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Dietary protein quality and quantity for Atlantic salmon (Salmo salar) reared in sea water

University of British Columbia

Two separate studies were conducted with Atlantic salmon (Salmo salar) reared in seawater. The first study investigated various in vitro and in vivo methods for the measurement of the quality of the protein in fish meals. The second study was designed to estimate the optimal dietary ratio of digestible protein (DP) to digestible energy (DE) for Atlantic salmon (0.5 -1.2 kg body weight). A second objective of the latter study was to investigate the effect of feeding diets varying in levels of digestible protein and lipid on the proximate composition, pigment deposition, and the total fatty acid profiles of whole-fillets of Atlantic salmon. Chemical (chemical composition, biogenic amines, total volatile basic-nitrogen, anisidine value, peroxide value, thiobarbituric acid value, and iodine value), in vitro (dilute-pepsin and multi-enzyme digestibilities) and in vivo assays using rats and fish as test animals were conducted on various fish meals. The results indicated that dilutepepsin digestibility was a suitable in vitro assay to evaluate the protein quality of herring meals for Atlantic salmon. However, this assay correlated poorly with the results from in vivo assays when other types offish meals (menhaden, mackerel, silver hake, groundfish) were included. Apparent metabolizable crude protein values determined using rats as the test animal, was the only in vivo assay that was found to correlate with digestibility values determined using salmon when the entire range of fish meals was assessed. Based on growth and protein and energy utilization data, the estimated optimal dietary ratio of DP to DE to rear Atlantic salmon over a size range of 0.5 kg to 1.2 kg in seawater was 17.4 g DP-MJ DE. This ratio was supplied by a diet containing 360 g DP (404 g crude protein) and 20.7 MJ DE (24.0 MJ gross energy) -kg"1 dry matter. It would also appear from this study that Atlantic salmon reared in seawater are able to tolerate up to 220 g starch-kg"1 dry matter without any detrimental effects on growth, although liver glycogen and hepatosomatic indexes were increased. Work is still needed to determine the optimal ratio of non-protein energy sources to reduce the utilization of protein for energy in salmon diets. Deposition of canthaxanthin in the fillets of Atlantic salmon was not influenced by changes in the ratio of dietary protein and lipid. The total lipid content in whole-fillets (red and white muscle with the skin removed) from Atlantic salmon was directly and significantly influenced by the dietary lipid level. The fatty acid profile of the fillets was not only affected by the dietary lipid level and the ratio of digestible protein to lipid, but also by the residual lipid content of the fish meal portion of the diet. Although the total n-3 fatty acid content of the fillets was not significantly changed by alterations of the dietary protein or lipid levels, the percentage of 20:5 n-3 did increase in direct relation to the dietary lipid level.

Thesis/Dissertation

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2009-03-19

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http://hdl.handle.net/2429/6229

Animal Science

University of British Columbia

UBCV

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