Genetic and non-genetic factors affecting some productive and reproductive traits in Holstein-Friesian dairy cows raised in Egypt for the first two lactations

Abstract EN

The present study was conducted to investigate the effects of some non-genetic factors as year and season of calving on productive and reproductive traits of dairy Holstein-Friesian cows together with the effect of genetic variation in the form of sire analysis on these traits.

A total of 3460 lactation records were used for 1059 dairy cows that represented the period from 1998 to 2010.

Studied traits were total milk yield (TMY), days in milk (DIM), fat yield (FY), protein yield (PY), dry period (DP), age at first calving (AFC), number of services per conception (NSC), days open (DO) and calving interval (CI).

Analysis was done using sire model by Harvey (1990) software for the first and second lactations.

The present herd showed high milk production around 8750 kg per lactation period.

Sire effects were significant (P ≤ 0.05) on all traits.

Year and season of calving had significant effects on most of studied traits.

Linear and quadratic regression coefficients of age at first calving, days open and total milk yield were significant for most of traits.

Balanced and unbiased estimates for genetic evaluation could be obtained if the environmental factors fitted in the statistical models.