Channel CatfishIctalurus punctatusreportedly require alpha-linolenic acid (18:3[n-3]) for normal growth. However, contradicting studies suggest that elevated dietary levels of this fatty acid might cause growth inhibition, and diets containing linoleic acid (18:2[n-6]) alone or in combination with 18:0 and 18:1(n-9) may support growth as well as fish oil (FO)-based diets containing increased levels of long-chain (LC) polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (20:5[n-3]), docosahexaenoic acid (22:6[n-3]), and arachidonic acid (20:4[n-6]). Further complicating the understanding of essential fatty acid (EFA) requirements in Channel Catfish are conflicting reports suggesting that feedingLC-PUFAs can either enhance or suppress growth. We evaluated growth performance and fatty acid composition of juvenile Channel Catfish that were fed seven diets containing n-3 and n-6 C18PUFAs and/orLC-PUFAs in different combinations: a positive control containing menhadenFO, a negative control containing hydrogenated soybean oil, and experimental diets containing hydrogenated soybean oil amended with ethyl esters of 18:3(n-3); 18:3(n-3) and 18:2(n-6); 22:6(n-3); 22:6(n-3) and 20:4(n-6); or 20:5(n-3), 22:6(n-3), and 20:4(n-6). After 18 weeks, we observed no differences in growth or conversion efficiency. However, fish that were fed diets supplemented with C18PUFAs andLC-PUFAs numerically outperformed those fed theFO-based positive control feed. Tissue fatty acid profiles generally mirrored that of the diet provided, except that saturates were underrepresented in the tissues. Channel Catfish that received theEFA-free negative control feed or the diets supplemented with 18:3(n-3) and 18:2(n-6) or 20:4(n-6) and 22:6(n-3) developed elevated ratios of 22:5(n-6) : 22:6(n-3), whereas an elevated ratio of 20:3(n-9) : 20:4(n-6) was observed among fish that were fed the 22:6(n-3) supplemented diet. Our findings suggest that C(18)PUFAandLC-PUFAdiets appear to equally satisfy theEFArequirements of this species; however, intact dietaryLC-PUFAs should be carefully balanced to avoid antagonistic effects of surplus n-3LC-PUFAon n-6LC-PUFAbiosynthesis.
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