Search

Abstract: Commercial diets fed to coho salmon (Oncorhynchus kisutch) contain high levels of fish meal and fish oil. Given concerns about future supplies and prices of these commodities, more nutritional research aimed at identifying alternative dietary ingredients for Pacific salmon is needed. Thus, utilizing a factorial design, terrestrial proteins and lipids were evaluated in practical diets fed to coho salmon. The two basal diets, containing mostly marine proteins or containing only terrestrial proteins, were extruded and top-coated with either marine fish oil or a 63:37 mixture of canola and flaxseed oils. Each of the four dietary treatments was fed to quadruplicate groups of juvenile coho salmon initially weighing 7.5g/fish. At the end of the 15-wk feeding trial, weight gain (WG), feed efficiency (FE) and survival were significantly higher in fish fed diets containing marine protein compared with fish fed diets containing terrestrial proteins. Similarly, WG and FE were significantly higher in fish fed diets containing fish oil compared with fish fed diets containing plant oils. Survival was not significantly affected by dietary lipid source. Hemoglobin, hematocrit and total protein concentrations in whole blood were significantly higher in fish fed the marine protein diets compared with fish fed the terrestrial protein diets. Hematological responses were not significantly affected by dietary lipid source. Tissue (liver, muscle and carcass) lipids in fish fed the diets with added fish oil contained significantly higher proportions of 20:5n-3 and 22:6n-3 and significantly lower 18:1n-9, 18:2n-6 and 18:3n-3 percentages compared with fish fed the diets with added plant oils. Tissue fatty acid profiles also were significantly affected by dietary protein source, as liver, muscle and whole body lipids of fish fed the terrestrial protein diets contained significantly higher percentages of 18:2n-6 and total n-6 PUFA and a significantly lower total n-3:n-6 fatty acid ratio compared with fish fed the marine protein diets. Results of this study indicate complete replacement of dietary fish meal or fish oil individually have similar inhibitory growth effects in coho salmon, but have different effects on survival, hematological responses and tissue fatty acid percentages in this species. [Copyright &y& Elsevier]

Juvenile Atlantic cod Gadus morhua (initial weight = 24.1 ± 1.4 g [mean ± SE) were fed diets in which fish meal (FM) was replaced with soy protein concentrate (SPC) and soybean meal (SBM) in isonitrogenous, isocaloric diets for 84 d. A standard marine finfish diet (3 mm, 54% protein, 14% fat) was modified to produce four experimental diets in which 50% of FM was replaced with soy at 0:1, 1:1, or 1:2 ratios of SPC:SBM and 100% FM replacement with a 1:1 ratio of SPC:SBM. No differences in mortality or feed intake were detected among treatments, and fish fed the 50% FM replacement diets, in any combination, grew as well or better than the control for all variables investigated. Cod fed the 100% FM replacement diet exhibited the lowest growth and differed from the control with respect to final body weight, growth, specific growth rate, and thermal-unit growth coefficient. No enteritis was observed in histological sections. These results indicate that 100% fish meal replacement is not recommended, but 50% replacement can be used without significant reductions in growth or condition indices. Received October 18, 2011; accepted January 11, 2012 [ABSTRACT FROM AUTHOR]

This study determined the digestibility of protein in partially dehulled sunflower meal (SFM) and then, as the main goal, the nutritive value of high-temperature extruded (≤149°C) partially dehulled SFM (SFMEX) for post-smolt Atlantic salmon Salmo salar in sea water. The digestibility study was conducted using the settling column approach (‘Guelph system’) for faeces collection as described by Hajen, Higgs, Beames and Dosanjh. In the nutritive value study, triplicate groups of 50 salmon (mean weight ∼116 g) in 4000-L outdoor fibreglass tanks supplied with 25–40 L min−1, filtered, oxygenated (dissolved oxygen, 7.0–8.5 mg L−1), 11–12°C sea water (salinity, 29–31 g L−1), were fed twice daily to satiation one of five steam-pelleted dry diets that contained 422 g of digestible protein (DP) kg−1 and ∼16.4 MJ of digestible energy (DE) kg−1 on a dry weight basis for 84 days. Low-temperature-dried anchovy meal (LT-AM) comprised 68.2% of the basal diet protein whereas in four test diets, SFMEX progressively replaced up to 33.0% of the DP provided by LT-AM in the basal diet (SFMEX≤271 g kg−1 of dry matter). Sunflower meal had 87.9% DP. Diet treatment did not significantly affect specific growth rate (1.39–1.45% day−1), feed efficiency (1.19–1.26), percentage of dietary protein retained (45.8–47.5), gross energy utilization (46.5–49.4%), per cent survival (96.0–99.3) or terminal whole body and muscle proximate compositions. We conclude that SFMEX can comprise ≥271 g kg−1 of the dry diet or ≥22.7% of the digestible dietary protein of post-smolt Atlantic salmon in seawater without any adverse effects on their performance. [ABSTRACT FROM AUTHOR]

A feeding trial was conducted in a closed recirculating aquaculture system with Nile tilapia Oreochromis niloticus juveniles (mean weight, 6.81 g) to examine the response to a practical diet containing protein primarily from menhaden fish meal (FM) and soybean meal (SBM) (control, Diet 1) or to diets with decreasing ratios of PBM to SBM (Diets 2–7; dose–response) as a total replacement for digestible protein from FM, and the efficacy of 1% supplemental taurine (Tau) at the highest level of plant protein inclusion by removing Tau (Diet 8). To the extent possible, the replacement diets were formulated using currently published amino acid availabilities for the ingredients of interest in order to estimate and supplement the first two limiting amino acids (Met and Lys) to match levels in the FM control diet. The test diets were formulated to contain 35% digestible protein. Fish were fed three times daily all they would consume in 30 min. All performance measures were quadratic with respect to PBM:SBM ratio in the diet. The highest weight gain, lowest average daily feed intake, lowest feed conversion, and greatest specific growth rate coincided with a dietary PBM:SBM ratio of 1.22 to 1.35 suggesting that the best tilapia performance in the current trial was achieved with replacement formula D3 that contained approximately 20% SBM, 30% PBM, and supplemental Lys, Met, and Tau. However, all growth performance measures were significantly linear and decreased with respect to increasing distance from the ideal protein amino acid profile for tilapia. Positive effects of taurine supplementation at the highest level of dietary plant protein inclusion were not observed and may have been overwhelmed by imbalances in other amino acids in the test diets. The current results provide evidence that total deviation from the ideal protein profile in tilapia is an important consideration for diet formulation when combinations of diet ingredients are used. Hence, the essential amino acid content of a fish meal control diet may be an inadequate target for optimizing fish meal replacement diets for tilapia; whereas the whole body or muscle amino acid pattern may be a more useful formulation target. Finally, while the database of ingredients that have been evaluated in tilapia is growing, the industry will benefit from more efficient diets as long-term averages of amino acid composition and digestibility accrue for a variety of traditional and novel ingredients. Statement of Relevance : The current results provide evidence that it is the total deviations from a postulated ideal protein profile that is a more important consideration for diet formulation than the combination of diet ingredients used to meet that profile. Therefore, it should be possible to formulate least-cost fish meal replacement diets for tilapia, irrespective of ingredient combinations, and diet intact protein level, as long as a reasonable amino acid model is chosen and a fairly robust set of ingredient composition and digestibility data are available. [ABSTRACT FROM AUTHOR]