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.

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.

Effects of cage netting colour and density on the skin pigmentation and stress response of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

The unnaturally dark pigmentation of cultured Australian snapper Pagrus auratus can be improved through dietary astaxanthin supplementation and by holding fish in tanks with a white background. The practical application of these  laboratory-based findings was examined with two experiments to establish if the advantages of transferring fish to light coloured tanks before harvest could be achieved on-farm using white cages and to determine the effects of fish density on skin colour. For the first experiment, snapper (mean TL=29.7 cm) were transferred from a commercial snapper sea cage to black or white netted cages and fed diets supplemented with unesterified astaxanthin (supplied as Lucantin^® Pink, BASF) at 0 or 39 mg kg⁻¹ for 42 days. Skin colour was measured using the CIE L* (black–white), a* (green–red), b* (blue–yellow) colour scale. Snapper held in white netting cages became significantly lighter (higher L* ) than snapper held in black cages; however, values were not as high as previous laboratory-based studies in which snapper were held in white plastic-lined cages. Snapper fed astaxanthin displayed significantly greater a*and b* values, and total carotenoid concentrations after 42 days. In addition, total carotenoids were higher in fish from black than white cages. The second experiment was designed to investigate whether density reduced the improvements in skin colour achieved by holding fish in white coloured cages and whether cage colour affected stress. Snapper (mean weight=435 g) were acclimated to black cages and fed 39 mg kg⁻¹ astaxanthin for 44 days before transferring to black or white plastic-lined cages at 14 (low), 29 (mid) or 45 (high) kg m⁻³ for 7 days after which time skin colour, plasma cortisol and plasma glucose concentrations were measured. Skin lightness (L* ) was greater in snapper transferred to white plastic-lined cages with the lightest coloured fish obtained from the lowest density after 7 days. Density had no effect on plasma cortisol or glucose levels after 7 days, although plasma cortisol was elevated in snapper from black cages. For improved skin colouration we recommend feeding unesterified astaxanthin at 39 mg kg⁻¹ for approximately 6 weeks and transferring snapper to white plastic-lined cages or similar at low densities for short periods before harvest rather than producing fish in white netting sea cages subject to biofouling.

Determination of astaxanthin steroisomers and colour attributes in flesh of rainbow trout (Oncorhynchus mykiss) as a tool to distinguish the dietary pigmentation source

The presence of carotenoids in animal tissue reflects their sources along the food chain. Astaxanthin, the main carotenoid used for salmonid pigmentation, is usually included in the feed as a synthetic product. However, other dietary sources of astaxanthin such as shrimp or krill wastes, algae meal or yeasts are also available on the market. Astaxanthin possesses two identical asymmetric atoms at C-3 and C-3' making possible three optical isomers with all-trans configuration of the chain: 3S,3'S, 3R,3'S, and 3R,3'R. The distribution of the isomers in natural astaxanthin differs from that of the synthetic product. This latter is a racemic mixture, with a typical ratio of 1:2:1 (3S,3'S:3R,3'S:3R,3'R), while astaxanthin from natural sources has a variable distribution of the isomers deriving from the different biological organism that synthesized it. The high-performance liquid chromatographic (HPLC) analysis of all-trans isomers of astaxanthin was performed in different pigment sources, such as red yeast Phaffia rhodozyma, alga meal Haematococcus pluvialis, krill meal and oil, and shrimp meal. With the aim to investigate astaxanthin isomer ratios in flesh of fish fed different carotenoid sources, three groups of rainbow trout were fed for 60 days diets containing astaxanthin from synthetic source, H. pluvialis algae meal and P. rhodozyma red yeast. Moreover, the distribution of optical isomers of astaxanthin in trout purchased on the Italian market was investigated. A characteristic distribution of astaxanthin stereoisomers was detected for each pigment sources and such distribution was reproduced in the flesh of trout fed with that source. Colour values measured in different sites of fillet of rainbow trout fed with different pigment sources showed no significant differences. Similarly, different sources of pigment (natural or synthetic) produced colour values of fresh fillet with no relevant or significant differences. The coefficient of distance computed amongst the feed ingredient and the trout fillet astaxanthin stereoisomers was a useful tool to identify the origin of the pigment used on farm.

