Responses of yellow catfish (Pelteobagrus fulvidraco Richardson) to low‐protein diets and subsequent recovery

A 4‐week growth trial was conducted to investigate the effect of low‐protein diets on the growth and amino acid (AA) composition of yellow catfish, and subsequent recovery when the fish were then switched back to the control diet for a further 4 weeks. Three isolipidic and isocaloric diets containing 390 g kg^?1 (Control), 320 g kg^?1 (D320) and 260 g kg^?1 (D260) graded protein levels were evaluated. During the protein restriction period, specific growth rate (SGR) of D320‐and D260‐treated fish was significantly reduced by 20.79% and 29.21% compared to the control fish, respectively (P < 0.05), while significant improvements in protein retention efficiencies were observed in fish fed with the D320 (12.82%) and D260 (19.58%) diets (P < 0.05). The D260‐treated fish had significantly lower (0.87%) whole‐body essential amino acid (EAA) and significantly higher (0.74%) non‐essential amino aci (NEAA) concentrations compared to the control fish. After a 4‐week realimentation, significant increases in the SGR of the protein‐restricted fish were observed. However, no significant differences in the whole‐body EAA or NEAA concentrations among groups were observed (P > 0.05). The results indicate that previously protein‐restricted yellow catfish can compensate completely in terms of final body weight, growth rate and whole‐body AA concentrations.     

Effect of dietary vitamin C on the growth performance,antioxidant ability and innate immunity of juvenile yellow catfish (Pelteobagrus fulvidraco Richardson)

A 12‐week feeding trial was conducted to evaluate the effects of dietary vitamin C on growth performance, antioxidant status and innate immune responses in juvenile yellow catfish, Pelteobagrus fulvidraco. Six isonitrogenous and isolipidic diets (44% crude protein and 7% lipid) were formulated to contain six graded dietary vitamin C (ascorbate‐2‐poly‐ phosphate, ROVIMIX^® STAY‐C^® 35) levels ranging from 1.9 to 316.0 mg kg^?1 diet. The results of present study indicated that fish fed the lowest vitamin C diet had lower weight gain (WG) and specific growth rate (SGR) than those fed the diets supplemented vitamin C. WG and SGR did significantly increase with dietary vitamin C levels increasing from 1.9 to 156.5 mg kg^?1. However, no significant increase was observed with further dietary vitamin C levels increasing from 156.5 to 316 mg kg^?1. Survival, protein efficiency ratio and feed efficiency were not significantly affected by the dietary vitamin C levels. The activities of serum superoxide dismutase, catalase and glutathione peroxidase significantly increased when dietary vitamin C levels increased from 1.9 to 156.5 mg kg^?1, fish fed the lowest vitamin C diet had higher serum malondialdehyde content than those fed the diets supplemented with vitamin C. Fish fed the diet containing 156.5 mg kg^?1 vitamin C had the highest lysozyme, total complement activity, phagocytosis index and respiratory burst of head kidney among all treatments. The challenge test with Aeromonas hydrophila indicated that lower cumulative survival was observed in fish fed the lowest vitamin C diet. Analysis by broken‐line regression of SGR and lysozyme activity indicated that the dietary vitamin C requirement of juvenile yellow catfish was estimated to be 114.5 and 102.5 mg kg^?1 diet, respectively.     

