In vitro gas production of 11 seaweeds as indicator for rate and extent of rumen fermentation

The European dairy cattle sector is exploring novel feed materials to increase protein self-sufficiency and mitigate environmental impact of animal production (i.e. CH4 emissions). In this direction, marine biomass has potential as alternative feed for ruminants, not competing for land. A study was executed to evaluate 11 North West European seaweed species as alternative feed material for dairy cattle. Proximate composition, phenols, and bromoform content were analysed. In vitro total gas production (TGP) was assessed as indicator for rumen fermentation, and CH4 production was determined. Grass silage was used as reference. After 72 h of incubation, Palmaria palmata, Laminaria digitata and Saccharina latissima had similar TGP as grass silage (334.9 ml/g OM), suggesting that rumen fermentation was not affected (P>0.05). CH4 production of P. palmata did not differ from grass silage as well. Undaria pinnatifida, Porphyra umbilicalis and Ulva lactuca were responsible for a mild reduction in TGP (234.8, 221.4 and 212.4 ml g/OM, respectively; P<0.05). Their CH4 production, along with L. digitata and S. latissima, was lower than grass silage (P<0.01). Chondrus crispus, Gracilaria gracilis, Ascophyllum nodosum. Asparagopsis armata and Fucus serratus had the strongest effect, severely inhibiting both TGP and CH4 production (P<0.01). Assuming that a mild reduction in TGP might be due to a lack of adaptation of rumen microflora to seaweeds, P. palmata, L. digitata, S. latissima, U. pinnatifida, P. umbilicalis and U. lactuca could be considered as possible substitute to grass silage. However, according to their protein content, only P. palmata, U. pinnatifida, P. umbilicalis might be considered as potential alternative feedstuff for dairy cows. Further investigations are required to better understand their nutritive value, their potential effect on animal health and the sustainability of their cultivation.