Arctic charr, Salvelinus alpinus (L.), weighing 1.6 g, were fed either commercial or one of 12 semipurified diets containing different concentrations and types of n-3 and n-6 polyunsaturated fatty acids (PUFA). The effects of dietary composition on growth, feed efficiencies, hepatosomatic indices, liver DNA and RNA concentrations and RNA/DNA ratios were investigated. The lowest growth occurred in charr fed diets deficient in PUFA and increasing dietary 18:3n-3 from 0.1 to 2.0% led to improvements in specific growth rates and feed efficiencies. The level of dietary 18:3n-3 required for adequate growth appears to fall within 1.0-2.0%. Dietary 22:6n-3 was more effective for growth enhancement than dietary 18:3n-3 and dietary 18:3n-3 was more effective than dietary 18:2n-6. No significant differences in growth and feed efficiency were found for charr fed diets containing combinations of 2.26-2.82% 18:3n-3 and 0.56-0.70% 18:2n-6 or 2.0% 18:3n-3 only. This implies that dietary 18:2n-6 has a minimal effect in the presence of adequate amounts of dietary 18:3n-3. DNA concentrations were lower in livers from fish fed diets containing <- 1.0% n-3 PUFA and this suggests histological and biochemical changes. However, a higher DNA concentration was found in charr fed the PUFA-free diet. Hepatosomatic indices were correlated with DNA concentrations for all casein-based diets. RNA concentrations in livers appeared to be correlated to anabolic events and RNA/DNA was of little value as an indicator of growth.
Bibliographical noteFunding Information:
We are indebtedt o Mingchuan Lu, Anindo Choudhury and Deping Ling for their technicalc ontributionsd uring manufactureo f experimentadl iets and sampling.W e also thank Jo-Anne Tabachek,M ike Papst, Mike Yur-kowski and Dan Tretiak for their help in various aspectso f this study.W e thank R. Olsen, M. Foster,C . Engel and D. Chaput of the Rockwood Aqua-cultureR esearchC entre (RARC) for their help with the cultures ide of the project.T his study could not have been done without accesst o the RARC facility. This project was supportedf inanciallyby the Agri-Food agreement (Province of Manitoba and the Governmento f Canada), an NSERC oper-atingg rantt o T. Dick and Arctic Fish TechnologyI nc.
ASJC Scopus subject areas
- Aquatic Science