Effects of E/Z Isomers and Coating Materials of Astaxanthin Products on the Pigmentation and Antioxidation of Rainbow Trout,Oncorhynchus mykiss

The objective of this study was to compare the effects of four astaxanthin preparations with different ratio of E/Z (trans/cis) isomers and different coating materials on the pigmentation and antioxidation properties of rainbow trout. Five diets were designed as basal diet (without astaxanthin supplementation) and four astaxanthin diets (100 mg/kg diet) supplemented with four astaxanthin products, BASF (79% all‐E, gelatin coated), Wisdom‐B (85% all‐E, gelatin coated), Wisdom‐C (94% all‐E, carrageenan coated), and Wisdom‐D (94% all‐E, gelatin coated). After 4 wk feeding, the flesh astaxanthin content, redness, and yellowness of astaxanthin‐supplemented groups were higher than those of control group at the second and fourth week (P < 0.05). Among these astaxanthin‐supplemented groups, the Wisdom‐B group had the highest flesh redness and astaxanthin content. The astaxanthin‐supplemented groups also had the lower flesh frozen loss and malondialdehyde level than control group at the fourth week (P < 0.05). The results indicated that dietary 100 mg/kg astaxanthin could improve the flesh redness and antioxidation abilities of rainbow trout. The ration of E/Z isomers and properties of coating materials of astaxanthin preparations influenced the pigmentation and antioxidation properties, and Wisdom‐B had a better pigmentation effect on the flesh than other astaxanthin preparations.     

Assessment of flesh colour in Atlantic salmon, Salmo salar L.

The degree of pigmentation in muscle of Atlantic salmon, Salmo salar L., fillets of fish that were fed eight diets fortified with 10, 20, 40, 60, 80.100, 150 and 200 mg astaxanthin kg^?1 and a non-supplemented control diet from 3 to 21 months was assessed using different methods. A tristimulus colorimeter (Minolta Chroma Meter) was used to measure the colour composition of the fillets instrumentally. The colour was also determined using the Roche Colour Card for Salmonids. The concentration of astaxanthin in the muscle was measured by chemical analyses. All measurements for colour were done directly on the epaxial muscle anterior to the dorsal fin. The lightness factor (L *). the red/green chromaticity (a*), the yellow/blue chromaticity (b*) and the saturation C* of the colorimetric readings and the Colour Card scores were compared with the chemical analyses. The astaxanthin concentration in the flesh varied from 1 to 10 mg kg^?1 and the visual appearance of the fillets varied from yellowish-white to red. The relationship between the a*, b* and C* values and the astaxanthin concentration in the muscle was non-linear. Non-linear regression lines were found between the a* value and the astaxanthin concentration in the flesh (r²= 0.974) and the b* value and the astaxanthin concentration in the flesh (r²= 0.984). The instrument was not able to detect differences in astaxanthin concentration at astaxanthin levels above 3-4 mg kg^?1 using the presented method directly on the fillet. The instrument might be useful for rejecting groups of salmon with poor pigmentation. A good linear regression was found between the Colour Card score and the mean astaxanthin concentration in the flesh (r² - 0.992). The Colour Card provided a better prediction of the astaxanthin concentration at higher astaxanthin levels than the Chroma Meter. None of the methods provided a satisfactory prediction of the astaxanthin concentration in the muscle of individual fish using the presented methods.     

Effects of dietary astaxanthin concentration and feeding period on the skin pigmentation of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

