Effects of hydroxyproline supplementation in low fish meal diet on growth, immunity and intestinal health of Litopenaeus vannamei

This experiment investigated the impacts of hydroxyproline (Hyp) supplementation in low fish meal diets on growth, antioxidant capacity, immunity and intestinal health of Litopenaeus vannamei . Six diets were formulated for the experiment, with the high fish meal diet containing 25 % fish meal (HF) and the remaining diets incorporating a mixture of soybean protein concentrate (SPC) and Clostridium autoethanogenum protein (CAP) replacing 15 % fish meal. These diets were supplemented with varying levels of Hyp (0 %, 0.2 %, 0.4 %, 0.6 %, and 0.8 %, designated as LF, H1, H2, H3, and H4, respectively). A total of 960 healthy shrimp (0.32±0.00 g) were divided into 6 groups at random; each group had 4 duplicates, each containing 40 shrimp. The shrimp were fed four times a day for a period of 51 days. The results indicated that dietary Hyp supplementation had no significant effects on growth performance and whole body composition of L. vannamei ( P > 0.05). The antioxidant enzyme activities of hemolymph and hepatopancreas were significantly decreased after fish meal was replaced, and were significantly increased after dietary Hyp supplementation ( P < 0.05). The expression of antioxidant-related genes in intestinal and hepatopancreas was significantly increased after dietary Hyp supplementation ( P < 0.05). In the intestine, the gene expression of penaeidins 3 ( pen3 ), dorsal , anti-lipopolysaccharide factor ( alf ) and crustins ( cru ) in the H2 group is the highest, and the gene expression of B-cell lymphoma-2 ( bcl2 ) in the H3 group is the highest ( P < 0.05). The genes expression of tumor necrosis factor-alpha ( tnf-a ), Bcl-2-assoxicated x protein ( bax ) and cytochrome c ( cyc-t ) in LF group reached the maximum ( P < 0.05). Intestinal H&E stained sections showed that low-fish meal diet reduced the mucosal folds height of shrimp, and H2 and H3 groups significantly increased the mucosal fold height of shrimp ( P < 0.05). Therefore, adding Hyp to the diet can improve the antioxidant capacity, immunity and intestinal health of L. vannamei . • Dietary Hyp supplementation in low fishmeal was improved the immunity of Litopenaeus vannamei. • Dietary Hyp supplementation in low fishmeal was improved the antioxidant capacity of Litopenaeus vannamei. • Dietary Hyp supplementation in low fishmeal was improved the intestinal health of Litopenaeus vannamei.