Estimation of genetic parameters of the reproductive traits affected to conception rate in Isfahan Holstein heifers
Linear animal model was used to estimate (co)variance components and genetic parameter for conception rate and traits related to in Holstein heifers in Esfahanian province. The traits included: age at first service (AFS), number of insemination to conception (INS) and success to first insemination (SF). A total of 84540 records in first parity from 84540 heifers from 1981 to 2010 were used. With use of GLM procedure in SAS software (9.2) fixed effects that be effected of these traits were identified. Bivariate linear models were used in the Restricted Maximum Likelihood (REML) method with DMU software to estimate genetic parameters. Estimated heritabilities for reproductive traits were low (below 0.1); also estimated genetic variance component was the lowest for success in first insemination (0.004 ± 0.0006) and was the highest for number of insemination per conception (0.18 ± 0.019) among these traits. Strong genetic correlations were estimated between conception rate and fertility trait. The results from current study showed that conception rate is a complex trait. Therefore several measurements related to fertility traits should be combined in selection goals.