Fecha/hora: 07/06/2024 15:35:43

Biblioteca(s): 	INIA La Estanzuela; INIA Las Brujas.	
Fecha corriente: 	21/02/2014	
Fecha de la última actualización: 	18/06/2019	
Autoria: 	PSZCZOLA, M.; AGUILAR, I.; MISZTAL, I.	
Afiliación: 	M. PSZCZOLA, Animal and Dairy Science Department, University of Georgia, United States; Animal Breeding and Genetics Group, Wageningen Institute of Animal Sciences, Wageningen University, Netherlands; IGNACIO AGUILAR GARCIA, INIA (Instituto Nacional de Investigación Agropecuaria), Uruguay; I. MISZTAL, Animal and Dairy Science Department, University of Georgia, United States.	
Título: 	Short communication: Trends for monthly changes in days open in Holsteins.	
Año de publicación: 	2009	
Fuente/Imprenta: 	Journal of Dairy Science, 2009, 92 (9): 4689-4696. OPEN ACCESS.	
ISSN: 	0022-0302	
DOI: 	10.3168/jds.2008-1985	
Idioma: 	Inglés	
Notas: 	Article history:  Received December 17, 2008. // Accepted May 5, 2009.	
Contenido: 	ABSTRACT.
A reaction norm approach was used to estimate trends for days open (DO) with a model that indirectly accounted for heat stress. Data included 3.4 million first-parity records of DO of US Holsteins. A fixed effect model included herd-year, month of calving within region (MOC), age class, and regression on 305-d milk yield. An index calculated from the standardized solutions to MOC derived from the fixed effect model was treated as a proxy for an index on heat stress (SI). The lowest index for any region was set to zero. The highest index was 1.00 for the Southeast, 0.56 for the Northeast, 0.54 for the Midwest, 0.33 for the Northwest, and 0.42 for the Southwest. In all regions except the Northwest, the highest DO and the corresponding highest indices were in March-April. Compared with the fixed model, the reaction norm model also included the effect of an animal and a random regression on the SI; the 2 animal solutions are subsequently referred to as an intercept and a slope. Genetic trends were calculated for cows and sires separately. For cows, the trend for the intercept was -0.1 d/yr, whereas the trend for the slope was 1 d/yr. For sires, the same trends were -0.3 and 1.5, respectively. Official proofs were used to characterize the 100 top and 100 bottom bulls with at least 50 daughters for the intercept and the slope. Compared with the top bulls, the bottom bulls for the intercept gave 56 kg more milk and their type performance index was higher by 212 points. For the slope, the same numbers were -435 kg and -242 points, respectively. Trends for seasonal changes of days open are unfavorable. 
© American Dairy Science Association, 2009.	
Palabras-Clave: 	DAIRY CATTLE; DAYS OPEN; DÍAS ABIERTOS; ESTRÉS TÉRMICO; FERTILIDAD; FERTILITY; HEAT STRESS; REPRODUCCIÓN ANIMAL; VACAS LECHERAS; VACAS VACÍAS.	
Thesagro: 	GANADO LECHERO.	
Categoría del tema: 	--
L53 Fisiología Animal - Reproducción	
URL: 	http://www.ainfo.inia.uy/digital/bitstream/item/12195/1/Pszczola-M.-2009.-Jr.Dairy-Science.pdf	
Registro original: 	INIA Las Brujas (LB)	
Ejemplares: 	LB - (12835-1) - PXI - AP - DD - PP/JR. DAIRY SCIENCE/2009 -  -  - DIS