Tillner R.,Leibniz Institute of Marine Science |
Ronnestad I.,University of Bergen |
Dhert P.,Skretting |
Ueberschar B.,Leibniz Institute of Marine Science |
Ueberschar B.,Society Association for Marine Aquaculture Ltd.
Aquaculture | Year: 2014
Improving the understanding of digestive physiology in first feeding larvae is a prerequisite for advancing diet formulations and feeding protocols. In marine fish larvae that lack a stomach at first-feeding trypsin represents the main proteolytic enzyme. CCK is one of the key regulators of digestive enzyme secretion in adult vertebrates and current knowledge suggests that it is also involved in early stages of teleosts, although this may vary between species. Here, we investigated the influence of Artemia and a commercial microdiet on the ontogenetic development of tryptic enzyme activity as an indicator for digestive capacity in first-feeding sea bass. In order to examine the regulation and feedback mechanisms in the digestive tract we followed the response of gut CCK and tryptic enzyme activity during a one-day observation depending on the feeding regime at 23. days post hatch. Larvae fed the microdiet showed a higher tryptic enzyme activity, probably as an adaptation to the higher content in complex protein in the diet. The plant protein phytohemagglutinin (PHA), added to the microdiet as a potential stimulator for the digestive system, did not induce elevated tryptic enzyme activity nor was it beneficial for growth. This was possibly due to adverse effects of too high doses. We observed an endogenous rhythm of CCK over the day, independent of the dietary treatment or short-term fasting. Higher tryptic enzyme activity in larvae fed Artemia during the day might indicate a better stimulation by live prey in the digestive tract or the superiority of a discontinuous feeding schedule in this group. We suggest that a reduction in tryptic enzyme activity after several feeding events indicates a limit in diurnal digestive capacity. Sea bass larvae are apparently able to adapt to the feeding schedule by synchronizing the tryptic enzyme activity like adult fish. © 2013 Elsevier B.V.
Agency: GTR | Branch: BBSRC | Program: | Phase: Research Grant | Award Amount: 309.70K | Year: 2013
Feeding and digestion has been and continues to be extensively studied for both fundamental and applied purposes, in a range of species from all animal groups. The current proposal represents a novel area of research that offers a new integrative perspective on the otherwise well studied phenomenon of digestion. It also provides a previously unforeseen mechanism for improving the conversion of food-to-growth within the globally important aquaculture of trout and salmon. The potential for commercial application has generated an industrial partnership with Skretting, the largest trout feed producer in the UK and worldwide. The proposal stems from our recent discovery in 2008 that a major phenomenon associated with feeding in mammals, the alkaline tide, also occurs in teleost (bony) fish, in which it had not previously been documented. The alkaline tide is a rise in blood bicarbonate (a base) and pH (i.e. more alkaline) lasting several hours following a meal, which results from the need to balance the secretion of acid into the stomach. This carries an energetic cost that we estimate to be between about 5 and 40 % (depending on buffer capacity of the diet) of the energy used by trout to digest a meal. The resulting acid-base disturbance in the blood will also result in a host of physiological consequences including potentially negative effects on respiratory gas exchange, salt and water balance, energy use that will ultimately limit food conversion efficiency and growth rates. In trout one key response to this blood acid-base disturbance is to excrete the excess bicarbonate base into the external water (via the gills), a compensatory process that can last 36 hours. Any treatments that might either lessen the extent of the alkaline tide, or improve the recovery time, could be extremely valuable to the aquaculture industry. This is because such treatments would reduce the energetic costs for the fish (promoting faster growth rates), reduce the economic costs for the fish farmer, and also lessen the impact on increasingly expensive and hard-fought-for marine resources that are currently used to make fishmeal (the primary ingredient in commercial trout food). The project will focus upon the physiological consequences and costs of the alkaline tide in rainbow trout, and specifically how this might influence the biological and economic efficiency of growth in aquaculture conditions. By understanding the physiological implications of the alkaline tide, and how they are affected by environmental and dietary variables, we should be able to understand how this varies in nature (with fishing feeding naturally on diets with very different buffer capacity), and also how to minimise the energetic costs for fish within aquaculture. We aim to study how the temperature and chemistry of freshwater the fish live in can influence their response and recovery time for the alkaline tide. We will also manipulate the diet to see if we can minimise the need for the fish to secrete acid in its stomach and minimising the alkaline tide, thus saving energy and optimising fish growth. We will investigate these phenomena using experimental physiology under laboratory conditions at Exeter, as well as carrying out commercial-scale feeding trials at Skrettings under conditions similar to aquaculture, using novel feeds designed by Skrettings Aquaculture Research Centre in Stavanger, Norway.
Reduced n-3 long chain fatty acid levels in feed for Atlantic salmon (Salmo salar L.) do not reduce growth, robustness or product quality through an entire full scale commercial production cycle in seawater
Sissener N.H.,National Institute of Nutrition And Seafood Research |
Waagbo R.,National Institute of Nutrition And Seafood Research |
Rosenlund G.,Nutreco Aquaculture Research Center |
Tvenning L.,Marine Harvest ASA |
And 6 more authors.
