The present paper represents a part of a major scientific effort aiming to reveal possible effects, nutritional or health related, of genetically modified (GM) feed ingredients for Atlantic salmon. For 3 months groups of post-smolt Atlantic salmon were treated with diets holding 130 g kg 1 of the protein as soybean, one which contained 800 g kg )1 GM type RR (Roundup Ready ä ), and compared with a standard counterpart (commercial hybrid, not isogenic line) analysed to be non-GM (nGM), and again compared with a standard fishmeal diet without soybean protein. All diets were composed to be within the category Ôcompositional equivalentÕ and held exactly the same proximate compositions, starch and sugar levels, above requirements for methionine and lysine, equal fatty acid profiles, vitamin, mineral and pigment contents. There was, however, a slight difference in levels of antinutrients between the three diets. The various dietary treatments resulted in more than tripling of fish weight in all groups. In addition no significant differences in feed utilization, whole body, liver and muscle proximate compositions, and no significant differences in muscle fatty acid profiles were measured. The diet without soybean of either type resulted in greater retention of lipid, but equal retention of protein (protein productive value). The relative sizes of liver, kidney, head-kidney and brain were the same in all dietary groups, while the relative size of the spleen showed significant differences between fish fed the genetically modified soy diet compared with fish fed the nGM soybeans. Fish fed the soy diets of either type also showed a somewhat reduced mean erythrocyte cell volume. All other haematological values were equal between diet groups. The detoxification system, measured as glutathione peroxidase (GPx) and lysozyme activities, showed equal values for all groups when measured in plasma and liver or head-kidney. The distal part of the intestine showed reduced sizes as an effect of soybean additions, without any differences between the GM and nGM type. Our results showed high growth, no mortality, haematological values within normal ranges, and efficient and equal responses in the detoxification system. This was a first indication that up to 130 g kg )1 RR-soybean protein can safely be used in diets for Atlantic salmon. However, there is still a need to elucidate higher inclusion levels of GM feed ingredients, and why spleen index was reduced, and if this was a long-or short-term effect. KEY WORDS

The present study was designed to evaluate if genetically modified (GM) maize (Bt maize, event MON810) compared with the near-isogenic nonmodified (nGM) maize variety, added as a starch source at low or high inclusions, affected fish health of post-smolt Atlantic salmon, Salmo salar L. To evaluate the health impact, selected stress-and immune-response biomarkers were quantified at the gene transcript (mRNA) level, and some also at the protein level. The diets with low or high inclusions of GM maize, and its near-isogenic nGM parental line, were compared to a control diet containing GM-free suprex maize (reference diet) as the only starch source. Total superoxide dismutase (SOD) activity in liver and distal intestine was significantly higher in fish fed GM maize compared with fish fed nGM maize and with the reference diet group. Fish fed GM maize showed significantly lower catalase (CAT) activity in liver compared with fish fed nGM maize and to the reference diet group. In contrast, CAT activity in distal intestine was significantly higher for fish fed GM maize compared with fish fed reference diet. Protein level of heat shock protein 70 (HSP70) in liver was significantly higher in fish fed GM maize compared with fish fed the reference diet. No diet-related differences were found in normalized gene expression of SOD, CAT or HSP70 in liver or distal intestine. Normalized gene expression of interleukin-1 beta in spleen and head-kidney did not vary significantly between diet groups. Interestingly, fish fed high GM maize showed a significantly larger proportion of plasma granulocytes, a significantly larger sum of plasma granulocyte and monocyte proportions, but a significantly smaller proportion of plasma lymphocytes, compared with fish fed high nGM maize. In conclusion, Atlantic salmon fed GM maize showed some small changes in stress protein levels and activities, but none of these changes were comparable to the normalized gene expression levels analysed for these stress proteins. GM maize seemed to induce significant changes in white blood cell populations which are associated with an immune response.

This study addresses the effects of increased mechanical load on the vertebral bone of post-smolt Atlantic salmon by forcing them to swim at controlled speeds. The fish swam continuously in four circular tanks for 9 weeks, two groups at 0.47 body lengths (bl) · s )1 (non-exercised group) and two groups at 2 bl · s )1 (exercised group), which is just below the limit for maximum sustained swimming speed in this species. Qualitative data concerning the vertebral structure were obtained from histology and electron microscopy, and quantitative data were based on histomorphometry, high-resolution X-ray micro-computed tomography images and analysis of bone mineral content, while the mechanical properties were tested by compression. Our key findings are that the bone matrix secreted during sustained swimming had significantly higher mineral content and mechanical strength, while no effect was detected on bone in vivo architecture. mRNA levels for two mineralization-related genes bgp and alp were significantly upregulated in the exercised fish, indicating promotion of mineralization. The osteocyte density of the lamellar bone of the amphicoel was also significantly higher in the exercised than non-exercised fish, while the osteocyte density in the cancellous bone was similar in the two groups. The vertebral osteocytes did not form a functional syncytium, which shows that salmon vertebral bone responds to mechanical loading in the absence of an extensive connecting syncytial network of osteocytic cell processes as found in mammals, indicating the existence of a different mechanosensing mechanism. The adaptive response to increased load is thus probably mediated by osteoblasts or bone lining cells, a system in which signal detection and response may be co-located. This study offers new insight into the teleost bone biology, and may have implications for maintaining acceptable welfare for farmed salmon.

