Ståle J. Helland

Adaptation to soybean meal in diets for rainbow trout, Oncorhynchus mykiss

Abstract Three experiments were conducted with rainbow trout maintained in fresh water. In Experiment 1, growth was measured in groups of 34-g trout fed either a fish meal control diet (Diet 1) or a diet containing 60% soybean meal (Diet 2) for two periods of 28 days each. In Experiment 2, Diets 1 and 2 were fed to groups of 100-g trout for 10 days prior to stripping of faeces and digestibility determination. In Experiment 3, groups of 200-g trout were fed either a fish meal control diet containing 100 mg Y2O3 kg−1 diet as an inert marker (Diet 3), or a diet containing 40% soybean meal and 100 mg Yb2O3 kg−1 diet as an inert marker (Diet 4) for an adaptation period of 7 days. Thereafter, both diets were offered in excess in a 1:1 mixture for 2 days. Qualitative preference for the two diets was estimated as the proportions of Y2O3 and Yb2O3 in faeces. Subsequently, digestibility was determined for all diets. In Experiment 1, growth was 1.4 times faster for the trout fed Diet 1 than for those fed Diet 2 during the first 28 days. Adaptation occurred, and the difference in growth was not significant during the last 28 days. In Experiment 3, the trout which were adapted to Diet 3 preferred this diet, consuming only a small portion of the soybean diet. The fish adapted to Diet 4 consumed 59% of the fish meal diet and 41% of the soybean diet, indicating a rapid adaptation in feed intake to the soybean diet. Only minor differences in digestibility were found between the fish meal control diets and the diets containing soybean meal in Experiments 2 and 3. These results indicate that given an adaptation period, trout previously adapted to fish meal diets consume and grow well on diets containing high levels of soybean meal. Temporary lower growth after offering diets with soybean meal than when continuously feeding fish meal diets is rationalized by adaptation in qualitative preference to the soybean diets.

Feed intake, growth and feed utilization of offspring from wild and selected Atlantic salmon (Salmo salar)

The aim was to assess whether selection for increased growth rate in Atlantic salmon (Salmo salar) is associated with increased feed intake and/or better feed utilization. Growth responses of offspring from selected and wild lines of Atlantic salmon (initial weight 814±14 g and 533±12 g, respectively) were tested in a 14-week experiment. Selected and wild salmon increased body weight by 79 and 39%, respectively, during the experiment. Relative feed intake (DFI), thermal growth coefficient (TGC) and feed efficiency ratio (FER) were significantly higher in the selected (DFI: 0.67% BW d−1, TGC: 2.96×10−3 and FER: 1.16), than in the wild, line (DFI: 0.48% BW d−1, TGC: 1.39×10−3 and FER: 0.93). FER was positively correlated with mean growth rate (r=0.90, n=6, P<0.05), and differences between the lines indicated a 4.6% increase in FER per generation of selection. Fish of the selected line had a significantly lower intake of protein and energy per kilogram gain, so the higher growth rate of the selected line was the result of both greater feed consumption and more efficient feed utilization for growth. This implies that selection for increased growth rate in Atlantic salmon may improve both of these traits.

The apparent digestibility of diets containing fish meal, soybean meal or bacterial meal fed to Atlantic salmon (Salmo salar): evaluation of different faecal collection methods

Abstract Digestibility measurements obtained from four faecal collection methods were compared in two experiments with Atlantic salmon, reared in freshwater. The fish were fed three diets with different protein sources: a diet with 55% fish meal (FM); a diet with 35% FM and 31% soybean meal; and a diet with 34% FM and 20% bacterial meal. In Expt. 1, faecal dry matter content and apparent digestibility coefficients (ADC) of macronutrients were compared using three different methods of faeces collection: stripping, mechanical sieving of faeces from the outlet water of the tanks and immediate freezing (sieving), and by dissection. In Expt. 2, stripping and sieving were compared to a procedure where the ice and faeces mixture from sieving was freeze dried prior to analysis (sieving with FD). Faecal dry matter content, and the ADCs of organic matter and fat differed significantly between all three diets (soybean meal diet

Soy protein concentrate in diets for Atlantic halibut (Hippoglossus hippoglossus)

