The effects of dietary inulin and Jerusalem artichoke (Helianthus tuberosus) tuber on the growth performance,haematological, blood chemical and immune parameters of Nile tilapia (Oreochromis niloticus) fingerlings

This study investigated the effects of dietary inulin or Jerusalem artichoke (JA) on the growth performance, haematological, blood chemical and immune parameters of Nile tilapia fingerlings. Five treatment diets were designed to incorporate inulin at 0 (basal diet), 2.5 and 5.0 g/kg and JA at 5.0 and 10.0 g/kg. Two basal diets including fish meal and formulated experimental feed were used for fry and fingerling growing periods, respectively. During the fry growing period, larvae were fed treatment diets for 4 weeks. There were no significant differences in growth performance or survival rate. Fingerlings were then nursed with the formulated experimental diets from weeks 5 to 12. Fingerlings fed on inulin at 5.0 g/kg or JA at either level had better growth performance and survival rate than that fed on the basal diets. There were no significant differences in body composition. Dietary prebiotic inulin and JA increased red blood cell number (p < .05). Among the five blood chemistry parameters examined, both inulin at 5.0 g kg and JA (5.0 and 10.0 g/kg) increased blood protein (p < .05). Dietary inulin at 5.0 g/kg and JA at 5.0 and 10.0 g/kg increased total immunoglobulin and lysozyme activity (p < .05). Both inulin and JA inclusion diets increased alternative complement activity (p < .05). Taken together, dietary inulin at 5 g/kg and JA at 5.0 and 10.0 g/kg had beneficial effects on the growth performance, survival rate and immune of Nile tilapia fingerlings.     

Effects of Bacillus subtilis strains and the prebiotic Previda® on growth,immune parameters and susceptibility to Aeromonas hydrophila infection in Nile tilapia,Oreochromis niloticus

This study was conducted to evaluate the individual and combined effects of long‐term feeding of diets containing two probiotic Bacillus subtilis group strains (Aqua NZ and AP193) and the prebiotic Previda^®, a commercial hemicellulose extract, on growth performance, immune parameters and Aeromonas hydrophila susceptibility of juvenile Nile tilapia, Oreochromis niloticus. Nile tilapia of average weight 7.47 ± 0.11 g were fed diets formulated with the probiotics and/or the prebiotic, or a control diet for 8 weeks and, subsequently, challenged with A. hydrophila by intragastric gavage at a dosage of 3.9 × 10⁷ CFU per fish. Fish attained a mean weight of 59.5 ± 0.99 g at the end of the growth period. Under the conditions of the present trial, none of the diets significantly improved mean per cent weight gain (P = 0.70), thermal growth coefficient (P = 0.88) or feed conversion ratio (P = 0.87) of Nile tilapia. Except for the diet containing the prebiotic Previda^® only (P = 0.17), all other diets resulted in significantly higher fish survival compared to the control (P < 0.05). The combined effect of the prebiotic and probiotic strains emerged as the most important diet with respect to mortality reduction. The mean lysozyme and respiratory burst activities did not show any significant differences between treatments and control (P = 0.14 and 0.32, respectively). Thus, these probiotic strains used in this study have the potential to prevent disease due to A. hydrophila in O. niloticus.     

Effects of replacing soybean meal with rubber seed meal on digestive enzyme activity,nutrient digestibility and retention in tilapia (Oreochromis niloticus × Oreochromis aureus)

A feeding trial was conducted to evaluate the effects of replacing soybean meal (SBM) with rubber seed meal (RSM) on digestive enzyme activity, nutrient digestibility and retention in juvenile tilapia (Oreochromis niloticus × Oreochromis aureus). Five isonitrogenous and isoenergetic diets were formulated with 0 (control), 100, 200, 300 and 400 g kg⁻¹ RSM replacing graded levels of SBM respectively. Each diet was randomly assigned to triplicate groups of 30 fish (initial average weight 5.2 g) per aquarium in a rearing system maintained at 29 ± 1°C for 8 weeks. The hepatic protease and lipase activities gradually decreased with increasing dietary RSM level, but no significant differences were observed among the low inclusion level (0–200 g kg⁻¹) groups. The apparent digestibility coefficients of dry matter, crude protein, crude lipid and ash showed a similar trend as the hepatic protease and lipase activities. The retentions of protein and individual essential amino acid (except lysine, threonine and leucine) in fish fed diet with 200 g kg⁻¹ RSM were similar to those in fish fed the control diet. These results indicate that dietary RSM inclusion level up to 200 g kg⁻¹ did not markedly affect the digestive enzyme activity, nutrient digestibility and retention in tilapia, whereas these were depressed by the inclusion of 400 g kg⁻¹ RSM.     

