Can white clover inclusion lower sheep methane emissions?

Methane is the primary greenhouse gas of concern for ruminant production systems globally, but research conducted at the Animal and Grassland Research and Innovation Centre, Teagasc Athenry, has shed new light on the potential of white clover inclusion in sheep diets to reduce its production.

Completed by Sarah Woodmartin as part of the Teagasc Walsh Scholarship Programme with Teagasc and University College Dublin, the paper stemming from this research: ‘Sward type alters enteric methane emissions, nitrogen output and the relative abundance of the rumen microbial ecosystem in sheep’ has recently been accepted into the Journal of Animal Science.

Given the increased interest in diverse swards – i.e. swards consisting of more than just perennial ryegrass monocultures – the study aimed to investigate the effect of including legumes, such as white or red clover, and herbs, such as chicory or plantain, on enteric methane output and nitrogen excretion in sheep. Alongside this, the ruminal microbiota and the fermentation profile of the rumen were also investigated.

Through the study, Belclare wethers were offered one of five diets: 100% perennial ryegrass; 75% perennial ryegrass and 25% white clover; 75% perennial ryegrass and 25% red clover; 75% perennial ryegrass and 25% chicory; and 75% perennial ryegrass and 25% plantain. All diets were fed through zero-grazing and formulated to 100% on the basis of dry matter.

To identify the differences, if any, in methane production (g/day) and methane yield (g/kg dry matter intake) between the different forage treatments, portable accumulation chambers were used. From this, it was found that animals consuming the perennial ryegrass and white clover swards ranked lower for methane production (g/day) when compared to sheep offered perennial ryegrass, perennial ryegrass and chicory, and perennial ryegrass and plantain swards.

Additionally, the study looked at the urinary nitrogen concentration of sheep consuming the various swards. Some of the key results show that herb diets (perennial ryegrass and chicory, and perennial ryegrass and plantain) reduced urinary nitrogen concentration of sheep by an average of 34% compared to legume diets (perennial ryegrass and white clover, perennial ryegrass and red clover), and 13% relative to the perennial ryegrass only diet.  Sheep consuming the perennial ryegrass and chicory diet had an enhanced dietary nitrogen use efficiency over those consuming perennial ryegrass and red clover.

Commenting on the study and the positive results obtained in relation to methane emissions and urinary nitrogen concentrations, Sarah Woodmartin said: “Results from this study support the implementation of binary swards – swards consisting of perennial ryegrass plus white clover, red clover, chicory or plantain - as a viable strategy for mitigating emissions and nitrogen excretion from pasture-based sheep production systems. Future research should expand on the current study to select functionally designed swards, targeting mitigation of methane and urinary nitrogen simultaneously.”

For further information on this research, access the paper in the Journal of Animal Science here.