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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Main Authors: Mahdi Elahi Torshizi, Homayoun Farhangfar, Mojtaba Hosseinpour Mashhadi
Format: Article
Language:English
Published: Asian-Australasian Association of Animal Production Societies 2017-10-01
Series:Asian-Australasian Journal of Animal Sciences
Subjects:
Online Access:http://www.ajas.info/upload/pdf/ajas-30-10-1382.pdf
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spelling 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
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AT mojtabahosseinpourmashhadi applicationofrandomregressionmodelsforgeneticanalysisof305dmilkyieldoverdifferentlactationsofiranianholsteins
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