Response of Nile tilapia (Oreochromis niloticus) to diet acidification: Effect on growth performance and feed utilization

A 12-week feeding trial was undertaken to assess growth, nutrient utilization, some hematological parameters, and proximate composition of Nile tilapia (Oreochromis niloticus) fed diets supplemented with graded levels (0.5%, 1.0%, and 1.5%) of two blends of organic acids or organic salts. Seven isonitrogenous (300 g CP kg^?1) and isocaloric (19.0 MJ gross energy kg^?1) diets were formulated. The control diet (D1) contained neither added blend of organic acids nor organic salts. Three diets (D2, D3, and D4) were supplemented with 0.5%, 1.0%, and 1.5% of malic acid + oxalic acid blend (OAB), respectively. The other three diets (D5, D6, and D7) were supplemented with 0.5%, 1.5%, and 1.5% of calcium lactate + sodium acetate blend (OSB), respectively. Fingerlings (7.05 ± 0.02 g) were randomly distributed into 21 glass aquaria (160 liter), with each aquarium holding 15 fish. At the end of the feeding trial, O. niloticus offered the control diet showed lower growth and feed utilization than all those fed the organic acids or organic salts blends supplemented diets. Fish fed the diet D3 showed the highest body weight (BW), body length (BL), weight gain (WG), specific growth rate (SGR), feed intake (FI), and the best feed conversion ratio (FCR) and protein efficiency ratio (PER). Fish fed diet supplemented by 1.5% OAB (D4) showed the highest serum protein content, while control group (D1) showed the lower level of total lipids compared with the other treatments. Fish group fed the diet supplemented with 0.5% of OSB (D5) showed the highest protein and ash contents and the lowest lipid content of the whole fish body, while the control group showed the lowest protein and the highest fat content. The present observations suggest that the growth, feed utilization, and health status of juvenile O. niloticus can be enhanced with a supplementation of 1% of OAB or OSB in the diet.     

Effect of probiotics on digestive enzyme activities and growth of cichlids,Etroplus suratensis (Pearl spot) and Oreochromis mossambicus (Tilapia)

In aquaculture, exposure to stressful conditions and problems related to diseases often occur resulting in serious economic loss. The use of probiotics that control pathogens through different mechanisms, aiding digestion by exoenzyme supply and establishment of beneficial microflora in the digestive tract has got increased attention recently. Two different bacterial species Micrococcus MCCB 104 and Bacillus MCCB 101 were tested as probiotics for two cichlid species Etroplus suratensis and Oreochromis mossambicus. The strains were administered separately and together, at a rate of 10³ CFU animal^?1 day^?1 for 28 days. The effects on digestive enzyme activity and growth were compared with those fed on control diet. FCR of E. suratensis was high in case of Bacillus alone as well as the mixed culture (Micrococcus and Bacillus together) than that of control. However, the SGR of E. suratensis was slightly lower than that of control during 14 days trial. SGR of both the treatments (Bacillus alone and mixed culture) was higher than that of the control on 28th day, and this might be due to the reason that specific duration is needed for the assimilation and conversion of nutrients into proteins. The intestinal digestive hydrolases of E. suratensis were profoundly enhanced mainly by Bacillus and mixed cultures. The hepatopancreatic versions of major digestive enzymes in E. suratensis were influenced variously by different probiotic treatments. The alpha‐amylase activity of hepatopancreas has been elevated significantly by mixed culture during 14 days experiments while on 28 days trials both Bacillus and mixed culture showed an enhancing effect. During 14 days feeding trials, the intestinal lipase activity has been prominently enhanced by all probiotic treatments. It is found that, in O. mossambicus, both 14 days and 28 days feeding experiments, the pepsin as well as intestinal digestive enzymes such as amylase, total alkaline protease, lipase and their hepatopancreatic counter parts showed a significant elevation in their specific activity. Intestinal alpha‐amylase and total alkaline proteases of O. mossambicus showed an increase in specific activities on both 14 days and 28 days feeding experiments with the Bacillus and Micrococcus combination. The hepatopancreatic enzymes were highly influenced by the Bacillus species in O. mossambicus. The results of this study suggest that live probiotic microorganisms such as Micrococcus MCCB 104 and Bacillus MCCB 101 may be incorporated while formulating the cost‐effective, nutritionally balanced diet of E. suratensis and O. mossambicus for better growth performance and nutrient utilization.     

