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Biblioteca(s): 	INIA Tacuarembó.	
Fecha corriente: 	11/09/2014	
Fecha de la última actualización: 	13/05/2020	
Autoria: 	DE BARBIERI, I.; HEGARTY, R.S.; ODDY, V.H.; BARNETT, M.C.; LI, L.; NOLAN, J.V.	
Afiliación: 	LUIS IGNACIO DE BARBIERI ETCHEBERRY, INIA (Instituto Nacional de Investigación Agropecuaria), Uruguay; ROGER S. HEGARTY, School of Environmental and Rural Science, University of New England, Trevenna Road, Armidale, NSW 2351, Australia; V. HUTTON ODDY, Beef Industry Centre, Department of Primary Industries NSW, Trevenna Road, Armidale, NSW 2351, Australia; MARK BARNETT, School of Environmental and Rural Science, University of New England, Trevenna Road, Armidale, NSW 2351, Australia; L. LI, School of Environmental and Rural Science, University of New England, Trevenna Road, Armidale, NSW 2351, Australia; JOHN V. NOLAN, School of Environmental and Rural Science, University of New England, Trevenna Road, Armidale, NSW 2351, Australia.	
Título: 	Sheep of divergent genetic merit for wool growth do not differ in digesta kinetics while on restricted intakes.	
Año de publicación: 	2014	
Fuente/Imprenta: 	Animal Production Science, May 2014, v. 54, no. 9, p. 1243-1247. DOI:  https://doi.org/10.1071/AN14319	
DOI: 	10.1071/AN14319	
Idioma: 	Inglés	
Notas: 	Received 12 March 2014; accepted 12 May 2014; published online 10 July 2014. Acknowledgements: The authors thank Evelyn Osborne, Jose Velazco, Alistair Donaldson, Carolina Silveira, Gary Cluley, Leanne Lisle, Sue Mortimer and Andrew Blakely for their technical support. Ignacio De Barbieri was supported by National Institute for Agricultural Research (INIA Uruguay).	
Contenido: 	Sheep selected for high wool growth were previously shown to exhibit higher microbial protein outflow from the rumen and higher uptake of amino nitrogen in portal blood than those selected for low wool growth. This suggests that genetic selection for wool growth may induce changes in foregut physiology. This study was undertaken to determine whether differences in digesta kinetics, especially mean retention mime (MRT), are associated with differences in fleece production between sheep with low or high estimated breeding values (EBVs) for fleece weight. Twenty mature Merino wethers with uniform EBVs for liveweight were allocated to two groups of 10 animals on the basis of high or low EBVs for yearling fleece weight. Five sheep with low-EBVs and five sheep with high-EBVs for fleece weight groups were allocated in a crossover design to low and high feeding-level treatments, which comprised a blended hay diet fed at maintenance or 1.5 times maintenance. All sheep were given single doses of chromium-mordanted fibre and cobalt-EDTA as inert, non-digestible markers. Digesta kinetics was determined by analysis of the faecal marker excretion patterns using
a compartmental model. Higher feed intakes from animals fed 1.5 times maintenance were associated with higher rates of wool growth and higher masses of indigestible fibre in the gut, but reduced MRT of digesta. Although sheep with higher EBVs for fleece weight had higher wool growth rates, there was no indication that these wool growth differences were associated with differences in digesta kinetics. The lack of interaction between feeding level and genotype suggests that MRT did not contribute to genotype differences in wool growth in sheep fed restricted intakes. The differences in wool growth among commercial Merino sheep with divergent fleece weight EBVs achieved by multi-trait selection are not attributable to differences in digesta kinetics, at least when feed is not available ad libitum.	
Palabras-Clave: 	ESTIMATED BREEDING VALUES; FEED INTAKE; FLEECE WEIGHT; MEAN RETENTION TIME.	
Thesagro: 	OVINOS.	
Categoría del tema: 	L01 Ganadería	
Registro original: 	INIA Tacuarembó (TBO)	
Ejemplares: 	TBO - (100040-1) - PXI - AP - PP - PP/ANIMAL PRODUCTION SCIENCE/2014 -  -  - DIS