Investigation of genetic parameters for milk production trait of Holstein cows in Kermanshah province using random regression model

In this research estimation of genetic parameters for milk production trait was performed by using 27065 test day records of first parity of Holstein cows in Kermanshah province.
The collected records were including 3123 cows in 22 herds that were calved from 1991 to 2013. Number of lactation days and calving age were limited to 5-305 days and 21-48 months, respectively. Test day milk records were analyzed by using a random regression model. The effects of additive genetic and permanent environment for production curve during lactation period were fitted using Legendre polynomials by GIBBS2F90 software. Results showed that the effects of herd, year and date of recording; age of calving; season and year of calving and days in milk were significant (p