations existed between all seminal quality characteristics except primary and secondary abnormalities. A t test with preassigned critical value was used to evaluate each ejaculate to determine rejection from the population. Percent of ejaculates rejected was lower when linear quality score was used than when five independent tests were used. Use of linear quality score to critique semen based on each ejaculate's innate quality could compensate for the loss of bull fertility estimates from declining number of technician-based AI programs.