A single‐factor experiment was conducted to investigate the effects of dietary astaxanthin concentration on the skin colour of snapper. Snapper (mean weight=129 g) were held in white cages and fed one of seven dietary levels of unesterified astaxanthin (0, 13, 26, 39, 52, 65 or 78 mg astaxanthin kg^?1) for 63 days. Treatments comprised four replicate cages, each containing five fish. The skin colour of all fish was quantified using the CIE L^*, a^*, b^* colour scale after 21, 42 and 63 days. In addition, total carotenoid concentrations of the skin of two fish cage^?1 were determined after 63 days. Supplementing diets with astaxanthin strongly affected redness (a^*) and yellowness (b^*) values of the skin at all sampling times. After 21 days, the a^* values increased linearly as the dietary astaxanthin concentration was increased before a plateau was attained between 39 and 78 mg kg^?1. The b^* values similarly increased above basal levels in all astaxanthin diets. By 42 days, a^* and b^* values increased in magnitude while a plateau remained between 39 and 78 mg kg^?1. After 63 days, there were no further increases in measured colour values, suggesting that maximum pigmentation was imparted in the skin of snapper fed diets >39 mg kg^?1 after 42 days. Similarly, there were no differences in total carotenoid concentrations of the skin of snapper fed diets >39 mg kg^?1 after 63 days. The plateaus that occurred in a^* and b^* values, while still increasing in magnitude between 21 and 42 days, indicate that the rate of astaxanthin deposition in snapper is limited and astaxanthin in diets containing >39 mg astaxanthin kg^?1 is not efficiently utilized. Astaxanthin retention after 63 days was greatest from the 13 mg kg^?1 diet; however, skin pigmentation was not adequate. An astaxanthin concentration of 39 mg kg^?1 provided the second greatest retention in the skin while obtaining maximum pigmentation. To efficiently maximize skin pigmentation, snapper growers should commence feeding diets containing a minimum of 39 mg unesterified astaxanthin kg^?1 at least 42 days before sale.     

The effect of feed pigment type on flesh pigment deposition and colour in farmed Atlantic salmon, Salmo salar L.

The characteristic pink colour of salmonid flesh is a result of deposition of naturally occurring carotenoid pigments. Achieving successful pigmentation in farmed salmonids is a vital aspect of fish farming and commercial feed production. Currently commercial diets for farmed salmonids contain either or both of the synthetic pigments commercially available, astaxanthin and canthaxanthin. Atlantic salmon, Salmo salar L. ( = 220 g initial weight) were given feeds where the pigment source was astaxanthin only, canthaxanthin only or a astaxanthin/canthaxanthin mix. The rearing environment was 12 × 3 m tanks supplied with sea water at the EWOS research farm Lønningdal, near Bergen, Norway. As the proportion of dietary canthaxanthin increased, flesh pigment levels also showed an increase; the pigment content in the muscle of canthaxanthin‐only fed fish was 0.4 mg kg^?1 (or 14%) higher than that of the astaxanthin‐only fed fish, with the mixed pigment fed fish being intermediate between the two extremes. Results of cross‐section assessment for Minolta colorimeter redness (a*) values and Roche Salmofan^TM scores also showed an increase in colour with increasing proportions of canthaxanthin in the feed. The data reported clearly indicates that S. salar ( = 810 g final weight) of this size deposit canthaxanthin more efficiently than they do astaxanthin. These results contrast with those obtained by other authors with rainbow trout, Oncorynchus mykiss (Walbaum), and imply that the absorption or utilization of the pigments differs between species.     

Astaxanthin deposition in fillets of Atlantic salmon Salmo salar L. fed two dietary levels of astaxanthin in combination with three levels of α-tocopheryl acetate

The influence of α-tocopheryl acetate (α-TOAc) on plasma concentration and fillet deposition of dietary astaxanthin was investigated in Atlantic salmon Salmo salar L. The diets were added 30 or 50 mg kg^–1 astaxanthin, and 200, 400 or 800 mg kg^–1α-TOAc at each astaxanthin level. Improved flesh deposition of astaxanthin by 8–14% was achieved for fish fed diets with 30 and 50 mg kg^–1 astaxanthin, respectively, by the dietary addition of 800 compared with 200 mg kg^–1α-TOAc. These results were supported by CIE[1976]L*a*b* tristimulus redness measurements (a* value). Plasma astaxanthin concentration mirrored the muscle astaxanthin concentration in the groups of fish fed a diet containing 30 mg kg^–1 astaxanthin. The salmon fed a high astaxanthin and low α-TOAc diet had the highest plasma concentration of idoxanthin (P < 0.05). Astaxanthin retention was significantly higher (P < 0.001) in salmon fed 30 mg kg^–1 astaxanthin than in those fed 50 mg kg^–1 astaxanthin, but was not significantly affected by dietary α-TOAc. Liver weight, body weight, specific growth rate, feed/gain ratio and mortalities were not affected by dietary α-TOAc levels. In conclusion, the dietary addition of α-TOAc appears to increase astaxanthin fillet deposition in salmonids and may reduce the demand for astaxanthin supplementation. The effect was rather small and requires verification.     

