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Reducing enteric methane emissions from ruminants

Reducing enteric methane emissions from ruminants


Development of methane mitigation strategies for ruminant production systems in the tropical and sub-tropical regions of South Africa.


Industry Sector: Cattle and Small Stock

Research focus areas: Sustainable natural resource utilization, Livestock production with global competitiveness

Research Institute: Bureau for Food and Agricultural Policy (BFAP), University of Pretoria

 
Researcher: Prof W.A van Niekerk

Research Team: Mr. C.J.L Du Toit MSc, Dr. H.H Meissner PhD, Prof L Erasmus PhD

Final report approved: 21 April 2015

Aims of the project

  • To determine the methane production from a range of South African pasture species that represent those utilised in rural and commercial ruminant production systems
  • To investigate the extent to which specific pasture components affect enteric methane emissions
  • To identify nutritional supplements that will reduce methane production from tropical grasses
  • To quantify the in vivo enteric methane production from sheep fed tropical pastures using respiration chambers

Executive Summary


Quantifying methane emissions from South African rangelands will enable researchers to develop decision support models which can form part of greenhouse gas mitigation strategies. South Africa is required by the Kyoto protocol to reduce national greenhouse gas emissions. If the methane production potential of South African forages can be accurately predicted it would be possible to manage methane emissions in animal production systems through the choice of pasture species and strategic supplementation and thus increase productivity and profitability. The loss of methane not only contributes to our changing climate, but also presents an opportunity to better efficiency gains in South African agricultural production systems. 

The overall objective of the project was to employ the in vitro gas production technique to identify practical methods to mitigate enteric methane emissions appropriate to South African pasture-based production systems. 

The aims of the project were to (i) determine the methane production from a range of South African pasture species that represent those utilised in rural and commercial ruminant production systems and (ii) to investigate the extent to which specific pasture components affect enteric methane emissions and (iii) to quantify the in vivo enteric methane production from sheep fed tropical pastures using respiration chambers.

The chemical composition and in vitro CH4 emission potential of the selected grass species harvested during the project indicated variation between grass species. This presents an opportunity to select grass species that have high nutritional quality and lower CH4 emissions potential. Physiological maturity had a negative effect on grass quality, with cellulose and lignin content (ADF) peaking during the early bloom stage of both tropical and temperate grass species. The application of nitrogen fertiliser increased grass quality with the CP concentration in temperate grass species showing the highest response to nitrogen fertilisation. The low level of crude protein at maturity beyond the vegetative stage of tropical grasses would make it essential to supplement ruminants grazing these grasses with protein for improved rumen fermentation.

The results of this study is only based on one season and further research is needed to describe the changes in chemical composition, feeding values and methane production potential between seasons. Improved grazing management, cultivation of improved grass species and pasture fertilization are possible options to reduce methane emissions from ruminants grazing tropical grasses. 

Additional comments: Due to constraints experienced throughout the project as described in the last project progress report project aims 2 and 3 could not be finalized. There are still nutrient analyses outstanding from experiment 2a and 2b. The University of Pretoria is experiencing problems with the operation and accuracy of methane measuring equipment. All project aims will be met by the end of 2015.



Please contact the Primary Researcher if you need a copy of the comprehensive report of this project –
Willem van Niekerk on willem.vanniekerk@up.ac.za