Dietary restraint and negative affect as mediators of body dissatisfaction and bulimic behavior in adolescent girls and boys

Stice's dual pathway model of dietary restraint and negative affect was examined in both adolescent girls and boys. Self-report measures assessing body dissatisfaction, dietary restraint, negative affect and bulimic behavior were administered to 267 girls and 199 boys aged between 12 and 16 years. The findings for the girls were consistent with Stice's model, in that they indicated that both dietary restraint and negative affect mediated the relationship between body dissatisfaction and bulimic behavior. For the boys who desired a thinner body size, only negative affect was found to mediate the relationship between body dissatisfaction and bulimic behavior. On the other hand, for boys who desired a larger body size, both body dissatisfaction and dietary restraint were found to exert an independent effect on bulimic behavior. As boys can aspire to two contrasting and seemingly opposite body size ideals, the findings highlight that the relationship between body dissatisfaction, dietary restraint, negative affect and bulimic behavior are more complex in males than in females. Further research using longitudinal designs is needed in order to test the directional and bidirectional nature of the observed interrelationships.

Growth of Australian shortfin eel (Anguilla Australis) elvers given different dietary protein and lipid levels

The Australian shortfin eel, Anguilla australis is a potential candidate for intensive aquaculture. The present study was undertaken to evaluate the growth of elvers (5.4 g ± 0.1 initial weight) fed with diets of varying protein and lipid content, and to assess the potential of using soya-bean meal as a dietary ingredient. A 10 week experiment was conducted at 24 (±1.0) °C by rearing fish, in 60 L conical fibre glass tanks using a closed recirculation system. Diets having protein concentrations of 40 or 50% (by dry weight) were tested at three lipid levels (15, 20, 25%); diets being designated P₄₀L₁₅, P₄₀L₂₀, P₄₀L₂₅, P₅₀L₁₅, etc. All these diets contained 5% soya-bean meal. In addition P₅₀L₂₀ diets were formulated to contain 10 and 20% soya-bean meal in the diet (Diets S1 & S2). Shortfin eel grew best on the P₅₀L₁₅ diet, with an average specific growth rate of 2.26%. Food conservation ratio (FCR) and Protein efficiency ratio (PER) ranged from 1.21 (P₅₀L₁₅) to 2.12 (P₄₀L₂₅), and 0.92 (P₅₀L₂₅) to 1.65 (P₅₀L₁₅), respectively. Based on all criteria the best growth performance of shortfin eel was on the P₅₀L₁₅ diet, followed by P₄₀L₂₀ and P₄₀L₁₅. At both protein levels fish reared on diets with 25% lipid performed poorly. The performance of shortfin eel was not affected by the amount of soya-bean meal in the diet, up to a maximum of 20% dietary inclusion. No significant differences in muscle protein were evident in shortfin eel reared on different dietary treatments, nor was the lipid content of muscle related to dietary lipid level.

Sustaining dietary changes for preventing obesity and diabetes: lessons learned from the successes of other epidemic control programs

A degree of success has been achieved in controlling several epidemics of infectious and non-infectious causes of death in countries, such as, Australia and New Zealand. Using the epidemiological triad (host, vector, environment) as a model, the key components of the control of these epidemics have been identified and compared to the current status of interventions to prevent obesity and its main disease consequence, type 2 diabetes. Reductions in mortality from tobacco, cardiovascular diseases, road crashes, cervical cancer and sudden infant death syndrome have been achieved by addressing all corners of the triad. Similarly, prevention programs have minimized the mortality from HIV AIDS and melanoma mortality rates are no longer rising. The main lessons learned from these prevention programs that could be applied to the obesity/diabetes epidemic are: taking a more comprehensive approach by increasing the environmental (mainly policy-based) initiatives; increasing the 'dose' of interventions through greater investment in programs; exploring opportunities to further influence the energy density of manufactured foods (one of the main vectors for increased energy intake); developing and communicating specific, action messages; and developing a stronger advocacy voice so that there is greater professional, public and political support for action. Successes in the other epidemics have been achieved in the face of substantial barriers within individuals, society, the private sector and government. The barriers for preventing obesity/diabetes are no less formidable, but the strategies for surmounting them have been well tested in other epidemics.

