Please use this identifier to cite or link to this item: https://hdl.handle.net/1959.11/20932
Title: Daily methane emissions and emission intensity of grazing beef cattle genetically divergent for residual feed intake
Contributor(s): Velazco, J I (author); Herd, Robert M  (author)orcid ; Cottle, David  (author)orcid ; Hegarty, Roger  (author)
Publication Date: 2017
DOI: 10.1071/an15111
Handle Link: https://hdl.handle.net/1959.11/20932
Abstract: As daily methane production (DMP; g CH₄/day) is strongly correlated with dry matter intake (DMI), the breeding of cattle that require less feed to achieve a desired rate of average daily gain (ADG) by selection for a low residual feed intake (RFI) can be expected to reduce DMP and also emission intensity (EI; g CH₄/kg ADG). An experiment was conducted to compare DMP and EI of Angus cattle genetically divergent for RFI and 400-day weight (400dWT). In a 6-week grazing study, 64 yearling-age cattle (30 steers, 34 heifers) were grazed on temperate pastures, with heifers and steers grazing separate paddocks. Liveweight (LW) was monitored weekly and DMP of individual cattle was measured by a GreenFeed emission monitoring unit in each paddock. Thirty-nine of the possible 64 animals had emission data recorded for 15 or more days, and only data for these animals were analysed. For these cattle, regression against their mid-parent estimated breeding value (EBV) for post-weaning RFI (RFI-EBV) showed that a lower RFI-EBV was associated with higher LW at the start of experiment. Predicted dry matter intake (pDMI), predicted DMP (pDMP) and measured DMP (mDMP) were all negatively correlated with RFI-EBV (P < 0.05), whereas ADG, EI, predicted CH₄ yield (pMY; g CH₄/kg DMI) were not correlated with RFI-EBV (P > 0.1). Daily CH₄ production was positively correlated with animal LW and ADG (P < 0.05). The associations between ADG and its dependent traits EI and pMY and predicted feed conversion ratio (kg pDMI/kg ADG) were strongly negative (r = -0.82, -0.57 and -0.85, P < 0.001) implying that faster daily growth by cattle was accompanied by lower EI, MY and feed conversion ratio. These results show that cattle genetically divergent for RFI do not necessarily differ in ADG, EI or pMY on pasture and that, if heavier, cattle with lower RFI-EBV can actually have higher DMP while grazing moderate quality pastures.
Publication Type: Journal Article
Source of Publication: Animal Production Science, 57(4), p. 627-635
Publisher: CSIRO Publishing
Place of Publication: Australia
ISSN: 1836-0939
1836-5787
Field of Research (FOR): 070204 Animal Nutrition
Socio-Economic Outcome Codes: 960302 Climate Change Mitigation Strategies
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
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Appears in Collections:Journal Article
School of Environmental and Rural Science

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