No abstract

A series of experiments were conducted with black tiger shrimp (Penaeus monodon) juveniles to firstly determine the effects of reducing fishmeal inclusion in a diet and then to evaluate the potential for a microbial bioactive to support complete replacement of both fishmeal and fish oil in feeds when fed under clear-water and green-water conditions. The isoproteic and isoenergetic replacement of fishmeal resulted in a consistent decline in growth performance indicating that at every decrease in fishmeal below an inclusion level of 45% there was a decline in performance. In a subsequent trial undertaken in a clear-water tank system diets devoid of both fishmeal and fish oil fed to shrimp were demonstrated to produce poorer performance than a fishmeal and fish oil reference diet. However the addition of a microbial bioactive to the diet resulted in not only a compensation for the replacement of these ingredients but additional growth. Replication of the clear-water trial in a green-water tank system produced similar results, but also showed that the green-water system largely compensated for the performance lost through replacement of fishmeal and fish oil. However it was also shown that the use of the microbial bioactive in the diets still resulted in improved growth performance of shrimp. This study has effectively demonstrated a viable strategy for not only a complete replacement of all fishery products in shrimp diets, but an improved performance strategy.

22This study examined the effect of including different dietary proportions of starch, protein 23 and lipid, in diets balanced for digestible energy, on the utilisation efficiencies of dietary energy by 24 barramundi (Lates calcarifer). Each diet was fed at one of three ration levels (satiety, 80% of initial 25 satiety and 60% of initial satiety) for a 42-day period. Fish performance measures (weight gain, feed 26 intake, and feed conversion ratio) were all affected by dietary energy source. The efficiency of energy 27 utilisation was significantly reduced in fish fed the starch diet relative to the other diets, but there 28 were no significant effects between the other macronutrients. This reduction in the efficiency of Barramundi are an obligate carnivorous fish species that is the basis of a significant 40 aquaculture industry in Southeast Asia and Australia (1). The development of high-nutrient density 41 formulated extruded feeds has been underpinned by the development of both a series of factorial 42 bioenergetic nutritional models and foundation empirical studies (1, 2, 3, 4, 5). These nutritional 43 models have so far relied on the assumption that the dietary digestible energy (DE) source is 44 irrelevant; that is that the dietary DE derived from protein, lipid and starch is utilised with equal 45 efficiency, subject to key nutrients (e.g. protein) being provided at/or above minimum critical ratios to 46 energy supply (4, 5, 6, 7, 8, 9, 10). 47 Each of the different macronutrients (starch, protein and lipid) supplies energy by distinct 48 metabolic pathways. In aquatic animals it is recognised that there are different levels of efficiency in 49 the utilisation of each these macronutrients for energy (11, 12). It is now recognised that this 50 difference requires an amendment of the digestible nutritional values of each macronutrient to those 51 of metabolisable nutritional values and/or net energy nutritional values (9, 12, 13, 14). Recent work 52 by Schrama et al. (14) examined the utilisation of both starch and lipid for growth by the omnivorous respectively. These observations clearly indicated that this fish species used lipid as an energy source 57 for growth more efficiently. However, the third key macronutrient, protein, was not considered in this 58 study. In that same study, Schrama et al. (14) in reviewing the literature identified that there was a 59 wide variability (0.31 to 0.82) in the kgDE of different studies. It was suggested that the three primary 60 reasons for this variability were: different dietary macronutrient compositions; trophic level of the fish 61 species; and the composition of the growth. In addition, there is increasing evidence that the roles of 62 gluconeogenesis, glycolysis and -oxidation play substantially different relative roles in energy 63 provision in fish compared to other vertebrates (11, 14, 15, 16, 17). 64 The objective of this study was to determine the partial efficiencies of utilisation of each of 65 the d...

The predominant carotenoid in prawn tissues is astaxanthin (Axn) and its role in pigmentation has been well studied. However, the effects of dietary Axn on other prawn physiological performance measures are uncertain and dietary carotenoid uptake and tissue deposition are poorly understood. This study fed juvenile prawns (Penaeus monodon) diets that contained 0, 25, 50 or 100 mg kg -1 Axn for 6 weeks. Animals fed carotenoid free diets had significantly reduced growth than those fed carotenoids, but survival was unaffected. Carotenoid uptake (digestibility) improved as dietary carotenoid levels increased, and was 98.5% in animals fed 100 mg kg -1 Axn. After 6 weeks, whole body carotenoid levels were significantly depleted in 0 or 25 mg kg -1 fed animals, compared with those fed 50 or 100 mg kg -1 . Specific fatty acid esters of Axn accumulated in epithelial tissue, with mono-esters enriched saturated fatty acids, while di-esters were enriched with monounsaturated and polyunsaturated fatty acids. These data suggest a minimum dietary requirement of 25 mg kg -1 Axn in clear water systems to maintain growth performance, and 50 mg kg -1 or more to avoid depletion of body carotenoid levels and improve efficiency of utilisation. These results also implicate specific fatty acids in the function of carotenoid esters within prawn tissues.