Microwave irradiation and pelleting method affected feed chemical composition and growth performance and feed utilization of sex‐reversed Nile tilapia,Oreochromis niloticus (L.)

Microwave processing and pelleting methods were assessed to improve aquafeed quality for sex‐reversed Nile tilapia. The 2 × 3 experimental feeds were prepared with and without microwave irradiation of ingredients prior to pelleting with either a meat mincer, extruder or steam conditioner followed by a meat mincer. Five feedstuff ingredients, including fish meal, meat and bone meal, soybean meal, broken rice and rice bran, were irradiated separately at optimal times, according to the third‐order polynomial regression analysis between in vitro digestibility and microwave irradiation times (r = 0.681–0.942, P < 0.001, n = 42). The prepared feeds were studied for chemical compositions and responses in fish growth performance and feed utilization efficiency. The fish (1.57 ± 0.01 g initial weight) were fed ad libitum for 4 months. All proximate chemical compositions of experimental feeds, except protein, were influenced by microwave processing, pelleting methods or their interaction (P < 0.05). There were no significant effects from either parameter on water quality during the fish trial. Fish fed steamed microwave‐irradiated feed, mechanically pelleted with a meat mincer, showed the highest growth performance (weight gain 18.91 ± 0.73 g and specific growth rate 2.15 ± 0.26% day^?1) and feed utilization efficiency (feed conversion ratio 1.31 ± 0.05 g feed g gain^?1 and protein efficiency ratio 2.27 ± 0.08 g gain g protein^?1) compared with the other dietary groups. These findings indicate that microwave irradiation of feed ingredients prior to steam conditioning followed by mincing can improve aquafeed production quality.     

蚕蛹油等7种油脂对吉富罗非鱼生长、体组成及脂质代谢影响的比较

为研究蚕蛹油在吉富罗非鱼饲料中应用的可行性,在饲料中分别添加5.0%的蚕蛹油(SPO)、海水鱼油(MFO)、罗非鱼油(TO)、猪油(PL)、鸡油(CO)、亚麻籽油(LO)和大豆油(SO),配制成7种等氮等脂实验饲料,饲喂初始均重为(47.51±0.52)g的实验鱼。每个处理设置3个重复,每个重复放鱼20尾,进行56 d的养殖实验。结果显示,罗非鱼终末均重、增重率和特定生长率均为LO和SO组显著高于SPO和MFO组,与TO、PL和CO组差异不显著。饲料系数SPO组显著高于除MFO组外的其余各组,而蛋白质效率与之相反。摄食量SPO组最低,SO组最高。TO组罗非鱼脏体比、体长/体高和腹脂率均为最低,而肥满度最高。肝体比PL组显著高于除LO组外的其他各组。腹脂率MFO组显著高于除CO组外的其余各组。同其他组相比,SPO可降低罗非鱼全鱼、组织粗脂肪及血清甘油三酯(TG)、葡萄糖和丙二醛的含量;MFO可降低全鱼粗脂肪的含量和提高肝脏乙酰辅酶A羧化酶(ACC)的活性;PL组罗非鱼血清TG和总胆固醇(TC)含量均较低,而肝脏肉碱脂酰转移酶-I和ACC活性均较高;CO组血清TG、TC、低密度脂蛋白胆固醇(LDL-C)含量和谷草转氨酶活性均为最高;LO和SO可显著提高罗非鱼对饲料脂肪的沉积率和全鱼、肌肉粗脂肪的含量,SO还可显著提高血清高密度脂蛋白胆固醇(HDL-C)和降低LDL-C、TC的含量;SPO、LO和SO可分别显著提高罗非鱼肌肉中高不饱和脂肪酸、α-亚麻酸和亚油酸的含量。研究表明,SPO作为吉富罗非鱼饲料的单一脂肪源,虽会影响其生长性能,但具有降体脂、血脂和血糖,保护鱼体健康和优化肌肉脂肪酸组成等优点。     

The synthetic antioxidant, ethoxyquin, adversely affects immunity in tilapia (Oreochromis niloticus)

