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Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian Holsteins.

Application of random regression models for genetic analysis of 305-d milk yield over different lactations of Iranian Holsteins.

Authors :
Torshizi ME
Farhangfar H
Mashhadi MH
Source :
Asian-Australasian journal of animal sciences [Asian-Australas J Anim Sci] 2017 Oct; Vol. 30 (10), pp. 1382-1387. Date of Electronic Publication: 2017 Apr 21.
Publication Year :
2017

Abstract

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.<br />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.<br />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.<br />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.

Details

Language :
English
ISSN :
1011-2367
Volume :
30
Issue :
10
Database :
MEDLINE
Journal :
Asian-Australasian journal of animal sciences
Publication Type :
Academic Journal
Accession number :
28427258
Full Text :
https://doi.org/10.5713/ajas.16.0885