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Persistency is a heritable economic trait and an important parameter of lactation curve in dairy cattle. Persistency is affected by factors such as animal
genetics, calving, age feeding, season of calving, lactation number, open days, changes in hormone production, and herd production level. In this research
218920 test day records on 23802 cows in a single trait random regression animal model with Gibbs sampling method were used to estimate genetic
parameters and animal breeding values (EBV). Differences in milk production between days 60 and 280, periods 61-160 and 205-305, and the sum of daily
EBV changes were used as persisteney criteria. Estimated heritabilities for persistency criteria were 0.28-0.34 and 0.18-0.26 for milk and fat yield
respectively. Genetic correlation between persistency criteria and 305-d milk yield were varied from 0.15 to 0.89. Correlation between EBV of 305-d milk
yield and persistency criteria were estimated from 0.05 to 0.95. Animals _ rank based on 305-d EBVs were varied from persistency EBVs, which explains that
persistency changes variedly from 305-d milk yield in dairy eattle, allowing selection for this trait.