Abstract/Summary

This study investigated the effect of seaweed supplementation in dairy cow diets on milk yield, basic composition, and mineral concentrations. 37 Icelandic cows were split into 3 diet treatments: control (CON, no seaweed), low-seaweed (LSW, 0.75% concentrate dry matter (DM), 13-40 g/cow/day), (iii) high-seaweed (HSW, 1.5% concentrate DM, 26-158g/cow/day). Cows were fed the same basal diet of grass silage and concentrate for a week, and then were introduced to the assigned experimental diets for 6 weeks. The seaweed mix of 91% Ascophyllum nodosum:9% Laminaria digitata (DM basis), feed, and milk samples were collected weekly. Data was analyzed using a linear mixed effects model, with diet, week, and their interaction as fixed factors, cow ID as random factor, and the pre-treatment week data as a covariate. When compared with CON milk, LSW and HSW milk had, respectively, less Se (-1.4 and -3.1 μg/kg milk) and more I (+744 and +1649 μg/kg milk); while HSW milk also had less Cu (-11.6 μg/kg milk) and more As (+0.17 μg/kg milk) than CON milk. The minimal changes or concentrations in milk for Se, Cu, and As cannot be associated to any effects on consumer nutrition, but care should be taken when I-rich seaweed is fed to cows, to avoid excessive animal I supply and milk I concentrations.