Genetic parameters and genetic trends of female fertility in Icelandic dairy cattle

Fertility, represented by calving interval, has been included in the genetic evaluation of Icelandic cattle since 1993. In spite this an unfavourable trend is seen and, recent implementation test-day models for milk production changed premise using interval to represent fertility. The aim study was estimate parameters and trends different female fertility traits dairy suggest new evaluation. Insemination records first three lactations heifer period 52,951 cows were used analyse traits: conception rate at insemination (CR), number inseminations per service (AIS), last (IFL), (ICF), (ICL) (CI). Correlations between also estimated. Five linear animal (co)variance components. Breeding values compared, investigated. Estimated heritabilities low, ranging from 0.01 (IFL) 0.08 (ICF). Genetic correlations cow performances within ranged 0.23 0.81. Between traits, 0.36 1.00. strong, they weak (-0.17) very strong (0.97). generally unfavourable, but more pronouncedly so AIS, IFL, ICL CI than ICF CR. seemed IFL favourable ICL. a revised cattle, should be fertility, CR