Wednesday, March 13, 2019

Putting seaweeds in your feed formulations

by Dr Thierry Chopin

Fishmeal is a main component of the feed used in many types of aquaculture. It is in high demand and can represent a major cost of an aquaculture operation.

Moreover, there are some controversies about the efficiency and the environmental impacts of using smaller fish to feed larger fish. Consequently, substitution of fishmeal by other protein sources has been investigated in recent years, mostly considering land-plant proteins.
 


As not many studies have considered using seaweeds as protein sources, we undertook a literature review and found 107 papers, in which a portion of the feed was replaced with seaweeds: 61 involved the culture of fish (40 of marine fish and 21 of freshwater fish), 24 the culture of crustaceans (shrimp, prawn, lobster), 11 the culture of mollusks (various species of abalone), 10 the culture of echinoderms (sea urchins) and one paper the culture of holothurians (sea cucumbers).

Seaweed substitutions in marine fish formulations
Twenty papers centred on various species of seabream (red, black, gilthead and silver). There were, generally, no negative effects on growth parameters such as growth rate, weight gain, feeding efficiency, or muscle protein at a substitution rate up to five percent seaweeds (Ulva pertusa, Ascophyllum nodosum), and in some cases at rates as high as 10-15 percent (U. pertusa, A. nodosum, wakame).

In some studies, the growth parameters improved at a substitution rate as low as one percent (with Ulva extract). Other effects included improved lipid metabolism, increased red blood cell numbers, and increased disease resistance without impairing overall growth.

Five papers focused on Asian and European seabass. For Asian seabass, growth parameters were not negatively affected at a substitution rate up to six percent (with Kappaphycus alvarezii), while European seabass tolerated substitution rates up to 10 percent (with U. rigida, Gracilaria cornea).

One study showed a five percent substitution rate enhanced stress resistance in European seabass (with U. lactuca, Pterocladia capillacea).

Five studies involved tropical fish (rabbitfish and white spotted snapper). They indicated that the substitution rates should be kept at 5-15 percent (with U. prolifera), as rates at 20 percent showed decreased body weight and specific growth rate (with G. lemaneiformis). A substitution rate as low as five percent increased antioxidant capacity in rabbitfish (with U. lactuca).


Read more HERE.

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