Astaxanthin deposition in the flesh of Atlantic Salmon, Salmo salar L., in relation to dietary astaxanthin concentration and feeding period

Atlantic salmon, Salmo salar L., were fed nine experimental diets containing from 0 to 200 mg astaxanthin per kg^?1 for six time periods, ranging from 3 to 21 months, in sea cages at Matre Aquaculture Research Station, Matredal, Norway. The sampled fish had an initial mean weight of 115 g and reached a weight of 3.2 kg at the termination of the experiment. Every third month, 10 fish from each dose and time group were sampled and the astaxanthin concentration in the flesh determined. The amount of astaxanthin in the flesh ranged from 0.7 to 8.9 mg kg^?1 at the termination of the experiment. This paper discusses deposition of astaxanthin in the flesh of Atlantic salmon in relation to dietary carotenoid levels in the 0–200 mg kg^?1 range and feeding times of 3–21 months. Under the conditions of this experiment, no significant effect on astaxanthin deposition rate could be achieved by increasing the astaxanthin level above 60 mg kg dry feed^?1. Atlantic salmon should be fed astaxanthin-supplemented diets during the whole seawater stage in order to obtain maximal astaxanthin level in the flesh.     

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

The effects 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 significantly 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.     

Effect of dietary bile extracts on serum response of astaxanthin in rainbow trout (Oncorhynchus mykiss): a preliminary study

Effects of porcine bile extracts added at three different dietary concentrations 0, 10 and 20 g kg^?1 were studied on astaxanthin serum concentration in rainbow trout (mean weight 200 ± 7 g). Astaxanthin from micro‐algae Haematococcus pluvialis and synthetic astaxanthin (CAROPHYLL® pink) were incorporated in diets of rainbow trout at a rate of 100 mg astaxanthin kg^?1 of feed. Fish were hand fed twice a day. After 5 days of feeding there was a significant effect of the pigment source on the ratio (total blood astaxanthin per unit body weight to cumulative astaxanthin intake per unit body weight). Trout receiving synthetic astaxanthin showed a significantly (P < 0.05) higher ratio than trout fed algal astaxanthin. Increasing dietary bile extract did not lead to produce any effect on this ratio. The power of the statistical analysis is discussed. Therefore, the interaction (pigment source × dietary bile concentration) showed no more effect.     

Effect of carotenoids and background colour on the skin pigmentation of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

Three 2‐factor experiments were conducted to determine the effects of background colour and synthetic carotenoids on the skin colour of Australian snapper Pagrus auratus. Initially, we evaluated the effects on skin colour of supplementing diets for 50 days with 60 mg kg^?1 of either astaxanthin (LP; Lucantin^® Pink), canthaxanthin (LR; Lucantin^® Red), apocarotenoic acid ethyl ester (LY; Lucantin^® Yellow), selected combinations of the above or no carotenoids and holding snapper (mean weight=88 g) in either white or black cages. In a second experiment, all snapper (mean weight=142 g) from Experiment 1 were transferred from black to white, or white to white cages to measure the short‐term effects of cage colour on skin L^*, a^* and b^* colour values. Skin colour was measured after 7 and 14 days, and total carotenoid concentrations were determined after 14 days. Cage colour was the dominant factor affecting the skin lightness of snapper with fish from white cages much lighter than fish from black cages. Diets containing astaxanthin conferred greatest skin pigmentation and there were no differences in redness (a^*) and yellowness (b^*) values between snapper fed 30 or 60 mg astaxanthin kg^?1. Snapper fed astaxanthin in white cages displayed greater skin yellowness than those in black cages. Transferring snapper from black to white cages increased skin lightness but was not as effective as growing snapper in white cages for the entire duration. Snapper fed astaxanthin diets and transferred from black to white cages were less yellow than those transferred from white to white cages despite the improvement in skin lightness (L^*), and the total carotenoid concentration of the skin of fish fed astaxanthin diets was lower in white cages. Diets containing canthaxanthin led to a low level of deposition in the skin while apocarotenoic acid ethyl ester did not alter total skin carotenoid content or skin colour values in snapper. In a third experiment, we examined the effects of dietary astaxanthin (diets had 60 mg astaxanthin kg^?1 or no added carotenoids) and cage colour (black, white, red or blue) on skin colour of snapper (mean weight=88 g) after 50 days. Snapper fed the astaxanthin diet were more yellow when held in red or white cages compared with fish held in black or blue cages despite similar feed intake and growth. The skin lightness (L^* values) was correlated with cage L^* values, with the lightest fish obtained from white cages. The results of this study suggest that snapper should be fed 30 mg astaxanthin kg^?1 in white cages for 50 days to increase lightness and the red colouration prized in Australian markets.     

