饲料中添加虾青素对红罗非鱼各组织类胡萝卜素含量和沉积率的影响

通过在饲料中添加不同含量虾青素,测定粉白、红斑、黑斑3种体色红罗非鱼各组织(皮肤、鳍、肌肉、眼球、鳃)类胡萝卜素含量的变化,分析不同虾青素含量对红罗非鱼不同组织类胡萝卜素含量的影响,从而推断类胡萝卜素在不同组织间的表达和沉积方式。结果显示,虾青素添加量为400 mg/kg时,红罗非鱼皮肤、鳍、肌肉、眼球和鳃中的类胡萝卜素含量与对照组相比均明显提高,体色明显改善,其中黑斑红罗非鱼鳃部类胡萝卜素沉积比对照组有显著提高(P0.05)。而当虾青素添加量为800 mg/kg时,粉白红罗非鱼鳍上和鳃部及黑斑红罗非鱼鳃部类胡萝卜素沉积比对照组有显著提高(P0.05),但3种体色红罗非鱼一些组织器官类胡萝卜素含量相对对照组及虾青素添加量为400 mg/kg时有所下降,红罗非鱼体色变化不明显。虾青素含量对红罗非鱼各组织类胡萝卜素总含量有显著影响(P0.01);而红罗非鱼体色对类胡萝卜素总含量影响不显著(P0.05);虾青素和体色交互作用对类胡萝卜素含量有较显著影响(P0.05)。聚类分析表明,类胡萝卜素在红罗非鱼的鳍中沉积率最高,其次为鳃,再次为眼球,皮肤和肌肉沉积率最低。     

罗非鱼无乳链球菌拮抗菌的分离、鉴定及多样性分析

采用径向扩散法筛选对罗非鱼致病性无乳链球菌具有拮抗作用的益生菌,利用16S r DNA对拮抗菌进行鉴定,构建系统发育树对拮抗菌的多样性进行分析,并通过腹腔注射法测定其对罗非鱼的安全性。结果表明,从8个采样点共分离细菌1 759株,其中59株对无乳链球菌具有较强的拮抗作用,抑菌圈直径为10.6mm~30.8 mm,平均21.9 mm;16S r DNA分子鉴定及系统进化树分析显示,59株拮抗菌分为5属8个种,其中芽孢杆菌属(Bacillus)45株、假单胞菌属(Pseudomonas)5株、肠球菌属(Enterococcus)2株、类芽孢杆菌属(Paenibacillus)2株和葡萄球菌属(Staphylococcus)5株。鱼体安全性试验显示,有22株拮抗菌对罗非鱼不具有致病性,可作为防治罗非鱼无乳链球菌病的备选菌株。     

Ongoing Activity of Toscana Virus Genotype A and West Nile Virus Lineage 1 Strains in Turkey: A Clinical and Field Survey

Toscana virus (TOSV), West Nile virus (WNV) and tickborne encephalitis virus (TBEV) are among major viral pathogens causing febrile disease and meningitis/encephalitis. The impact of these viruses was investigated at a referral centre in Ankara Province, Central Anatolia in 2012, where previous reports suggested virus circulation but with scarce information on clinical cases and vector activity. Serum and/or cerebrospinal fluid samples from 94 individuals were evaluated, in addition to field‐collected arthropod specimens that included 767 sandflies and 239 mosquitoes. Viral nucleic acids in clinical samples and arthropods were sought via specific and generic nested/real‐time PCRs, and antibody responses in clinical samples were investigated via commercial indirect immunofluorescence tests (IIFTs) and virus neutralization. A WNV antigen assay was also employed for mosquitoes. WNV neuroinvasive disease has been identified in a 63‐year‐old male via RNA detection, and the WNV strain was characterized as lineage 1. TOSV infections were diagnosed in six individuals (6.3%) via RNA or IgM detection. Partial sequences in a 23‐year‐old female, presented with fever and transient pancytopenia, were characterized as TOSV genotype A. Febrile disease with arthralgia and/or peripheral cranial nerve involvement was noted in cases with TOSV infections. Previous WNV and TOSV exposures have been observed in 5.3% and 2.1% of the subjects, respectively. No confirmed TBEV exposure could be identified. Morphological identification of the field‐collected mosquitoes revealed Culex pipiens sensu lato (74.4%), Anopheles maculipennis (20.9%), An. claviger (2.1%) and others. Sandfly species were determined as Phlebotomus papatasi (36.2%), P. halepensis (27.3%), P. major s. l. (19.3%), P. sergenti (8.9%), P. perfiliewi (4.4%), P. simici (2.6%) and others. Viral infections in arthropods could not be demonstrated. TOSV genotype A and WNV lineage 1 activity have been demonstrated as well as serologically proven exposure in patients. Presence of sandfly and mosquito species capable of virus transmission has also been revealed.     