Ethoxyquin (EQ) has been used as an antioxidant in livestock, aquaculture and pet foods. Animal food safety law has established the upper limit of EQ in animal feed at 150 mg kg⁻¹. However, the risk of EQ at the approved level for aquaculture feed (150 mg kg⁻¹) to fish health is unknown. Here, we examine the effect of EQ on the immunity of tilapia ( Oreochromis niloticus ). EQ concentration in the blood reached 0.16 mg L⁻¹ in fish fed EQ at the approved level. This level of EQ inhibited phagocytic activity of leucocytes in vitro and antibacterial activity of whole blood in vivo . Furthermore, pyknosis in the liver was observed throughout the duration of feeding. However, after 30 days of experimental challenge with feed containing 150 mg kg⁻¹ of EQ, no significant difference was observed in mortality. Although EQ at the approved level in feed causes immunosuppression in fish, the severity of immunosuppression does not lead to a lowering of disease resistance for short feeding periods.     

Live Spirulina (Arthrospira platensis) as a growth and immunity promoter for Nile tilapia, Oreochromis niloticus (L.), challenged with pathogenic Aeromonas hydrophila

The use of antibiotics to control fish disease is one of the constraints in tilapia farming. Hence, the use of probiotic and live organisms as alternative strategies has received much more attention. This study was undertaken to evaluate the use of Spirulina (Arthrospir platensis) as a growth and immunity promoter for Nile tilapia, Oreochromis niloticus (L.). Fish (1.88 g) were randomly distributed at 20 fish per 100 L aquarium and fed a diet containing either 0.0, 1.25, 2.5, 5.0, 7.5 or 10.0 g Spirulina kg^?1 diet for 12 weeks. After the feeding trial, fish of each treatment were challenged by pathogenic Aeromonas hydrophila, which was given by an interperitoneal injection, and they were kept under observation for 10 days to record any abnormal clinical signs and the daily mortality rate. The growth‐promoting influence of Spirulina was observed with fish, and the optimum growth and feed utilization were obtained at 5.0 g Spirulina kg^?1 diet. No significant changes were observed in fish survival among the different treatments. Spirulina supplementation improved the protein and lipid contents in fish bodies without significant differences among them, especially when fed 2.5–10.0 g kg^?1 diet, but no significant differences in the moisture and ash contents were observed among different treatments. The physiological parameters were improved when fish were fed a Spirulina‐enriched diet. However, the highest red blood cells, white blood cells and nitro blue tetrazolium values were obtained at 5.0–10.0 g Spirulina kg^?1 diet; meanwhile, the lowest value was obtained in the control. Total fish mortality due to A. hydrophila infection decreased with an increase in the Spirulina level in fish diets. These results indicate that Spirulina supplement is promising as an alternative method to antibiotics for disease prevention in tilapia aquaculture, and the optimum level of Spirulina in the fish diet should be 5.0–10.0 g kg^?1 diet.     

Effect of dietary protein regime during the growing period on growth performance, feed utilization and whole-body chemical composition of Nile Tilapia, Oreochromis niloticus (L.)

This study was conducted to evaluate the effect of various dietary protein regimes on growth performance, feed utilization and whole-body chemical composition of Nile tilapia, Oreochromis niloticus (L.). Twenty cages (1 m³ each) were randomly allocated to a four-replicate experiment to represent five treatments (T1–T5) where fish were randomly stocked at a rate of 50 fish (1.5–2.2 g) per cage. Fish in T1–T5 fed on a 45% crude protein (CP) diet for the first 4 weeks. In T1, T2 or T3 fish fed on 45%, 35% or 25% CP diets for the last 8 weeks respectively. In T4 fish fed 35% CP diet for the second 4 weeks followed by 25% CP diet for the last 4 weeks and in T5 fish fed 25% CP diet for the second 4 weeks followed by 35% CP diet for the last 4 weeks. Diets were offered to satiation and provided manually twice a day in the morning and in the afternoon, 6 days a week. The optimum fish growth and feed utilization were obtained at T1, T2 and T4. Protein efficient ratio and apparent protein utilization were lower at T1 and T2 than those of T3–T5. On the other hand, no significant changes in energy utilization were observed among the different treatments. There were no major changes in the carcass composition except in ash content, which was higher in T3 and T5 only. This study recommended that the dietary protein regime is an important management in tilapia culture, and the protein level could be reduced from 45% to 35% then to 25% on increasing the fish size.