不同剂型维生素C对黄颡鱼生长和几种免疫指标的影响

黄颡鱼(Pelteobagrus fulvidraco)是新兴淡水养殖对象,其养殖技术和适宜饲料蛋白及维生素C磷酸酯的需要量等已有报道,但对包膜维生素C的生长和免疫反应目前尚未见报道,而维生素C是鱼正常生长和抗病的重要微量营养素。为此,在水温(22.0±3.0)℃下,将平均体质量10.0 g的黄颡鱼幼鱼放养在30个60 cm×60 cm×120 cm的微流水网箱中,投喂以鱼粉为蛋白源,粗蛋白含量40.0%和粗脂肪8.0%的半精制饲料,按300 mg.kg-1、600 mg.kg-1、900 mg.kg-1、1 200 mg.kg-1和1 500 mg.kg-1的剂量分别添加维生素C磷酸酯和包膜维生素C。经90 d的饲养表明,饲料中维生素C磷酸酯和包膜维生素C的添加量分别为1 110~1 200 mg.kg-1和659~900 mg.kg-1时,黄颡鱼生长最快,饲料系数最低;添加量为1 200 mg.kg-1和600 mg.kg-1时,血清总蛋白含量最高;961 mg.kg-1和981 mg.kg-1时,溶菌酶活性最高;747 mg.kg-1和507 mg.kg-1时,淀粉酶活性最高;1 014 mg.kg-1和919 mg.kg-1时,蛋白酶活性最高。包膜维生素C的效果优于磷酸酯维生素C,这与其具稳定性且进入机体后缓释及蛋白酶活性和免疫力高有关     

Effect of dissolved oxygen levels on growth performance,energy budget and antioxidant responses of yellow catfish,Pelteobagrus fulvidraco (Richardson)

This study was conducted to determine the effect of dissolved oxygen (DO) levels on growth performance, energy budget and antioxidant responses of yellow catfish Pelteobagrus fulvidraco. Yellow catfish was exposed to four levels of DO, consisting of hypoxia (2.28 mg L^?1), moderate hypoxia (4.04 mg L^?1), saturation (6.51 mg L^?1) and super‐saturation groups (9.11 mg L^?1), respectively, for 8 weeks. Specific growth rate and feed efficiency in dry matter were lowest in hypoxia and highest in the saturation and super‐saturation groups. Apparent digestibility coefficients of dry matter and energy increased with increasing DO levels. Gross energy and growth energy were lowest for hypoxia, followed by moderate hypoxia and the highest for other two groups. Faecal energy was highest in hypoxia and lowest in saturation and super‐saturation group. DO levels also significantly influenced activities of antioxidant enzymes and malondialdehyde level in liver and serum. Based on the observation described previously, saturated DO level helps to improve growth performance, feed utilization and antioxidant responses in yellow catfish. Super‐saturation did not increase fish performance. To our knowledge, this is the first study involved in the effect of DO levels on energy budget of fish and provides new insight into aeration regime for yellow catfish culture.     

Osteological development and anomalies in larval stage of hatchery‐reared yellow catfish Pelteobagrus fulvidraco

Comprehensive knowledge of osteological development of fish not only provides means for understanding its functional development, but also allows early detection of skeletal anomalies. The present study was conducted to determine osteological development and occurrence of anomalies from the first to the 40th day after hatching (DAH) for yellow catfish Pelteobagrus fulvidraco, a commercially important species in China. Vertebral ontogeny started with formation of anterior neural arches at 3 DAH, and completed at 6 DAH. Vertebral centra started to develop at 4 DAH and ossification in all centra was visible at 15 DAH. Caudal fin appeared at 2 DAH and ossification was visible at 26 DAH. The onset of dorsal and anal fins appeared at 4 DAH and their ossifications were visible at 20 DAH. Pectoral fins were present before first feeding and formed entirely at 9 DAH, and their ossifications were visible at 21 DAH. Pelvic fins appeared at 9 DAH, and formed completely at 21 DAH. The ossification of pelvic fins was not finished until the end of the experiment (40 DAH). 24 types of skeletal anomalies were observed. About 20% of individuals showed at least one anomaly. Haemal vertebrae anomalies occurred at the highest frequency, followed by pre‐haemal, caudal vertebrae and anal fin anomalies, and caudal fin had the lowest anomalies frequency. For the first time, our study determined osteological development and anomalies incidence in larval yellow catfish, which help further investigations into rearing conditions leading to appearance of these anomalies to prevent their incidence.     

