Effects of increasing replacement of dietary fishmeal with plant protein sources on growth performance and body lipid composition of Atlantic salmon (Salmo salar L.)

The effects of high levels of replacement of dietary fish meal (FM) by mixtures of plant protein (PP) sources on growth performance, lipid composition, protein and lipid digestibility and fatty acid profile were investigated in Atlantic salmon, Salmo salar. Experimental diets containing 35% protein and 28% lipid were formulated with a low level of FM that was replaced by increasing levels of PP resulting in four diets of 25/45 ((% FM/% PP, F25), 18/50 (F18) 11/55 (F11) and 5/60 (F5). Dietary oil was supplied by a fish oil (FO) and rapeseed oil blend at a ratio of ~40/60 so this formulation was effectively a dual replacement of FO and FM. Diets were supplemented with crystalline amino acids, to compensate for the reduction in indispensible amino acids due to reduced FM content, and all diets were supplemented with lecithin. Salmon, initial weight 1.30 ± 0.1 kg, were fed one of the four experimental diets for 19 weeks. Feed consumption decreased as PP inclusion in diets increased, probably as a result of reduced palatability. Fish fed the F18, F11 and F5 diets had significantly lower final body weights than fish fed the F25 diet, with SGR decreased by 5 %, 11 % and 23 %, respectively. The lower growth as FM inclusion in diets decreased was associated with decreased feed intake throughout the trial. In contrast, nutrient utilization was significantly affected in the first phase with increased FCR and decreased PER as FM inclusion decreased. However, there were no significant differences in these parameters in the second phase suggesting that there was metabolic adaptation to the diets. Changes in feed physical texture and/or chemical olfactory attractants possibly reduced the palatability of the diets. Essential fatty acid composition, in particular EPA, DHA and ARA in salmon flesh and liver were not negatively affected by dietary treatment and there was some evidence of increased retention and/or synthesis of LC-PUFA

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Not AvailableSeven groups of kids were fed on isonitrogenous diets identical in all respects, except in the nature of the protein. Proteins in all test diets were derived from fish subjected to heat treatment under different conditions. Control group had skim milk as the sole source of protein. 5 test groups their proteins from muscle of the lean fish whiting, heat processed under different conditions. The seventh group had a spray dried and solvent extracted functional fish protein concentrate prepared from fatty fish capelin as the sole source of protein.The effect of the mode and extent of thermal denaturation of fish protein on the rate of abomasum emptying in kids was studied using these diets with a view to check the possiblity that increased thermal denaturation causes lesser coagulation of the protien in the abomasum resulting in reduced digestibility. Results however, indicate that in kids, the extent of thermal denaturation of the protein in the diet cannot be directly correlated to the rate of abomasal emptying. Resulting are discussed in the light of earlier reported differences in protein digestibility between these diets in calves.Not Availabl

Racemization kinetics of aspertic acid in fish material under different conditions of moisture, pH, and oxygen pressure

The racemization kinetics of aspartic acid in heat-treated whole herring have been studied under conditions of treatment comparable to those that may occur in processing of fish meal. D-Aspartic acid content in the samples has been measured by RP-HPLC with precolumn automatic derivatization. The major parameters affecting the rate of racemization of aspartic acid k(Asp) have been demonstrated to be temperature (elevation of temperature from 95 to 120 \ub0C resulted in an increase of k(Asp) from 0.46 to 3.39 x 10-3 min-1), moisture of the raw material (reduction of the moisture content of the raw material from 80 to 15% lowered k(Asp) measured at 95 \ub0C from 0.46 to 0.06 x 10-3 min-1), and to a lesser extent, pH (k(Asp) at 95 \ub0C was lowered from 0.46 to 0.37 x 10-3 min-1 following a decrease of pH from 7.0 to 4.0). No significant effects on the racemization rate of aspartic acid was observed for reducing the oxygen pressure to 0.8 %. The results from the present study show that the content of D-aspartic acid in fish material is a function of heat exposure and may be used to predict the thermal history of fish meal