Three isonitrogenous diets containing 60 g kg -1, 90 g kg -1 or 120 g kg -1 lipid were formulated and fed to the Litopenaeus vannamei (2.00 ± 0.08 g) under two salinities (25 or 3 psu) in triplicate for 8 weeks. Shrimp fed 90 g kg -1 lipid had higher weight gain and specific growth rate than shrimp fed the other two diets regardless of salinity, and the hepatosomatic index increased with increasing dietary lipid at both salinities. The shrimp at 3 psu had significantly lower survival and ash content, higher condition factor, weight gain and specific growth rate than the shrimp at 25 psu. Increasing dietary lipid level induced the accumulation of serum MDA regardless of salinity, and at 3 psu, it reduced the serum GOT and GPT activities and the mRNA expression of TNF-α in intestine and gill of L. vannamei. The hepatopancreatic triacylglycerol lipase (TGL) and CPT-1 mRNA expression showed the highest value in shrimp fed 90 g kg -1 lipid diet at 3 psu. This study indicates that 120 g kg -1 dietary lipid may negatively affect the growth and induce oxidative damage in shrimp, but can improve immune defence at low salinity; 60 g kg -1 dietary lipid cannot afford the growth and either has no positive impact on the immunology for L. vannamei at 3 psu. K E Y W O R D Sgrowth, health status, histology, lipid, Litopenaeus vannamei, salinity | INTRODUCTIONThe Pacific white shrimp Litopenaeus vannamei is a popular species for commercial aquaculture production in the world because of its high tolerance of salinity from 1 to 50 practical salinity unit (psu) (Cheng, Hu, Liu, Zheng, & Qi, 2006;Pante, 1990;Saoud, Davis, & Rouse, 2003).However, poor survival and growth performance (Diaz, Farfan, Sierra, & Re, 2001;Li et al., 2007), low stress tolerance and disease resistance (Li et al., 2007Lin & Chen, 2001, 2003 Hwang, 2008). Therefore, the provision of sufficient nutrients and energy through dietary manipulation is effective to enhance the ability for L. vannamei to adapt to low salinity (Li et al., 2011Schwartz, Austen, & Wasserman, 1979;Tseng & Hwang, 2008;Welcomme & Devos, 1991).Lipids have the highest energy density among the three major nutri- In this study, two levels of salinity were set at 3 psu and 25 psu.The former is the salinity usually used for L. vannamei culture in inland saline water, and the latter is the salinity close to the isotonic point | MATERIALS AND METHODS | Experimental dietsThree isonitrogenous practical diets (380 g kg -1 crude protein) were formulated with three levels of crude lipid (60, 90 or 120 g kg).Before adding oil (fish oil: soybean oil = 1:1), all dry ingredients were finely ground and mixed thoroughly. The mixture was dissolved by adding water (250 ml/kg) and then extruded into 2-mm-diameter pellets using a meat grinder. The scattered pellets were air-dried at room temperature to <100g dry matter/kg moisture. Pellets were sieved to various sizes and stored at −20°C until use. Ingredient and proximate composition of the experimental diets are presented in Table 1. adding seawater a...

Because of the increasing market potential of Pacific white shrimp (Litopenaeus vannamei) and limited availability of coastal areas for production, culture of L. vannamei at low salinity is a growing trend throughout the world. Dietary manipulation could improve the growth performance of L. vannamei at low salinity. This study reared L. vannamei with glucose, sucrose and corn starch as dietary carbohydrate sources, respectively, at a low salinity. The results indicated that the sucrose and glucose feeding groups showed better growth performance. An Illumina‐based sequencing method was used to examine the intestinal bacterial composition and the results indicated that Proteobacteria were the most prevalent members, but abundance of Actinobacteria decreased while Firmicutes increased in the corn starch‐fed group. Furthermore, bacteria related to complex carbohydrate degradation were in lower abundance, whereas the abundance of opportunistic pathogenic bacteria increased in corn starch‐fed group than the other two groups, suggesting that the diet imposes selective pressure on the intestinal microbiota. Complex carbohydrates were not the ideal energy sources for L. vannamei at low salinity because the host has higher energy demand in the stressful conditions while the complex carbohydrate degradation efficiency of the gut microbiota in L. vannamei is limited.

A 6‐month trial was conducted to evaluate the effects of dietary cottonseed meal (CSM) and free gossypol (FG) on allogynogenetic silver crucian carp, Carassius auratus gibelio♀ × Cyprinus carpio♂ with 4 replicates of each treatment. Isonitrogenous and isocaloric diets were formulated with the 0 g kg−1 (control), 200 g kg−1, 400 g kg−1, and 560 g kg−1 CSM. Diets with FG were made by supplementing batches of control diet with 214 mg kg−1, 428 mg kg−1, and 642 mg kg−1. Weight gain, specific growth rate, and protein efficiency ratio increased significantly up to an inclusion level of CSM of 400 g kg−1 in the diet, with a significant decrease in food conversion ratio. Further increase in CSM to 560 g kg−1 did not cause further changes in fish performance. Free gossypol did not affect fish performance significantly at any inclusion level. Neither CSM nor FG caused significant effects in any of the other evaluated parameters such as whole body composition, haemoglobin concentration, activities of serum lysozyme, superoxide dismutase, alanine aminotransferase and aspartate aminotransferase, and histology of hepatic tissues and midgut. Our results suggested that crucian carp can tolerate at least 642 mg kg−1 FG and that it is safe to including 400 g kg−1 CSM in crucian carp feed.

The impact of dietary a-tocopherol on juvenile Chinese mitten crab Eriocheir sinensis was experimentally evaluated in a 10-week study. Crab were fed with nine diets including three levels of a-tocopherol (0, 100 and 300 mg kg À1 diet) and three levels of fish oil oxidation (fresh, moderate and high) in triplicates. Fresh and moderate oil oxidization enhanced weight gain, but moderate and high oil oxidization lowered survival and feed efficiency. The 100-mg a-tocopherol kg À1 diet resulted in higher hepatopancreas MDA than other a-tocopherol diets. High oil oxidization led to the lowest serum superoxide dismutase (SOD) and glutathione peroxidase (GPH-PX). The serum SOD and GPH-PX activities in crab fed 100 mg a-tocopherol were higher than in those fed other a-tocopherol diets. The diet without a-tocopherol addition lowered lysozyme and phenoloxidase (PO) activities compared to other a-tocopherol diets. Fresh fish oil diet increased PO activity compared to oxidized oils. High oil oxidization caused significantly more mortality than fresh or moderate oxidization after 7-d postchallenge with Aeromonas hydrophila. Supplementation with a-tocopherol significantly enhanced resistance to bacterial infection. This study indicates that a-tocopherol can protect lipid from peroxidation and enhance disease resistance.