Genetic evaluation of reproductive traits in Holstein cows of Mahdasht Milk and Meat Company in Mazandaran province

The aim of this study was to estimate the (Co) variance components and genetic correlations of reproductive traits in Holstein cows in Mazandaran province. For this purpose, records related to the age at first calving(AFC), calving interval (CI), dry period (DP), open days (OD) and number of days between calving and first insemination (DFS) were collected. Pedigree data were edited using CFC software and variance-covariance components and genetic parameters of reproductive traits were estimated in the form of univariate animal model with restricted maximum likelihood method using wombat software. Heritabilities of reproductive trait were calculated in this study as 0.18, 0.17, 0.16, 0.08 and 0.12 for AFC, CI, OD, DFS and DP, respectively. Phenotypic and genotypic correlations were estimated positive between all reproductive traits. Genetic correlation between reproductive traits ranged from 0.62 (calving to first insemination length - dry period) to 0.94 (open days - calving interval).The low heritability of these traits indicates that phenotypic selection will not lead to an optimal response to selection and the use of breeding values and genetic evaluation using pedigree information is recommended for animal genetic evaluation.