Estimation of genetic parameters for production traits and some reproduction disorders of dairy cows in one of the East Azerbaijan herds

In this study, 2554 calving records from 1484 Holstein cows were used.
The data were collected from one of the East Azerbaijan herds, during 2009 to 2013. The studied traits were production traits (305 d milk and 305 d fat yields) and reproduction disorders (dystocia and retained placenta).
Estimation of genetic parameters was performed by repeatability animal linear (305 d milk and 305 d fat yields) and threshold models (dystocia and retained placenta), by single and two-trait analyses.
Heritability for 305 d milk yield and 305 d fat with single-trait analysis were estimated 0.33 and 0.23, respectively and the repeatability of these traits were estimated 0.35 and 0.25, respectively. Heritability of dystocia and retained placenta were estimated 0.09 and 0.1, respectively and the repeatability for both was estimated 0.11. Genetic correlation between production traits were estimated 0.98 and genetic correlation between reproduction disorders were estimated 0.51. Estimated genetic correlations between production traits and reproduction disorders were from -0.85 (305 d fat and retained placenta) to 0.21 (305 d milk yield and dystocia).
Considering negative genetic correlation between milk production and dystocia and a relatively strong positive correlation between these two reproductive disorders, planning of selection programs in dairy cows based on a combination of production and reproduction traits is recommendable. Also ignoring these relationships in selection may negatively influence overall performance in a long term.