Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian Holsteins
Objective During the last decade, genetic evaluation of dairy cows using longitudinal data (test day milk yield or 305- day milk yield) using random regression method has been officially adopted in several countries. The objectives of this study were to estimate covariance functions for genetic and...
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Asian-Australasian Association of Animal Production Societies
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doaj-48919f2eb05f4a89af9b09adf12e6df02020-11-24T23:21:44ZengAsian-Australasian Association of Animal Production SocietiesAsian-Australasian Journal of Animal Sciences1011-23671976-55172017-10-0130101382138710.5713/ajas.16.088523751Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian HolsteinsMahdi Elahi Torshizi0Homayoun Farhangfar1Mojtaba Hosseinpour Mashhadi2 Department of Animal Science, Mashhad Branch, Islamic Azad University, Mashhad 918714578, Iran Department of Animal Science, Faculty of Agriculture, University of Birjand, Birjand 9719113944, Iran Department of Animal Science, Mashhad Branch, Islamic Azad University, Mashhad 918714578, IranObjective During the last decade, genetic evaluation of dairy cows using longitudinal data (test day milk yield or 305- day milk yield) using random regression method has been officially adopted in several countries. The objectives of this study were to estimate covariance functions for genetic and permanent environmental effects and to obtain genetic parameters of 305-day milk yield over seven parities. Methods Data including 60,279 total 305–day milk yield of 17,309 Iranian Holstein dairy cows in 7 parities calved between 20 to 140 months between 2004 and 2011. Residual variances were modeled by homogeneous and step functions with 7 and 10 classes. Results The results showed that a third order polynomial for additive genetic and permanent environmental effects plus a step function with 10 classes for the residual variance was the most adequate and parsimonious model to describe the covariance structure of the data. Heritability estimates obtained by this model varied from 0.17 to 0.28. The performance of this model was better than repeatability model. Moreover, 10 classes of residual variance produce the more accurate result than 7 classes or homogeneous residual effect. Conclusion A quadratic Legendre polynomial for additive genetic and permanent environmental effects with 10 step function residual classes are sufficient to produce a parsimonious model that explained the change in 305-day milk yield over consecutive parities of Iranian Holstein cows.http://www.ajas.info/upload/pdf/ajas-30-10-1382.pdfHolstein Dairy CattlePhenotypic and Genetic CorrelationsRandom Regression Model305-d Milk Yield |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Mahdi Elahi Torshizi Homayoun Farhangfar Mojtaba Hosseinpour Mashhadi |
spellingShingle |
Mahdi Elahi Torshizi Homayoun Farhangfar Mojtaba Hosseinpour Mashhadi Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian Holsteins Asian-Australasian Journal of Animal Sciences Holstein Dairy Cattle Phenotypic and Genetic Correlations Random Regression Model 305-d Milk Yield |
author_facet |
Mahdi Elahi Torshizi Homayoun Farhangfar Mojtaba Hosseinpour Mashhadi |
author_sort |
Mahdi Elahi Torshizi |
title |
Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian Holsteins |
title_short |
Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian Holsteins |
title_full |
Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian Holsteins |
title_fullStr |
Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian Holsteins |
title_full_unstemmed |
Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian Holsteins |
title_sort |
application of random regression models for genetic analysis of 305-d milk yield over different lactations of iranian holsteins |
publisher |
Asian-Australasian Association of Animal Production Societies |
series |
Asian-Australasian Journal of Animal Sciences |
issn |
1011-2367 1976-5517 |
publishDate |
2017-10-01 |
description |
Objective During the last decade, genetic evaluation of dairy cows using longitudinal data (test day milk yield or 305- day milk yield) using random regression method has been officially adopted in several countries. The objectives of this study were to estimate covariance functions for genetic and permanent environmental effects and to obtain genetic parameters of 305-day milk yield over seven parities. Methods Data including 60,279 total 305–day milk yield of 17,309 Iranian Holstein dairy cows in 7 parities calved between 20 to 140 months between 2004 and 2011. Residual variances were modeled by homogeneous and step functions with 7 and 10 classes. Results The results showed that a third order polynomial for additive genetic and permanent environmental effects plus a step function with 10 classes for the residual variance was the most adequate and parsimonious model to describe the covariance structure of the data. Heritability estimates obtained by this model varied from 0.17 to 0.28. The performance of this model was better than repeatability model. Moreover, 10 classes of residual variance produce the more accurate result than 7 classes or homogeneous residual effect. Conclusion A quadratic Legendre polynomial for additive genetic and permanent environmental effects with 10 step function residual classes are sufficient to produce a parsimonious model that explained the change in 305-day milk yield over consecutive parities of Iranian Holstein cows. |
topic |
Holstein Dairy Cattle Phenotypic and Genetic Correlations Random Regression Model 305-d Milk Yield |
url |
http://www.ajas.info/upload/pdf/ajas-30-10-1382.pdf |
work_keys_str_mv |
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