Astaxanthin is a high value keto-carotenoid pigment renowned for its commercial application in various industries comprising aquaculture, food, cosmetic, nutraceutical and pharmaceutical. Among the verified bio-resources of astaxanthin are red yeast Phaffia rhodozyma and green alga Haematococcus pluvialis. The supreme antioxidant property of astaxanthin reveals its tremendous potential to offer manifold health benefits among aquatic animals which is a key driving factor triggering the upsurge in global demand for the pigment. Numerous scientific researches devoted over a number of years have persistently demonstrated the instrumental role of astaxanthin in targeting several animal health conditions. This review article evaluates the current best available evidence to judge the beneficial usage of astaxanthin in aquaculture industry. Most apparent is the profound effect on pigmentation, where astaxanthin is frequently utilized as an additive in formulated diets to boost and improve the coloration of many aquatic animal species, and subsequently product quality and price. Moreover, the wide range of other physiological benefits that this biological pigment confers to these animals is also presented which include various improvements in survival, growth performance, reproductive capacity, stress tolerance, disease resistance and immune-related gene expression.

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Astaxanthin as feed supplement in aquatic animals

Inland aquaculture of shrimp in low salinity waters is widespread in many regions worldwide. Owing to its ability to grow and survive in low salinity environments the Pacific white shrimp, (Litopenaeus vannamei Boone) has become the candidate of choice for low salinity culture. Remediation techniques have been developed to improve the osmoregulatory capacity of shrimp reared in low salinity waters. These techniques have evaluated water modification strategies that improve low salinity waters used for production by adding potassium and magnesium fertilizers and dietary approaches that involve modification of the feeds offered to shrimp with supplements that might improve osmoregulatory capacity. Based on our own experience as well as what we found predominantly in the literature, it appears that modification of the rearing medium with potassium and magnesium fertilizers is more effective than dietary modification techniques at improving the growth, survival and osmoregulatory capacity of shrimp reared in low salinity waters.

Shrimp culture in inland low salinity waters.

Crustaceans are cultured extensively around the world in intensive farming systems. High-performance formulated feeds have been developed for crustacean aquaculture, which are often supplemented with a number of natural and synthetic carotenoid sources. Studies over a number of years have consistently shown that dietary carotenoid supplementation is beneficial for crustacean aquaculture across a range of commercially relevant parameters. Most obvious is the effect on pigmentation, where carotenoid inclusion levels in feeds and duration of feeding diets with carotenoids have been optimised across many species to improve product colour, and subsequently quality and price. However, beneficial effects of carotenoid inclusion have increasingly been demonstrated on other parameters. This review updates the recent progress in our understanding of dietary carotenoid utilisation and storage, and the combined effects of diet, genetics and environment on crustacean pigmentation. In addition, the range of other physiological benefits this class of molecules brings to these animals is summarised. These include improvements in survival, growth, reproductive capacity, disease resistance and stress resistance.

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A review of carotenoid utilisation and function in crustacean aquaculture

Astaxanthin (ATX) is a dietary carotenoid of crustaceans and fish that contributes to their coloration. Dietary ATX is important for development and survival of salmonids and crustaceans and has been shown to reduce cardiac ischemic injury in rodents. The purpose of this study was to examine whether ATX can protect against ischemic injury in the mammalian brain. Adult rats were injected intracerebroventricularly with ATX or vehicle prior to a 60-min middle cerebral artery occlusion (MCAo). ATX was present in the infarction area at 70-75 min after onset of MCAo. Treatment with ATX, compared to vehicle, increased locomotor activity in stroke rats and reduced cerebral infarction at 2 d after MCAo. To evaluate the protective mechanisms of ATX against stroke, brain tissues were assayed for free radical damage, apoptosis, and excitoxicity. ATX antagonized ischemia-mediated loss of aconitase activity and reduced glutamate release, lipid peroxidation, translocation of cytochrome c, and TUNEL labeling in the ischemic cortex. ATX did not alter physiological parameters, such as body temperature, brain temperature, cerebral blood flow, blood gases, blood pressure, and pH. Collectively, our data suggest that ATX can reduce ischemia-related injury in brain tissue through the inhibition of oxidative stress, reduction of glutamate release, and antiapoptosis. ATX may be clinically useful for patients vulnerable or prone to ischemic events.

Astaxanthin reduces ischemic brain injury in adult rats

The Pacific white shrimp Litopenaeus vannamei is a euryhaline species with optimal salinity of 20–25 practical salinity unit (psu) for growth and survival, but has been cultured in inland water with salinity <5 psu worldwide. In the past decade, much research progress has been made on the physiological and nutritional requirements of white shrimp at low salinity. This study reviews the recent findings in the aspects of growth, survival, energy metabolism, stress resistance and immunity of white shrimp at low salinity and synthesizes recent research outcomes in nutritional requirements in an attempt to improve the shrimp performance in aquaculture at low salinity. The white shrimp at low salinity usually show slow growth, low immunity, high susceptibility to pathogens and high energy demand. The diet containing 30–36% protein, 15–20% carbohydrate and supplementations of potassium, sodium, vitamin E and C, free amino acids (glycine, alanine, proline and taurine), antioxidants and probiotics can improve shrimp growth and immunity at low salinity. The white shrimp has demonstrated the ability to synthesize DHA and EPA from LNA at low ambient salinity, but further studies are needed to further confirm this finding. Future research should focus on the understanding of physiological mechanism and adaptation associated with salinity change and nutritional manipulation. The specific dietary requirements of essential fatty acids, essential amino acids, vitamins and minerals and the nutrition-mediated immune response also warrant further study on shrimp at low salinity.

Physiological change and nutritional requirement of Pacific white shrimp Litopenaeus vannamei at low salinity

The eiects of dietary astaxanthin supplemented at 0, 40, 80 or 150 mg astaxanthin kg � 1 on growth, survival, moult frequency, osmoregulatory capacity (OC) and selected metabolic and haematological variables in Litopenaeus vannamei acclimated to low-salinity water (3 g L � 1 ) were evaluated. Supplemented astaxanthin at 80 mg kg � 1 improved growth, survival and moult frequency in shrimp. The lowest OC was also exhibited in shrimp fed with dietary astaxanthin at 80 mg kg � 1 . Shrimp haemolymph concentrations of glucose, lactate, haemocyanin and total haemocyte count were all signi¢cantly enhanced by feeding the diet supplemented with 80 mg astaxanthin kg � 1 compared with shrimp fed with the other diets. On the basis of these results, dietary astaxanthin supplementation of 80 mg kg � 1 is recommended for juvenile L. vannamei cultured in low-salinity water.

Physiological, metabolic and haematological responses in white shrimp Litopenaeus vannamei (Boone) juveniles fed diets supplemented with astaxanthin acclimated to low-salinity water

Rebeca Medina

Papers

Physiological, metabolic and haematological responses in white shrimp Litopenaeus vannamei (Boone) juveniles fed diets supplemented with astaxanthin acclimated to low-salinity water