مشخصات پژوهش

Productive and reproductive traits have great importance in international dairy cattle breeding objectives. Production, reproduction (days open and calving interval) and pedigree data of Iranian Holstein dairy cat-tles were collected between 2002 and 2012 from 47 herds in Isfahan province. The data set consisted of 30179 records from 18837 registered Iranian Holstein dairy cattles. Single trait repeatability animal model was used to estimate genetic parameters by restricted maximum likelihood procedures. Estimates of herita-bility of milk, fat and protein yields were 0.30 ± 0.014, 0.065 ± 0.0089 and 0.083 ± 0.0098 respectively and also these value for calving interval (CI) and days open (DO) were 0.074 ± 0.0094 and 0.023 ± 0.0057 re-spectively. Low heritability for reproductive traits indicates the importance of using available relatives’ information for selection of these traits. Average increase in breeding value for milk, fat and protein over the 11 years period were 130, 0.22 and 0.09 kg/year, respectively. The means of breeding value of DO in-creased by 0.08 d/year from -0.17 d in 2002 to 0.58 d in 2012 and for CI decreased irregularly by -0.01 d/year from 0.05 d in 2002 to -0.03 d in 2012. In general, all traits showed negative phenotypic trends for the studied period.