运输对养殖黄颡鱼血液生化和肌肉物性分析指标的影响

测定了在10.4~11.2℃下运输4 h后不同时间(0 h、1 h、3 h、6 h、12 h、1 d、3 d、7 d和20 d)养殖黄颡鱼(Pelteobagrus fulvidraco)血液生理生化指标和肌肉物性分析指标的变化。结果显示,运输引起了黄颡鱼血清皮质醇和血糖浓度的显著升高(P0.05),在运输结束12 h后恢复到正常水平。运输后鱼体血清超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)活性和总抗氧化能力(T-AOC)均有显著性升高,随着恢复时间的推移逐渐回降到正常水平;但过氧化物酶(POD)活性并未出现显著性差异,维持稳定的水平。运输后肌肉硬度、弹性、胶黏性、凝聚性、咀嚼性、回复性等物性分析指标均显著性降低。除了凝聚性和咀嚼性之外,其他肌肉物性分析指标在运输结束72 h后恢复到正常水平。研究表明,长途运输造成了养殖黄颡鱼的应激反应,对肌肉物性特征产生了显著的影响,但运输后的恢复可使鱼体抗氧化能力和肌肉物性分析指标回复到正常水平。     

Growth performance and whole‐body composition of yellow catfish (Pelteobagrus fulvidraco Richardson) under feeding restriction

Fish growth is an important index in aquaculture practice. However, the effect of growth under restricted feeding on quality of fish grown to the same size remains poorly unknown. In this study, yellow catfish were reared by feeding them at three different feeding rates such as low (FR‐L group), medium (FR‐M group) and high (apparent satiation) ration levels for 82, 58 and 34 days to reach the same size, respectively. After this period, the growth performance, whole‐body amino acid composition and fatty acid profile of the fish were evaluated. Feeding restriction led to significant decreases in specific growth rate and feed conversion efficiency. Significant increases in dry matter, protein and energy contents were observed in fish under both restricted feeding treatments. FR‐L‐treated fish had significantly lower whole‐body essential amino acid contents, and significantly higher Ala and non‐essential amino acid contents compared to fish fed to satiation. Fish in restricted feeding treatments had significantly higher n‐3 PUFA and n‐3/n‐6 ratio compared to the fish fed to satiation. The present results indicate that from a quality perspective, there are certain advantages in improvement of whole‐body composition and enrichment of n‐3 PUFA associated with the restricted feeding of yellow catfish at slow growth rate.     

蝇蛆粉替代鱼粉对黄颡鱼肌肉品质的影响

选用初始体质量约2.02 g的黄颡鱼(Pelteobagrus fulvidraco)960尾,随机分为6组,分别投喂6种用蝇蛆粉替代饲料中0%、20%、40%、60%、80%、100%鱼粉配制的等氮(39.5%)等能(16.8 MJ/kg)饲料,分别记为G0、G20、G40、G60、G80和G100。养殖期为60 d。结果显示,黄颡鱼肌肉水分、粗蛋白质、粗脂肪含量受蝇蛆粉替代鱼粉水平的影响不显著(P>0.05),但G60～G100灰分含量与G0相比显著升高(P<0.05)。蝇蛆粉替代鱼粉对肌肉pH、滴水损失(DL)、蒸煮损失(CL)和超氧化物歧化酶(SOD)活性影响不显著(P>0.05)。与G0相比,G20～G100肌肉胶原蛋白含量差异不显著(P>0.05),G40～G60肌肉丙二醛(MDA)含量显著降低(P<0.05)。与G0相比,G80肌肉精氨酸(Arg)、组氨酸(His)、苯丙氨酸(Phe)、必需氨基酸(TEAA)含量显著高(P<0.05),各替代组总氨基酸含量差异不显著(P>0.05)。各组肌肉谷氨酸(Glu)、甘氨酸(Gly)、丙氨酸(Ala)、天冬氨酸(Asp)等风味氨基酸和总风味氨基酸(TFAA)含量差异不显著(P>0.05)。肌肉C14:0、C18:3n-3、DHA、EPA+DHA、多不饱和脂肪酸(PUFA)、n-3 PUFA含量和n-3/n-6比值随蝇蛆粉替代鱼粉水平的升高而降低,其中G60～G100显著低于G0(P<0.05);C16:1、单不饱和脂肪酸(MUFA)含量随替代水平增加而升高,其中G60和G100显著升高(P<0.05)。结果表明,当蝇蛆粉替代鱼粉水平不超过40%时,除MDA含量显著降低外,蝇蛆粉对黄颡鱼肌肉常规成分、理化指标、氨基酸和脂肪酸含量影响不显著。     

