Building on the dietary supplements research undertaken in PICCC's earlier enteric methane project, this study focused on a range of novel supplements and forages that contain compounds reported to mitigate methane production.
The research aimed to quantify the impacts of various feed options on both methane emissions and animal production.
Researchers studied methods for integrating novel feed supplements, pasture forages and pre-treatment techniques of cereal based grains into feeding systems for livestock in southern Australia, quantifying the impacts on both methane emissions and animal production.
The team are also examined pre-treatment techniques of existing dietary supplements to reduce digestion in the rumen (and hence methane production) and allow digestion further down the intestinal tract, so that there is no impact on animal production.
In vitro and in vivo methodologies were used to elucidate the potential of feeding and management strategies to mitigate methane emissions. This allowed for rapid screening of potential material, plus detailed studies using in vitro techniques and subsequent selection of the most promising options for feeding studies using dairy cattle and sheep.
In vitro studies compared methane production from i) a range of perennial and summer-active annual forages collected over summer, ii) different pasture forages (plantain, chicory and perennial ryegrass) collected at six different dates between June and December 2012, and iii) wheat grain treated with BioProtect, to determine whether it reduces the rate of fermentation of wheat grain and therefore reduces methane emissions.
The first in vivo experiment compared methane production from dairy cows offered different amounts of crushed wheat: 0, 3, 6 or 9 kg DM. Total methane production and milk yield were measured to enable quantification of the effects on both productivity and emissions intensity. Subsequent studies have examined the effect of almond hulls and citrus pulp, different grape marc products, and chicory or plantain, using dairy cows at various stages of lactation.
In vitro studies
The comparison of perennial and summer-active annual forages showed that in vitro methane production reflected differences in nutrient availability, with maximum gas produced in forages containing more fermentable organic matter. The comparison of different forages harvested at different times over winter, spring and summer indicated that pasture species has a greater influence on amount of gas produced than did date of harvest. Meanwhile, treatment of wheat grains with BioProtect reduced the rate of gas production, with eight litres per tonne found to be the optimum dose rate.
Studies have been conducted on grape marc products ranging from whole grape marc derived from different grape varieties, through to seeds and stalks. The results have shown marked differences in gas production between the different products, and when tested in combination with different forages, the volume of methane produced was higher from chicory than from perennial ryegrass and hay.
In vivo studies
In the dairy in vivo experiments, wheat feeding was shown to substantially reduce dairy methane emissions in one study but had little effect in a subsequent experiment, indicating that further research is needed to understand the mechanisms and circumstances under which wheat will reduce methane production.
The team also found that grape marc products caused a reduction in total methane emissions and methane yield from dairy cows, and while there was an associated reduction in milk production, methane emissions intensity was also reduced. Other supplements tested included citrus pulp, almond hulls, chicory and forage brassica. The former three made no difference to methane emissions or intensity, while forage brassica reduced emissions intensity compared to a hay-based control diet.
In vivo experiments with sheep highlighted that methane production is influenced by the type of diet fed, although some of the feeds hypothesised to reduce methane emissions were not as successful as anticipated. This information is important to Australian producers as it further validates that methane production can be altered using dietary manipulations.
The research has resulted in significant refinements to a number of emissions measurement methodologies. In particular, the research undertaken in this project has resulted in significant refinements to the sulphur hexafluoride methodology, with this technique now being adopted by a range of international collaborators. The improvements have resulted in more cost effective research and greater confidence in the data being generated.
Further methane mitigation research is required, with larger sample sizes over longer periods, to determine if observed responses from the more promising strategies are consistent and maintained. Further research is also required on complementary strategies, where various successful mitigants are fed in combination (e.g. wheat, forages, grape marc) to determine if there are further benefits through synergistic additivity effects.
|Methane mitigation in livestock fact sheet||Fact sheet profiling the project 'Enteric methane mitigation strategies through manipulation of feeding systems for ruminant production in southern Australia'.|
|Methane publications||A bibliographic survey of research publications produced by PICCC's enteric methane projects.|
|Wheat boosts milk yield||The Weekly Times||25 October 2013|
|Reducing methane from dairy cows: it’s all in the oil||The Conversation||22 March 2013|
|Decades away from solution to animal emissions||ABC Radio Australia||7 December 2012|