Tracing seaweeds as mineral sources for farm-animals

This study characterized the mineral composition of 15 common Portuguese seaweed (green, brown, and red) species. Total measured mineral content ranged from 10.9 g kg(-1) dry matter (DM) in Gracilaria vermiculophylla to 71.0 g kg(-1) DM in Codium adhaerens, calcium being the mineral generally found in higher amounts. Overall, the results suggest that seaweeds have great potential as mineral sources for animal feeding, but a great variability between species was observed regarding their mineral profile. Compared to common animal feed ingredients, the studied seaweeds can be considered as good sources of calcium, magnesium, iron, iodine, copper, manganese, and selenium but are poor sources of phosphorous and zinc. The maximum level of dietary inclusion will be strongly dependent on the mineral profile of the seaweeds. Depending on the seaweed, the upper level of inclusion in poultry and swine diets may reach more than 40 %. The high iodine content of studied seaweeds limits their use in diets for horses, and, to a lesser extent, for ruminants. This work constitutes a paramount contribution regarding the use of seaweeds as mineral sources in animal diets, allowing a more precise choice of the algae species and level of inclusion to be used, thus assuring animal health and strengthening the seaweed industry through this underexploited application field.