Differential Incorporation of Dietary Fatty Acids from Flax and Fish Oils into Lipid Classes of White Bass Ova

Abstract

The extent to which flax oil can replace fish oil in diets fed to female broodstock of white bass Morone chrysops was determined by evaluating growth performance and the fatty acid (FA) profile of ovum lipid classes. Four experimental diets containing increasing levels of flax oil as 0, 33, 67, and 100% replacement of menhaden (Brevoortia spp.) fish oil were fed to female white bass for 30 weeks prior to spawning. Overall, growth and survival were unaffected when flax oil replaced fish oil in the diets. However, ovum FA composition did differ by lipid class and according to dietary intake. The FA profile of the neutral lipid classes largely resembled dietary intake, resulting in monounsaturated FAs (MUFAs) and long-chain polyunsaturated FAs (LC-PUFAs; FAs with ≥20 carbons and ≥3 double bonds) as the most predominant FAs found within ova produced by 100% fish-oil-fed broodstock, while MUFAs and 18-carbon PUFAs dominated the ovum neutral lipid in females from the 100% flax oil treatment. Although the phospholipid fraction of ova produced by the 100% flax-oil-fed broodstock was also significantly enriched with 18-carbon PUFAs, accumulation of these FAs did not displace n-3 LC-PUFAs as comparable levels of n-3 LC-PUFAs were found in both the 100% fish oil and 100% flax oil treatments. Overall, flax oil has potential for use as an alternative to menhaden fish oil in diets for female white bass broodstock without altering phospholipid LC-PUFA content. However, further investigation is needed to determine how these modifications to ovum FA profile affect embryonic and larval survival.

Received January 19, 2010; accepted August 17, 2010

ACKNOWLEDGMENTS

We are grateful to Keo Fish Farm, the Iowa Department of Natural Resources, and the Gravois Arm Lions Club; this research would not have been possible without their assistance in obtaining white bass broodstock. We also thank Andy Coursey, Shawn Meyer, John Boesenberg, and Mike Hill for assistance in data collection. The research was performed by the first author as a portion of a dissertation to partially meet the requirements for a Doctor of Philosophy degree at the Department of Zoology, Southern Illinois University. The project was supported by National Research Initiative Competitive Grant Number 2005-35203-15894 from the U.S. Department of Agriculture's Cooperative State Research, Education, and Extension Service. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the U.S. Department of Agriculture.