بعض العوامل المؤثرة في نسبة الهلاكات عند الولادة ومعدل التوائم لدى ابقار الهولشتاين

Abstract

At the Nasr Dairy Cattle Station , United Company for Animal Resources Ltd., and over the period from 1991 to 2001 , 9522 records Holstein cows were analyzed statistically . The study conducted to investigate the effects of some non-genetic factors on the mortality at calving and twining rate , and estimate of regression coefficient of mortality rate on birth weight , and estimate of heritability and repeatability .Overall mean of mortality and twining rate were 0.17 and 1.0362 respectively . The effect of calving year on mortality rate was significant . The regression coefficient of mortality rate on birth weight was highly significant (0.613% / kg). The effects of parity , season (P < 0.01) , year (P < 0.05) , on twining rate were significant . Heritability estimated of mortality and twining rate was 0.08 and 0.005 and repeatability estimated was 0.26 and 0.16 respectively