Digestibility,growth and pigmentation of astaxanthin,canthaxanthin or lutein diets in Lake Kurumoi rainbowfish,Melanotaenia parva (Allen) cultured species

New cultured ornamental fish namely Lake Kurumoi rainbowfish Melanotaenia parva (Allen) run into reduced of colour performances when reared in the aquaria, consequently, fish feed must be added with carotenoids as a pigment source. The aim of this study was to evaluate the digestibility, growth and pigmentation of astaxanthin, canthaxanthin and lutein in diet. Apparent digestibility coefficients (ADC) of dry matter, lipid, protein, carotenoids, growth and pigmentation were studied in twenty fish after 14 and 56 days of observation. The single‐dose supplementation of 100 mg/kg of astaxanthin, canthaxanthin, or lutein diets on fish was fed by apparent satiation. The basal diet without carotenoids was used as control. The result showed that the ADC of carotenoids of test diets was higher compared to control. Fish fed astaxanthin diet had higher survival rate (96.67 ± 2.89%), colour measurements of lightness (57.60 ± 7.46%), a*‐values (4.66 ± 1.20), total carotenoids content in skin (33.75 ± 5.02 mg/kg) and muscle (2.16 ± 0.74 mg/kg). Astaxanthin also increased the growth after 14 days (2.00% ± 0.19%/days) but there was no significantly different at the end of experiment. The yellowish‐orange colour performance was more rapidly achieved by fish fed astaxanthin diet after 28 days experimentation. These values suggested that dietary carotenoids were required and astaxanthin diet was superior to other diets for skin pigmentation of Lake Kurumoi rainbowfish.     

Comparison of diets for the tropical spiny lobster Panulirus ornatus: astaxanthin-supplemented feeds and mussel flesh

The fast‐growing tropical lobster Panulirus ornatus is a good aquaculture candidate generating increased research to develop potential feeds. We conducted a 12‐week experiment, assessing growth, survival and tissue carotenoid levels of juvenile P. ornatus. Lobsters were fed either pelleted feeds supplemented with astaxanthin and containing 30, 60, 90 or 120 mg total carotenoid kg^?1; or one of two fresh mussel reference feeds – blue Mytilus edulis and green‐lipped Perna canaliculus. There was no clear dose response, in terms of growth rate, to increasing dietary astaxanthin content; mussel‐fed lobsters had inferior growth rates. Twelve‐week survival was unaffected by treatment. Whole lobster carotenoid (4.7, 16.7, 27.8 and 32.8 mg kg^?1, dry matter basis) increased with increasing dietary astaxanthin; pre‐treatment carotenoid was 22.2 mg kg^?1. Apparent total carotenoid content of the mussel‐fed lobsters was unexpectedly high because of interference by other pigments. High‐performance liquid chromatographic analysis of free astaxanthin levels varied from a pre‐treatment value of 7.3 mg kg^?1 to 2.0, 7.6, 12.5 and 23.6 mg kg^?1 with increasing dietary astaxanthin, and 3.5 (green‐lip) and 5.9 (blue) mg kg^?1 for the mussel‐fed lobsters. Although dietary astaxanthin, over the investigated range, did not affect growth rate or survival, there was a dose–response increase in tissue carotenoid content and darkening of the exoskeleton pigmentation, which may have important implications for immunocompetency and marketing. These implications are discussed in the context of pelleted feed development for this species.     

Calanus oil as a natural source for flesh pigmentation in Atlantic salmon (Salmo salar L.)

