Table 4 Studies investigating effects on rumen microbiomes after addition of seaweeds/bioactive compounds as feed additives
Seaweeds/ compounds added | Animal | Type of study | Basal diet | Dosage rate | Effects on microbiome | Effect on CH4 emissions | References |
|---|---|---|---|---|---|---|---|
Bromochloromethane | Murciano-Granadina lactating goats | In vivo: BCM administered 2 equal doses per day from parturition to 2 weeks postweaning | Alfalfa hay with 600Â g/d concentrates | 0.3Â g of BCM/100Â kg body weight | No effect on overall abundance of microbial populations | 33% reduction in CH4 | [29] |
Bromochloromethane | Brahman-crossbred steers | In vivo: 97Â d trial- for first 63 d 100Â g cotton seed meal was added to basal diet and for 34 d BCM added to the cotton seed meal | Rhodes grass and grain pellets | 0.3Â g of BCM/100Â kg body weight | Decrease in Methanobrevivacter spp. observed when treated with BCM 34% average decrease in methanogenic archaea | 30% reduction in CH4 emissions | [31] |
Bromochloromethane | Non-lactating Friesian-Holstein cattle | In vitro: Batch and continuous fermentation tested | Batch: hay Continuous: 20 g/d hay | Batch: 5 µmol/L and 10 µmol/L tested Continuous: 5 µmol/L | Batch fermentation: 48% decrease in Ruminococcus flavefaciens, 68% increase in Fibrobacter succinogenes and 30% increase in ruminal fungi Continuous fermentation: significant decrease in Ruminococcus flavefaciens and methanogens, no change to Fibrobacter succinogenes population, increase in rumen fungi | Batch: 89%–94% reduction of CH4 at both concentrations tested Continuous fermentation resulted in 85%–90% CH4 reduction | [75] |
Asparagopsis taxiformis Bromoform | Brahman steers cattle | In vitro: batch fermentation | Rhodes grass | 2% of organic matter 2 concentrations tested: 1µmol/L and 5µmol/L | Decrease in CH4 production correlated with a decrease in relative abundance of methanogens; particularly Methanobacteriales, Methanomassiliicoccales, Methanomicrobiales. | > 99% reduction compared to basal substrate only control Addition of 1 µmol/L reduced CH4 by 77% and 5 µmol/L reduced CH4 by > 99% compared to basal substrate-only control | [13] |
Bromochloromethane | Japanese native (Shiba) goats | In vivo: animals sequentially adapted to low, medium, and high doses of BCM | 50% timothy grass 50% concentrates | Low dose: 0.5Â g/100 kg live weight Medium dose: 2Â g/100 kg live weight High dose: 5Â g/100Â kg live weight | Decrease in abundance of methanogens and fungi, and decrease in Ruminococcus albus Increases in Prevotella spp. and Fibrobacter succinogenes No change to Ruminococcus flavefaciens or protozoa | Low dose: 5% reduction in CH4 Medium dose: 71% reduction in CH4 High dose: 91% reduction in CH4 | [76] |
Asparagopsis taxiformis | Angus-Hereford beef steers | In vitro: RUSITEC | Super basic ration containing 70% alfalfa pellets, 15% rolled corn, 15% dried distillers grains | 5% w/w | Decrease in relative abundance of methanogens compared to the control; decrease was significant when averaged over the course of the experiment | 95% reduction in CH4 formation | [45] |
Phlorotannins extracted from Ascophyllum nodosum | Steers | In vitro: batch fermentation | Mixed forage (50:25:25 ground barley silage:alfalfa hay:grass hay) | 500 µg/mL phlorotannin extract Extract determined to contain 220 mg phlorotannin/g dry matter | At 500 µg/mL phlorotannin addition, growth of Fibrobacter succinogenes reduced by 78% at 6 h, 83% at 12 h, and 65% at 24 h No effect on Ruminococcus flavefaciens Ruminobacter amylophilus, Prevotella bryantii, Selenomonas ruminantium were increased at 12 and 24 h | Not analysed in this study | [66] |
Undaria pinnatifida Sargassum fusiforme Sargassum fulvellum | Non-lactating Hanwoo cows | In vitro batch fermentation | 300Â mg timothy hay 200Â mg corn grain | 0.25Â mg/mL | Sargassum fusiforme increased the overall abundance of total bacteria, ciliate protozoa, fungi, methanogenic archaea, Fibrobacter succinogenes. Relative proportions of Butyrivibrio fibrisolvens, Butyrivibrio proteoclasticus, and Prevotella ruminicola decreased with addition of seaweeds | Undaria pinnatifida reduced CH4 emission by 26.8% at 12Â h and 21.3% at 24Â h Sargassum fusiforme reduced CH4 emission by 23.4% at 12Â h and 24.4% at 24Â h Sargassum fulvellum reduced CH4 emission by 26.3% at 12Â h and 24.6% at 24Â h | [50] |
Ecklonia stolonifera Eisenia bicyclis Sargassum fulvellum Undaria pinnatifida Sargassum fusiforme | Holstein cows | In vitro batch fermentation | Timothy grass | 5% dry matter basis | At 12 and 24Â h, the abundance of methanogenic archaea decreased in the presence of Ecklonia stolonifera, Eisenia bicyclis and Sargassum fulvellum At 12 and 24Â h, the abundance of methanogenic archaea increased in the presence of Undaria pinnatifida and Sargassum fusiforme | For all seaweeds except Sargassum fusiforme, CH4 emission increased at 6 and 24Â h incubation After 48Â h, CH4 was reduced by: 36.1% for Ecklonia stolonifera 32.4% for Eisenia bicyclis 10.4% for Sargassum fulvellum 26.7% for Undaria pinnatifida 13.9% for Sargassum fusiforme | [51] |