Abstract Four experimental diets were fed to triplicate groups of Atlantic halibut in a 2×2 factorial design, testing the effects of protein source and the use of an attractant. The diets contained 61% fish meal (FM) or 37% FM and 28% soy protein concentrate (SPC) with or without a coating of squid meal. In the SPC diets, 44% of nitrogen was supplied from the SPC. The mean initial fish weight was 633 g, and at the end of the 12-week trial, the mean fish weight was 874 g. There was no significant effect of dietary treatment on specific growth rate (0.43±0.02% body weight d−1, mean±S.E.M.). Feed efficiency ratio was significantly lower in the group fed the SPC diet (1.22±0.02) compared with those fed the FM diet (1.28±0.02). Fish fed the SPC diets had a higher feed intake (0.64±0.02%) than those fed the FM diet (0.59±0.02%). Addition of squid had no effect on feed intake. The groups fed diets not supplemented with squid were used for determination of whole body chemical composition, and the remaining fish from these groups were subsequently stripped for feces for digestibility estimations. There were no effects of protein source on digestibility or protein or energy retention in whole fish. The fish fed the diet containing soy protein had a slightly higher dry matter (DM) content (P

Estimation of gastrointestinal evacuation rate in Atlantic salmon (Salmo salar) using inert markers and collection of faeces by sieving: evacuation of diets with fish meal, soybean meal or bacterial meal

Abstract Gastrointestinal evacuation of Atlantic salmon was estimated using yttrium and ytterbium oxides (Y2O3 and Yb2O3) and collection of faeces from the outlet water of the tanks by sieving. The fish were fed three diets with different protein sources: fish meal (FM) (55% FM); soybean meal (SBM) (35% FM and 31% SBM); and bacterial meal (BM) (34% FM and 20% BM). The fish size was 0.15–0.20 kg and the water temperature was 9°C. Rate of passage was estimated by first feeding the fish the diets labelled with the inert marker Y2O3 and then changing to the same diets labelled with Yb2O3. Faeces were obtained by sieving of the outlet water and were pooled by tank every 3 h for 81 h after the switch in diets. The evacuation of the diets was expressed as the percent-wise ratio between Yb2O3 and the sum of inert markers (Y2O3+Yb2O3) in the faeces. For all three diets, ytterbium (Yb2O3) was first quantifiable in the faeces 12–15 h after the change of marker, and the gastrointestinal evacuation was almost complete 30 h after the switch, when yttrium (Y2O3) still accounted for up to 2% of the marker. The estimated rates of passage were described by s-shaped curves (R2≥0.98). The estimated time for Yb2O3 to reach 50% of the maximum marker concentration was approximately 18 h after the marker change in the fish fed the diets with FM and BM, while the corresponding value was approximately 20 h for the SBM diet. This was attributed to a slower onset of evacuation for the diet with SBM. The combination of two inert dietary markers and continuous collection of faeces permitted accurate estimation of gastrointestinal evacuation in salmon during feeding, without disturbing or stressing the fish.

Aerobic training stimulates growth and promotes disease resistance in Atlantic salmon (Salmo salar)

Improving fish robustness is of utmost relevance to reducing fish losses in farming. Although not previously examined, we hypothesized that aerobic training, as shown for human studies, could strengthen disease resistance in Atlantic salmon (Salmo salar). Thus, we exercised salmon pre-smolts for 6 weeks at two different aerobic training regimes; a continuous intensity training (CT; 0.8bls(-1)) and an interval training (IT; 0.8bl s(-1) 16h and 1.0bl s(-1) 8h) and compared them with untrained controls (C; 0.05bl s(-1)). The effects of endurance training on disease resistance were evaluated using an IPN virus challenge test, while the cardiac immune modulatory effects were characterized by qPCR and microarray gene expression analyses. In addition, swimming performance and growth parameters were investigated. Survival after the IPN challenge was higher for IT (74%) fish than for either CT (64%) or C (61%) fish. While both CT and IT groups showed lower cardiac transcription levels of TNF-α, IL-1β and IL-6 prior to the IPN challenge test, IT fish showed the strongest regulation of genes involved in immune responses and other processes known to affect disease resistance. Both CT and IT regimes resulted in better growth compared with control fish, with CT fish developing a better swimming efficiency during training. Overall, interval aerobic training improved growth and increased robustness of Atlantic salmon, manifested by better disease resistance, which we found was associated with a modulation of relevant gene classes on the cardiac transcriptome.

Purine-induced expression of urate oxidase and enzyme activity in Atlantic salmon (Salmo salar). Cloning of urate oxidase liver cDNA from three teleost species and the African lungfish Protopterus annectens.

