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...
An experiment was conducted with barramundi (Lates calcarifer) juveniles to examine the marginal efficiency of utilisation of long chain-polyunsaturated fatty acids (LC-PUFA). A series of five diets with blends of fish (anchovy) oil and poultry fat (F100:P0, F60:P40, F30:P70, F15:P85, F0:P100) were fed to 208 ± 4.1 g fish over a 12-week period. The replacement of fish oil with poultry fat had no impact on growth performance (average final weight of 548.3 ± 10.2 g) or feed conversion (mean = 1.14 ± 0.02). Analysis of the whole body composition showed that the fatty acid profile reflected that of the fed diet. However it was also shown that there was a disproportional retention of some fatty acids relative to others (notably LOA,. By examining the body mass independent retention of different fatty acids with differential levels of intake of each, the marginal efficiencies of the use these nutrients by this species were able to be determined. The differential retention of fatty acids in the meat was also examined allowing the determination of oil blending strategies to optimise meat n-3 LC-PUFA levels.
A series of experiments were conducted to examine the nutrient and energy digestibility of a suite of diets and specific test raw materials when fed to juvenile (179 to 439 g) barramundi, Lates calcarifer. Each of the diets was prepared using a twin-screw extruder to mimic modern aquafeed manufacturing processes. Each of the diets was fed to juvenile barramundi for a minimum of a week to allow acclimation to the diet before the faeces were collected using stripping methods. A broad range of digestible nutrient and energy values among the different raw materials were observed, with protein digestibilities ranging from 36% to 106% and energy digestibilities ranging from 36% to 93%. This range in nutritional values of the different raw materials provides substantial utility in allowing the formulation of diets on a digestible nutrient and energy basis across the Asia Pacific region. These results also provide critical data to help underpin the replacement of both fishmeal and fish oil in barramundi diets. K E Y W O R D Sanimal by-products, Asian seabass, digestibility, ingredients, plant proteins 1 CSIRO Aquaculture,
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