P.PSH.1351 | Efficacy and safety of Asparagopsis extract in a canola oil carrier for feedlot cattle

Summary

Asparagopsis taxiformis (Asparagopsis) has been shown to be highly efficacious at inhibiting the production of methane (CH4) in ruminants. To date, Asparagopsis has been produced as a dietary supplement by freeze-drying to retain the volatile bioactive compound bromoform (CHBr3) in the product. Extraction of Asparagopsis bioactive compounds in a vegetable oil solvent (Asp-Oil) is an alternative method of stabilising Asparagopsis as a ruminant feed additive. For Asp-Oil to be further commercialised and incorporated into National Greenhouse Gas Inventory methods, it must be demonstrated to be safe (for animals and consumers of product) and efficacious at inhibiting CH4 production.

The aim of this project was to provide critical knowledge on the CH4 reduction efficacy and safety of Asp-Oil, and elucidate the minimum effective inclusion level in feedlot diets.

Objectives

The objectives of this project were to determine the effect of an Asparagopsis extract in a
canola oil carrier (Asp-Oil) on:

• Enteric CH4 production of feedlot cattle (using respiration chambers as the emissions
  monitoring technique).
• Rumen temperature, rumen pH and redox potential, rumen volatile fatty acids and
  ammonia, thyroid hormone production (T3 & T4), blood haematology, blood iodine and
  bromine, haptoglobin and cortisol.
• Gross rumen pathology at slaughter as assessed by trained veterinary pathologists. Histopathology on all trial animals.
• Concentrations of bromoform, iodide and bromide in carcase and offal depots.
• Shear force and MSA sensory evaluation of striploins.
• Inform industry partners regarding the food safety aspects of feeding Asp-Oil to cattle.

Key findings

This project measured the CH4 reduction potential and safety of Asparagopsis extract in oil (Asp-Oil) in a trial with 20 Angus heifers, fed feedlot diets containing one of three levels of Asp-Oil to deliver the corresponding bromoform inclusion levels or a control oil with no bromoform.

• Compared to the control, the bromoform inclusion levels of 17, 34, and 51 mg/kg (Low, Med, High) reduced CH4 yield (g CH4/kg DMI) by 54.5, 85.2, and 95.0%, respectively.
• There were no effects on animal production or carcase characteristics.
• There were no impacts on animal health, welfare or rumen function.
• Carcase samples contained levels of iodine and bromide that were either not different compared to the control or were safe for human consumption, and there was no bromoform detected in any carcase samples.
• Overall, Asp-Oil was found to be effective for reduction of CH4 emissions and safe for animals and consumers of meat and edible offal.

Benefits to industry

This project has provided a dataset on product safety and efficacy for stakeholders considering adoption of asparagopsis.

MLA action

MLA is committed to supporting R&D on a range of methane suppressing feed additives aligned with the CN30 initiative.

Future research

Whilst the current project was adequate to look at product safety and methane reduction efficacy, larger trials are required to detect any productivity effects.

Future research is required by the commercialisers of asparagopsis under replicated pen conditions to determine the effects of asparagopsis on feedlot performance, carcase characteristics and feeding profit/loss. The Federal Government MERIL grants program is currently funding multiple asparagopsis productivity trials.