Search

Growth, feed conversion and cortisol

English: This report gives an estimate of biological production based on dissolved nutrients and particulate organic matter from Norwegian aquaculture. It provides an estimate of the quantitative importance this has in the marine food chain, where nutrients form the basis for marine algae production, while animals can benefit from organic material directly. Norwegian aquaculture production of salmonids represents about 30% of total world aquaculture production of marine finfish (FishstatJ, www.FAO.org). Production is very efficient, also in terms of turnover of feed to edible food. Norwegian aquaculture used almost 1.5 million tonnes of fish feed in 2012. The protein retention (protein retention = protein in fish x 100 / protein in the diet) was in 2012 at 45%. Emissions from ranching of salmon can be divided into three categories; waste feed (nutrients), soluble nutrients and fecal matter (inorganic /organic nutrient). Waste feed can be eaten directly by fish living around the fish farms. 3 We do not have measurements of the proportion waste feed that is eaten by wild fish, but based on an estimate that about 50% consumed by wild fish, this represents an additional production of 50 000 tonnes of harvestable fish. Inorganic nutrients provide a basis for algae production and as such food up through the food chain (trophic level). Cod is located at trophic level 4.4. Since approximately 90% of the energy is lost in each trophic level, the additional production of fish at trophic level 4.4 would be between 1,000 and 2,000 tonnes at best. Nutrients will thus not provide an additional production of harvestable fish that is significant. We find the same proportion when we look at feces. Here again, one or two levels up through the food chain and the amount of harvestable fish will be negligible. However, if we estimate the maximal production capacity of blue mussel, a primary consumer of phytoplankton, the enhanced food availability will allow an additional production in the scale of 350 000 tonnes. Norsk: Rapporten gir en indikasjon på biologisk produksjon basert på næringssalter og næringsstoff fra norsk havbruk. Den gir et estimat av den kvantitative betydningen biologisk produksjon har i den marine næringskjeden, der næringssalter danner grunnlag for algeproduksjon, mens dyr kan nytte næringsstoff direkte. Norsk oppdrettsproduksjon av laksefisk utgjør om lag 30 % av verdens akvakulturproduksjon av marin fisk (FishstatJ, www.FAO.org). Produksjonen er svært effektiv, også når det gjelder omsetning av fôr til spiselig mat. Norsk havbruksnæring fôret ut nesten 1,5 millioner tonn fiskefôr i 2012. Proteinretensjonen (proteinretensjon = protein i fisken x 100 / protein i fôret) var i 2012 på 45 %. Utslipp fra oppfôring av laksefisk kan deles i tre kategorier; spillfôr (næringsstoffer), løselige næringssalter og fekalier (næringsstoffer/næringssalter). Spillfôr kan spises direkte av fisk som oppholder seg rundt anlegget. Vi kjenner ikke til målinger av andel spillfôr som blir spist, men anslår vi at ca. 50 % spises, så representerer dette en produksjon på 50 000 tonn høstbar fisk. Næringssalter gir grunnlag for algeproduksjon og for mat oppover i næringskjeden (trofisk nivå). Torsk ligger på trofisk nivå 4,4. Siden 90 % av energien går tapt i hvert nivå, vil tilleggsproduksjon av for eksempel fisk på trofisk nivå 4,4 være mellom 1000 og 2000 tonn, i beste fall. Næringssalter vil dermed ikke gi en tilleggs-produksjon som er målbar for arter på et høyt trofisk nivå. Vi finner samme forhold når vi ser på fekalier. Også her må en gjennom ett eller to nivåer i næringskjeden, og økt mengde høstbar fisk vil ikke være målbar. Går vi ned i den marine næringskjeden til arter som beiter direkte på planteplanktonet kan vi estimere en mulig dyrking av blåskjell på opp mot 350 000 tonn.

In the future, an increasing number of salmon farms may be located in areas with fast water current velocity due to limited availability of more sheltered locations. However, there is little information as to how fast currents affect fish health and welfare. We used raceways to expose Atlantic salmon post-smolts (98.6 g, 22.3 cm) to homogeneous water velocities corresponding to 0.2, 0.8 and 1.5 body lengths s-1 (slow, moderate and fast, respectively) over 6 wk. Fish at fast velocity had a 5% lower weight gain compared to fish at moderate and slow velocities, with a corresponding reduction in length. Fish at moderate and fast velocities had lower lipid content in the muscle compared to fish at slow velocity. Hence, fish at slow and moderate velocities had the same weight gain, but fish at slow velocity gained more fat and fish at moderate velocity more muscle protein. Fish at fast velocity had a higher relative ventricular mass, indicating an increased cardiac workload. At slow velocity, individual fish displayed elevated plasma levels of lactate, osmolality and potassium. Our results suggest that post-smolts had the best growth and welfare at moderate velocity and that a current velocity of 1.5 body lengths s-1 could compromise production performance. © The authors 2015. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are un -restricted. Authors and original publication must be credited.

