GENETIC-ANALYSIS OF SOMATIC-CELL SCORE AND FEMALE FERTILITY OF ISRAELI HOLSTEINS WITH AN INDIVIDUAL ANIMAL-MODEL

The individual animal model was used to analyze the conception index, defined as the inverse of the number of inseminations to conception, a nd mean lactation somatic cell scores (SCS) of Israeli Holsteins. in a ddition, multitrait variance components were estimated for these trait s and far milk production traits. The animal model analyses included 4 40,558 lactation records for conception index and 224,869 SCS records collected over 10 yr. First parity heritabilities were 0.035 for conce ption index and 0.158 for SCS. Genetic correlations were negative betw een conception index and milk production traits and positive between S CS and milk production traits. Genetic correlations between first and second lactations were 0.9 for conception index and 0.7 for SCS. Pheno typic correlations were 0.08 and 0.3, respectively. Despite the low he ritability for conception index, the standard deviation of the sire ev aluations was 2%, and the range of evaluations was 10%. Predicted gene tic trends for conception index and SCS were computed based on the cur rent selection index of Israel. The realized genetic trend for the con ception index was slightly positive, despite the predicted negative tr end, and the realized genetic trend for SCS, although positive as pred icted, was fourfold the predicted value. The reasons for these discrep ancies are not known.