EBV changes due to different age adjustment factors in the Italian Friesian

Mature equivalent productions are often used as input for breeding values estimation. Adjustment factors can affect genetic trend, thus efforts should be put in order to verily projected production. Adjustment factors used in different countries refer to various ages. EBV changes with adjustment factors projecting lactations to primiparous vs. adjustment factors projecting production to pluriparous were compared. No evident difference was found both in genetic trend and in ranking of sire and cows by changing reference age except for some re-ranking for top 10,000 cows. Effect on genetic trend and EBV variability was found when base parameters of heterogeneity of herd variance were different