Table 1 In vitro studies incorporating whole macroalgal biomass in ruminant feed and effects on CH4 emission
Seaweed species | Animal | In vitro system | Basal diet | Inclusion rate | Impact on CH4 emissions | References |
|---|---|---|---|---|---|---|
Red seaweeds | ||||||
 Asparagopsis taxiformis | Holstein cows | Ankom gas production system | 70% alfalfa 15% dried distillers grain 15% rolled corn | 5% dry matter | Reduction of 74% CH4 in comparison with control | [38] |
 Asparagopsis taxiformis | Lactating Swedish Red cows | Gas production recorder | Timothy grass, rolled barley, rapeseed in ratio 545:363:92 g/kg diet dry matter | 20 g/kg organic matter 0 g/kg 0.06 g/kg 0.13 g/kg 0.25 g/kg 0.5 g/kg 1.0 g/kg diet organic matter | 99% CH4 inhibition compared to control, when included at 20 g/kg organic matter Dose dependent response observed with CH4 emission decreasing curvilinearly | [39] |
 Mastocarpus stellatus  Palmaria palmata  Porphyra sp. | Murciano-Granadina goats | Batch fermentation | 1:1 oat hay and concentrate (containing cereals at 633 g/kg fresh matter) | 84 g/kg fresh matter 130 g/kg fresh matter 150 g/kg fresh matter | No statistically significant reduction in CH4 emission observed | [19] |
 Halymenia floresii  Hypnea pannosa | Brahman steers cattle | Ankom gas production system | Rhodes grass | 20% organic matter | No statistically significant reduction in CH4 emission observed | [18] |
 Asparagopsis taxiformis | Brahman steers cattle | Ankom gas production system | Rhodes grass | 0.5%–10% organic matter | Dose dependent response observed with total inhibition of CH4 at dose rates ≥ 2% | [40] |
 Bonnemaisonia hamifera  Euptilota formisissima  Plocamium cirrhosum  Vidalia colensoi | Non-lactating Friesian × Jersey dairy cows | Batch fermentation | Ryegrass hay | 0 2% 6% 10% feed organic matter | Bonnemaisonia hamifera reduced CH4 emission by 17.1% at 2% inclusion rate, 95.4% at 6% inclusion rate, and 98% and 10% of inclusion rate Euptilota formisissima and Plocamium cirrhosum when included at 10% reduced CH4 by 50.5% and 39.5% respectively | [41] |
 Chondrus crispus  Furcellaria spp. | Lactating Holstein cows | Continuous fermentation vessel | Total mixed ration containing timothy grass, alfalfa, cereals supplemented with vitamins and minerals | 0.14 g/d | 13% reduction in CH4 compared to control 12% reduction in CH4 compared to control | [42] |
 Asparagopsis taxiformis  Halymenia floresii  Hypnea pannosa  Laurencia filiformis | Brahman steers cattle | Ankom gas production system | Flinders grass | 20% w/w total feed | 98.9% reduction of CH4 26.6% reduction of CH4 42.5% reduction of CH4 42.5% reduction of CH4 | [17] |
 Asparagopsis taxiformis | Brahman steers cattle | Ankom gas production system | Rhodes grass | 0–16.7% organic matter | 99% reduction of CH4 at doses ≥ 2% | [43] |
 Gigartina sp.  Gracilaria vermiculophylla | Non-lactating Holstein cows | Batch fermentation | Incubated with meadow hay and corn silage | 25% dry matter | 44% CH4 reduction when incubated with meadow hay but not with corn silage 59% CH4 reduction when incubated with meadow hay and 63% with corn silage | [14] |
 Gracilaria   vermiculophylla | Non-lactating Holstein cows | RUSITEC | Total mixed ration containing 230 g/kg corn silage, 430 g/kg haylage, 150 g/kg wheat straw, 190 g/kg concentrate | 25% dry matter | No effect on CH4 emission | [44] |
 Asparagopsis taxiformis | One Jersey and one Holstein | RUSITEC | Super basic ration containing 70% alfalfa pellets, 15% rolled corn, 15% dried distillers grains | 5% w/w | 95% reduction in CH4 formation | [45] |
 Asparagopsis taxiformis | Lactating Holstein cows | Ankom gas production system | Total mixed ration | 1% dry matter | 98% reduction in CH4 yield | [16] |
 Asparagopsis taxiformis | Brahman steers cattle | Ankom gas production system | Rhodes grass | 2% of organic matter | Post-harvesting processes including rinsing, freezing, drying tested; the frozen then freeze-dried treatment totally inhibited CH4 emission | [46] |
 Asparagopsis taxiformis | Brahman steers cattle | Batch fermentation | Rhodes grass | 2% of organic matter | > 99% reduction in CH4 compared to basal substrate only control | [13] |
 Palmaria palmata | Swedish Red cows | Batch fermentation | Total mixed ration (grass silage/concentrate ratio 600/400 g/kg dry matter basis) | Silage replaced by: 0 g/g 0.15 g/g 0.3 g/g 0.45 g/g dry matter | No effect on CH4 emission | [47] |
Brown seaweeds | ||||||
 Ascophyllum nodosum  Sargassum fulvellum  Ecklonia maxima  Lessonia flavicans  Lessonia nigrescens  Laminaria japonica | Non-lactating cows | Batch fermentation | 50:50 grass hay:concentrates | Two inclusion rates tested: As a feed additive each seaweed was added in addition to basal diet, at 20%. As feed where each seaweed replaced 20% of concentrates in basal diet | As feed additive no effect on CH4 was observed As feed CH4 was reduced by 18% in the case of E. maxima and 21% in the case of L. japonica | [48] |