拟态弧菌感染黄颡鱼的动态病理损伤及病原分布研究

以1.0×106CFU·m L~(-1)拟态弧菌(Vibrio mimicus)浸浴感染黄颡鱼(Pelteobagrus fulvidraco),于第0、第4、第8、第16、第24、第36、第48、第60、第72小时剖杀取样,研究病理损伤及病原菌的体内动态分布。结果显示,皮肤肌肉、鳃、肠道出现病变最早,其中皮肤肌肉损伤最严重。第16小时表皮变性、坏死,鳃上皮肿胀,肠绒毛水肿;第24~第48小时表皮坏死、脱落,真皮严重出血,肌纤维变性、坏死,鳃出血,上皮局部坏死,肠上皮变性与灶性坏死;第48~第72小时皮肤肌肉坏死更严重,形成溃疡灶,鳃灶性坏死。肾、肝、脾与心36 h后相继出现不同程度的淤血、出血,变性和灶性坏死。q PCR检测发现,第4小时即在鳃、肠、皮肤肌肉检出病菌,细菌含量分别为1.3×102CFU·mg~(-1)、2.6×102CFU·mg~(-1)、4.7×102CFU·mg~(-1);鳃与皮肤肌肉中菌量随时间延长而增加,第72小时皮肤肌肉中菌量达到4.5×107CFU·mg~(-1);第24小时后相继在肾、肝、脾、心检出病菌,菌量介于1.9×10~4.7×102CFU·mg~(-1)之间。结果表明皮肤、鳃和肠道是病菌的入侵位点,并在体内多组织、器官分布。     

大豆小肽蛋白替代鱼粉对黄颡鱼幼鱼生长性能、消化酶活性和抗氧化功能的影响

为研究大豆小肽蛋白替代鱼粉对黄颡鱼(Pelteobagrus fulvidraco)生长性能、体成分、消化酶活性和抗氧化功能的影响,以30％鱼粉组为对照组(A0),大豆小肽蛋白分别替代17％、33％和50％的鱼粉作为实验组(A17、A33和A50),配制4种等氮配合饲料.每组设置4个重复,每个重复饲喂30尾平均体重为(...     

黄颡鱼鲇爱德华氏菌的分离鉴定及其致病性研究

从患头顶溃疡症的黄颡鱼(Pelteobagrus fulvidraco)内脏组织中分离出致病力强的菌株JZ086,对该菌进行了形态学、生理生化特性的测定,并进行了Biolog全自动微生物分析系统及16S rDNA序列鉴定。结果显示:人工感染实验证实该菌为黄颡鱼的病原菌,其半数致死量(LD50)为1.7×105CFU。Biolog全自动微生物分析系统鉴定结果显示该菌为鲇爱德华氏菌(Edwardsiella ictaluri)。16S rDNA序列分析显示该菌与鲇爱德华氏菌的亲缘关系最近,同源性高达99%;系统进化树中与鲇爱德华氏菌(AB050826)自然聚为一支,二者遗传距离约为0.002。鉴定结果确认JZ086为鲇爱德华氏菌。药物敏感性试验结果显示,该菌对所测试的15种药物都敏感,其中对氨苄西林、环丙沙星、左氧氟沙星、妥布霉素等尤其敏感。     

