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 dairy cattle since 1993. In spite of this an unfavourable genetic trend is seen and, recent implementation of test-day models for the genetic evaluation of milk production has changed the premise of using calving interval to represent fertility. The aim of this study was to estimate genetic parameters and genetic trends of different female fertility traits in Icelandic dairy cattle and suggest new traits for the genetic evaluation. Insemination records for the first three lactations and the heifer period of 52,951 Icelandic cows were used to analyse the traits: conception rate at first insemination (CR), number of inseminations per service period (AIS), interval form first to last insemination (IFL), interval from calving to first insemination (ICF), interval from calving to last insemination (ICL) and calving interval (CI). Correlations between fertility and production traits were also estimated. Five different linear animal models were used to estimate (co)variance components. Breeding values were compared, and genetic trends were investigated. Phenotypic averages of CR and AIS were more favourable for heifers than for cows. Estimated heritabilities for the fertility traits were low in all cases, using both multi-trait models (0.01 – 0.08) and single-trait models (0.02 – 0.06). ICF in second lactation had the highest heritability, and the lowest estimates were found for the heifer traits. Estimated heritabilities of yield traits analysed in the study were in the range from 0.15 to 0.25. Genetic correlations between heifer and cow performances within traits ranged from 0.23 to 0.81. Genetic correlations between lactations within traits ranged from 0.36 to 1.00. Genetic correlations between different heifer traits were strong. Genetic correlations between different fertility traits ranged from weak (-0.17) to very strong (0.97). Genetic correlations between the fertility and production traits were generally unfavourable, but more pronouncedly so for AIS, IFL, ICL and CI than for ICF and CR. Estimated genetic trends seemed unfavourable for the traits AIS, IFL and CI and favourable for ICF and ICL. Heifer and cow fertility should not be considered as the same trait. Fertility between different lactations should be considered as different but correlated traits. In a revised genetic evaluation for fertility in Icelandic cattle, the traits ICF and IFL should be included to represent cow fertility, and CR to represent heifer fertility. These traits represent the time it takes for the animals to resume the estrous cycle after calving and conceiving once the insemination period has started. Rank correlations between EBVs suggested there will be some reranking of sires in a new evaluation.

Author dc:creator

• Þórdís Þórarinsdóttir 1995-

Contributors dc:contributor

• Landbúnaðarháskóli Íslands

• Frjósemi
• Kynbótamat
• Erfðaframfarir
• Arfgengi
• Nautgripir
• Icelandic cattle
• Fertility
• Genetic evaluation
• Genetic trends
• Genetic correlation
• Heritability

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/1946/35122

OAI identifier oai:identifier

oai:skemman.is:1946/35122