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Dietary methionine requirement of juvenile Arctic charr Salvelinus alpinus (L.)

Authors


RichardMoccia Associate Professor of Aquaculture, Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada, N1G 2W1. E-mail: rmoccia@aps.uoguelph.ca

Abstract

The dietary methionine requirement of juvenile Arctic charr Salvelinus alpinus (L.) was assessed by feeding diets supplemented with graded levels of DL-methionine (9, 12, 15, 18, 21, and 24 g kg−1dietary protein) for 16 weeks at 12°C. All diets contained 400 g kg−1 protein, 170 g kg−1 lipid, 66 g kg−1 ash and an estimated 17.5 MJ digestible energy (DE) kg−1. When live-weight gain was examined using quadratic regression, the estimate of methionine requirement for optimal growth was 17.6 g kg−1 of dietary protein (DP) or 7 g kg−1 of the diet. Requirements estimated on the basis of carcass protein and energy gains were 18.8 and 17.9 g kg−1 DP, respectively. Plasma methionine concentrations and ocular focal length variability measurements did not provide a sensitive measure of requirement, because each responded in a linear fashion to increasing dietary methionine levels. Based on the prevalence of cataracts, the methionine level required to prevent lens pathology (26.7 g kg−1 DP) appears to be higher than that required for maximum growth.

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