Induced ovulation of yellow catfish (Pelteobagrus fulvidraco) using a combination of a gonadotrop‐releasing hormone analogue and domperidone

The effects of an intraperitoneal hormone injection of gonadotropin‐releasing hormone agonist (D‐Ala⁶, Pro⁹‐NEt GnRHa) alone or in combination with a dopamine antagonist, domperidone (DOM), on ovulation induction in yellow catfish Pelteobagrus fulvidraco were tested. The hormone treatments were as follows: 6 mg kg⁻¹ body weight (BW) of carp pituitary extract as a positive control, GnRHa 10, 20, 40 and 80 μg kg⁻¹ BW and a combination of GnRHa and DOM as follows: 10 μg+5 mg, 20 μg+10 mg, 40 μg+20 mg and 80 μg+40 mg kg⁻¹ BW. Physiological saline (0.7% NaCl) was used as a negative control. Significant differences in the ovulation ratio, latency period and ovulation index (OI) were observed among treatments (P<0.05). The combination of GnRHa and DOM at doses of 40 μg+20 mg kg⁻¹ BW had higher values of the ovulation ratio and OI, and a shorter latency period compared with other treatments. The highest OI in GnRHa treatments was only 56.67%, suggesting a dopaminergic tone on gonadotropin secretion in this fish at the pre‐ovulatory stage. Therefore, ovulation can be successfully induced in yellow catfish with 40 μg kg⁻¹ GnRHa+20 mg kg⁻¹ DOM without affecting the egg quality.     

Effects of dietary protein to carbohydrate ratios on growth and body composition of juvenile yellow catfish, Pelteobagrus fulvidraco (Siluriformes, Bagridae, Pelteobagrus)

The present experiment was conducted to investigate the effects of dietary protein to carbohydrate ratios on growth and body composition of juvenile yellow catfish, Pelteobagrus fulvidraco . Nine diets were formulated to contain three protein levels (30%, 36% and 42%), each with three carbohydrate levels (24%, 30% and 36%). Each diet was randomly assigned to triplicate groups of 20 fish (initial mean body weight: 8.24±0.20 g) in indoor flow – through fibreglass tanks. The experiment continued for 8 weeks. Weight gain and specific growth rate were similar for the fish fed the 36% and 42% protein diets but higher than that fed the 30% protein diet. At the 36% protein level, carbohydrate contents varying from 24% to 36% ( P / E ratio of 24.0–28.2 mg protein kJ⁻¹) had no significant effects on growth performance and feed utilization ( P >0.05). Protein efficiency ratio tended to increase with dietary carbohydrate level at the same protein level. Dietary treatments significantly influenced body composition ( P <0.05), but not the condition factor, viscerosomatic index, hepatosomatic index and intraperitoneal fat ratio ( P >0.05). Based on these observations, 36% protein and 24–36% carbohydrate with the P / E ratio of 24.0–28.2 mg protein kJ⁻¹ seemed suitable for optimal growth and feed utilization, and carbohydrate could cause protein-sparing effect in diets for juvenile yellow catfish.     

Effects of ration level on growth,nitrogenous excretion and energy budget of juvenile yellow catfish,Pelteobagrus fulvidraco (Richardson)

Growth, nitrogenous excretion and energy budget of juvenile yellow catfish, Pelteobagrus fulvidraco (initial body weight 1.17 ± 0.28 g) at various levels (50%, 60%, 70%, 80%, 90% and 100% satiation per day) were investigated with feeding diet containing 40% protein. Specific growth rate of yellow catfish increased (2.79–3.34% day) significantly (P<0.05) with ration level (RL) increasing. Feed conversion efficiency, feed protein retention efficiency and feed energy retention efficiency increased with the increase in RL, peaked at 70% of satiation, and then decreased at higher ration, with the ranges of 78.97–97.28%, 31.31–37.93% and 26.55–31.88% respectively. Both nitrogenous excretion (u, mg g^?1 day^?1) and faecal production (f, mg g^?1 day^?1) increased significantly with the increased RL, and ranged between 0.94–1.38 and 0.69–1.24 mg g^?1 day^?1 respectively. Apparent digestibility coefficients in dry matter, protein, energy decreased significantly as ration increased, with ranges of 54.42–69.64%, 78.24–89.90% and 69.66–82.07% respectively. Energy budgets of juvenile yellow catfish at satiation RL was: 100C=30F+8U+33R+29G or 100A=54R+46G.     

