Table_1_Dietary Phytogenics and Galactomannan Oligosaccharides in Low Fish Meal and Fish Oil-Based Diets for European Sea Bass (Dicentrarchus labrax) Juveniles: Effects on Gill Structure and Health and Implications on Oxidative Stress Status.xlsx

An effective replacement for fish meal (FM) and fish oil (FO) based on plant-based raw materials in the feed of marine fish species is necessary for the sustainability of the aquaculture sector. However, the use of plant-based raw materials to replace FM and FO has been associated with several negative health effects, some of which are related to oxidative stress processes that can induce functional and morphological alterations in mucosal tissues. This study aimed to evaluate the effects of dietary oligosaccharides of plant origin (5,000 ppm; galactomannan oligosaccharides, GMOS) and a phytogenic feed additive (200 ppm; garlic oil and labiatae plant extract mixture, PHYTO) on the oxidative stress status and mucosal health of the gills of juvenile European sea bass (Dicentrarchus labrax). The experimental diets, low FM and FO diets (10%FM/6%FO) were supplemented with GMOS from plant origin and PHYTO for 63 days. GMOS and PHYTO did not significantly affect feed utilization, fish growth, and survival. GMOS and PHYTO downregulated the expression of β-act, sod, gpx, cat, and gr in the gills of the fish compared with that in fish fed the control diet. The expression of hsp70 and ocln was upregulated and downregulated, respectively, in the GMOS group compared with that in the control group, whereas the expression of zo-1 was downregulated in the PHYTO group compared with that in the GMOS group. The morphological, histopathological, immunohistochemical, and biochemical parameters of the fish gills were mostly unaffected by GMOS and PHYTO. However, the PHYTO group had lower incidence of lamellar fusion than did the control group after 63 days. Although the tissular distribution of goblet cells was unaffected by GMOS and PHYTO, goblet cell size showed a decreasing trend (−11%) in the GMOS group. GMOS and PHYTO significantly reduced the concentration of PCNA+ in the epithelium of the gills. The above findings indicated that GMOS and PHYTO in low FM/FO-based diets protected the gill epithelia of D. labrax from oxidative stress by modulating the expression of oxidative enzyme-related genes and reducing the density of PCNA+ cells in the gills of the fish.

为实现水产养殖业的可持续发展，在海水鱼类饲料中采用植物源性原料替代鱼粉（fish meal, FM）与鱼油（fish oil, FO）已成为必然需求。然而，使用植物源性原料替代FM与FO会引发诸多负面健康效应，其中部分与氧化应激过程相关，该过程可诱导黏膜组织出现功能与形态学改变。本研究旨在评估植物源性饲用低聚糖（添加量5000 ppm，半乳甘露聚糖低聚糖（galactomannan oligosaccharides, GMOS））与植物源性饲料添加剂（phytogenic feed additive, PHYTO，添加量200 ppm，由大蒜油与唇形科植物提取物复配而成）对幼年欧洲海鲈（Dicentrarchus labrax）鳃组织氧化应激状态与黏膜健康的影响。实验采用低FM/FO日粮（10%FM/6%FO），分别添加植物源性GMOS与PHYTO，养殖周期为63天。GMOS与PHYTO对饲料利用率、鱼类生长性能及存活率均无显著影响。与投喂对照日粮的鱼只相比，GMOS与PHYTO组鱼鳃组织中β-肌动蛋白（β-act）、超氧化物歧化酶（sod）、谷胱甘肽过氧化物酶（gpx）、过氧化氢酶（cat）及谷胱甘肽还原酶（gr）的基因表达均被下调。相较对照组，GMOS组鱼鳃中热休克蛋白70（hsp70）的表达上调，而咬合蛋白（ocln）的表达下调；相较GMOS组，PHYTO组鱼鳃中紧密连接蛋白-1（zo-1）的表达被下调。鱼鳃的形态学、组织病理学、免疫组织化学及生化参数大多未受GMOS与PHYTO的显著影响。但养殖63天后，PHYTO组的鳃小片融合发生率低于对照组。尽管GMOS与PHYTO未影响杯状细胞的组织分布，但GMOS组的杯状细胞尺寸呈现下降趋势（降幅11%）。GMOS与PHYTO可显著降低鱼鳃上皮组织中增殖细胞核抗原阳性（PCNA+）细胞的密度。上述结果表明，低FM/FO日粮中添加GMOS与PHYTO，可通过调控氧化应激相关酶类基因的表达、降低鱼鳃组织中PCNA+细胞密度，从而保护欧洲海鲈的鳃上皮免受氧化应激损伤。