Genetics aspects of reproductive performance for Holstein Al-Samarai F.R .Al-Anbari N.N . and Al-tmimi Y.K.

Abstract

A total of 16678 records of age at first calving and ages at next calving ,
in addition to 14058 records of calving interval belonged to Holstein cows were
analysed over period from 1992 to 2003 , at the Nasr Dairy Cattle Station,
United Company for Animal Resources Ltd., Al-Soueira ( 50 Km South of
Baghdad ). Data was analaysed using General Linear Model within the SAS
program to study the effects of some fixed factors on the studied traits .
Components of variance for the random effects was estimated by the
Minimum Variance Quadratic Unbised Estimation Procedure ( MIVQUE ) , also
phenotypic trend was estimated for all traits .
The overall means for age at first calving till the age at sixth calving were
48.17 , 62.77 , 77.41 , 91.35 , 105.53 months respectively , and the heritability
for the same traits was 0.10 , 0.01 , 0.03 , 0.04 , 0.02 , 0.11 respectively .
whereas the overall mean of calving interval and heritability was 458.59 days
and 0.07 .
The results obtained that there was a significant effect of year of birth on
age at first calving , whereas the season of birth was not .
All the estimates of heritability were low so it’s reflect the role of
environment factors in the traits variation.Phenotypic trend was negative and
significant ( p <0.01 ) for age at first calving ( - 1.05 month / year ) and calving
interval (- 2.03 day / year ) .