Estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of Los Ríos region in Chile

Abstract In dairy cattle, genetic selection for milk yield was generally based on 305 days lactation records that were calculated from available monthly test-day milk yield records. A test-day milk yield record, multiplied by the number of days between the current and following test-day, was the mon...

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Autores principales:	Uribe,Héctor, Lembeye,Felipe
Lenguaje:	English
Publicado:	Universidad Austral de Chile. Facultad de Ciencias Veterinarias 2020
Materias:	milk test day random regression genetic parameters
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0719-81322020000300103
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spelling	oai:scielo:S0719-813220200003001032020-10-08Estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of Los Ríos region in ChileUribe,HéctorLembeye,Felipe milk test day random regression genetic parameters Abstract In dairy cattle, genetic selection for milk yield was generally based on 305 days lactation records that were calculated from available monthly test-day milk yield records. A test-day milk yield record, multiplied by the number of days between the current and following test-day, was the monthly milk yield and summed to all other monthly milk yields represented a 305 days lactation yield. Cows that for any reason did not complete their lactation got a 305 days yield via correction factors assuming a common lactation curve. Random regression models allow individual deviation from a common curve. The objective of this study was to estimate genetic parameters for daily milk yield using a random regression model (RRM) in Chilean dairy cows. A data set containing 97,683 monthly test-day records of 10,528 cows from 15 commercial dairy herds of Los Ríos Region in southern Chile was used. Days in milk (DIM) were modelled using the fourth-order Legendre polynomials and the model also included, as fixed effects, contemporary group and cow age at test-day as a covariate. The average daily milk yield was 17.83 ± 5.25 kg. Average estimated heritability and repeatability from five to 305 DIM was 0.26 ± 0.02 and 0.61 ± 0.04, respectively. The heritability estimate varied from 0.23 to 0.31. Both parameters did not vary dramatically except after 270 DIM when repeatability increased while heritability decreased. Although the estimated genetic parameters did not seriously depart from the most recent results available in the Chilean literature, they are mathematically more precise for estimating the true parameters than those calculated using adjustment factors, suggesting that the model used could be the starting point to develop a genetic evaluation system for dairy cattle in Chile.info:eu-repo/semantics/openAccessUniversidad Austral de Chile. Facultad de Ciencias VeterinariasAustral journal of veterinary sciences v.52 n.3 20202020-09-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0719-81322020000300103en10.4067/S0719-81322020000300103
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	milk test day random regression genetic parameters
spellingShingle	milk test day random regression genetic parameters Uribe,Héctor Lembeye,Felipe Estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of Los Ríos region in Chile
description	Abstract In dairy cattle, genetic selection for milk yield was generally based on 305 days lactation records that were calculated from available monthly test-day milk yield records. A test-day milk yield record, multiplied by the number of days between the current and following test-day, was the monthly milk yield and summed to all other monthly milk yields represented a 305 days lactation yield. Cows that for any reason did not complete their lactation got a 305 days yield via correction factors assuming a common lactation curve. Random regression models allow individual deviation from a common curve. The objective of this study was to estimate genetic parameters for daily milk yield using a random regression model (RRM) in Chilean dairy cows. A data set containing 97,683 monthly test-day records of 10,528 cows from 15 commercial dairy herds of Los Ríos Region in southern Chile was used. Days in milk (DIM) were modelled using the fourth-order Legendre polynomials and the model also included, as fixed effects, contemporary group and cow age at test-day as a covariate. The average daily milk yield was 17.83 ± 5.25 kg. Average estimated heritability and repeatability from five to 305 DIM was 0.26 ± 0.02 and 0.61 ± 0.04, respectively. The heritability estimate varied from 0.23 to 0.31. Both parameters did not vary dramatically except after 270 DIM when repeatability increased while heritability decreased. Although the estimated genetic parameters did not seriously depart from the most recent results available in the Chilean literature, they are mathematically more precise for estimating the true parameters than those calculated using adjustment factors, suggesting that the model used could be the starting point to develop a genetic evaluation system for dairy cattle in Chile.
author	Uribe,Héctor Lembeye,Felipe
author_facet	Uribe,Héctor Lembeye,Felipe
author_sort	Uribe,Héctor
title	Estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of Los Ríos region in Chile
title_short	Estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of Los Ríos region in Chile
title_full	Estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of Los Ríos region in Chile
title_fullStr	Estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of Los Ríos region in Chile
title_full_unstemmed	Estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of Los Ríos region in Chile
title_sort	estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of los ríos region in chile
publisher	Universidad Austral de Chile. Facultad de Ciencias Veterinarias
publishDate	2020
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0719-81322020000300103
work_keys_str_mv	AT uribehector estimationofgeneticparametersformilkyieldusingarandomregressiontestdaymodelinfirstparitydairycowsunderpasturebasedsystemsoflosriosregioninchile AT lembeyefelipe estimationofgeneticparametersformilkyieldusingarandomregressiontestdaymodelinfirstparitydairycowsunderpasturebasedsystemsoflosriosregioninchile
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Estimation of genetic parameters for milk yield using a random regression test-day model in first parity dairy cows under pasture-based systems of Los Ríos region in Chile

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