Abstract

Iranian crossbred cattle performance was considered from the years 1991-2003. Holstein × native and Brown Swiss × native crossbreed cattle were surveyed for milk yield (kg), fat yield (kg), fat percent and milk-days traits. Nine genetic groups were defined according to the percentage of imported breed genes at 12.5% intervals. Data were analyzed with mixed model procedure in SAS (8.2) software. Analysis of variance showed that the Holstein breed effect was significant on fat percent, milk yield and milk- days traits, but not significant on fat yield trait. However, the effect of Brown Swiss breed was in the same trend with that of Holstein breed. But results in fat yield and fat percent traits were reversed. Total means for milk yield, fat yield, fat percent and milk- day traits were estimated to be 2722.68 ± 1541.12 kg, 122.97 ± 47.40 kg, 3.97 ± 0.73% and 260.10 ± 89.51 days for Holstein cross and 2489.19 ± 914.58 kg, 117.31 ± 49.49 kg, 3.87 ± 1.27% and 252.56 ± 81.64 days for Brown Swiss crosses. The least square means comparison with Duncan multiple range test showed that the peak of production was obtained in 50 to 87.5 shares of Holstein and Brown Swiss breeds. The result suggests that Brown Swiss is a favorable breed for crossbreeding program in Iran.

Key words: Crossbreeding, Holstein, Brown Swiss, breed combination