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Non-Nutritive Feed Additives: Ionophores

alternative practice names:

Methane Inhibitors; Rumen Modifiers; Non-Nutritive Supplements; Ionophores (e.g., Rumensin®); Monensin

Feed additives are optional ingredients that are not nutrients but can affect digestion, metabolism, and production. They alter the metabolic pathways of the rumen environment to illicit some improvement in health status or feed efficiency. A litany of these additives exists in the market, all of which claim different modes of action and their efficacy on the animal when fed. 


One well-researched feed additive, ionophores, has demonstrated improvements in feed efficiency by suppressing the growth of certain populations of bacteria in the rumen. Ionophores improve feed conversion efficiency and milk yield by selectively inhibiting the growth of gram-positive bacteria rumen microbes. As a secondary benefit, many of these additives may reduce absolute enteric methane emissions and lower emission intensity by altering the microbial fermentation processes in the rumen.

When used, in what regions in the U.S. is the practice found: 

Northwest, West, Upper Midwest, Southwest, Northeast, Southeast

FARM SIZE 

When used, typically found on farms of the following sizes:

All Sizes

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Practice Benefits 

Enhanced feed efficiency: Ionophores like monensin are commonly used in dairy diets to improve feed efficiency. Research supports that ionophores can reduce dry matter intake (DMI) while maintaining or slightly improving milk yield, enhancing feed efficiency. By inhibiting specific rumen microbes, ionophores shift fermentation to favor propionate, which boosts the cows' energetic status and benefits milk production. It is also observed that ionophore-fed cows may eat smaller, more frequent meals, stabilizing rumen fermentation. While these effects are generally supported, responses can vary based on herd conditions, diet, and management practices. Overall, ionophores effectively increase the energy cows extract from their feed, enabling similar or higher milk production with reduced feed intake.

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Implementation Insights

Site-specific or Farm-specific requirements 

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In most cases, there are no specific site or farm requirements.

Required Capital Expenditures (CapEx)

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  • Infrastructure: Feed additives typically make up no more than 1% of the total mixed ration (TMR); most are incorporated into a feed supplement by a feed mill. In some cases, implementing the practice of feeding feed additives may necessitate minor infrastructure changes, such as upgrading feed storage facilities or delivery systems to handle the new additives.

Required Operational Expenditures (OpEx)

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  • Ongoing feed additive costs: The primary ongoing cost of ionophores is the recurring expense of purchasing them. These costs vary based on the type of additive, the required dosage, and the herd size. While the cost of individual additives may appear small, the cumulative expense can become considerable, particularly for larger operations that need substantial quantities.

  • Labor and management costs: Ionophores are typically obtained by the farm as part of a feed supplement made by a feed mill, making them simple to add to the diet. However, if added directly on the farm, feed additives can increase labor costs due to the need for precise measurement, mixing, and monitoring of additive use. Dairy farms may require additional training for staff to ensure the correct application of these additives, further increasing operational expenses.

Implementation Considerations

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  • Precision in application: Implementing the practice of feeding feed additives requires precise application to achieve the desired outcomes without negative side effects. This precision demands careful dosage calculation and consistent monitoring, adding complexity to the management of dairy operations unless the additive is obtained by the farm as part of a feed supplement made by a feed mill. 

  • Management and training: Successful implementation of feed additives often requires additional training for farm staff to understand the benefits and proper usage of these products unless the farm obtains the additive as part of a feed supplement made by a feed mill.

Financial Considerations and Revenue Streams

PROFIT POTENTIAL

If the rumen modifier results in less dietary energy lost in the form of enteric methane, cows should obtain more energy from their diet to increase “feed efficiency” and profit for the dairy producer. However, the actual impact on feed costs depends on the cost of the additives themselves, the specific feed savings achieved, and other factors like herd management and feed quality.


CARBON MARKETS

This practice is commonly credited in carbon markets. The practice can generate both offset and inset credits.

Notes:  

  • Producers may be required to have 2-3 years of herd records prior to the start of a project. Methane reductions are calculated using researched emissions factors or direct monitoring of methane emissions on site.   

  • Producers need to integrate a new feed ingredient that has proven to result in reduced methane emissions. Eligible feed ingredients cannot already be commonly integrated into feed rations.

  • This practice is usually credited over 7- to 10-year crediting periods, but there is generally no risk of "reversing" emissions (see Verra and Gold Standard methodologies).

  • Depending on the efficacy of available feed additives, the expected credit volume is typically between 0.1-0.4 tons per head per year (Gadberry et al., 2002), though higher efficient feed additives are currently in the testing phase.

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Environmental Impacts

MAY REDUCE GREENHOUSE GAS EMISSIONS
The ability of feed additives to reduce greenhouse gas (GHG) emissions from dairy farms largely depends on the farm’s basal diet and management practices. Although current evidence on the effectiveness of most additives in reducing methane emissions is weak, ionophores stand out with strong evidence for improving feed efficiency and lowering emissions intensity, including both enteric methane and upstream emissions from reduced feed cultivation. By altering fermentation in the rumen, ionophores may improve feed conversion efficiency. This lowers feed requirements, boosts production, and, in turn, results in reduced GHG emissions per unit of milk produced (emission intensity) (Duffield et al., 2008). Ionophores may also directly suppress the growth of methanogens in the rumen, leading to an overall reduction in absolute methane emissions (Appuhamy et al., 2013).


See research highlights below: 

  • The meta-analysis by Appuhamy et al. (2013) reported an average decrease in total CH₄ production of 3.6% in dairy cows.

  • Arikan et al. (2018) found that the inclusion of monensin in dairy cow diets did not affect manure CH₄ production.

  • Guan et al. (2006) found that ionophore supplementation (monensin or a rotation with lasalocid) reduces enteric methane emissions in cattle by 27-30% during the first 2-4 weeks. However, this reduction is temporary, as rumen protozoa, which influence methane production, adapt over time. Rotating ionophores did not extend the methane reduction period or improve outcomes compared to monensin alone, indicating limited long-term effectiveness due to microbial adaptation.

REFerences

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Alignment with FARM Program

FARM Environmental Stewardship (ES) V2-V3 Alignment

FARM ES Version 3 allows users to specify the use of certain methane-reducing feed additives: Monensin.

Contents

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We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights. 

We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights. 

Contents

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Practice Overview

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Practical Insights.png
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Research Results.png
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Feed additives are optional ingredients that are not nutrients but can affect digestion, metabolism, and production. They alter the metabolic pathways of the rumen environment to illicit some improvement in health status or feed efficiency. A litany of these additives exists in the market, all of which claim different modes of action and their efficacy on the animal when fed. 


One well-researched feed additive, ionophores, has demonstrated improvements in feed efficiency by suppressing the growth of certain populations of bacteria in the rumen. Ionophores improve feed conversion efficiency and milk yield by selectively inhibiting the growth of gram-positive bacteria rumen microbes. As a secondary benefit, many of these additives may reduce absolute enteric methane emissions and lower emission intensity by altering the microbial fermentation processes in the rumen.

Practices and technologies

Non-Nutritive Feed Additives: Ionophores

alternative practice name:

Methane Inhibitors; Rumen Modifiers; Non-Nutritive Supplements; Ionophores (e.g., Rumensin®); Monensin