Digestive Efficiency, Growth and Qualities of Muscle and Oocyte in Atlantic Salmon (Salmo Salar L.) Fed on Diets With Krill Meal as an Alternative Protein Source

Abstract

Atlantic krill meal and Antarctic krill meal were tested to replace fish meal in Atlantic salmon diets. Different techniques were applied to precisely evaluate dietary quality and quality of fish growth performance. Inverse relationship between trypsin specific activity (T) and ratio of trypsin to chymotrypsin (T/C ratio) as a result of increased chymotrypsin specific activity (C) in the pyloric ceca indicated fish growth status as a reduction in growth rate. These protease values in the feces could also indicate fish digestive efficiency, but could not predict fish growth status. There were relationships among feed conversion efficiency (FCE), in vitro digestibility, and pyloric cecal T/C ratio, with inverse levels of krill meal in the diets. Krill meal seemed to increase muscle protein concentration through increasing protein retention, as capacity for protein synthesis was reduced. Dietary quality tests by in vitro digestibility were corresponded with growth studies, and indicated a possibility of inclusion of krill meal at 50–60% replacements, and larger fish were more sensitive to dietary quality than smaller ones. At 80–100% replacements, in vitro digestibility and FCE reduced, and oocyte quality changed through increased trypsin‐like specific activity probably because of less or abnormal oocyte development. PRACTICAL APPLICATIONS The work illustrates differences in digestive efficiency and the quality of growth performance (protein growth efficiency and capacity for protein synthesis in muscle and oocytes) in fish feeding on diets with different levels of krill meal as fish meal replacer. The advantage of using various methods simultaneously for evaluating digestive efficiency and the quality of fish growth performance is to precisely provide reasonable information for some important biological differences between fish groups that could not be explained by using growth parameter alone, especially when the numbers of samples are not high. The methods are very practical for studying food quality, food utilization and growth quality of fish in different environmental conditions and with different behaviors in aquaculture as well as in natural ecosystem where food consumption rate cannot be measured. The in vitro digestibility method, using fish crude enzyme extracts and standardized by trypsin activity, could also compare the digestive ability between different species and provide information on food quality in fish growth trials that may not be necessary to be performed.

Different Dietary Levels of Protein to Lipid Ratio Affected Digestive Efficiency, Skeletal Growth, and Muscle Protein in Rainbow Trout Families

“…[20,[28][29][30]. The protein concentration of the standards was determined using TRIzol reagent (Life Technologies, NY, USA) to obtain complete solubilisation of protein, as described in RungruangsakTorrissen [11] modified from Sunde et al [10,18].…”

“…Traditionally in aquaculture, dietary protein and lipid are varied throughout the life cycle to optimise the economic return. In the current work, we aim to understand a basic knowledge on long-term protein growth by investigating the effects of maintaining dietary protein and lipid concentrations throughout the fish life cycle on digestive efficiency and protein growth using a unique combination of techniques recently described by Rungruangsak-Torrissen's research team [11,12,14]. In addition, we also aim to study the potential for maximising protein growth efficiency in rainbow trout (Oncorhynchus mykiss Walbaum) families with differences in growth capacity by varying the concentrations of dietary protein and lipid.…”

“…The growth efficiency of several fish species has been studied through variation of dietary protein levels, and the results have shown not only the relationships between dietary protein concentration and physiological parameters of consumption, growth, and protein content in body or muscle, but also shown certain increased levels of dietary protein limited consumption and growth of the fish recently, that is, [1][2][3][4][5][6][7][8][9]. Increased growth is usually not associated with an increase in protein deposition rate, that is, [10][11][12], but rather an increase in lipid deposition rate, that is, [8,13]. Traditionally in aquaculture, dietary protein and lipid are varied throughout the life cycle to optimise the economic return.…”

“…The digestive efficiency was studied at the end of the experiment at the late stage of life cycle. It is advantageous to use the different methods simultaneously, as they could precisely provide practical important biological informations between fish groups with differences in genetics (growth capacity) and environmental impacts (diet quality) that could not be explained by using growth parameter alone, especially when feeding regime were not completely under control see [11,12,14]. Intestinal, gonad, and carcass weights were measured.…”

“…Feed intake was measured by X-ray method using diets labelled with radio-opaque markers [15]. The in vitro protein digestibility of formulated fish feeds was determined using fish crude enzyme extracts, as it has been correlated with the feed efficiency [11,16] and the chemical properties of dietary proteins, positively with the levels of reactive sulphydryl group and negatively with the levels of disulphide bond and D-aspartic acid [16]. Fish digestive efficiency [trypsin specific activity and the protease activity ratio of trypsin to chymotrypsin (T/C ratio)] was measured because of their known positive associations with fish growth rate [10-12, 14, 17, 18].…”