Growth and fry production of Nile tilapia, Oreochromis niloticus (L.), on different feeding schedules

The effect of scheduled use of high‐protein and low‐protein diets on body weight and fry production of Nile tilapia, Oreochromis niloticus (L.), was determined. A preliminary feeding trial was first conducted on fingerlings. These were fed a high‐protein diet (H, 25% protein) or a low‐protein diet (L, 18% protein) daily, or diet H for 1–3 days followed by diet L for 1–4 days. Final body weight was significantly higher (P < 0.05) in fish fed diet H daily and in fish fed diet H for 2–3 days followed by diet L for 1 day (2H?1L and 3H?1L). Fingerlings on 1H?1L and 3H?2L had slightly lower growth. Based on the response of the fingerlings, five feeding schedules were tested with the broodstock. A high‐protein diet (HP, 40%) and a low‐protein diet (LP, 25%; same as H for fingerlings) were used. Feeding schedules significantly influenced body weight of female but not the male fish. Fry production was not significantly affected by the feeding schedule for broodstock. When growth, fry production and saving in feed cost were all considered, the broodstock on 1HP?1LP and 3HP?2LP feeding schedules both gave the highest overall performance. These findings give fish farmers an option in the management of feeding of tilapia broodstock.     

Growth performance and feed utilization of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) and tilapia galilae Sarotherodon galilaeus (Linnaeus, 1758) fingerlings fed plant protein-based diets

This study was designed to determine the effect of complete substitution of fish meal (FM) by three plant protein sources including extruded soybean meal (SBM), extruded full‐fat soybean (FFSB) and corn gluten meal (CGM) on growth and feed utilization of Nile tilapia Oreochromis niloticus and tilapia galilae Sarothrodon galilaeus. Four isonitrogenous of crude protein (ca. 28.0%) and isocaloric (ca. 19 MJ kg⁻¹) experimental diets were formulated. The control diet (diet 1) was prepared with FM as the main protein sources. Diets 2–4, each FM control diet, were completely substituted with SBM (diet 2), FFSB (diet 3) and CGM (diet 4). l ‐lysine and dl ‐methionine were added to plant protein diets to cover the nutritional requirements of tilapia. Each treatment was allocated to three net pens and fed for 17 weeks. Nile tilapia fed the control diet showed significantly higher (P≤0.05) values for final body weight (FBW), feed intake (FI), weight gain (WG) and specific growth rate (SGR), whereas fish fed the diet with CGM achieved the lowest values. Tilapia galilae fed SBM diet recorded the highest (P≤0.05) values for growth performance. Better feed conversion ratio (FCR) for both Oreochromis niloticus and Sarothrodon galilaeus was observed when fish were fed SBM diet, whereas the worse FCR was recorded for FFSB diet. Feed utilization parameters including protein productive value (PPV), fat retention (FR) and energy retention (ER) showed significant differences (P≤0.05) for both the species fed different dietary protein sources. The present results suggest that, for Nile tilapia, both SBM and FFSB supplemented with dl ‐methionine and l ‐lysine can completely replace dietary FM. Meanwhile, S. galilaeus fed SBM diet exhibited comparable growth and feed utilization with those fish fed a fish‐meal‐based diet.     

