January | February 2010

Feature title: Preventing the impact of seawater transfer on feed intake in salmon

The International magazine for the aquaculture feed industry

International Aquafeed is published five times a year by Perendale Publishers Ltd of the United Kingdom.All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2010 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058

Changes in diet, environ-ment or physiology rep-resent many stress factors for farmed animals that

can impact their appetite, health and performance. In salmon farming, the transfer of smolts from freshwater to seawater is a stressful event.

Stradmeyer (1994) has shown that the weeks following this transfer see a dra-matic drop of appetite and feed intake: in his observations, only 10 percent of the fishes were feeding within the first week following transfer, increasing to no more than 65

percent after five weeks. Reducing this gap in feed consumption is

an important factor to optimise production and reduce economic losses. A sensory feed

additive, designed to improve feed intake and induce feed loyalty in fish (Optifeed® Aqua), has recently been evaluated in Norway for its capacity to optimise appetite and feed intake following the transfer of Atlantic Salmon smolts into seawater.

It showed an interesting potential for a profitable and sustainable aquaculture.

Trial conditionsA production trial was conducted in

Norway at the Nofima Marine experimental station, SunndalsØra, and supervised by AVS Chile.

At the beginning of the trial, 252 Atlantic salmon smolts (Salmo salar, SalmoBreed strain), weighing 100-120g, were transferred to six 200-litre seawater tanks (42 fishes/tank). The experiment was conducted in triplicates over a six-week period (January-February 2009). Three tanks were allo-cated to each diet: control (basal diet), and Optifeed® Aqua treatment (basal diet plus 0.2 percent Optifeed® Aqua KX 81 P1).

The basal feed contained 31.7 percent fishmeal and 24.3 percent fish oil (see table 1).

The feed was extruded and vacuum coated with the oil. Feed nutritional analysis was: 43.8 percent crude protein, 6.6 percent moisture, 6.8 percent ash and 28 percent fat. Both feed were given by auto-

matic feeders (one meal every 15 minutes), during six weeks following the seawater transfer. The daily feeding was continuously adjusted according to feed intake the previ-ous two days, aiming at an overfeeding of 20 percent to allow optimal feed intake.

Feed waste were collected from the out-let and dried in order to quantify feed intake.

The water average temperature was 8.7°C, salinity 33ppt. The fishes were weighted individually at start and at the end of the trial.

Preventing the impact of seawater transfer on feed intake in salmonThe importance of sensory stimulation in fish feeding

by Virginie Noirot, Laboratoires Phodé, Albi, France

Table 1: Salmon diet composition

Ingredient %

LT Fish Meal-Norway 31.7

Soybean meal 5.0

Soy Protein Concentrate 10.0

Hydrolysed feather meal 8.0

Wheat gluten 5.0

Wheat 12.0

Fish oil (NorSalmOil) 24.3

Vitamin premix 2.0

Mineral premix 0.4

L-Lysine HCl 0.38

DL-Methionine 0.2

Carophyll Pink (10% astaxanthin) 0.064

Mono calcium phosphate 1.0

"Transfer to seawater represents a stressful event and can have a detrimental effect on smolts feeding behaviour"

24 | InternatIonal AquAFeed | January-February 2010 January-February 2010 | InternatIonal AquAFeed | 25

F: Nutrition

IAF1001.indd 24 12/01/2010 09:42

Improved feed intake after smolts transfer

At the end of the six week period, the smolts that received Optifeed® Aqua had consumed significantly more feed than with the control diet (487g/tank vs. 366, P=0.006).

The cumulated feed intake per tank over the six-week trial was improved by 33 percent with Optifeed® Aqua.

The difference between treatments started to appear around 10 days after the beginning of the experiment (see Figure 1).

The effects of sensory stimulation in fish

As mentioned earlier, transfer to sea-water represents a stressful event and can have a detrimental effect on smolts feeding behaviour. Fishes have a well-developed sensory system.

Depending on the species, they have a variable number of sensory receptors located in various parts of their body, from the tongue to the entire body surface in the case of cat fish (the animal with the larger number of gustative receptors!). Salmons have 3000-4000 receptors. To this,

we can add a good sensory memory, since salmons smolts have the abil-ity to ‘record’ the smells of a river along their migration towards the sea in order to find their way back, s o m e t i m e s years later.