The present study was to understand how efficiently the astaxanthin in Calanus oil is utilized for flesh colouration in Atlantic salmon ( Salmo salar ). Postsmolts of the fish (309 g) were held at 7.9 °C and they were fed diets containing 20 or 60 mg astaxanthin per kilogram feed derived from a synthetic source or from Calanus oil for 181 days. Besides growth and feed intake assessments, at day 81 and 181, fish flesh were subjected to colour analysis and astaxanthin determination. Growth and feed performance did not vary between the groups. There were significant differences in the amount of astaxanthin in muscle between almost all groups both at day 81 ( P  < 0.05) and at day 181 ( P  < 0.001). However, a notable similarity between fish receiving 20 mg astaxanthin from the synthetic source and those receiving 60 mg astaxanthin from Calanus oil ( P  > 0.05) at day 181 indicated that comparable amounts were deposited only with the greater level of the natural source. Tristimuli colorimeter a* values support the analytical results at day 181. Although Calanus oil did serve as a natural dietary pigment source for farmed salmon, its inclusion level should provide more than 60 mg astaxanthin per kilogram feed to achieve colouration preferred by the market.     

Effects of dietary astaxanthins on pigmentation of flesh and tissue antioxidation of rainbow trout (Oncorhynchus mykiss)

The present study was conducted to evaluate the effects of three commercial astaxanthin preparations (100 mg kg^?1 diet) with different solubilities in water, from DSM (Dutch State Mines), BASF (Badische Anilin and Soda Fabrik) and Wisdom Company on pigmentation of flesh and antioxidation of flesh, serum and liver in rainbow trout with an initial weight of 52.07 g. After 60 days of feeding, there were no significant differences in growth or flesh proximate composition of rainbow trout among groups (P > 0.05); the Salmo Fan score, redness and astaxanthin content of flesh in rainbow trout fed diets supplemented with astaxanthins were higher than those of the control group (P < 0.05). At 0, 12, 24, 48 and 72 h after thawing, the flesh malondialdehyde (MDA) content of the three astaxanthin groups was lower than that of the control group (P < 0.05). The total antioxidation capacity (T-AOC) of liver in the three astaxanthin groups was significantly higher, but serum catalase (CAT) activities were lower, than that of the control group (P < 0.05). The results indicate that addition of 100 mg kg^?1 astaxanthin from DSM, BASF or Wisdom to the diet could improve flesh redness and liver T-AOC, reduce serum CAT, SOD and flesh MDA and extend the shelf life of flesh, in spite of the different solubilities of the three sources in water.     

The effects of synthetic pigments on pigmentation of Pethia conchonius (Hamilton, 1822)

This study evaluated the effects of diets containing 20, 40, 60, 80 and 100 mg kg^?1 diet astaxanthin or canthaxanthin on Pethia conchonius (Hamilton, 1822) pigmentation. A completely randomized experimental design was developed with ten treatments and three replicates. Three hundred rosy barb with a mean weight of 0.92 ± 0.06 g were assigned to thirty aquaria for period of eight weeks. Carotenoid contents of fish fed canthaxanthin were always lower than those fed astaxanthin. Yellowness (b*) was not affected by pigments. While Luminosity (L*) decreased in fish fed astaxanthin diets, this parameter increased by feeding on canthaxanthin. The most pronounced effect was higher a* values in fish fed astaxanthin. Astaxanthin retention rate was higher than that of canthaxanthin. The present results demonstrate that canthaxanthin cannot be considered as a proper replacement with astaxanthin. Inclusion of 80 and 100 mg astaxanthin kg^?1 diet can be suitable dietary levels to ensure pigmentation and this condition may improve market value of rosy barb.     

Dietary astaxanthin improved the body pigmentation and antioxidant function,but not the growth of discus fish (Symphysodon spp.)

