Abstract
An 82-day study was conducted to assess the effect of the dietary lipid levels on growth performance, feed utilization, lipid deposition, and hepatopancreas lipometabolism of large-sized common carp (Cyprinus carpio). Six isonitrogenous (300 g/kg protein) pelletized diets with different dietary lipid levels (30, 60, 90, 120, 150, and 180 g/kg) were fed in triplicate to fish groups with 75 individuals (with an initial mean weight of 247.00 ± 16.67 g). The results showed that there was a significant increase in weight gain (WG) rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) as dietary lipid levels increased from 30 to 60 g/kg (p < 0.05) and then there was a decline. Feed conversion rate (FCR) was observed to be significantly lower in 60 g/kg lipid treatments (p < 0.05). Muscle crude protein contents were obtained to be significantly higher in 60 and 90 g/kg treatments (p < 0.05). The crude lipid content in the hepatopancreas increased significantly with an increase in dietary lipid levels (p < 0.05). The expression of lipoprotein lipase (LPL) and carnitine palmitoyltransferase-1 (CPT1) in the hepatopancreas was significantly downregulated with an increase in dietary lipid levels while the expression of growth hormone (GH), insulin-like growth factor-1 (IGF-1), fatty acid synthase (FAS), acetyl-CoA carboxylase-1 (ACC-1), and sterol regulatory element binding protein (SREBP) was upregulated first in 30 and 60 g/kg lipid treatments and then downregulated significantly in other treatments. The results revealed that excess dietary lipid supplements (more than 60 g/kg) would inhibit WG and would aggravate the lipid decomposition in the hepatopancreas. Based on WGR and FCR, the dietary lipid levels of 59.5 and 70.4 g/kg were optimal for growth performance and feed utilization of large-sized common carp.
Highlights
The exploration of an approach to minimizing the dietary protein consumption and simultaneously maximizing the protein utilization efficiency has been extremely imperative for the sustainable development of the aquaculture feed industry [1,2,3]
Significant enhancements in WGR and specific growth rate (SGR) were observed by increasing dietary crude lipid levels from 30 to 60 g/kg (p < 0.05), and further increase of the dietary lipid levels from 90 to 180 g/kg resulted in a significant decrease in growth performance (p < 0.05)
The optimal growth performance of fish with the highest WGR and SGR was found in the 60 g/kg dietary lipid treatment, with a significant difference in comparison with other groups (p < 0.05)
Summary
The exploration of an approach to minimizing the dietary protein consumption and simultaneously maximizing the protein utilization efficiency has been extremely imperative for the sustainable development of the aquaculture feed industry [1,2,3]. Investigators have begun to perform feasibility studies on the protein-sparing effect of lipids in fish diets [4,5,6,7]. In addition to the prominent protein-sparing effect, the traditional functions of lipids involve the provision of high energy values, promotion of the absorption of fat-soluble vitamins, inhibition of dust, improvement of the palatability, etc., which are important for the feed industry [8]. From a fish nutrition perspective, dietary lipids play a crucial role in furnishing essential fatty acids, phospholipids, sterols, and fat-soluble vitamins and maintaining the stability of biological structures and cell membrane functions [9,10,11]. There has been a visible tendency to supply higher concentration of lipids in commercial diets
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