Genetic and nongenetic variation of heifer fertility in Italian Holstein cattle

Summary: Pregnancy diagnosis is important to characterize fertility earlier and on a larger proportion of individuals. In the present study, such information was exploited to derive genetic parameters for fertility in nulliparous Italian Holstein heifers. A selection index for heifer fertility was developed using selection index methodology, and phenotypic variation of heifer fertility traits across systematic environmental effects was estimated. The present study demonstrated that although lowly heritable, heifer fertility manifested ample and exploitable genetic variation for selective breeding. The derived selection index can be included in the national breeding objective as an additional source of information for fertility. Efforts should be made on the collection of pregnancy diagnosis to improve the genetic evaluation of fertility.