To assess the effects of dietary astaxanthin on the growth and body colour of red discus fish (Symphysodon spp.), synthetic astaxanthin was added into the basal diet (beef heart hamburger) with the levels of 0 (control diet), 50, 100, 200, 300 and 400 mg kg^?1 respectively. The six experimental diets were fed to discus fish with an initial body weight of 10.3 ± 0.8 g for 8 weeks. The results showed that the supplementation of 50–200 mg kg^?1 astaxanthin had no significant effects on growth performance of discus fish, but the high supplementation of astaxanthin (300 or 400 mg kg^?1) significantly reduced the weight gain and increased the feed coefficient ratio (P < 0.05). After 4 or 8 weeks of feeding, the L* (lightness) values in astaxanthin‐supplemented groups were significantly lower, while a* (redness), b* (yellowness) and skin astaxanthin contents were significantly higher than the control group (P < 0.05). When the astaxanthin supplementation reached 200 mg kg^?1, skin redness and astaxanthin contents remained relatively stable. When b* was relatively stable, the supplemental astaxanthin was 300 (4 weeks) and 50 mg kg^?1 (8 weeks) respectively. With the supplemental astaxanthin increasing, the astaxanthin retention rate significantly decreased and hepatic total antioxidant capacity was strengthened. The dietary astaxanthin also significantly increased the reduced glutathione level (P < 0.05) when the astaxanthin inclusion was higher than 50 mg kg^?1. The above results showed that dietary astaxanthin could effectively improve the skin pigmentation of red discus fish in 4 weeks and the supplementation level was suggested to be 200 mg kg^?1.     

Antioxidant vitamins, minerals and lipid levels in diets for Atlantic salmon (Salmo salar, L.): effects on growth performance and fillet quality

An experiment with 2^{(7 ? 3)} reduced factorial design was conducted to study the biological effects of pro‐ and antioxidant micronutrients and lipid in Atlantic salmon. Vitamins C and E, astaxanthin, lipid, iron, copper and manganese were supplemented at high and low levels. For vitamins and minerals, high levels were chosen to be below the anticipated toxic level and the low levels were just above the requirement (vitamin C, 30 and 1000 mg kg^?1; vitamin E, 70 and 430 mg kg^?1; Fe, 70 and 1200 mg kg^?1; Cu, 8 and 110 mg kg^?1; Mn, 12 and 200 mg kg^?1). For astaxanthin, the dietary levels were 10 and 50 mg kg^?1 and for lipid, 150 and 330 g kg^?1. The experiment was started with postsmolts (148 ± 17 g) and lasted for 5 months. The variation in micronutrients had only minor effects on growth, feed conversion and fillet quality, measured as lipid and astaxanthin deposition. High dietary lipid had a profound positive effect on growth and feed conversion but gave fillets nearly two times the fat content that was found in fish fed the low lipid diet. Astaxanthin deposition in the fillet was primarily affected by dietary astaxanthin with a positive effect of high dietary lipid in week 14 but not in week 23. Vitamin E protected the fillet against iron ascorbate stimulated oxidation, with no effect of the other nutrient variables.     

Given the same dietary carotenoid inclusion, Atlantic salmon, Salmo salar (L.) display higher blood levels of canthaxanthin than astaxanthin

Atlantic salmon, Salmo salar, fitted with permanent dorsal aorta cannulae were fed diets containing either 0, 30, 60 mg kg^?1 or combinations of astaxanthin and canthaxanthin, with the aim of comparing the uptake efficiencies to blood of the two pigments and evaluating possible interactions during absorption when formulated in the same diet. Given either astaxanthin or canthaxanthin in separate diets, at dietary levels of <30 mg kg^?1, an identical linear relationship (R² = 0.97) between dietary levels and blood concentrations was observed for both carotenoids. At dietary astaxanthin inclusions above 30 mg kg^?1, blood astaxanthin concentration approached saturation at an average level of 1.2 ± 0.04 μg mL^?1 (arithmetic mean ± SD), whereas blood levels of canthaxanthin continued to increase linearly throughout the inclusion range tested (0–60 mg kg^?1). When both carotenoids were presented in the same diet, a reduction in the absorption efficiency of both pigments was observed (P < 0.05). This manifested itself as a lower level in blood than the level observed when each carotenoid was administered separately. The negative interaction was most prominent for astaxanthin, the maximum average blood saturation level of which fell (P < 0.05) to 0.73 ± 0.03 μg mL^?1 (arithmetic mean ± SD). Our data support the conclusion that at higher dietary inclusions, canthaxanthin is more efficiently absorbed from the digestive tract into the blood of S. salar than astaxanthin.     

