Document Detail

Short communication: genetic trends of milk yield under heat stress for US Holsteins.
MedLine Citation:
PMID:  20338455     Owner:  NLM     Status:  MEDLINE    
Data included 90,242,799 test-day milk records from 5,402,484 Holstein cows in the first 3 parities and 9,326,754 animals in the pedigree. Additionally, daily temperature-humidity indexes from 202 weather stations were available. Analyses were done by a random regression model in which each parity was treated as a separate trait and that accounted for heat stress. The fixed effects included herd test-day, age at calving, milking frequency, and days in milk classes. Random effects included additive genetic, permanent environment, and herd-year effects, all fit as random regressions. Five covariates in the random regressions included linear splines with 4 knots at 5, 50, 200, and 305 DIM and a function of a temperature-humidity index (THI). Mixed model equations were solved by using an iteration on data approach with a preconditioned conjugate gradient algorithm. Genetic trends for daily milk yield in absence of heat stress (intercept) were 0.140 kg/yr, 0.172 kg/yr, and 0.168 kg/yr for the first, second, and third parity, respectively. Genetic trends for decline of milk yield at temperature of 5 degrees C THI over the threshold of sensitivity to heat stress were -0.002 kg/yr, -0.035 kg/yr, and -0.038 kg/yr, for first, second, and third parity, respectively. Genetic profiles were created by contrasting the 100 most and 100 least heat-tolerant bulls for the official proofs. The most heat-tolerant bulls transmitted lower production and dairy form but higher fertility, productive life, and type, especially udder and locomotion traits. In later parities, the type advantages were smaller. Test-day records capture only a fraction of information due to heat stress, and the real trends for heat stress may be stronger. Studies on heat stress for production should include records on later parities.
I Aguilar; I Misztal; S Tsuruta
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of dairy science     Volume:  93     ISSN:  1525-3198     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  2010 Apr 
Date Detail:
Created Date:  2010-03-26     Completed Date:  2010-05-31     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985126R     Medline TA:  J Dairy Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1754-8     Citation Subset:  IM    
Copyright Information:
Copyright (c) 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
Animal and Dairy Science Department, University of Georgia, Athens 30602, USA.
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MeSH Terms
Cattle / genetics*,  physiology
Cattle Diseases / genetics*
Heat Stress Disorders / genetics,  veterinary*
Hot Temperature / adverse effects
Humidity / adverse effects
Lactation / genetics*
Milk / secretion*
Models, Genetic
Regression Analysis

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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