Genetic parameters for test day milk yields of first lactation Holstein cows by random regression models

Covariance components for test day milk yield using 263 390 first lactation records of 32 448 Holstein cows were estimated using random regression animal models by restricted maximum likelihood. Three functions were used to adjust the lactation curve: the five-parameter logarithmic Ali and Schaeffer...

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Main Authors: C.M.R. de Melo, I.U. Packer, C.N. Costa, P.F. Machado
Format: Article
Language:English
Published: Elsevier 2007-01-01
Series:Animal
Subjects:
Online Access:http://www.sciencedirect.com/science/article/pii/S1751731107685036
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author C.M.R. de Melo
I.U. Packer
C.N. Costa
P.F. Machado
author_facet C.M.R. de Melo
I.U. Packer
C.N. Costa
P.F. Machado
author_sort C.M.R. de Melo
collection DOAJ
description Covariance components for test day milk yield using 263 390 first lactation records of 32 448 Holstein cows were estimated using random regression animal models by restricted maximum likelihood. Three functions were used to adjust the lactation curve: the five-parameter logarithmic Ali and Schaeffer function (AS), the three-parameter exponential Wilmink function in its standard form (W) and in a modified form (W*), by reducing the range of covariate, and the combination of Legendre polynomial and W (LEG+W). Heterogeneous residual variance (RV) for different classes (4 and 29) of days in milk was considered in adjusting the functions. Estimates of RV were quite similar, rating from 4.15 to 5.29 kg2. Heritability estimates for AS (0.29 to 0.42), LEG+W (0.28 to 0.42) and W* (0.33 to 0.40) were similar, but heritability estimates used W (0.25 to 0.65) were highest than those estimated by the other functions, particularly at the end of lactation. Genetic correlations between milk yield on consecutive test days were close to unity, but decreased as the interval between test days increased. The AS function with homogeneous RV model had the best fit among those evaluated.
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spelling doaj.art-6dfc51da8f894d459a45f17b0a3796b92022-12-21T22:32:52ZengElsevierAnimal1751-73112007-01-0113325334Genetic parameters for test day milk yields of first lactation Holstein cows by random regression modelsC.M.R. de Melo0I.U. Packer1C.N. Costa2P.F. Machado3Aqüiculture Department – AQI/UFSC, 88040-900 Florianópolis/SC, BrazilAnimal Science Departament – USP/ESALQ, 13418-900 Piracicaba/SP, BrazilEmbrapa Gado de Leite, 36038-330 Juiz de Fora/MG, BrazilAnimal Science Departament – USP/ESALQ, 13418-900 Piracicaba/SP, BrazilCovariance components for test day milk yield using 263 390 first lactation records of 32 448 Holstein cows were estimated using random regression animal models by restricted maximum likelihood. Three functions were used to adjust the lactation curve: the five-parameter logarithmic Ali and Schaeffer function (AS), the three-parameter exponential Wilmink function in its standard form (W) and in a modified form (W*), by reducing the range of covariate, and the combination of Legendre polynomial and W (LEG+W). Heterogeneous residual variance (RV) for different classes (4 and 29) of days in milk was considered in adjusting the functions. Estimates of RV were quite similar, rating from 4.15 to 5.29 kg2. Heritability estimates for AS (0.29 to 0.42), LEG+W (0.28 to 0.42) and W* (0.33 to 0.40) were similar, but heritability estimates used W (0.25 to 0.65) were highest than those estimated by the other functions, particularly at the end of lactation. Genetic correlations between milk yield on consecutive test days were close to unity, but decreased as the interval between test days increased. The AS function with homogeneous RV model had the best fit among those evaluated.http://www.sciencedirect.com/science/article/pii/S1751731107685036genetic parametersmilk yieldrandom regression modeltest day modelvariance components
spellingShingle C.M.R. de Melo
I.U. Packer
C.N. Costa
P.F. Machado
Genetic parameters for test day milk yields of first lactation Holstein cows by random regression models
Animal
genetic parameters
milk yield
random regression model
test day model
variance components
title Genetic parameters for test day milk yields of first lactation Holstein cows by random regression models
title_full Genetic parameters for test day milk yields of first lactation Holstein cows by random regression models
title_fullStr Genetic parameters for test day milk yields of first lactation Holstein cows by random regression models
title_full_unstemmed Genetic parameters for test day milk yields of first lactation Holstein cows by random regression models
title_short Genetic parameters for test day milk yields of first lactation Holstein cows by random regression models
title_sort genetic parameters for test day milk yields of first lactation holstein cows by random regression models
topic genetic parameters
milk yield
random regression model
test day model
variance components
url http://www.sciencedirect.com/science/article/pii/S1751731107685036
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