 Ascophyllum nodosum  Laminaria digitata | Holstein-Friesian cows | RUSITEC | 50:50 forage:concentrates | 5% dry matter | No effects on CH4 emissions | [49] |
 Zonaria farlowii | Holstein cow | Ankom gas production system | 70% alfalfa 15% dried distillers grain 15% rolled corn | 5% dry matter | 11% reduction in CH4 | [38] |
 Undaria pinnatifida  Sargassum fusiforme  Sargassum fulvellum | Non-lactating Hanwoo cows | Batch fermentation | 300 mg timothy hay 200 mg corn grain | 0.25 mg/mL | Undaria pinnatifida reduced CH4 emission by 26.8% at 12 h and 21.3% at 24 h Sargassum fusiforme reduced CH4 emission by 23.4% at 12 h and 24.4% at 24 h Sargassum fulvellum reduced CH4 emission by 26.3% at 12 h and 24.6% at 24 h | [50] |
 Ecklonia stolonifera  Eisenia bicyclis  Sargassum fulvellum  Undaria pinnatifida  Sargassum fusiforme | Holstein cows | Batch fermentation | Timothy grass | 5% dry matter | For all seaweeds except Sargassum fusiforme CH4 emission increased at 6 and 24 h incubation After 48 h, CH4 reduced by 36.1% for Ecklonia stolonifera, 32.4% for Eisenia bicyclis, 10.4% for Sargassum fulvellum, 26.7% for Undaria pinnatifida, and 13.9% for Sargassum fusiforme | [51] |
 Cystoseira trinodis  Padina australis  Dictyota spp. | Brahman steers cattle | Ankom gas production system | Rhodes grass | 20% feed total (diet organic matter) | Cystoseira trinodis significantly reduced CH4 emission | [18] |
 Cystoseira trinodis  Dictyota bartayresii  Padina australis  Sargassum flavicans | Brahman steers cattle | Ankom gas production system | Rhodes grass | 0.5%–10% organic matter | No significant reduction in CH4 observed | [40] |
 Cystoseira trinodis  Dictyota bartayresii  Hormophysa triquetra  Padina australis  Sargassum flavicans  Colpomenia sinuosa | Brahman steers cattle | Ankom gas production system | Flinders grass | 20% w/w total feed | Strongest CH4 inhibition observed from Dictyota bartayresii, inhibiting CH4 by 92.2% | [17] |
 Laminaria ochroleuca  Saccharina latissima | Non-lactating Holstein cows | Batch fermentation | Incubated with meadow hay and corn silage | 25% dry matter | With meadow hay, no change in CH4 emission With corn silage, addition of Laminaria ochroleuca increased CH4 emission | [14] |
 Saccharina latissima | Non-lactating Holstein cows | RUSITEC | Total mixed ration containing 230 g/kg corn silage, 430 g/kg haylage, 150 g/kg wheat straw, 190 g/kg concentrate | 25% dry matter | No effect on CH4 emission | [44] |
 Sargassum horneri | Holstein cows | Batch fermentation | Total mixed ration containing grain, cereal meal, alfalfa hay | 0 0.5% 1% 2% 3% 4% dry matter | CH4 emission was decreased at 24 h after inclusion of S. horneri | [52] |
 Saccharina latissima  Alaria esculenta | Swedish Red cows | Batch fermentation | Total mixed ration (grass silage/concentrate ratio 600/400 g/kg dry matter basis) | Silage replaced by: 0 0.15 0.3 0.45 g/g dry matter | Reduction in CH4 emission with increasing inclusion of A. esculenta | [47] |
Green seaweeds | ||||||
 Caulerpa lentillifera  Caulerpa taxifolia  Cladophora coelothrix  Ulva ohnoi  Cladophora patentiramea  Ulva sp.  Derbesia tenuissima | Brahman steers cattle | Ankom gas production system | Rhodes grass | 20% feed total organic matter | No significant change in CH4 emission observed | [18] |
 Caulerpa taxifolia  Cladophora patentiramea  Ulva ohnoi | Brahman steers cattle | Ankom gas production system | Rhodes grass | 0.5%–10% organic matter | No significant change in CH4 emission observed | [40] |
 Caulerpa taxifolia  Chaetomorpha linum  Cladophora coelothrix  Cladophora patentiramea  Derbesia tenuissima  Ulva sp.  Ulva ohnoi | Brahman steers cattle | Ankom gas production system | Flinders grass | 20% w/w total feed | Addition of Derbesia tenuissima increased CH4 emission Addition of Cladophora patentiramea reduced CH4 by 66.3% compared to control | [17] |
 Ulva sp | Non-lactating Holstein cows | Batch fermentation | Incubated with meadow hay and corn silage | 25% dry matter | When incubated with meadow hay CH4 decreased by 55% When incubated with corn silage no reduction observed | [14] |
 Ulva rigida | Non-lactating Holstein cows | RUSITEC | Total mixed ration containing 230 g/kg corn silage, 430 g/kg haylage, 150 g/kg wheat straw, 190 g/kg concentrate | 25% dry matter | No effect on CH4 emission | [44] |
 Ulva species B (taxonomically unresolved cultivated species) | Non-lactating Friesian × Jersey dairy cows | Batch fermentation | Ryegrass hay | 0 2% 6% 10% organic matter | No effect on CH4 emission | [41] |
 Ulva sp. | Holstein cows | Batch fermentation | Total mixed ration containing grain, cereal meal, alfalfa hay | 0 0.5% 1% 2% 3% 4% dry matter | 4% inclusion of Ulva sp. reduced CH4 significantly in comparison with control | [52] |