蟋蟀粉替代鱼粉对黄颡鱼幼鱼生长性能、肌肉氨基酸组成和血清生化指标的影响

为研究蟋蟀(Gryllus bimaculatus)粉替代鱼粉对黄颡鱼(Pelteobagrus fulvidraco)幼鱼生长性能、肌肉成分和血清生化指标的影响,以黄颡鱼幼鱼[(2.0±0.13) g]为研究对象,分别使用蟋蟀粉替代0 (对照组)、15%、30%、45%和60%的鱼粉配制成5组等氮等能的实验饲料,分别记为T0、T15、T30、T45和T60组。实验幼鱼在室内循环水系统进行为期10周的养殖实验。结果显示,随着蟋蟀粉替代量的增加,黄颡鱼幼鱼生长呈先增加后降低的趋势;T30组的终末均重(FBW)、增重率(WGR)和特定生长率(SGR)最高,且均显著高于T0组;T30组的饲料系数(FCR)显著低于T0和T15组;T30的肝体比(HSI)显著高于T0和T15,而与T45和T60组无显著差异。与T0组相比,各替代组的脏体比(VSI)、摄食量(FI)、肥满度(CF)和成活率(SR)均无显著差异。黄颡鱼幼鱼肌肉必需氨基酸(EAA)含量中,T60组肌肉中精氨酸(Arg)和缬氨酸(Val)含量显著高于T0组;且蟋蟀粉替代不同比例的鱼粉对黄颡鱼幼鱼肌肉中的总呈味氨基酸(TFAA)含量均未产生显著影响。T30、T45和T60组血清中的葡萄糖(GLU)含量显著高于T0组;相反,其总胆固醇(TCHO)含量显著低于T0组。在本研究条件下,蟋蟀粉替代不同比例的鱼粉不影响黄颡鱼幼鱼的生长性能和肌肉氨基酸含量,且能增加血清GLU和降低TCHO含量,以30%的蟋蟀粉替代鱼粉比例能生长最佳,且优于对照组。本研究对揭示蟋蟀粉在黄颡鱼饲料中替代鱼粉应用的可行性、为今后昆虫蛋白源在水产饲料中的开发提供科学依据。     

Effect of dietary iron (Fe) levels on growth performance,hepatic lipid metabolism and antioxidant responses in juvenile yellow catfish Pelteobagrus fulvidraco

This study was conducted to determine effects of dietary Fe levels on growth performance, hepatic lipid metabolism and antioxidant response for juvenile yellow catfish Pelteobagrus fulvidraco. Yellow catfish were fed six isonitrogenous and isolipidic diets containing Fe levels of 16.20, 34.80, 54.50, 76.44, 100.42 and 118.25 mg/kg for 8 weeks. Weight gain (WG) and specific growth rate (SGR) increased with dietary Fe levels from 16.20 to 54.50 mg/kg diet and then plateaued over the level. Feed conversion rate (FCR) was highest and protein efficiency rate (PER) was lowest for fish fed the lowest Fe levels of diet. Fe contents in whole body and liver increased with increasing dietary Fe levels. Hepatic lipid content was lowest, but mRNA levels of carnitine palmitoyltransferase (CPT‐1) and peroxisome proliferator‐activated receptor α (PPARα) were highest for fish fed 54.50 mg Fe/kg diet. Fish fed adequate dietary Fe levels reduced hepatic malondialdehyde (MDA) level and increased activities of antioxidant enzymes Superoxide dismutase (SOD), Catalase (CAT) and GS. Based on the broken‐line regression analysis of WG against dietary Fe levels, optimal dietary Fe requirement for yellow catfish was 55.73 mg Fe/kg diets. Fe‐induced changes in MDA levels and antioxidant enzymatic activities paralleled with the change in hepatic lipid content, suggesting the potential relationship between oxidative stress and hepatic lipid accumulation in yellow catfish.     

