Methane emissions of Australian feedlot cattle as influenced by 3-Nitrooxypropanol (Bovaer-10)

Summary

This project determined the effect of increasing diet concentration of 3-Nitrooxypropanol (3-NOP; Bovaer®, DSM) on methane (CH4) emissions and rumen fermentation patterns of cattle fed typical Australian feedlot diets. It also evaluated the current baseline CH4 prediction-equations for feedlot cattle in the Australian Government GHG accounting framework. Australian National Greenhouse Accounts uses the Moe & Tyrell (1979) methane calculation methodology for inventory purposes, whereas countries such as the United States utilise the IPCC Tier 2 methodology for estimating feedlot emissions. A comparison of the two methods is required. Overall, Bovaer-10 was a highly efficacious feed additive for decreasing methane emissions of Australian feedlot cattle. Validation of the current and an alternative model for predicting CH4 emissions of feedlot cattle demonstrated that the National Inventory currently overpredicts the contribution of feedlot finishing of cattle to Australia’s Greenhouse Gas (GHG) emissions.

Objectives

(1) Determine the effect of 3-NOP titration regimen on rumen fermentation and methane emissions during starter- and finishing phases in beef cattle.
(2) Validate current methods for predicting methane production of feedlot cattle, including the Moe and Tyrrell equations and the IPCC Tier 2 methodology.

Key findings

• 3-NOP supplemented from 50 to 125 of mg 3-NOP/kg DM to Australian finishing diets containing 25 ppm of monensin and 7% fat (DM-basis) can reduce both production and yield of CH4 by up to 99%.
• All 3-NOP titration regimens significantly reduced methane production and methane yield of feedlot cattle from d 21 to 112.
• The optimal methane suppression was obtained by feeding 50 mg/kg DM from d 0 to 7, 75 mg/kg DM from d 8 to 14, 100 mg/kg from d 15 to 112; with reductions in methane yield (g/kg) and emissions (g/d) by 61 to 99% in the finishing phase. For the overall feeding period, methane emissions (g/d) was 78% lower for this regimen compared with control.
• Although this experiment was not designed to make conclusions on an effect of 3-NOP on feedlot performance (cattle were limit fed to 2.7 x maintenance; 4 steers per regimen) no negative effects of 3-NOP diet supplementation on the animal performance parameters measured were observed.
• The current equation used to predict methane emissions from feedlot cattle in the Australian National Inventory, from Moe and Tyrrell (1979), resulted in substantial overprediction of CH4 by 95.5 g/day when tested against observed CH4 emissions from the control cattle in this trial. An alternative equation, from IPCC (2006), predicted CH4 production from control group cattle accurately and is more appropriate than Moe and Tyrrell (1979) for the diets tested, which are typical of the white-grain, high-fat diets of the Australian feedlot industry.

Benefits to industry

Supplemental 3-NOP in white-grain and high-fat finishing diets can allow Australian feedlots to produce low-methane-emission beef from the grain-finishing phase. It has also demonstrated that there is a low baseline level of CH4 production from feedlot diets tested during this project.

Ultimately, the knowledge on the CH4 suppression pattern of 3-NOP may facilitate sustainable pathways for the feedlot industry as well as enabling Australian producers to benefit from carbon credit trading schemes.

Validation of the current and an alternative model for predicting CH4 emissions of feedlot cattle demonstrated that the National Inventory currently overpredicts the contribution of feedlot finishing of cattle to Australia’s Greenhouse Gas (GHG) emissions.

MLA action

The results of this research have been extended to:
- The Australian Lot Feeders' Association Moving toward Carbon Neutrality webinar - 12 May, 2021.
- ALFA/MLA Consulting Veterinarian and Nutritionist meeting - October, 2021.

Future research

MLA is currently investing in a number of projects to evaluate the efficacy of Bovaer-10 to improve feedlot cattle performance (P.PSH.1375) and reduce backgrounding emissions (B.FLT.5015).