| Short communication: genetic trends of milk yield under heat stress for US Holsteins. | |
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MedLine Citation:
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PMID: 20338455 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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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. |
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Authors:
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I Aguilar; I Misztal; S Tsuruta |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Journal of dairy science Volume: 93 ISSN: 1525-3198 ISO Abbreviation: J. Dairy Sci. Publication Date: 2010 Apr |
Date Detail:
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Created Date: 2010-03-26 Completed Date: 2010-05-31 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 2985126R Medline TA: J Dairy Sci Country: United States |
Other Details:
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Languages: eng Pagination: 1754-8 Citation Subset: IM |
Copyright Information:
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Copyright (c) 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved. |
Affiliation:
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Animal and Dairy Science Department, University of Georgia, Athens 30602, USA. iaguilar@inia.org.uy |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Breeding Cattle / genetics*, physiology Cattle Diseases / genetics* Female Heat Stress Disorders / genetics, veterinary* Hot Temperature / adverse effects Humidity / adverse effects Lactation / genetics* Milk / secretion* Models, Genetic Parity* Pregnancy Regression Analysis Seasons |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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