Although differences exist between breeds and countries, dairy cow fertility has generally declined since around 1980. However, for many countries, an improvement in phenotypic and genetic trends for female fertility has been observed from the early to mid 2000s largely as a consequence of introducing breeding values for fertility and increased emphasis on fertility in breeding objectives. However, for some countries, fertility is still deteriorating genetically. Barriers to genetic improvement include: 1) the low heritability of fertility - genomic selection tools have helped to increase the reliability of bull breeding values; 2) insufficient selection intensity on fertility as a consequence of economic drivers of milk production versus fertility; 3) a possible association between level of milk production and the genetic correlation of fertility and milk production and 4) the impact of inbreeding on reproductive performance and increased probability of lethal recessives arising.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Genetics of Trait Complexes: Reproduction, , 154, 2014
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