The review briefly describing the importance of macroalgae “seaweed” as renewable source of fish feed. Fish aquaculture costs have including investment and operational costs including feed, energy, labor, fuel, oxygen, water, and medicament costs. The feed cost regarding about 40-60% from fish production. Hence, there is a need to reduce the cost of feed with increasing the growth performance and high survival rate of fish. Seaweed are a shelter for different generations of marine organisms to promote growth and feed efficiency. Moreover, they act as possible alternative protein sources for farmed fish because of their high protein content and productivity. They have been declared as a “super feed”, which has significant positive effects on fish performance due to their nutritive and biological values.
Algae are aquatic photosynthetic organisms and the base of food chain. They are the food producing resources that fish are adapted to consume. They can divide into two major groups “microalgae and microalgae (seaweed)” according to their size. Seaweeds are classified into three taxonomic groups: Rhodophyta (red), Chlorophyta (green) and Phaeophyta (brown). They act as a major feed ingredient in nutrional studies and are not considered as an essential fish feed source, but rather as enhancing “standard” feed formulations. Marine macroalgae have been used for healthy feed supplement providing necessary amino acids, beneficial polysaccharides, fatty acids, antioxidants, vitamins and minerals [1,2]. They prefer as food by herbivorous fishes since their stomach have low pH levels and specialize guts required for the digestion of plant materials . Moreover, they improve the immune system, antiviral, antimicrobial, improved gut function and stress resistance serves as an alternative for fish meal, since their proteins do not contain such high P levels, and they would help to take the pressure off wild fish stocks . There is limited evidence that herbivorous and omnivorous fish “.g. trout, salmon, sea basss and seabream” were more effective at digesting and utilizing seaweed in diet.
Recently, there are many researches have been carried out on the use of seaweed as ingredient for aquafeed for different fish species. Cladophora, Enteromorpha and Ulva species were preferred by Scartichthys viridis (Blennidae) and Sargassum and Dictyota spp. were preferred by Kyphosus spp. (Kyphosidae) and Siganus spp. (Siganidae) . The green seaweed “Ulva and Enteromorpha”
exhibited a positive effect on growth performance of rabbit fish fry and reduce of the feed cost as half of the feeding rate with artificial feed, but replacement of artificial feed with fresh seaweeds had negative effect on growth performance of rabbit fish fry . The inclusion of 20 -30 % different seaweeds (Cystoseira barbata, Ulva lactuca, U. rigida and Gracilaria cornea) in different species of fish meals decreased all growth performance and feed utilization parameters . The incorporation 5% of green seaweed Ulva lactuca in Oreochromis niloticus feeds promoted growth, diet utilization, immune response, and body composition of O. niloticus . The inclusion of 5% red seaweed Pterocladia capillacea enhanced some growth performance parameters of European seabass “Dicentrarchus labrax” fry, with an increase in body weight, and weight gain . The carcass lipid levels of O. niloticus” tended to increase with increasing levels of Cystoseira meal . The total cholesterol and triglyceride of Lates calcarifer decreased by addition Gracilaria pulvinata this may relate to high algal fiber content and n-3 fatty acids .
Macroalgal polysaccharides play vital role in feeding process since they have direct impact on the efficiency of nutrient assimilation in fish gut since polysaccharide can affect digestibility . Alginate extracted from Ascophyllum nodosum etimulated lysozyme activity of Salmo salar . Besides the nutritional value, seaweed contain bioactive compounds which exhibited antimicrobial, antiviral, antioxidative, anti-inflammatory, and neuroprotective so improved the immune response and stress resistance and act as scavenger to reactive oxygen species “ROS” . Fucoidan from Sargassum wightii increased immunological parameterssuch as phagocytic activity, total leucocyte count and respiratory
burst activity of Pangasianodon hypophthalmus .Inclusion of
agar from red seaweed enhanced the survival rate of Aeromonas
hydrophila. Interestingly, seaweed act as the major market for
astaxanthin so act as pigmentation source in aquaculture .
Astaxanthin, a carotenoid equipped with two asymmetric carbon
located at the 3 and 3΄ position of the benzenoid rings on either
end of the molecule. In 1987, the United States Food and Drug Administration
approved the use of astaxanthin as a feed additive
for aquaculture and subsequently in 1999 astaxanthin where be
approved as a nutraceutical. It was the most important carotenoid
in salmons and rainbow trouts .
Seaweed or ingredients made of seaweed may be of prime
interest for use in fish feed formulations since they are not only
profoundly nutritious but also extremely versatile, making them
compatible with many foodstuffs already consumed globally.
Compared to other aquafeed ingredients, seaweeds are not a supply
of nutrients only but also, they are a good source for bioactive
compounds that can benefit farmed finfish so they could offer an
alternative to the demands of other ingredients used in aquafeed.
Abdel Aziz M F A, Ragab M A(2017)Effect of use fresh macro algae (seaweed) Ulva fasciata and Enteromorpha flaxusa with or without artificial feed on growth performance and feed utilization of rabbit fish (Siganus rivulatus) fry. Journal of Aquaculture Researchand Development 8: 482.
Natify W, Droussi M,Berday A, Araba M (2015)Effect of the Seaweed Ulva lactuca as a feed additive on growth performance, feed utilization and body composition of Nile Tilapia (Oreochromis Niloticus L.). International Journal of Agronomy and Agricultural Research 7 (3): 85-92.
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