25The present study compared the effects of diets formulated with reduced fishmeal 26 (FM) content and either 100% fish oil (FO) or 100% of a vegetable oil (VO) blend in 27 post-smolts of three family groups of Atlantic salmon. Two groups were selected as 28 being either "Lean" or "Fat" based on estimated breeding values (EBV) for flesh 29 adiposity of their parents derived from a breeding programme, while the third group 30 (CAL) was a mix of non-pedigreed commercial families unrelated to the two groups 31 above. The VO blend comprised rapeseed, palm and a new product, Camelina oil in 32 a ratio of 5/3/2, and diets were fed to duplicate pens of each salmon group. After an 33 ongrowing period of 55 weeks, to reach a mean weight of 3kg, the fish from all 34 treatments were switched to a decontaminated FO for a further 24 weeks to follow 35 restoration of long-chain n-3 polyunsaturated fatty acids (LC-PUFA) in the fish 36 previously fed VO. Final weights were significantly affected by family group and 37 there was also an interaction between diet and group with Fat and Lean FO fish being 38 larger than the same fish fed VO. Specific growth rate (SGR) was highest in CAL 39 fish (1.01), feed conversion ratio (FCR) was highest in the Lean fish but there were 40 no significant effects on thermal growth coefficient (TGC). Condition Factor (CF) 41 was lowest in CAL fish while the hepato-somatic index (HSI) was highest in Lean 42 fish and viscero-somatic index (VSI) highest in Fat fish. Flesh and viscera lipid 43 content was affected by both family group and diet with a significant interaction 44 between the two. Flesh lipid in fish fed FO was in the order Fat > CAL > Lean 45 although this order was Fat = Lean > CAL when fed VO. Flesh fatty acid 46 compositions were affected mainly by diet although some minor fatty acids were also 47 3 influenced by group. Fish fed VO had n-3 LC-PUFA reduced by ~65% compared to 48 fish fed FO but this could be restored by a 16 week FO finishing diet phase. The 49 differences observed in lipid and fatty acid deposition suggested that genetics 50 affected lipid deposition and metabolism and that breeding programmes could select 51 for fish that retained more n-3 LC-PUFA in their flesh, particularly when fed diets 52 low in these fatty acids. 53 54

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The study investigated cataract preventive effects of dietary histidine (His) supplementation in triploid Atlantic salmon during seawater grow-out. Groups of individually PIT tagged diploid (2N) and triploid (3N) postsmolts were fed one of two supplemented dietary histidine levels; low (L, 12.6 g kg-1 diet) or high (H, 17.4 g kg-1 diet) from March to September following their first sea winter. Low severity cataracts were detected in both ploidy prior to supplemented His diet application. Thereafter, 3N-L showed progression of cataract development in the second spring-summer period, while development was inhibited in 3N-H. Severity of cataract showed a strong family effect. A positive correlation between initial triploid seawater growth (weight and TGC) under increasing water temperature and cataract severity was identified as a major risk factor. The relationship was reversed at harvest, where triploids were on average 7.5% smaller than their diploid siblings. Lens N-acetyl-histidine content reflected dietary His inclusion level and cataract severity, although no significant differences in lens His content were evident between ploidy or dietary groups. Results indicate that triploid Atlantic salmon appear to have a higher dietary histidine requirement than diploids and that preventative measures can be taken to mitigate further cataract development

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