Innovative livestock systems to adapt to climate change and reduce emissions

Summary

We have demonstrated that sheep produce less methane from some pasture species than others.  Biserrula reduces methane emissions more than other legumes when fed to animals in the animal house and this effect is greater when it was fed as fresh pasture compared to hay. Our results from testing different legumes in the laboratory reflected these results in the animal house, but we did not find a significant direct reduction in methane emissions in the field.  

The most consistent, key, driver of methane and animal productivity in this project, was pasture quality. High digestibility and low fibre feed reduced methane yields and methane intensity and increased productivity. We have some evidence that a “choice” pasture can improve rumen efficiency compared to ryegrass pasture alone, which was reflected in higher daily live weight gains in the sheep, but not in methane intensity. In addition, legume-based pastures provide an option to increase growth rates and decrease methane emissions (total and emissions intensity) during a period when perennial ryegrass pastures are declining in nutritive value.  Our greatest challenge has been to demonstrate the differences we predicted from the laboratory and animal house experiments in grazing animals.  We think the variability in timing of grazing and grazing behaviour of animals prior to measurement may well be masking the differences that exist in the field.

Key findings

Our results show that farmers should be able to make better choices of pasture species to reduce emissions and emissions intensity in grazing livestock without reducing productivity, but that it is difficult to demonstrate the effects on methane emissions in-field.  The clearest message for producers and policy makers is emphasising the importance of managing pastures and grazing techniques to maintain the highest quality of feed, because it improves rumen efficiency and animal productivity and ultimately improves emissions intensity. The bio-economic modelling showed that the critical control points that would provide the largest industry gains (eg. lamb survival, survival post-weaning) were traits that could be influenced by genetic selection and improved feed management. 

Based on the results and modelling in this project it is possible that a systems-based methodology, similar to the beef cattle herd management method that uses change in emissions intensity multiplied by level of production as the basis of calculating the reduction in emissions, could offer the potential for sheep farmers to be involved in the ERF and to concurrently increase profit. The difficulties we faced in demonstrating the reduction in emissions we predicted should occur in the field based on our animal house work, means there are three main questions that remain only partially answered; 1)  does Biserrula have the potency to reduce methane emissions in commercial farming scenarios; 2) can a “choice” pasture reduce methane intensity and; 3) what is the ability of Biserrula to reduce methane emissions while maintaining animal performance when used as a “choice” pasture. 

Future research

We are confident that the different effects that pasture species are having on methane emissions are real, but more work needs to be done in the methodology around determining those effects in-field.