Rödalger som metanreducerande fodertillskott till nötkreatur - litteraturstudie och kostnadsberäkningar av att utfodra ett algtillskott i olika uppfödningsmodeller

The tropical red seaweed Asparagopsis Taxiformis has shown great potential to reduce methane production from rumen fermentation in several laboratory studies without any negative effects on rumen fermentation. The anti-methanogenic activity of Asparagopsis depends on its relatively high concentration of metabolites containing bromine, iodine, and chlorine, which have antimicrobial activity, and where bromoform is the most abundant metabolite produced. These metabolites prevents an important step in the process of converting hydrogen and carbon dioxide to methane by the rumen archaea. The number of in vivo studies investigating the effect of feeding Asparagopsis on methane production in ruminants are few. However, the ones published have shown promising results. For example, including Asparagopsis in feed to growing beef steers resulted in a reduction in daily methane production by 59% and 98% when the ration contained high (60% roughage) or low (8% roughage) proportion of roughage, respectively, without any negative effects on the growth of the animals. Two studies on dairy cows have also reported positive effects of including Asparagopsis in the diet, where daily methane production decreased by 26% to 80% without affecting milk production. However, the concentration of bromoform in Asparagopsis as well as the dose levels have varied between the different studies. This variation made it difficult to perform correct comparisons of the efficiency of feeding the red seaweed, as well as to determine what the optimal dose should be in order to achieve a desired reduction in methane production. Due to the limited number of in vivo studies, it is not possible to draw any conclusions about how the methane reducing ability of Aspargopsis may be affected by the composition of the ration. Therefore, more studies are required in order to evaluate the effect of including Asparagopsis in rations with different proportions of roughage (50% to 100%), and with different roughage qualities, e.g. high and low fibre concentration and digestibility. The cost of feeding an additive based on Asparagopsis to different categories of cattle was calculated. The results showed that at a dose level of 100 g additive per day, and at a price of 150 SEK/kg additive, a higher payment of 13.00 to 24.50 SEK/kg slaughter weight for growing cattle and a higher payment of 0.54 SEK/kg milk would be required, in order to cover the higher production costs of the producers. The higher cost per kilo slaughter weight and milk was more dependent on the dose levels used than on the price of the additive. The results also showed that it would be most expensive to feed the additive to young dairy bulls and least expensive to feed it to crossbred dairy×beef heifers. However, the cost of feeding the additive to different animal categories must be viewed in relation to the reduction in methane production that can be achieved. Young bulls of dairy- and beef breeds constitute the greatest proportion of the Swedish beef produced. Hence, Abstract we believe that feeding the additive to these animals will have the greatest potential of reducing methane emissions at a reasonable cost. However, many questions remains. One is if the methane reducing ability of Asparagopsis is long-term or if it declines over time, as the longest published animal trial only lasted for five months. Another question is if feeding of Asparagopsis will result in bromine and iodine residues ending up in meat and milk? Some of these questions might get their answers from a recently finalized study on dairy cows, as well as in an upcoming dairy trial that will be conducted during 2021 and 2022. In addition, there are no studies where Asparagopsis have been fed to growing beef or suckler cows during Swedish conditions. Such studies are needed in order to evaluate its methane reducing effect when fed in combination with our traditional high-roughage rations, as well as to study its effect on growth in young animals and its long-term effects on production, health and fertility in beef and dairy cows. The final question is how a business model should be constructed for meat and milk produced from animals fed with a red seaweed additive, as the additive only will be fed in practice if the producer will get paid for the higher costs.