Based on an expertise of sensory stimu-

lations in fish, a range of feed additive has been developed specifically to encourage feed consumption in aquatic species, with a specific formula for salmonids /carnivorous fishes, and shrimps: Optifeed® Aqua. This additive combines three activities:

Attraction: fishes and crustaceans are particularly attracted to amino acids (L-isomers). Optifeed® Aqua for salmon and carnivorous fish contains a formulation of amino acids composed of two blends: one present in a plant and an other in a seawa-ter animal, both being particularly attractive for these types of fish.

Appetite stimulation: a specific core based on plant extracts has been developed to stimulate the appetite center and path-way within the nervous system.

Feed loyalty: specific plant extracts are used as a natural source of alkaloids to induce habituation to the feed.

The present trial confirms the effi-ciency of Optifeed® Aqua in optimising feed intake in salmons after transfer to seawater. Moreover the smolts were fed a diet with a relatively high level of plant proteins, potentially representing a second stress fac-tor with negative impact on their appetite.

Other feed additives have also been shown to increase feed intake during trans-fer to seawater. But, when compared to Optifeed® Aqua, which is essentially com-posed of sensorial feed additives (botanicals and aromatic molecules); most appetite stimulants studied in fish have been of marine origin.

Compared to existing alternatives, therefore, Optifeed® Aqua can be considered as a favourable factor for a sustainable aquaculture.

ReferenceStradmeyer L., 1994. Survival, growth and feeding of Atlantic salmon, Salmo salar L., smolts after transfer to seawater in relation to the failed smolt syndrome. Aquacult. Fish. Manage. 25: 103-112.

Figure 1: Daily cumulated feed intake (g/tank)

The natural choice for

Core vacuum coating0ptimum penetration of liquidHigh energy feed www.forberg.no

About PhodéPhodé is born from the conviction

that the sense of smell is our pri-mary sense, and one of the driving forces behind the behavior and well-being of living beings. Its mission is to capitalise on its expertise of olfaction and nutrition to improve the well-being and health of humans and animals, both through their food and their environment. Phodé develops, produces and distributes innovative solutions for animal nutrition, the environment and the food industry thanks to its unique expertise in taste and smell physiology.

Based in Albi, in the South-West of France, Phodé has 49 co-workers and operates in over 20 countries through a network of local distributors and research partners. For more informa-tion, visit www.phode.com

24 | InternatIonal AquAFeed | January-February 2010 January-February 2010 | InternatIonal AquAFeed | 25

F: Nutrition

IAF1001.indd 25 12/01/2010 09:42

www.aquafeed.co.uk

LINKS• Seethefullissue• VisittheInternationalAquafeedwebsite

• ContacttheInternationalAquafeedTeam

• SubscribetoInternationalAquafeedTHE INTERNATIONAL MAGAZINE FOR THE AQUACULTURE FEED INDUSTRY

Member of the World Aquaculture Society, European Aquaculture Society, American Feed Industry Association and the International Aquafeed Association

VOLUME 13 I S SUE 1 2 010

Utilization of spray-dried Hemoglobin powder

- in Shrimp feeds

Evaluation of Fishmeal Substitution

Opportunities for fish pheromones:

- their applications and role in the sustainability of wild fish stocks

Active ingredients for healthy animals

- Rice, the technological ingredient for aquafeed

IAF1001.indd 1 12/01/2010 09:39

Thisdigitalre-printispartoftheJanuary|February2010editionofInternationalAquafeedmagazine.Contentfromthemagazineisavailabletoviewfree-of-charge,bothasafullonlinemagazineonourwebsite,andasanarchiveofindividualfeaturesonthedocstocwebsite.Pleaseclickheretoviewourotherpublicationsonwww.docstoc.com.

Topurchaseapapercopyofthemagazine,ortosubscribetothepapereditionpleasecontactourCirculationandSubscriptionsManageronthelinkabove.

INFORMATIONFORADVERTISERS-CLICKHERE