Dietary items of the black falcon falco subniger and zebra finch taeniopygia guttata in Northern Victoria

This note reports an incidental observation of a Black Falcon Falco subniger taking a Zebra Finch Taeniopygia guttata. The captured Finch voided the contents of its crop, revealing that it had been feeding on Onion Grass Romulea rosea. Zebra Finches have not been reported in the diet of Black Falcons, and Onion Grass seeds have not been reported in the diet of Zebra Finches previously.

Dietary regulation of fat oxidative gene expression in different skeletal musle fiber types

Objective: To determine the effect of a high-fat diet on the expression of genes important for fat oxidation, the protein abundance of the transcription factors peroxisome proliferator-activated receptor (PPAR) isoforms α and γ, and selected enzyme activities in type I and II skeletal muscle. Research Methods and Procedures: Sprague-Dawley rats consumed either a high-fat (HF: 78% energy, n = 8) or high-carbohydrate (64% energy, n = 8) diet for 8 weeks while remaining sedentary. Results: The expression of genes important for fat oxidation tended to increase in both type I (soleus) and type II (extensor digitorum longus) fiber types after an HF dietary intervention. However, the expression of muscle type carnitine palmitoyltransferase I was not increased in extensor digitorum longus. Analysis of the gene expression of both peroxisome proliferator-activated receptor-γ coactivator and forkhead transcription factor O1 demonstrated no alteration in response to the HF diet. Similarly, PPARα and PPARγ protein levels were also not altered by the HF diet. Discussion: An HF diet increased the expression of an array of genes involved in lipid metabolism, with only subtle differences evident in the response within differing skeletal muscle fiber types. Despite changes in gene expression, there were no effects of diet on peroxisome proliferator-activated receptor-gamma coactivator and forkhead transcription factor O1 mRNA and the protein abundance of PPARα and PPARγ.

Decreasing dietary sodium while following a self-selected potassium-rich diet reduces blood pressure

Reducing dietary sodium reduces blood pressure (BP), a major risk factor for cardiovascular disease, but few studies have specifically examined the effect on BP of altering dietary sodium in the context of a high potassium diet. This randomized, crossover study compared BP values in volunteer subjects self-selecting food intake and consuming low levels of sodium (Na+; 50 mmol/d) with those consuming high levels of sodium (> or =20 mmol/d), in the context of a diet rich in potassium (K+). Sodium supplementation (NaSp) produced the difference in Na+ intake. Subjects (n = 108; 64 women, 44 men; 16 on antihypertensive therapy) had a mean age of 47.0 ± 10.1 y. Subjects were given dietary advice to achieve a low sodium (LS) diet with high potassium intake (50 mmol Na+/d, >80 mmol K+/d) and were allocated to NaSp (120 mmol Na+/d) or placebo treatment for 4 wk before crossover. The LS diet decreased urinary Na+ from baseline, 138.7 ± 5.3 mmol/d to 57.8 ± 3.8 mmol/d (P < 0.001). The NaSp treatment returned urinary Na+ to baseline levels 142.4 ± 3.7 mmol/d. Urinary K+ increased from baseline, 78.6 ± 2.3 to 86.6 ± 2.1 mmol/d with the LS diet and to 87.1 ± 2.1 mmol/d with NaSp treatment (P < 0.001). The LS diet reduced home systolic blood pressure (SBP) by 2.5 ± 0.8 mm Hg (P = 0.004), compared with the NaSp treatment. Hence, reducing Na+ intake from 140 to 60 mmol/d significantly decreased home SBP in subjects dwelling in a community setting who consumed a self-selected K+-rich diet, and this dietary modification could assist in lowering blood pressure in the general population.

Energy density of foods and beverages in the Australian food supply: influence of macronutrients and comparison to dietary intake

Objectives: The energy density (ED) of the diet is considered an important determinant of total energy intake and thus energy balance and weight change. We aimed to compare relationships between ED and macronutrient content in individual food and beverage items as well as population diet in a typical Western country. Design: Nutrient data for 3673 food items and 247 beverage items came from the Australian Food and Nutrient database (AusNut). Food and beverage intake data came from the 1995 Australian National Nutrition Survey (a 24-h dietary recall survey in 13 858 people over the age of 2). Relationships between ED and macronutrient and water content were analysed by linear regression with 95% prediction bands. Results: For both individual food items and population food intake, there was a positive relationship between ED and percent energy as fat and negative relationships between ED and percent energy as carbohydrate and percent water by weight. In all cases, there was close agreement between the slopes of the regression lines between food items and dietary intake. There were no clear relationships between ED and macronutrient content for beverage items. Carbohydrate (mostly sucrose) contributed 91, 47, and 25% of total energy for sugar-based, fat-based, and alcohol-based beverages respectively. Conclusions: The relationship between ED and fat content of foods holds true across both population diets and individual food items available in the food supply in a typical Western country such as Australia. As high-fat diets are associated with a high BMI, population measures with an overall aim of reducing the ED of diets may be effective in mediating the growing problem of overweight and obesity.