Effects of dietary astaxanthin source and light manipulation on the skin colour of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

Two experiments were conducted with Australian snapper Pagrus auratus (Bloch and Schneider, 1801). The first was aimed at determining the dietary level of astaxanthin that improved skin redness (CIE a^*values) of farm‐reared snapper. Farmed snapper (ca. 600 g) fed a commercial diet without carotenoids were moved to indoor tanks and fed the same diet supplemented with 0, 36 or 72 mg astaxanthin kg^?1 (unesterified form as Carophyll Pink?) for nine weeks. Skin redness (CIE a^* values) continued to decrease over time in fish fed the diet without astaxanthin. Snapper fed the diet containing 72 mg astaxanthin kg^?1 were significantly more red than fish fed the diet with 36 mg astaxanthin kg^?1 three weeks after feeding, but skin redness was similar in both groups of fish after 6 and 9 weeks. The second experiment was designed to investigate the interactive effects of dietary astaxanthin source (unesterified form as Carophyll Pink? or esterified form as NatuRose?; 60 mg astaxanthin kg^?1) and degree of shading (0%, 50% and 95% shading from incident radiation) on skin colour (CIE L^*a^*b^*) and skin and fillet astaxanthin content of farmed snapper (ca. 800 g) held in 1 m³ floating cages. After 116 days, there were no significant interactions between dietary treatment and degree of shading for L^*, a^* or b^* skin colour values or the concentration of astaxanthin in the skin. Negligible amounts of astaxanthin were recovered from fillet samples. The addition of shade covers significantly increased skin lightness (L^*), possibly by reducing the effect of melanism in the skin, but there was no difference between the lightness of fish held under either 50% or 95% shade cover (P>0.05).     

Effect of microalgal biomass concentration and temperature on ornamental goldfish (Carassius auratus) skin pigmentation

The aim of this work was to investigate the effect of different carotenoid sources/concentrations and temperature on goldfish (Carassius auratus) skin pigmentation. In the first trial (trial A), the effect of carotenoid source (natural – microalgae Chlorella vulgaris and synthetic – Carophyll Pink) and carotenoid concentration (45, 80 and 120 mg pigment kg^?1 diet) was tested. Six homogeneous duplicate groups of juvenile goldfish (7.4 g) were fed, for 5 weeks, one of the diets containing 45, 80 or 120 mg of total pigments of C. vulgaris biomass or synthetic astaxanthin per kg of diet (Cv45, Cv80, Cv120, Ax45, Ax80, Ax120), respectively. In trial B, the effect of water temperature on skin pigmentation was studied. Five homogeneous duplicate groups of 25 goldfish each (5.2 g) were fed diet Ax45 over 9 weeks, to test the following temperatures: 22, 24, 26, 28 and 30 °C. At the end of both trials, samples of skin along the dorsal fin were withdrawn for subsequent analysis of total carotenoid content, intensity of colour, red and yellow hue and visual observation. The best carotenoid concentrations were achieved with astaxanthin diets. There was a tendency to an overall improvement of colour parameters (L and b) in fish fed diets with high levels of C. vulgaris. The results indicated that the best temperature range to maximize skin pigmentation was 26–30 °C.     

Intestinal absorption of astaxanthin, plasma astaxanthin concentration, body weight, and metabolic rate as determinants of flesh pigmentation in salmonid fish

Experiments were conducted to determine whether poor intestinal absorption of astaxanthin or some other metabolic factor is primarily responsible for pigmentation failure in white chinook salmon and small juvenile fish of other salmonid species. None of the fish studied failed to absorb astaxanthin from a single oral dose of the pigment. Intensity of flesh pigmentation in coho ranging in weight from 30–400 g, and fed a diet supplemented with astaxanthin, was significantly correlated with body weight. There was no correlation, however, between flesh colour and plasma astaxanthin concentration or between body weight and plasma astaxanthin concentration. Dietary triiodothyronine reduced both flesh pigmentation and plasma astaxanthin. It is concluded that poor flesh pigmentation results from rapid metabolism of absorbed pigment to colourless derivatives rather than from failure of the fish to absorb pigment.