Lolium multiflorum (ryegrass) diet modifies the productive response and enhances the meat of grass carp (Ctenopharyngodon idella Val.) with omega 3 fatty acid beneficial to human health

Summary

This experimental trial examined the effects of substituting conventional grain-based diets with Lolium multiflorum (ryegrass) in juvenile grass carp rearing. Whilst ryegrass feeding reduced growth performance compared to grain diets, it substantially improved the fatty acid composition of the meat, increasing beneficial omega-3 polyunsaturated fatty acids and lowering saturated fatty acids and the n-6/n-3 ratio. The authors conclude that the superior nutritional quality of meat from ryegrass-fed fish compensates for slower growth, suggesting potential benefits for consumers seeking omega-3 rich aquaculture products.

Regional applicability

This research may be of limited direct relevance to UK aquaculture, as grass carp are not widely farmed in the UK climate. However, the methodological approach of using herbivorous fish species to convert forage crops (common UK grassland species like ryegrass) into nutrient-dense protein could inform the development of alternative, pasture-fed aquaculture systems compatible with UK conditions and farm management practices.

Key measures

Weight gain, specific growth rate, feed conversion rate, protein efficiency, viscerosomatic index, condition factor, fatty acid profile (including alpha-linolenic acid, eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid, linoleic acid), n-6/n-3 ratio, atherogenic index, thrombogenicity index, peroxidability index

Outcomes reported

The study compared growth performance and fatty acid composition in grass carp meat under two dietary regimes: grain-based diet versus Lolium multiflorum (ryegrass) diet over 120 days. Ryegrass feeding reduced growth rates but significantly improved the nutritional profile of the meat, with elevated healthy fatty acids and reduced atherogenic indices.

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