Blood pressure response to dietary modifications in free-living individuals 1,2

A diet rich in fruits, vegetables, and low-fat dairy foods has been shown to lower blood pressure (BP) when all foods are provided. We compared the effect on BP (measured at home) of 2 different self-selected diets: a low-sodium, high-potassium diet, rich in fruit and vegetables (LNAHK) and a high-calcium diet rich in low-fat dairy foods (HC) with a moderate-sodium, high-potassium, high-calcium DASH-type diet, high in fruits, vegetables and low-fat dairy foods (OD). Subjects were randomly allocated to 2 test diets for 4 wk, the OD and either LNAHK or HC diet, each preceded by a 2 wk control diet (CD). The changes in BP between the preceding CD period and the test diet period (LNAHK or HC) were compared with the change between the CD and the OD periods. Of the 56 men and 38 women that completed the OD period, 43 completed the LNAHK diet period and 48 the HC diet period. The mean age was 55.6 ± 9.9 (±SD) years. There was a fall in systolic pressure between and the CD and OD [-1.8 ± 0.5 mm Hg (P < 0.001)]. Compared with OD, systolic and diastolic BPs fell during the LNAHK diet period [-3.5 ± 1.0 (P < 0.001) and -1.9 ± 0.7 (P < 0.05) mmHg, respectively] and increased during the HC diet period [+3.1 ± 0.9 (P < 0.01) and +0.8 ± 0.6 (P = 0.15) mm Hg, respectively]. A self-selected low-sodium, high-potassium diet resulted in a greater fall in BP than a multifaceted OD, confirming the beneficial effect of dietary intervention on BP in a community setting.

How well do Australian women comply with dietary guidelines?

Objective: To investigate the proportion of middle-aged Australian women meeting national dietary recommendations and its variation according to selected sociodemographic and behavioural characteristics.

Design: This cross-sectional population-based study used a food-frequency questionnaire to investigate dietary patterns and compliance with 13 commonly promoted dietary guidelines among a cohort of middle-aged women participating in the Australian Longitudinal Study on Women's Health.

Setting: Nation-wide community-based survey.

Subjects: A total of 10 561 women aged 50–55 years at the time of the survey in 2001.

Results: Only about one-third of women complied with more than half of the guidelines, and only two women in the entire sample met all 13 guidelines examined. While guidelines for meat/fish/poultry/eggs/nuts/legumes and ‘extra’ foods (e.g. ice cream, chocolate, cakes, potatoes, pizza, hamburgers and wine) were met well, large percentages of women (68–88%) did not meet guidelines relating to the consumption of breads, cereal-based foods and dairy products, and intakes of total and saturated fat and iron. Women working in lower socio-economic status occupations, and women living alone or with people other than a partner and/or children, were at significantly increased risk of not meeting guidelines.

Conclusions: The present results indicate that a large proportion of middle-aged Australian women are not meeting dietary guidelines. Without substantial changes in their diets, and help in making these changes, current national guidelines appear unachievable for many women.

Do dietary changes of Australasian gannets (Morus serrator) reflect variability in pelagic fish stocks?

The relationship between changes in the diet of Australasian gannets (Morus serrator) and commercial fisheries landings was investigated. The contribution of pilchard (Sardinops sagax) to the diet of gannets was significantly related to the commercial catch of that species, suggesting that changes in the relative proportion of pilchard in the diet of gannets may be a useful index of pilchard abundance and availability. Equivalent relationships, however, were not found for other common prey species in the gannet diet. It is considered that the abundance of important prey items in the gannet diet, such as pilchards, and commercial landings are proportional to stock abundance. The implications of this relationship for fisheries management are examined.