Effect of Heifers Age at First Breeding and Calving on Some Performance Traits and Economic Returns in Friesian cows in Egypt

The primary data used an actual study on 874 Friesian cows management from birth to end lifetime production was collected of El- Karada and Sakha Farms pertain to the Animal Production Research Institute (APRI), from 1990 to 2016. These data were analyzed to determine genetic parameters with REML using animal model and using a general linear model of SAS to determine the main effects. Means of MY, LTMY, LP NLC, AFB, AFC DO, CI, CFB, CFC, LTC, LPP and NP were 3571.63 kg, 17538.70 kg, 303.66 d, 3.48, 31.02month, 40.11month, 77. 54 d, 360.97 d, $961.63, $1259.73, $4638.59, $4858.78 and$1478.58, respectively. The highest rate of culling was in third parity 24.10% following by second parity of 23.59%. Direct heritability of MY, LTMY, LP NLC, AFB, AFC DO and CI was 0.57, 0.31, 0.35, 0.29, 0.38, 0.41, 0.13 and 0.09, respectively. Appraising genetic correlations between aforesaid feature were between (-0.54 to 0.53), the same features phenotypic correlations between same features were from (-0.46 to 0.22). That introduces the major possibility of improvement genetic and optimization management for MY, LTMY, LP, NLC, AFB and AFC. While possibility improvement DO and CI through optimization management. Therefore, management can play a major role in improving these traits. Reducing AFB and AFC bring about to decrease the direct rearing costs subsequently decrease total costs in lifetime vice versa increase LTMY, LPP, and NP. Therefore, it is the best to select replacement heifer for AFB or AFC so that maximum lifetime milk yield and net profit in Friesian farms.