A recent study published in the Journal of Dairy Science explored the effects of feeding various seaweed mixtures to lactating dairy cows, with a focus on reducing enteric methane emissions while remaining within European Union regulatory limits for iodine in livestock diets.
The study tested three seaweed mixtures in 40 Holstein cows over a seven-week period. The treatments included:
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A control diet with no seaweed.
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A mix of Ascophyllum nodosum, Fucus vesiculosus, and Asparagopsis taxiformis (AN:FV:AT).
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A high-iodine mix of Ascophyllum nodosum and Fucus vesiculosus (AN:FV).
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A high-inclusion mix of Fucus vesiculosus and Ascophyllum nodosum (FV:AN).
Key Findings:
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Methane Reduction: Only the seaweed mixture that included Asparagopsis taxiformis (AT) resulted in a measurable reduction in methane output, lowering emissions by 9%, methane yield by 12%, and methane intensity by 20% compared to other groups. The other two mixtures (AN:FV and FV:AN), which did not include AT, showed no significant methane reduction.
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Milk Composition: All seaweed treatments increased milk iodine levels by 1.7 to 2.2 times, with peak differences occurring in week 3 and 5. While these levels stayed within EU regulatory thresholds, they highlight the potential impact on human iodine intake.
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Nutritional Effects: The AN:FV diet led to lower milk urea concentrations, indicating possible effects on rumen protein metabolism from bioactive compounds like phytotannins.
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Fatty Acid Profile: The AT-containing mix slightly altered milk fatty acid profiles, decreasing C18:3n6 and increasing C15:1 and C17:0.
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Milk Yield and Quality: No significant differences in overall milk production or general composition were observed among the groups, apart from changes in iodine and select fatty acids.
Conclusion:
This research supports the targeted use of low-level Asparagopsis taxiformis inclusion (0.075% of dietary DM) as a feasible strategy to modestly reduce methane emissions in dairy cows without compromising milk production. However, the iodine content and potential presence of harmful elements such as bromoform and heavy metals warrant careful monitoring. Additionally, brown seaweeds like Ascophyllum nodosum and Fucus vesiculosus alone showed limited methane mitigation benefit but may influence nitrogen metabolism.
The findings contribute to ongoing efforts to develop sustainable feeding practices that balance environmental impact, animal productivity, and product safety in dairy systems.
