Author(s)

Yaser Fazel^1*, Masoud Asadi Fozi², Ali Esmailizadeh², Fatemeh Fazel³, Ahmad Massoud Niazi⁴, Shahpoor Rahmati⁴, Mohammad Ibrahim Qasimi¹

¹Department of Animal Science, Faculty of Veterinary, Kabul University, Kabul, Afghanistan.
²Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran.
³Faculty of Veterinary, Ferdowsi University of Mashhad, Mashhad, Iran.
⁴Department of Clinic, Faculty of Veterinary, Kabul University, Kabul, Afghanistan.

(Co) variance components and genetic parameters were estimated for milk yield of Iranian Holstein cows. A total number of 68,945 milk test-day records of first, second and third lactations of 8515 animals from 100 sires and 7743 dams originated from 34 herds collected during 2007 to 2009 by Iranian animal breeding center were used. The ASReml computer program was used to analyze the milk test-day records using the random regression procedure. Herd test date (HTD), milking times per day (milking frequency), number of lactations, year of birth, year of calving, age of animal at calving and days in milk (DIM) considered as fixed effects and additive genetic effects and animal permanent environmental effects were considered as the random effects. Additive genetic variance, animal permanent environment variance, residual variance, phenotypic variance, heritability and repeatability were estimated during different months of lactation between 5.7 - 19.6, 15.3 - 27.1, 31.4 - 17.2, 45.8 - 64.83, 0.1 - 0.32 and 0.4 - 0.6, respectively. Genetic correlation and phenotypic correlation were also estimated between months of lactation in range of -0.35 - 0.98 and 0.03 - 0.67, respectively. Genetic correlation and phenotypic correlation both showed the same changing pattern and they decreased as the interval between months of lactation increased.

Genetic Parameters, Random Regression Model, Test-Day Records, Milk Yield, Holstein Cows

Fazel, Y. , Fozi, M. , Esmailizadeh, A. , Fazel, F. , Niazi, A. , Rahmati, S. and Qasimi, M. (2018) Use of Random Regression Test-Day Model to Estimate Genetic Parameters of Milk Yield in Holstein Cows. Open Journal of Animal Sciences, 8, 27-38. doi: 10.4236/ojas.2018.81003.