Effect of dietary lipid level on growth, feed utilization and body composition by juvenile grass carp (Ctenopharyngodon idella)

Abstract

A study was undertaken to determine the effect of dietary lipid level on growth, feed efficiency and body chemical composition of juvenile grass carp. Seven isonitrogenous diets (400 g kg−1 crude protein) containing seven dietary lipid level (0, 20, 40, 60, 80, 100 and 120 g kg−1 dry matter) were fed to triplicate groups of 40 fish with initial weight 6.52 g, for 70 days. No obvious and assured essential fatty acid deficiency symptom appeared in fish fed the lipid‐free diet. Excess dietary lipid level (100 and 120 g kg−1) resulted in decreased feed intake. The best growth performance and feed utilization was observed in fish fed 20–40 g kg−1 dietary lipid. The fish fed a lipid‐free diet had the lowest protein efficiency and protein retention. Growth performance and feed utilization increased with the increasing dietary lipid levels up to 40 g kg−1 dietary lipid. Higher dietary level (above 40 g kg−1) made growth performance and feed utilization decrease and no protein sparing effect was observed. Lipid retention decreased as dietary lipid level increased. Mesenteric fat index (MFI) increased, hepatosomatic index (HSI) decreased with dietary lipid level. The increased MFI and simultaneous decrease lipid retention can be explained by differences in growth. The effect of dietary lipid levels on the chemical composition of tissues was significant only for whole body and muscle. The excess lipid content of liver in all groups was regarded as a slight symptom of fatty liver, which was partly identified by microscopic structural study and lower plasma lipid indexes, comparing to the initial plasma data. In conclusion, grass carp is a fish with low energy requirement and excess dietary lipid level should be avoided.

Dietary low or excess levels of lipids reduced growth performance, and impaired immune function and structure of head kidney, spleen and skin in young grass carp (Ctenopharyngodon idella) under the infection of Aeromonas hydrophila

“…However, dietary lipids have no effect on FE of young grass carp, a similar result was observed in turbot (Psetta maxima) [73]. It was reported that serum triglyceride and cholesterol concentrations were depend upon the nutritional status and lipids metabolism of fish [42,74]. In our study, both serum triglyceride and cholesterol increase with dietary lipids levels from a basal diet to 80.1 g lipids/kg diet, indicating increasing dietary lipids can induce a more active endogenous lipids transport in fish.…”

“…Each cage was equipped with a disc of 100 cm diameter in the bottom to collect the uneaten feed, according to Tang et al [51]. Each cage was randomly assigned to one of three replicates of the six dietary treatments, and fish were fed with the respective diet four times daily for 8 weeks, according to Du et al [42]. Thirty minutes after feeding, uneaten feed was collected, dried, and weighed to calculate the feed intake, as described by Tang et al [51].…”

“…To date, studies have indicated that lipids requirements are elevated in carnivorous fish (80e154 g/kg) [1,38e40], relative to the requirement herbivorous fish (40e60 g/kg) [41,42]. However, the lipids requirement of grass carp (as a commercial herbivorous species, is widely distributed in many countries [43]) was investigated only in the juvenile stage [28,41,42].…”

“…However, the lipids requirement of grass carp (as a commercial herbivorous species, is widely distributed in many countries [43]) was investigated only in the juvenile stage [28,41,42]. The growth process of grass carp can be divided into different stages such as juvenile, young and adult [44].…”

Desempenho e conversão alimentar de juvenis de carpa capim (Ctenopharyngodon idella) alimentadas com Azolla filiculoides e ração com baixo teor lipídico

“…A carpa capim é utilizada em diversos países, no controle de macrófitas em lagos e canais, sendo observado por Catarino, Ferreira e Moreira (1997) que esta espécie prefere entre várias plantas, a Azolla filiculoides e a Lemna sp. As exigências nutricionais da carpa capim foram estabelecidas por Du et al (2005), sendo elas: 20-40 g kg -1 de lipídios, 350-400 g kg -1 de proteínas e a relação energia/proteína de 7,62 kJ g -1 , evidenciando que a espécie exige baixo conteúdo energético e alto teor protéico na ração. A aeração foi constante e feita através de pedra porosa, acoplada a um compressor de ar central e a temperatura de 28 °C era mantida por aquecedores e termostatos.…”