Gustatory sensitivity of the external taste buds of Oreochromis niloticus L. to amino acids

The gustatory sensitivity of the Nile tilapia, Oreochromis niloticus L., to different amino acids was studied using an electrophysiological approach. The electrical responses were recorded from a branch of the facial nerve innervating the external taste buds of the upper lip. The relative stimulatory effectiveness (RSE) of nine amino acids and betaine were determined at a concentration of 1 mm and all of them elicited neural responses. This species responded well to the neutral, basic and acidic amino acids. The most stimulatory amino acids were L‐histidine, L‐arginine, L‐serine, L‐methionine and L‐glutamine; L‐proline and betaine were the least stimulatory. The results of this study suggest that the Nile tilapia has high external gustatory sensitivity to some amino acids as a physiological adaptation to search effectively for their sources. The effect of the pH, ranging from 4.0 to 9.0, on the RSE of three neutral amino acids and artificial pond water (APW) was also studied. The RSE increased below pH 6.0 and was relatively unaffected from 7.0 to 9.0, indicating that acidified stimulants are highly stimulatory in this species. Nile tilapia did not discriminate the pH of APW as effectively as some of the species studied earlier.     

Effect of salinity on carrying capacity of adult Nile tilapia Oreochromis niloticus L. in recirculating systems

Effect of salinity on carrying capacity of a recirculation system for Nile tilapia, Oreochromis niloticus L.; production was assessed. Survival, growth and feed conversion ratio of adult Nile tilapia fed 30% crude protein diet for 88 days were measured at three different salinity levels (8, 15 and 25 g L^?1) and two stocking densities (20 and 40 m^?3) in three independent recirculating systems. Highest survival (98%) and a linear growth in net biomass (P<0.01) was observed in both densities at 8 g L^?1 and in 20 m^?3 treatment at 15 g L^?1. Highest net biomass growth was observed in the 40 m^?3 stocking density treatment at 8 g L^?1 salinity level (P<0.05). Overall biomass growth was significantly affected by salinity indicating a decrease in Nile tilapia carrying capacity with increased salinity. About 11 000 kg ha^?1 crop^?1 of Nile tilapia can be obtained in recirculating systems at 8 g L^?1 salinity, significantly higher than the net production at 15 g L^?1 (5200 kg ha^?1 crop^?1) and 22 g L^?1 (4425 kg ha^?1 crop^?1).     

Observations on the reproductive performance of three mouth-brooding tilapia species in low-salinity underground water

The reproductive performance and seed production of three mouth‐brooding tilapia species, Oreochromis spilurus (Günther), Oreochromis aureus (Steindachner) and Taiwanese red tilapia hybrid, were compared in low‐salinity underground water (3–5 g L^?1) to select species with the highest reproductive rate. Two‐year‐old males and females having average body weights of 454 and 259 g, respectively, were stocked in 2‐m³ fibreglass breeding tanks (two tanks per species) at 1:3 male to female sex ratio and at average density of three fish m^?2. Seeds (unhatched eggs; yolk‐sac fry and the swim‐up fry) were collected weekly for 112 days. The results showed O. spilurus to have significantly higher (P<0.05) mean spawning parameters expressed as total seed tank^?1 (84 154), seed kg female^?1 day^?1 (284), seed m^?2 day^?1 (190.3) and seed female^?1 day^?1 (76.3), than O. aureus and red tilapia. Monthly seed production in O. spilurus and red tilapia gradually increased from May, peaked in July and declined in August, while in O. aureus, it continued to decrease from May to August. In this study, the observed production levels of seed in O. spilurus were among the highest levels reported for tilapia; therefore, O. spilurus could be selected as a potential candidate for mass seed production in commercial tilapia hatcheries.     

Digestibility, faeces recovery, and related carbon, nitrogen and phosphorus balances of five feed ingredients evaluated as fishmeal alternatives in Nile tilapia, Oreochromis niloticus L.

