Estimates of Heritability, Repeatability and Correlation of Some Productive and Reproductive Traits of Holstein Cows in Egypt

This study aimed to estimate genetic parameters, including direct and maternal heritability, repeatability, and genetic correlations for productive and reproductive traits in Holstein cows in Egypt. Data from 10,834 productive records of 2,656 Holstein cows collected from 2002 to 2014 at El-Lahhamy farm were analyzed. The characteristics studied included total milk yield (TMY), lactation period (LP), service period (SP), and calving interval (CI). Results showed moderate direct heritability for TMY 0.28 and low estimates for LP 0.04, SP 0.029, and CI 0.027. Maternal heritability estimates were generally low across all traits, ranging from 0.02 to 0.027. Repeatability estimates were moderate for TMY (0.46) but low for reproductive traits ranging from 0.081 to 0.095. Strong positive genetic correlations were found between LP and SP (0.77) and between SP and CI (0.81), while a strong negative correlation was observed between age at first calving and CI (-0.83). The findings suggest that while genetic improvement for milk production is achievable through selection, reproductive traits are more heavily influenced by environmental factors.