Energy relations in cattle can be quantified using open-circuit gas-quantification systems

Autor:	Wayne S. Pitchford, P. I. Hynd, S. J. Lee, M. J. Wilkes, Mariana Caetano
Rok vydání:	2018
Předmět:	0301 basic medicine 0402 animal and dairy science 04 agricultural and veterinary sciences Beef cattle 040201 dairy & animal science Energy requirement Respiratory quotient 03 medical and health sciences Rumen chemistry.chemical_compound 030104 developmental biology Animal science chemistry Grazing Carbon dioxide Energy density Animal Science and Zoology Carbon dioxide output Food Science Mathematics
Zdroj:	Animal Production Science. 58:1807
ISSN:	1836-0939
Popis:	This study was conducted to evaluate the relationships between metabolisable energy (ME) intake and outputs of methane (CH4), rumen-derived carbon dioxide (rCO2), lung-derived carbon dioxide (lCO2), and total carbon dioxide output (tCO2) measured using an open-circuit gas-quantification system (GQS). Three trials were conducted to produce a wide range of energy intake and gas emissions to allow relationships between gas outputs and ME intake to be quantified. Gas emissions and ME intake were measured in eight Angus steers (455 ± 24.6 kg initial bodyweight; Trials 1 and 2), and in eight pregnant Angus heifers (503 ± 22.0 kg initial bodyweight; 5 months pregnant; Trial 3). Animals were fed twice daily to allow ad libitum intake in Trial 1, whereas in Trials 2 and 3, feed intake was restricted and energy density was varied to provide a wide range of ME intakes. Animals were allocated to individual pens during a 20-, 19- and 15-day experimental periods, and total faecal output was measured for the last 8, 4 and 4 days in Trials 1, 2 and 3 respectively. Gas emissions were measured for 16, 8 and 8 days after the adaptation period (4, 11 and 7 days) and each animal was allowed to visit the GQS every 2 h. Total CO2 in breath (tCO2) was separated into CO2 arising from rumen fermentation (rCO2) and CO2 in expired air from the lungs (lCO2) by manually identifying the eructations from normal breaths using the GQS gas-output trace. All CO2 outputs (lCO2, rCO2 and tCO2) were highly correlated with each other (r = 0.74–0.99; P < 0.01). Measurement of CO2 output was more repeatable with fewer days of measurement than was CH4 output. Metabolisable-energy intake was closely related to all three measures of CO2 output (rCO2, r = 0.69, P < 0.001; lCO2, r = 0.70, P < 0.001; and tCO2, r = 0.73, P < 0.001). Heat production was estimated from lCO2 output by assuming a value of 0.85 for the respiratory quotient of metabolised products. The heat production estimated at the extrapolated zero ME intake (0.52 MJ/kg0.75) was 60% higher than previous estimates of fasting heat production in cattle. However, our estimate was made under non-fasting, non-sedentary, non-thermoneutral conditions, so it may be a realistic estimate of maintenance energy requirement excluding heat increment of feeding. In conclusion, the open-circuit GQS can be used to provide estimates of the ME intake and heat production of cattle, and, as such, provides a valuable opportunity to describe the energy relations and efficiency of beef cattle in the field, with minimal interference to normal grazing patterns and behaviour.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::7cd393b4fae829f0b8993f4ca46b8191 https://doi.org/10.1071/an16745 Zobrazit plný text záznamu Plný text ve formátu PDF Plný text ve formátu HTML
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