Aquaculture | Year: 2016
As fish oil is an increasingly limited input-factor, content of the n-3 fatty acids eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) is being gradually reduced in feeds for farmed salmon, and consequences for fish health and fillet quality need to be addressed. In the present study, Atlantic salmon (Salmo salar L.) were fed two levels of EPA and DHA through the seawater rearing period from six weeks after smolt transfer (~150 g) until harvest (~5000 g). The trial was conducted under commercial production conditions, with triplicate net pens used for each diet group. The control (standard) diet contained 8% EPA + DHA of total fatty acids (FAs, 26 g kg-1 feed), while the low n-3 diet contained 6% EPA + DHA of FAs until 1200 g body weight and 4.5% in following feeds, averaging out to 5% of FAs (16 g kg-1 feed) during the entire production cycle. Growth performance and measured health parameters including cataract, liver lipid accumulation and vaccine side-effects did not differ significantly between the two diet groups. Through the production period, the fish faced stressful and challenging conditions such as five treatments against sea lice (one oral and four bath treatments), as well as an outbreak of pancreas disease and considerable mortality from gill infections. Despite this, mortality did not differ significantly between the diet groups, indicating that fish fed low dietary n-3 FAs were equally robust as fish fed the standard diet. Quality classification at slaughter did not reveal any diet effects, and neither did sensory evaluation of the fish fillets. As expected, the fillet FA profile differed, with 5.4% EPA + DHA of total FA (0.9 g 100 g-1) in the fillet of fish fed the low n-3 diet and 7.5% (1.3 g 100 g-1) in fish fed the standard diet. The fish fed low EPA + DHA showed a higher frequency of fillet melanin spots, 28.2%, compared to 21.5% in the salmon fed the standard diet, possibly related to dietary FA composition affecting inflammatory processes. Statement of relevance: Supply of fish oil is limiting growth of the salmon industry. © 2016 Elsevier B.V.
Dhert P.,Skretting |
King N.,Skretting North America |
Aquaculture | Year: 2014
In order to verify the hypothesis that a formulated live food diet could completely substitute any enrichment step, an existing rotifer culture diet was transformed to slowly release the enrichment components such as protein, fat, vitamins and minerals in non-suffocating concentrations. Nutrients being present at metabolizing concentrations allowed not only gut filling but also gradually enriched the tissue of the rotifers without consuming excessive oxygen or compromising health nor reproduction of the rotifers. Similar growth and reproduction figures were registered with the traditional culture diet as with the stand-alone diet in a lapse of 9. weeks corresponding with 15 rotifer cycles and average FCR's of 1.0. The nutritional profile of the rotifers was similar to that of rotifers undergoing a classic enrichment for all major nutrients (protein, HUFA, vitamins) except for some slow enriching nutrients (i.e. taurine, Zn, Se) that could be incorporated successfully thanks to the long term enrichment approach.Besides the nutritional advantage, benefits were noticed on the practical use of the diet (i.e. direct available enriched live food at any moment); the reduced amount of losses and handling of rotifers and the stability in the process thanks to a higher degree of standardization of the operations. These optimizations lead to less damage of the live food resulting in stronger and better quality rotifers. © 2014 Elsevier B.V.
Sudheesh P.S.,University of Idaho |
Zimmerman J.K.,Skretting |
Cain K.D.,University of Idaho
Aquaculture | Year: 2016
The effects of feeding a commercially available health enhancing aquaculture feed (Bio-Oregon's BioPro/Protec® diet) on the efficacy of two coldwater disease (CWD) vaccine formulations consisting of Flavobacterium psychrophilum 259-93B.17 (B.17) and B.17 grown in iron limited medium (ILM) were carried out in two separate trials. The primary aim of this study was to compare efficacy of the B.17 and ILM formulations in rainbow trout ( Oncorhynchus mykiss). A secondary aim was to determine if dietary alterations could enhance the immune response and/or elicit greater levels of protection. Therefore, a basal diet (BioOlympic fry diet; control feed) and an immunostimulatory diet (BioPro; IS feed) were fed to rainbow trout at 2% body weight (bwt) per day for 2. weeks prior to immersion immunization with the B.17 vaccine, ILM vaccine, or a TYES media control. A booster immunization was administered two weeks post initial vaccination, and feeding of the respective feeds continued for one additional week at which time all groups received the control diet until the end of the experiment. In trial 1, an acute chlorine spike occurred just prior to pathogen challenge (week 7) resulting in substantial mortality among treatment groups. Interestingly, fish fed the IS feed had significantly lower mortality (36.7%) than fish fed the control feed (67%). Vaccinated fish had significantly higher antibody titers than the control fish at week 2 through 7 in trial 1. In trial 2, antibody titers for all vaccinated fish were significantly greater than controls at week 4, but at weeks 6 and 8 the titers of B.17 vaccinated fish were not significantly different from controls. However, average titers for ILM vaccinated were significantly greater than control fish at weeks 6 and 8. Cumulative percent mortality (CPM) in B.17 and ILM vaccinated groups was significantly lower than control groups at the point where CPM reached 60% (mid-way through outbreak), but by the end of the challenge (28. days) ILM vaccinated fish had significantly lower CPM than either control or B.17 vaccinated fish. When comparing dietary effects, CPM was not significantly different but RPS values for fish fed the BioPro IS feed were consistently elevated over groups fed the control diet regardless of the vaccine formulation administered. This study demonstrates increased efficacy of the ILM vaccine in rainbow trout, and provides evidence that a commercial "health enhancing" diet can provide benefits in response to an acute stress event and may contribute to increased vaccine performance. Statement of relevance: This manuscript addresses an important and very practical problem in aquaculture. Coldwater disease is a major disease affecting salmonid aquaculture around the world. There is no approved vaccine available in the US. This manuscript reports the beneficial effects of feeding commercial immunostimulatory functional feeds on the efficacy of two formulations of a coldwater disease vaccine. The results presented here are highly relevant to the development of aquaculture and finding sustainable and non-antibiotic based aquatic animal health management strategies. This study will contribute towards coldwater disease management and identifies potential benefits of commercial functional feeds commonly used in the aquaculture industry. © 2015 Elsevier B.V.