Methane emissions from enteric fermentation in cattle represent a significant portion of Canada’s agricultural greenhouse gas output. As part of targeted mitigation strategies, seaweed-based feed additives have attracted growing interest due to their potential to alter rumen fermentation and reduce methane production. However, most research has focused on tropical red seaweeds like Asparagopsis taxiformis, which are not ecologically available or sustainable in the northern Pacific of western Canada. This thesis investigates three seaweed species native or abundant in British Columbia: Macrocystis pyrifera (giant kelp), Saccharina latissima (sugar kelp), and Mazzaella japonica (M. japonica), to evaluate their potential as methane supressing additives in cattle feed through chemical profiling of omega-6s and omega-3s, phlorotannins, and heavy metal content.
Fatty acid analysis using low-solvent and rapid proton nuclear magnetic resonance (1H NMR) spectroscopy revealed that both sugar kelp and giant kelp contain favourable omega-6 to omega-3 (n-6/n-3) ratios, supporting their nutritional value and possible methane-reducing potential. Dehydration was identified as the preferable drying method for seaweed samples, yielding clearer and more consistent spectra compared to oven-dried samples. In contrast, M. japonica showed minimal fatty acid content and was excluded from quantitative analysis due to spectral resolution limitations.
Phlorotannins, polyphenolic compounds plentiful in brown seaweeds, were quantified using Folin-Ciocalteu (F-C) assay, identified using 1H NMR, and trialled using capillary electrophoresis (CE). Sugar kelp showed slightly higher mean concentrations of polyphenolic content than giant kelp, however, method variability limited the reliability of the results. Additionally, phloroglucinol aromatic H (hydrogen) peaks were successfully identified by 1H NMR near 8.4 ppm. Although CE trials showed inconsistencies, the phlorotannin analysis results highlighted the promise and current limitations of minimal solvent techniques for phlorotannin detection and quantification.
The concentration of trace elements, including heavy metals, in seaweeds was analysed to assess potential toxicity risks these additives may pose to livestock. Through inductively coupled plasma mass spectrometry (ICP-MS), concentrations of key elements of interest including aluminum, arsenic, cadmium, lead, and mercury were determined and compared to Governmental Action Levels for livestock feed. All species had concentrations of key elements well below acceptable levels, with M. japonica containing the lowest concentrations.
These findings underscore the importance of site- and species-specific monitoring when considering harvesting for livestock feed. Altogether, this study demonstrates that two locally abundant brown seaweeds, giant kelp and sugar kelp, exhibit promise as cattle feed additives for improved ruminant nutrition and potential methane mitigation. Favourable fatty acid ratios and phlorotannin content support their potential efficacy, while trace elements including heavy metals levels suggest they are safe for animal consumption under current guidelines. This research also highlights the utility of minimal solvent analytical techniques including 1H NMR and CE for more environmentally conscious seaweed analysis.