The objective of this study was to evaluate whether standard fish meal diets prepared with increasing levels of genetically modified (GM; 150 and 300 g kg−1) maize (event MON810®) as a starch source, showed any nutritional or physiological adverse effects on Atlantic salmon, Salmo salar L. postsmolt. The diets with low or high inclusions of GM maize and its near‐isogenic parental line (nongenetically modified; nGM maize), were balanced with Suprex maize (Reference) to obtain compositional equivalency of diet starch, sugars and all other nutrients. Total starch level in all diets was 160 g kg−1. After 82 days of feeding, fish growth was high in all groups, however fish fed the GM maize showed slight but significant lower feed intake, which was followed by slight but significant lower specific growth rate and final body weights, compared with fish fed nGM maize, none of the groups varied significantly from fish fed the Reference diet. There was no variation in feed conversion ratios (FCR), protein and lipid efficiency ratios (PER and LER), or protein‐ and lipid‐productive values (PPV and LPV) in this study. No significant effect of maize type was detected on apparent digestibility coefficients (ADC) of dry matter, protein or lipid. Hematological analysis and plasma nutrients varied within normal ranges for Atlantic salmon in all diet groups, except for somewhat elevated aspartate aminotransferase (ASAT) values in all groups. Hepatosomatic index (HSI) with values ranging from 1.37 to 1.60, was significantly higher for the high GM maize group compared with the high nGM maize group but not when compared with the Reference diet group. Lowered spleen (SSI) and head‐kidney somatic indices (H‐KSI) were registered when fed GM compared with nGM maize, the Reference treatment was however, equal to both. Distal intestine somatic index (DISI) was significantly higher for GM maize‐fed fish compared with nGM maize‐fed fish, but not significantly different from the Reference diet group. Histological evaluation of the mid‐ and distal intestine, liver, spleen and head‐kidney did not reveal any diet‐related morphological changes. Maltase activities in the mid‐ and distal intestinal tissue homogenates were affected by diet, the fish fed high GM maize having higher activities compared with high nGM maize‐fed fish. Leucine aminopeptidase (LAP) and alkaline phosphatase (AP) activities were not affected by diet. Sodium‐dependent d‐glucose uptake in brush border membrane vesicles (BBMV) isolated from pyloric caeca of fish fed high GM maize was significantly higher than that found in fish fed the analogous diet with high nGM maize. Based on the present findings, the conclusions made are: Atlantic salmon smolts fed GM maize (event MON810®), its near‐isogenic parental line and suprex maize (Reference diet), all resulted in high growth rates, ADC and feed utilization. Health, when evaluated by means of mortality (low), normal ranges of blood and plasma parameters, except somewhat elevated ASAT values and minor variations in organ siz...

The present experiment was conducted to study the possible effects of genetically modified (GM), full-fat soybean meal (FFSBM) from Round-up Ready Ò soybeans compared to its parental, and closest near-isogenic, non-modified (nGM) soybean variety, added at moderate (150 g kg )1 ) and high (300 g kg )1 ) inclusion levels. The fish showed a high specific growth rate (SGR 1.27-1.52), and nearly doubled their body weight (BW), with final weights varying from 1009 to 1110 g. Increased levels of dietary FFSBM, independent of the soy being GM or not, significantly decreased mean values of SGR, thermal growth rate, condition factor, final BW, liver somatic index, lipid efficiency ratio, apparent digestibility coefficients (ADC) of protein and gross energy, liver lipid content and plasma cholesterol, and significantly increased ADC of starch and muscle fatty acid levels of 18:3n-3, 20:4n-6, 20:5n-3 and total n-3. Increasing dietary GM FFSBM significantly increased feed conversion ratio, and significantly decreased protein efficiency ratio, ADC of lipid and dry matter and plasma triacylglycerol (TAG) levels. Spleen somatic index was significantly larger in fish groups fed GM FFSBM compared to groups fed nGM FFSBM, which might indicate a possible immune response exerted by the GM soybeans. Mean normalized expression of heat shock protein 70 mRNA in distal intestine was significantly up-regulated while normalized expression of catalase in liver was down-regulated, in fish fed FFSBM compared to fish fed FM. In conclusion, substituting moderate to high levels of GM Round-up Ready Ò FFSBM in diets for Atlantic salmon and compared to the closest nearisogenic counterpart available, resulted in many effects independent of the soy being GM or not, but with the notable exceptions of enlarged spleen and lowered plasma TAG. KEY WORDS