Effects of Imported Semen Based on Different Selection Indices on Some Production and Reproduction Traits in Iranian Holstein Cattle

SIMPLE SUMMARY: We evaluated the impact of imported semen of Holstein bulls from different countries on their daughters’ economic traits using the Lifetime Net Income (LNI) index in different climates of Iran. The first lactation records were collected from 10 big dairy farms in various regions of Iran. Studied traits included milk, fat and protein yields, calving age and calving interval. There were significant differences between sire groups for studied traits in each climate (p < 0.01). In semi-cold, moderate and warm climates, daughters of French sires had the highest least-square means of LNI index. In cold climate, daughters of German sires had the highest least-square means. ABSTRACT: The aim of the present study was to evaluate the effects of imported semen of Holstein bulls from different countries on the economic traits of their daughters using the Lifetime Net Income (LNI) index in various climates of Iran. The data included the first lactation records of 274,057 Holstein cows collected during 1993 to 2017 by the Animal Breeding Center of Iran from 10 large dairy farms located in various provinces of Iran. The investigated traits included milk, fat and protein yields, calving age and calving interval. Breeding values of progenies were predicted by the Best Linear Unbiased Prediction (BLUP) method under the multi-trait animal model using DMU software. The genetic-economic merit of the progenies was estimated by the LNI index. There were significant differences between the estimated breeding values (EBVs) of sire groups (based on bull semen origin) for milk, fat and protein yields, calving age and calving interval in each climate (p < 0.01). The obtained results showed that the highest least-square means of LNI index in semi-cold, moderate and warm climates belonged to the daughters of French sires; however, daughters of German sires were estimated to have the highest least-square means in the cold climate.