This study shows that alternatives for fishmeal in a fish diet affect not only fish growth but also faeces stability and nitrogen (N) and phosphorus (P) waste production. Wheat gluten diet (WGD), soybean meal extract diet (SBE), soybean meal diet (SBM), duckweed diet (DWD) and single‐cell protein diet (SCP) were evaluated as a fishmeal replacement on a 15% weight weight^?1 basis in tilapia diets. Fishmeal replacement affected dry matter (dm), protein, ash and P digestibility significantly. Faeces recovery (6.8–11.2%) was not significantly affected, although the amount of non‐recovered faeces and total faeces showed significant differences. Duckweed diet and SCP resulted in the largest amounts of non‐recovered and total faeces (199–210, 224–225 g dm kg^?1 feed dm). Compared with fishmeal diet (FMD), the WGD and SBE resulted in similar growth, but higher non‐faecal N losses (471–495 vs. 416 g N kg^?1 N). Soybean meal diet, DWD and SCP resulted in lower growth but less non‐faecal loss (409–450 g N kg^?1 N). The DWD and FMD had the highest N retention (480 g N kg^?1 N) compared with the other diets (431–451 g N kg^?1 N). Carbon retention, faecal and non‐faecal losses and P retention were similar for all diets (302–358, 142–176 and 489–523g C kg^?1 C, 606–704 g P kg^?1 P). Phosphorus faecal loss was lower for all diets (329–381 g P kg^?1 P) than for the FMD (401 g P kg^?1 P).     

Effect of diets containing gossypol on blood parameters and spleen structure in tilapia, Oreochromis sp., reared in a recirculating system

The high cost of fish meal in tilapia diets warrants the potential use of cottonseed meal (CSM) as an alternative source of high quality protein. The effects of varying levels of CSM (0, 25, 50, 75 and 100%) as fish meal protein replacement on growth, blood parameters, spleen characteristics, free and bound gossypol in blood plasma, haemoglobin and haematocrit were determined in tilapia. Gossypol (C(30)H(30)O(8)) is a polyphenolic substance found in cottonseed that has known toxic effects in fish. Tilapias (n = 219, average weight = 11.3 +/- 3.9 g) were randomly distributed into 15, 32-L glass aquaria, representing five dietary treatments and three replicates per treatment. Each aquarium containing 13-16 fish was supplied with thermoregulated, recirculating water (27 +/- 1 degrees C) at 1 L min(-1) flow rate and photoperiod was constant (12 h L/12 h D). Fish fed 25-50% CSM protein replacement showed similar body weights and total lengths as the controls at the completion of the 16-week trial. Fish fed 75 and 100% CSM protein replacement showed a significant decline in body weight and total length. Fish fed 25-100% CSM protein replacement had significantly lower haematocrit and haemoglobin (ANOVA/LSD, P < 0.05) compared with levels in controls. The decline was most prominent in groups fed diets with 50-100% CSM protein replacement. Total and free gossypol concentrations of blood plasma significantly increased with increasing levels of CSM replacement (P < 0.05). No gossypol was found in blood plasma of fish from the control group. The occurrence of immature and abnormal erythrocytes was significantly greater among fish fed 75 and 100% CSM diets compared with fish fed 0-50% CSM diets. Spleen-somatic index (spleen weight/body weight x 100) did not differ between control fish and fish fed 50-100% CSM diets. Spleen abnormalities, such as large depositions of haemosiderin and melanin pigments and proliferation of melano-macrophage centres, lymphocytic depletion of the white pulp areas (hypocellularity), and presence of vacuoles and necrotic areas were observed among fish fed 50-100% CSM protein diets. In general, the pathological effects of gossypol in tilapia (low haemoglobin and haematocrit levels, abundance of immature red blood cells or polychromatocytes, abnormal spleen morphology) were similar to the effects of vitamin E and/or vitamin C deficiencies observed in other studies.