Antimicrobials revolutionized human as well as animal medicine in the 20th century by providing effective treatment of diseases caused by pathogenic microorganisms. However, microorganisms have the ability to develop antimicrobial resistant strains. This occurs when microorganisms mutate or when resistance genes are exchanged between them. The use of antimicrobial drugs accelerates the emergence of drug-resistant strains. A priority is to safeguard the efficacy of antimicrobial drugs we depend on for treatment of infectious diseases in humans. Use of antimicrobials in food animals can create a source of antimicrobial resistant bacteria that can spread to humans both by direct contact and through the food supply. Coccidiosis is an intestinal disease in animals caused by unicellular parasites called coccidia. As most of the damage of this infection is done by the time signs of the disease are widespread, preventive measures are preferred. Coccidiostats are animal feed additives used to prevent coccidiosis by inhibiting or killing coccidia. There are two major groups of coccidiostats; ionophores and non-ionophores, the latter also referred to as “non-ionophore coccidiostats” (but also called chemicals). One main difference between these groups is that ionophores also inhibit or kill some bacterial species, whereas non-ionophore coccidiostats do not. Consequently, some bacterial infections may also be controlled by ionophore coccidiostats, e.g. the poultry disease necrotic enteritis caused by the bacterium Clostridium perfringens (C. perfringens). Eleven different coccidiostats have been authorised for use in the EU, both ionophores and non-ionophore coccidiostats. Norway has been exempted from the EEA Agreement in this field and has approved only five; all ionophores. The two ionophore coccidiostats currently used in Norway are narasin for broilers and monensin for turkeys.

We investigated the effect of temperature on the limiting oxygen saturation (LOS) of gilthead sea bream Sparus aurata. This threshold was defined as the % O2 saturation where fish no longer upheld their routine metabolic rate (RMR, the metabolic rate of fed and active fish) during a progressive decline in oxygen saturation. S. aurata (398 ± 10 g, mean ± SE) were kept in 3 replicate tanks and subjected to 3 changes in temperature: 16 to 20°C, 20 to 16°C and 16 to 12°C. At each temperature, fish were left to acclimatize for 8 to 10 d, before daily feed intake (DFI), the routine oxygen consumption rate (routine MO2, mg kg−1 min−1) and the LOS were measured. In addition, at 20°C the swimming speed was measured in fish subjected to a decline in O2 from full air saturation to levels below the LOS (minimum of 8−10% O2). For the temperature range tested (12−20°C), DFI, MO2 and LOS increased exponentially with temperature (7.5-, 3.6- and 2.2-fold, respectively) with mean (± SE) LOS being 17 ± 1, 21 ± 0 and 35 ± 5% O2 at 12, 16 and 20°C, respectively. A gradual decline in swimming activity was observed as O2 declined below the LOS, indicating increasing metabolic stress and/or a ‘sit-out’ coping strategy which may prolong survival time in severe hypoxia. The results show the importance of temperature as an influential variable over the environmental O2 requirements of S. aurata. © The authors 2015. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are un restricted. Authors and original publication must be credited.

Farmed Atlantic salmon can escape from fish farms at various stages of their life, from juveniles to large mature fish. Escapees that enter rivers to spawn pose a threat to the genetic integrity of wild populations. Knowledge about the timing of these escapes can provide important information for wildlife management and the aquaculture industry, enabling them to prevent or mitigate the negative impacts of escapees. Farmed salmon food has a high content of terrestrial lipids; thus, we used fatty acid (FA) profiling to monitor the escape history of farmed salmon. Escaped salmon captured in rivers (n = 251) presented a wide range of FA profiles that we used to classify the fish as (1) early-escaped wild-like fish that were assumed to have escaped at smolt or early post-smolt stage (24%), (2) recently escaped fish with high levels of FAs typically found in commercial salmon food (61%) and (3) intermediate escapees whose FA profiles lay between those 2 groups (15%). To estimate the size at escape of the intermediate escapees, we performed a feeding experiment that monitored the development of FA profiles after a shift in diet from terrestrial to marine lipids. Most intermediate escapees appeared to have escaped when they were

