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Genetic parameters for some milk production traits were estimated in a herd of Holstein Friesian (HF) cattle in Egypt. A total number of 502 lactation records of 300 HF cows sired by 29 bulls form a herd belonging to Alexandria Copenhagen Company for Dairy and Meat Production was used in the present study. Data were collected during 7 years (2005-2011) and analyzed using SAS and WOMBAT. Means of total milk yield (TMY), 305 day milk yield (305-DMY) and lactation period (LP) were 10718 kg, 8805 kg and 397 days, respectively. Parity had no significant effect on all traits, except for 305-DMY (P<0.0001). Season of calving, also, had no significant effect on all traits, except for LP (P<0.0025). Heritability estimates of TMY, 305-DMY and LP were 0.19, 0.25 and 0.15, respectively. The moderate estimate of heritability of 305 milk yield indicated that this trait could be made through selection as well as better managemental practices Repeatability of TMY, 305-DMY and LP were 0.48, 0.39 and 0.34, respectively. Positive genetic and phenotypic correlation coefficients were obtained for all traits and ranged from 0.01 to 0.77 and from 0.12 to 0.75, respectively. Results indicated possibility of genetic improvement of milk yield by selection for 305DMY only due to having higher estimate of heritability compared to TMY, and also because of its reasonably high genetic correlation coefficient with TMY.

ESTIMATION OF GENETIC PARAMETERS FOR MILK PRODUCTION TRAITS IN A HERD OF HOLSTEIN FRIESIAN CATTLE IN EGYPT