Fecha/hora: 23/05/2024 04:40:13

Biblioteca(s): 	INIA Las Brujas.	
Fecha corriente: 	21/02/2014	
Fecha de la última actualización: 	04/11/2019	
Autoria: 	AGUILAR, I.; MISZTAL, I.; TSURUTA, S.	
Afiliación: 	IGNACIO AGUILAR GARCIA, Instituto Nacional de Investigación Agropecuaria (INIA), Uruguay; I. MISZTAL, Animal and Dairy Science Department, University of Georgia,United States; S. TSURUTA, Animal and Dairy Science Department, University of Georgia,United States.	
Título: 	Short communication: Genetic trends of milk yield under heat stress for US Holsteins.	
Año de publicación: 	2010	
Fuente/Imprenta: 	Journal of Dairy Science, 2010, v.93, no.4, p. 1754-1758.	
DOI: 	10.3168/jds.2009-2756	
Idioma: 	Inglés	
Notas: 	Article history: Received September 21, 2009. /  Accepted December 4, 2009.	
Contenido: 	ABSTRACT.

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°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. 
© 2010 American Dairy Science Association.	
Thesagro: 	ESTRES CALORICO; GANADO LECHERO.	
Categoría del tema: 	L01 Ganadería	
URL: 	http://www.ainfo.inia.uy/digital/bitstream/item/3652/1/Aguilar-I.-2010-Jr.Dairy-Sc.v.93-p.1754-1758.pdf	
Registro original: 	INIA Las Brujas (LB)	
Ejemplares: 	LB - (12836-1) - PXI - AP - DD - PP/JR.DAIRY SC./2010 -  -  - DIS