Effects of dietary lysine level on the growth performance, protein metabolism, and antioxidant status in Hemibagrus wyckioides juveniles

Abstract

An 11‐week feeding trial was conducted to assess the dietary lysine requirement for juvenile Hemibagrus wyckioides. Six isoproteic and isoenergetic diets (41.66% crude protein, 20.56 kJ/g gross energy) containing 1.1%, 1.5%, 1.9%, 2.3%, 2.7%, and 3.1% lysine were prepared to feed juveniles (average initial body weights of 1.25 g), respectively. The weight gain, specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio significantly improved with the dietary lysine level up to 2.3%, 1.9%, 2.3%, and 2.3%, and then plateaued afterwards. The highest midgut trypsin and lipase activities as well as plasma antioxidant enzyme activities and nitric oxide content but the lowest plasma malondialdehyde content were recorded in fish fed diet with 2.3% lysine. Fish fed diets with 1.9% or 2.3% lysine exhibited the highest plasma total protein and insulin contents, the lowest plasma ammonia content, and relative expression levels of glutamate dehydrogenase in the liver and adenosine monophosphate deaminase in the liver and muscle. Similarly, fish‐fed diet with 2.7% lysine showed the lowest hepatic alanine aminotransferase activity but the highest hepatic expression level of the mammalian target of rapamycin. Broken‐line regression analysis based on SGR and FCR showed that the dietary lysine requirement for juvenile H. wyckioides was 2.04% to 2.09%, while dietary lysine of 2.3% was optimum for the antioxidant status of H. wyckioides.

Effects of Dietary Lysine Level on Growth Performance and Protein Metabolism in Juvenile Leopard Coral Grouper (Plectropomus leopardus)

“…In this study, dietary lysine inclusion of 1.69–2.30% upregulated the relative expression levels of TOR and S6K1 but downregulated the relative expression level of 4E-BP2, indicating that the optimum dietary lysine activated the mTOR signaling pathway and thereby promoted the protein synthesis in P. leopardus . Similarly, the optimum dietary lysine significantly upregulated the relative expression levels of hepatic TOR in juvenile Hemibagrus wyckioides [ 36 ] and hepatic TOR and S6K1 in hybrid grouper [ 15 ] and upregulated the relative expression level of intestinal TOR but downregulated the relative expression level of intestinal 4E-BP in grass carp [ 26 ]. Therefore, it is believed that a balanced dietary amino acid profile plays an important role in sustaining efficient protein synthesis [ 37 ].…”

“…In this study, the hepatic AMPD activity was linearly depressed with the increase of dietary lysine level, indicating that dietary lysine inclusion was conducive to reducing protein catabolism and thereby improving protein deposition. In the study of juvenile Hemibagrus wyckioides , optimal lysine also downregulated the relative expression levels of GDH in the liver and AMPD in the liver and muscle [ 36 ]. Additionally, dietary protein or amino acid deficiency will trigger a series of signal processes, collectively referred to as AAR [ 47 , 48 ].…”