Estimation of heritabilities, genetic correlations, phenotypic correlations and genetic trends for production and reproduction traits of Holstein-Friesian dairy cattle using sire model

الملخص EN

A total of 3460 lactation records that represented 1059 dairy Holstein-Friesian cows were used in the present study that aimed to estimate genetic parameters such as heritability, genetic correlations, phenotypic correlations and genetic trends for some productive and reproductive traits.

Studied traits were total milk yield, days in milk, fat %, protein %, dry period, age at first calving, number of services per conception, days open and calving interval.

Data were collected from Egyptian Copenhagen Company in Alexandria-Cairo desert road for cows calved from 1998 to 2010.

Least square analysis of mixed sire model was used in analysis using Harvey (1990) program.

Heritability estimates were high for all traits and very high for fat and protein % that exceeded 0.83 in two lactations.

Genetic correlations were higher than phenotypic correlations and were high especially among production traits.

Regression coefficients of genetic trends were positive for all studied traits except for days in milk and days open (in second lactation) and age at first calving.

Generally, the current results showed genetic improvement of most of traits that reflect the efficiency of selection programs.