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

ABSTRACT Ctenopharyngodon idella (grass carp) is one of the most widely produced herbivorous species worldwide. However, forage feeding is not well studied in this species. This work aimed to evaluate the effect of feeding a diet based on Lolium multiflorum (ryegrass) on the growth performance and fatty acid composition in the meat of juvenile C. idella. For this purpose, juveniles were fed two different diets for 120 days: i) grains and their by-products (GD) and ii) Lolium multiflorum (PD). At 60 and 120 days of feeding, the weight gain, specific growth rate, feed conversion rate, protein efficiency, viscerosomatic index and condition factor were determined. The fatty acid profile and lipid nutritional indices of the meat were measured at 120 days. The GD group exhibited higher weight gain, specific growth rate and condition factor than the PD group. The GD group also had a higher conversion rate at the expense of greater fat content and elevated viscerosomatic index. The greater viscera development may explain the higher weight gain in the GD group. Healthy fatty acids, such as Alpha-linolenic, eicosapentaenoic, docosapentaenoic and docosahexaenoic fatty acids, were more elevated in the PD group while linoleic fatty acid (LA) was lower. Hence, LA induced a decrease in the n-6/n-3 ratio. In addition, hypercholesterolemic and atherogenetic saturated fatty acids were lower in the PD. This variation reduced the atherogenic, thrombogenicity and peroxidability indices. Therefore, better nutritional quality in the meat compensated for the lower growth of the fish on the PD.