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Lysosomal acid phosphatase activity and histological analyses of Atlantic salmon fillets fed different oil sources

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Kjetil Aune

Bibliotekleder
kjetil.aune@nofima.no

4th Euro Fed Lipid Congress. Oils, fats and lipids for a healthier future; University of Madrid, Spain, 2006-10-01–2006-10-04

Bahuaud, Diane; Maurstad, Torunn; Rørå, Mia B.; Thomassen, Magny S.; Ofstad, Ragni; Ruyter, Bente

So far, marine oils have been the main feed lipid sources for farmed salmonids. However, the need to use other lipid sources is increasing. The aim of this experiment was thus to study the impact of different lipid sources in the feed, on the quality and stability of the fish fillet. Our interest was focussed on the lysosomal fraction of the muscle for an eventual implication of these organelles in the quality and quality deterioration of the muscle post slaughter. Results from lysosomal studies were compared with histological analyses of the fish muscle. The experiment was carried out at Akvaforsk?s research station, Sunndalsøra, Norway. Groups of Atlantic salmons (Salmo salar) were fed a basic diet supplemented with 13.5% of either fish oil, rapeseed oil, EPA enriched oil or DHA enriched oil, for 17 weeks. After slaughter, muscle sampling was performed, up to 96h after slaughter. The lysosomal fraction was isolated and the activity of the acid phosphatase analysed. Further, light microscopy studies determined the amount of myofibre-myofibre as well as mycocommata-myofibre detachments for each diet and time point as an evaluation of the fillet?s degradation. Lysosomal acid phosphatase activity significantly increased with time for each diet, indicating levels of degradation of the muscle. EPA and DHA diets induced the highest enzyme activity (from 0.112 to 0.284 U/ml; from 0.091 to 0.285 U/ml), indicating a reaction of the organism to an additional inner stress. On the contrary, the enzymatic response of the lysosomal fraction was lower for both FO and RO diets (from 0.063 to 0.224 U/ml; from 0.067 to 0.282 U/ml), the FO diet giving the lowest activity. At the same time, microscopic observations showed a disturbance in the muscle degradation for fish fed EPA and DHA, as well as a high amount of central placed nuclei; perhaps again indicating a reaction of the organism to an inner stress. In addition to comparing the response of the fish to different sources of lipids in the feed, these results highlighted the possibility that lysosomes may participate actively in determining the final fish flesh quality and stability. So far, marine oils have been the main feed lipid sources for farmed salmonids. However, the need to use other lipid sources is increasing. The aim of this experiment was thus to study the impact of different lipid sources in the feed, on the quality and stability of the fish fillet. Our interest was focussed on the lysosomal fraction of the muscle for an eventual implication of these organelles in the quality and quality deterioration of the muscle post slaughter. Results from lysosomal studies were compared with histological analyses of the fish muscle. The experiment was carried out at Akvaforsk?s research station, Sunndalsøra, Norway. Groups of Atlantic salmons (Salmo salar) were fed a basic diet supplemented with 13.5% of either fish oil, rapeseed oil, EPA enriched oil or DHA enriched oil, for 17 weeks. After slaughter, muscle sampling was performed, up to 96h after slaughter. The lysosomal fraction was isolated and the activity of the acid phosphatase analysed. Further, light microscopy studies determined the amount of myofibre-myofibre as well as mycocommata-myofibre detachments for each diet and time point as an evaluation of the fillet?s degradation. Lysosomal acid phosphatase activity significantly increased with time for each diet, indicating levels of degradation of the muscle. EPA and DHA diets induced the highest enzyme activity (from 0.112 to 0.284 U/ml; from 0.091 to 0.285 U/ml), indicating a reaction of the organism to an additional inner stress. On the contrary, the enzymatic response of the lysosomal fraction was lower for both FO and RO diets (from 0.063 to 0.224 U/ml; from 0.067 to 0.282