This study investigated the production performance of the Atlantic salmon postsmolt (Salmo salar L.) subjected to cyclic oxygen reductions (hypoxia) of varying severity. Triplicate groups (N = 955) were kept at constant 80% O2 (control) or subjected to 1 h and 45 min of hypoxia (50, 60 or 70% O2, termed 80:70, 80:60 and 80:50 groups) every 6 h at 16°C for 69 days. Feed was provided in normoxia. One third of the fish were kept further for 30 days in normoxia to study possible compensatory growth. Cyclic hypoxia did not alter the oxygen uptake rates of fish, measured in night-time. Fish subjected to 50% and 60% O2 reduced feeding by 13% and 6% compared with the controls, respectively, with corresponding reductions in specific growth rates. Feed utilization was not reduced. Compensatory growth was observed in fish from the 80:50 group, but full compensation was not achieved. The main conclusions were that feeding in normoxia does not fully alleviate negative effects of cyclic hypoxia on feeding and growth, when oxygen is reduced to 60% or below in hypoxic periods, that feed utilization is maintained, and that compensatory growth may lessen negative effects. acceptedVersion

The knowledge on the effect of different stress factors on Atlantic salmon, Salmo salar Linnaeus, 1758, is far from complete and therefore we decided to find out how the low water level stress could effect pathophysiological parameters such as: plasma cortisol level, haemoglobin, haematocrit, chloride (Cl–), sodium (Na+), osmolality, lactate, and glucose in this fish; and how this stressor affects the gut morphology. Two hundred and four juvenile Atlantic salmon were randomly distributed into six fibreglass tanks and divided into two groups: group 1 (control) and group 2 (low water level stress). The low water level stress did not affect growth performance and the pathophysiological parameters. Light- and transmission electron microscopy evaluations of the pyloric caeca and the distal intestine revealed that chronic stress had no effect on gut morphology. Low water level stress had no clear effects on pathophysiological parameters and gut morphology of Atlantic salmon.

Doc.nr 09/804-Final - "Opinion of the Panel on Animal Health and Welfare of the Norwegian Scientific Committee for Food Safety"

A thorough review of different aspects on the health implications of using vegetable feed ingredients, both protein and lipid alternatives to fishmeal and fish oil, plus possible additions of immunostimulants, also including a short chapter on undesirable components, the use of genetically modified plants, and how processing may affect feed quality and availability, are given in the different chapters of the present risk assessment. Discussed in particular are Atlantic salmon (Salmo salar), rainbow trout (Onchorhyncus mykiss), Atlantic halibut (Hippoglossus hippoglossus) and Atlantic cod (Gadus morhua). Deemed necessary, since literature on these species is scarce, some theoretical background in the assessment chapter (Chapter 4) includes studies on other species when relevant for the present terms of reference, and to better be able to conclude on possible health implications due to changes in diet ingredients. The answers to the present Terms of Reference are given in Chapter 5 (Risk characterization and conclusions). Chapter 6 presents future challenges that need focus in research to be able to have healthy farming of fish even when volumes increase.

Wild caught saithe were fed on commercial diets made for salmon or cod from October 2006 to June 2007. Several flesh quality measurements were made. Growth turned out to be very low for a part of the population, while the rest were growing well. From those we could find clear differences in quality parameter connected to growth, like liver size and condition factors. Differences in colour and pH were also found. It is not recommended to feed saithe on a salmon diet, while the use of a leaner cod diet will mainly giva saithe of a good quality. Norsk: I det gjennomførte eksperimentet vart villfanga sei fôra opp med laksefôr eller torskefôr frå oktober 2006 til juni 2007 og ei rekke parametrar knytta til kvalitet vart målt. Det vart tidleg i eksperimentet tydeleg at det kun var ein del av fisken som vaks, medan ein relativ stor del av fisken hadde liten eller ingen vekst. Den andre delen av fisken var i god vekst, og vi har bevisst valt ut individ frå desse til kvalitetsmålingane for å få representative målingar frå fisk som eter tørrfôr. Det som viste tydelegast forskjell mellom fôrgruppene og mellom fôrgruppene og villfisk var parametrar knytta til vekst. I tillegg fann vi forskjell i farge mellom sei fôra på laksefôr og torskefôr, samt forskjellar i pH mellom villsei og mellom fôrgruppane. Det er ikkje å anbefale å fôra villfanga sei med laksefôr, medan bruk av eit magrare fôr i hovudsak vil gje sei av god kvalitet.