The peroxisomal enzyme urate oxidase plays a pivotal role in the degradation of purines in both prokaryotes and eukaryotes. However, knowledge about the purine‐induced expression of the encoding gene is lacking in vertebrates. These are the first published sequences of fish urate oxidase, which were predicted from PCR amplified liver cDNAs of Atlantic salmon (Salmo salar), Atlantic cod (Gadus morhua), Atlantic halibut (Hippoglossus hippoglossus) and African lungfish (Protopterus annectens). Sequence alignment of different vertebrate urate oxidases revealed amino acid substitutions of putative functional importance in the enzyme of chicken and lungfish. In the adult salmon, expression of urate oxidase mRNA predominated in liver, but was also identified in several nonhepatic organs including brain, but not in skeletal muscle and kidney. Juvenile salmon fed diets containing bacterial protein meal (BPM) rich in nucleic acids showed a significant increase in liver urate oxidase enzyme activity, and urea concentrations in plasma, muscle and liver were elevated. Whereas salmon fed the 18% BPM diet showed a nonsignificant increase in liver mRNA levels of urate oxidase compared with the 0% BPM‐fed fish, no further increase in mRNA levels was found in fish receiving 36% BPM. The discrepancy between urate oxidase mRNA and enzyme activity was explained by rapid mRNA degradation or alternatively, post‐translational control of the activity. Although variable plasma and liver levels of urate were detected, the substrate increased only slightly in 36% BPM‐fed fish, indicating that the uricolytic pathway of Atlantic salmon is intimately regulated to handle high dietary purine levels.

Disease resistance is related to inherent swimming performance in Atlantic salmon

BackgroundLike humans, fish can be classified according to their athletic performance. Sustained exercise training of fish can improve growth and physical capacity, and recent results have documented improved disease resistance in exercised Atlantic salmon. In this study we investigated the effects of inherent swimming performance and exercise training on disease resistance in Atlantic salmon.Atlantic salmon were first classified as either poor or good according to their swimming performance in a screening test and then exercise trained for 10 weeks using one of two constant-velocity or two interval-velocity training regimes for comparison against control trained fish (low speed continuously). Disease resistance was assessed by a viral disease challenge test (infectious pancreatic necrosis) and gene expression analyses of the host response in selected organs.ResultsAn inherently good swimming performance was associated with improved disease resistance, as good swimmers showed significantly better survival compared to poor swimmers in the viral challenge test. Differences in mortalities between poor and good swimmers were correlated with cardiac mRNA expression of virus responsive genes reflecting the infection status. Although not significant, fish trained at constant-velocity showed a trend towards higher survival than fish trained at either short or long intervals. Finally, only constant training at high intensity had a significant positive effect on fish growth compared to control trained fish.ConclusionsThis is the first evidence suggesting that inherent swimming performance is associated with disease resistance in fish.

Exercise induced mechano-sensing and Substance P mediated bone modeling in Atlantic salmon

Mechanical stress plays a vital role in maintaining bone architecture. The process by which osteogenic cells convert the mechanical signal into a biochemical response governing bone modeling is not clear, however. In this study, we investigated how Atlantic salmon (Salmo salar) vertebra responds to exercise-induced mechanical loading. Bone formation in the vertebrae was favored through increased expression of genes involved in osteoid production. Fourier transform infrared spectroscopy (FT-IR) showed that bone matrix secreted both before and during sustained swimming had different properties after increased load compared to control, suggesting that both new and old bones are affected. Concomitantly, both osteoblasts and osteocytes in exercised salmon showed increased expression of the receptor nk-1 and its ligand substance P (SP), both known to be involved in osteogenesis. Moreover, in situ hybridization disclosed SP mRNA in osteoblasts and osteocytes, supporting an autocrine function. The functional role of SP was investigated in vitro using osteoblasts depleted for SP. The cells showed severely reduced transcription of genes involved in mineralization, demonstrating a regulatory role for SP in salmon osteoblasts. Investigation of α-tubulin stained osteocytes revealed cilia-like structures. Together with SP, cilia may link mechanical responses to osteogenic processes in the absence of a canaliculi network. Our results imply that salmon vertebral bone responds to mechanical load through a highly interconnected and complex signal and detection system, with SP as a key factor for initializing mechanically-induced bone formation in bone lacking the canaliculi system.

Does temperature preference relate to the anaerobic capacity of Atlantic cod (Gadus morhua L.) with different haemoglobin phenotype

Abstract The effect of Hb-I* phenotype on white muscle lactate dehydrogenease (LDH, E. C. 1.1.1.27) activity and buffering capacity was studied in Atlantic cod (Gadus morhua), acclimated and measured at temperatures near their behavioral temperature preference. It was hypothesized that these conditions would optimize biochemical processes but no difference was found in LDH activity between the Hb-I* phenotype after 56 d of acclimation to 6 and 14°C. However, LDH activity was both mass- and temperature-dependent; mean activity was 162.2±5.0 and 275.9±6.4 IU g−1 wet mass (mean±SEM) at 6 and 14°C respectively and larger fish had the highest rate of enzyme activity. White muscle buffer capacity was unaffected by Hb-I* phenotype but higher in cod held at 14°C.