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The effect of dietary lipid and vitamin E on the reproduction of Arctic charr, Salvelinus alpinus (L.) Tabachek, J. L.


This research was conducted in an attempt to improve embryonic survival of Labrador Arctic charr by altering the concentrations of lipid and vitamin E in the diets fed to broodstock. Four-year old Labrador Arctic charr broodstock were fed diets containing two levels of dietary lipid at two levels of vitamin E acetate (dl-a-tocopheryl acetate) supplementation. The diets were designated LLLE, LLHE, HLLE and HLHE to denote low lipid (12%)(LL), high lipid (19%)(HL), low vitamin E (30 mg/kg)(LE) and high vitamin E (600 mg/kg)(HE). For comparison, a fifth group was fed their normal diet - a commercial grower diet (COMM) containing 17% lipid and 100 mg vitamin E acetate/kg. Since Arctic charr broodstock used in this research were valuable, diets that might have a deleterious effect on the survival or fecundity of the broodstock could not be used. Dietary lipid concentrations were selected based on the requirements for juvenile Arctic charr. Dietary vitamin E concentrations were selected based on requirements stated in the literature for other salmonids. Fish were fed for 71 days before withdrawal of feed prior to spawning in Year 1 and for 252 days in Year 2. Since fish fed the LL diets in Year 1 spawned 5 weeks later than those fed the HL diets, a crossover in diets was conducted to see if this would also occur in Year 2. Keeping the vitamin E level the same, those fed LL diets in Year 1 were fed HL diets in Year 2 and vice versa. No effect of dietary lipid on spawning time was observed in Year 2. The proportion of females failing to spawn was not related to the concentrations of dietary lipid or vitamin E. A significantly higher proportion of males fed the higher concentration of vitamin E produced milt in two successive spawning seasons. Fecundity of 3894 and 4532 eggs in Year 1 and 4154 and 8305 eggs in Year 2 for the four experimental and COMM diets, respectively, was directly correlated with female weight and was not affected by the level of dietary lipid or vitamin E. The fatty acid composition of the eggs reflected that of the diet and was not indicative of essential fatty acid deficiency. In Year 2, concentrations of total (22.3%), neutral (10.6%) and polar lipids (11.7%) in the eggs were not significantly affected by the concentrations of dietary lipid or vitamin E. The vitamin E concentrations of the eggs were 52, 202, 54 and 156 u,g/g in Year 1 and 38, 208, 51 and 140 ixg/g in Year 2 for the LLLE, LLHE, HLLE and HLHE diets respectively. The increase in dietary vitamin E resulted in a greater increase in vitamin E concentration in eggs from fish fed the LL compared to the HL diets. Diets containing 30 or 600 mg vitamin E acetate/kg with 12 or 19% lipid met the vitamin E requirements of 4- and 5-year old broodstock to the extent that fertilization and embryonic survival was not affected significantly. Fertilization was 89% in Year 2 and 80% in Year 2. There was a high degree of within treatment variation in embryonic survival. Fertilization and embryonic survival were not correlated with vitamin E concentration of the eggs. Survival to swimup of fertilized eggs was 27% for the LE diets and 55% for the HE diets in Year 2. Embryonic survival to the eyed, hatch and swimup stages were negatively correlated with the percent neutral lipid and with 16:ln7 in the neutral lipid of the eggs.

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