Assessment of macroalgae and macroalgal extracts as a source of minerals in need of fine-tuning in multiple livestock production systems

This study evaluates the levels of macrominerals (Ca, Mg, P, K, Na, S), essential trace elements (Co, Cr, Cu, Fe, I, Mn, Mo, Ni, Se, Zn) and potentially toxic trace elements (Cd, Hg, Pb, As (inorganic and organic)) in seven species of macroalgae and in their extracts. The potential maximum levels of inclusion of macroalgal biomass and extracts in feed were assessed in multiple livestock (swine, ruminant, poultry, leporine and pisciculture). Overall, macroalgae contained high levels of I, reaching its highest levels in S. latissima (4131 mg/kg DM) and L. ochroleuca (2780 mg/kg DM). Arsenic concentrations ranged from 4.10 mg/kg DM in Ulva spp. to 68.9 mg/kg DM in S. latissima. Arsenic was mainly present as arsenosugars, of relatively low toxicity. Extracts had higher macrominerals and I levels, and lower essential and toxic trace elements levels compared to the biomass. Macroalgal biomass and extracts can be added to feed at 1–5 % to fulfill the physiological needs of multiple livestock, being I contents the main factor limiting highest inclusion rates. Inclusion of S. latissima and L. ochroleuca should be limited to 0.72 and 0.66 %, respectively. Maximum level of inclusion of different macroalgal products, as dried biomass or extracts, must be finely tuned. Low levels of inclusion of macroalgae and/or extracts in feed can be considered as an efficient and natural strategy to fulfill the macrominerals and iodine needs of multiple livestock.