Early scientific studies conducted at the turn of the twentieth century failed to support the inclusion of seaweeds into animal rations at high inclusion rates. At that time, based on proximate analysis and energy availability studies, dried seaweeds or kelp meal largely fell out of favor as a recommended animal feed source. Nevertheless, kelp meal was still regarded by some as having properties which improved animal health and productivity which were not conveniently explained by conventional feed analysis. In the 1970s, research leads to the discovery that chelated micromineral sources were more efficient for the delivery of microelements than conventional inorganic sources. This prompted renewed interest in seaweeds as rich sources of over 60+ microelements. However, it was only in the early 2000s, when detailed analysis of the complex structure of the polysaccharides associated with seaweeds was tied to their prebiotic actions, that a clear explanation for the basis of productivity and health enhancement was attained. Further analysis indicated that other constituents in various brown seaweeds such as phlorotannins and antioxidants also contributed to the observed bioactivities. Of all of the brown seaweeds cited in studies, the one most scientifically documented is Ascophyllum nodosum, and of all of these sources, Tasco®, a sundried, high-quality macroalgal product, produced by Acadian Seaplants has been the most studied. The latest studies of Tasco® suggest prebiotic potencies at least five times that of the reference prebiotic inulin with additional performance-enhancing benefits in animal rations that rival antibiotic inclusions.