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Biblioteca(s): 	INIA Treinta y Tres.	
Fecha corriente: 	27/11/2020	
Fecha de la última actualización: 	22/02/2021	
Autoria: 	HERD, R.M.; ARTHUR, P.F.; HEGARTY, R.S.; BIRD-GARDINER, T.; DONOGHUE, K.A.; VELAZCO, J.I.	
Afiliación: 	NSW Department of Primary Industries, Livestock Industry Centre.  Environmental and Rural Science, University of New England, Australia.; NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute; Environmental and Rural Science, University of New England.; NSW Department of Primary Industries, Agricultural Research Centre. Australia; NSW Department of Primary Industries, Agricultural Research Centre. Australia; JOSÉ IGNACIO VELAZCO DE LOS REYES, INIA (Instituto Nacional de Investigación Agropecuaria), Uruguay.	
Título: 	Predicting metabolisable energy intake by free-ranging cattle using multiple short-term breath samples and applied to a pasture case-study.  (Article in Press)	
Año de publicación: 	2020	
Fuente/Imprenta: 	Animal Production Science, 4 Nov. 2020, 61(4), p. 381-389  Doi: https://doi.org/10.1071/AN20162	
DOI: 	10.1071/AN20162	
Idioma: 	Inglés	
Notas: 	Article history: Received 3 April 2020, accepted 11 October 2020, published online 4 November 2020.	
Contenido: 	Context. Research into improving feed efficiency by ruminant animals grazing pastures has historically been restrained by an inability to measure feed intake by large numbers of individual animals. Recent advances in portable breath measurement technology could be useful for this purpose but methodologies need to be developed.
Aims. To evaluate predictive models for metabolisable energy intake (MEI) by free-ranging cattle using multiple short-term breath samples and then apply these to predict MEI by free-ranging cattle in a historic grazing experiment with cattle genetically divergent for residual feed intake (feed efficiency).
Methods. Predictive models for MEI were developed using bodyweight (BW) data, and carbon dioxide production rate (CPR) and methane production rate (MPR) from multiple short-term breath measurements, from an experiment with long-fed Angus steers on a grain-based diet, and an experiment with short-fed Angus heifers on a roughage diet.
Heat production was calculated using CPR and MPR. Energy retained (ER) in body tissue gain by steers was calculated from BW, ADG, initial and final subcutaneous fat depths, and for both groups using feeding-standards equations.
Key results. Metabolic mid-test BW (MBW) explained 49 and 47% of the variation in MEI in the steer and heifer experiment, respectively, and for the steers adding ADG and then subcutaneous fat gain resulted in the models accounting for 60 and then 65% of the variation in MEI. In the steer experiment, MBW with CPR explained 57% of the variation in MEI, and including MPR did not account for any additional variation. In the heifer experiment, MBW with CPR explained 50%, and with MPR accounted for 52% of the variation in MEI. Heat production plus ER explained 60, 35 and 85% of the variation in MEI in the steer and the heifer experiments, and in the pooled data from both experiments, respectively.
Conclusions. Multiple short-term breath measurements, together simple BW data, can be used to predict MEI by free-ranging cattle in studies in which animals do not have feed-intake or ADG recorded.
Implications. This methodology can be used for research into improving feed efficiency by farm animals grazing pastures.	
Palabras-Clave: 	AVERAGE DAILY GAIN; CARBON DIOXIDE; FEED EFFICIENCY; FEED INTAKE; GRAZING; METABOLISABLE ENERGY INTAKE; METHANE; METHANE PRODUCTION RATE; OXYGEN; PASTURE.	
Categoría del tema: 	L02 Alimentación animal	
Registro original: 	INIA Treinta y Tres (TT)	
Ejemplares: 	TT - (103152-1) - PXI - AP - DD - PP/ANIMAL PRODUCTION SCIENCE/2020 -  -  - DIS