Birth weight of 149 Friesian, 270 Sharabi and 121 crossbred calf's males and females were utilized. The mortality rates have been obtained from birth until weaning for each breed in males and females. Average birth weight in male's survival group for sharabi, Friesian and crossbred were 20.94, 30.82 and 30.19 kg respectively, and in females were 18.42, 29.11 and 28.10 kg, respectively. Birth weight in Sharabi was significantly different (P<0.01) from Friesian and crossbred in both males and females. In mortal group the birth weight was significantly (P<0.01) less than survival group in both sexes and for each breed.
Mortality rate in males and females were (14.1%, 16.7%) in Frieasian, (21.2%, 23.6%) in Sharabi and (8.8%, 7.5%) in crossbred respectively, which differ significantly (P<0.01) among breeds. But, no significant difference between males and females was detected.
The Point-Biserial correlations between mortality anb birth weight were negative and highly significant for the three breeds in males and females. The threshold point of birth weight values which gave the best efficiency, the efficiency were for Friesian (89%, 85%), Sharabi (86%, 80%) and crossbred (93%, 94%) for males and females calves respectively, Fm and Fc, as well as efficiency were determined. Advantageous results were in least specificity Fm and Fc, and in high efficiency and sensitivity.
The threshold values of birth weight for classifying mortal and survival groups were (25.6, 26.6 kg) in Friesian, (16.6, 16.1 kg) in Sharabi, and (24.6, 22.6 kg) in crossbred in male and female, respectively.