Bahreini Behzadi, M., Ghane, A., Habibizad, J. (2018). Estimation of Genetic Parameters of Milk Yield Trait Using Test-Day Model with Random Regression in Iranian Holstein Cows. , 7(26), 33-46. doi: 10.22092/aasrj.2017.114651.1113
Mohammad Reza Bahreini Behzadi; Amine Ghane; Javad Habibizad. "Estimation of Genetic Parameters of Milk Yield Trait Using Test-Day Model with Random Regression in Iranian Holstein Cows". , 7, 26, 2018, 33-46. doi: 10.22092/aasrj.2017.114651.1113
Bahreini Behzadi, M., Ghane, A., Habibizad, J. (2018). 'Estimation of Genetic Parameters of Milk Yield Trait Using Test-Day Model with Random Regression in Iranian Holstein Cows', , 7(26), pp. 33-46. doi: 10.22092/aasrj.2017.114651.1113
Bahreini Behzadi, M., Ghane, A., Habibizad, J. Estimation of Genetic Parameters of Milk Yield Trait Using Test-Day Model with Random Regression in Iranian Holstein Cows. , 2018; 7(26): 33-46. doi: 10.22092/aasrj.2017.114651.1113

Estimation of Genetic Parameters of Milk Yield Trait Using Test-Day Model with Random Regression in Iranian Holstein Cows

علوم و فنون دامپروری
Article 3, Volume 7, Issue 26, June 2018, Pages 33-46    PDF (1.41 M)
DOI: 10.22092/aasrj.2017.114651.1113
Authors
Mohammad Reza Bahreini Behzadi* 1; Amine Ghane2; Javad Habibizad2
1Department of Animal Science, Faculty of Agriculture, Yasouj University
2Department of Animal Science, Yasouj University
Abstract
The aim of this study was to estimate genetic parameters for test-day milk yield in Iranian Holstein cows, applying Legendre polynomials func‌tions of random regression models. A total of 111252 test-day milk yield records of the first lactation that collected by the Animal Breeding and Milk Improvement Centre of Iran during 1986 and 2013 were used. The genetic parameters were estimated by restricted maximum likelihood method and average information algorithm using the WOMBAT software. The fixed effects of herd-year-season of test day as contemporary group and age at calving as covariates were fitted in the model of analysis. Legendre polynomials with order of fitting 2 to 6 were implemented to take account of genetic and environmental aspects of milk production over the course of lactation. The model with 6th-order Legendre polynomial for additive genetic effect and permanent environmental effect was more appropriate model to describe the covariance structure of the data. The results of this study show that heritability estimates for test-day records were highest in the first half part of the lactation, ranging from 0.14 to 0.35. Genetic correlations between test-day records were high for consecutive records and decreased as the interval between tests increased. Random regression model suggested to the lactation curve of the animals due to considering genetic and permanent environmental level and account the genetic correlations to be used between test days for more accurate assessment records of test day.
Keywords
Genetic parameters; Random regression; Milk yield; Test-day records; Holstein cow
References
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