Dietary supplementation of N‐carbamylglutamate and effects on growth,intestinal enzyme activities,immunological and antioxidant abilities of juvenile yellow catfish (Pelteobagrus fulvidraco)

The effects of N‐carbamylglutamate (NCG) on growth, intestinal enzyme activities, immunological and antioxidant parameters were evaluated by a 56‐d feeding trial in Pelteobagrus fulvidraco fed diets containing NCG with 0, 250, 500, 1,000 or 2,000 mg/kg, respectively. The results showed that 250 mg/kg of NCG resulted in significantly higher weight gain, intestine fold height, intestine lipase, serum lysozyme, glutathione peroxidase and total antioxidant capacity than control (p < 0.05). However, higher intestine trypsin, arginase, arginine decarboxylase, ornithine decarboxylase, diamine oxidase activities and serum nitric oxide content were observed in 500 mg/kg NCG group compared to control or 2,000 mg/kg (p < 0.05). The survival rate, intestine muscular layer thickness, serum lysozyme and superoxide dismutase activities in 2,000 mg/kg NCG group were significantly lower than those in control and 250 mg/kg group, accompanied by the higher feed conversion ratio in the same group (p < 0.05). Together, dietary NCG level at 250 or 500 mg/kg improved growth, intestinal enzyme activities, immunological and antioxidant abilities, while high NCG level of 2,000 mg/kg had a negative effect. Quadratic regression analysis on weigh growth, diamine oxidase and lysozyme activities indicated that the recommended optimum dietary NCG level was 213.48–314.50 mg/kg of the dry diet.     

Effects of feeding frequency on the enzymes and genes involved in oxidative stress in juvenile yellow catfish Pelteobagrus fulvidraco (Richardson) exposed to ammonia

Optimal feeding strategies improve fish growth and health but may be affected by ammonia stress in closed rearing systems such as tanks or ponds. This study aimed to evaluate the effects of feeding frequency and ammonia levels in rearing water on the enzymes and genes involved in oxidative stress of yellow catfish. Experiment (ammonia exposure) and control groups were randomly assigned to one of three feeding frequencies (1, 2 and 4 times daily) for 8 weeks. Weight gain increased as feeding frequency increased from 1 to 4 times daily, but feed conversion ratio values decreased. The highest survival in ammonia group was found when fish was fed 2 times daily. Glutathione peroxidase activity and total antioxidant capacity in liver and brain of fish exposed to ammonia increased as feeding frequency increased from 1 to 4 times daily. Liver malondialdehyde content in control group decreased as feeding frequency increased from 1 to 4 times daily. The lowest liver malondialdehyde content in ammonia group was observed when fish was fed 2 times daily. Liver mRNA expression of superoxide dismutase and catalase in control group increased as feeding frequency increased from 1 to 4 times daily, but the highest superoxide dismutase and catalase expression in ammonia group were observed when fish were fed 2 times daily. This study indicates that higher feeding frequency of yellow catfish exposed to ammonia could result in oxidative stress and poor survival. The optimal feeding frequency of yellow catfish exposed to ammonia is 2 times daily.     

The effect of dietary methionine on growth,antioxidant capacity,innate immune response and disease resistance of juvenile yellow catfish (Pelteobagrus fulvidraco)

An 11‐week feeding trial was conducted to evaluate the effect of dietary methionine on the growth, antioxidant status, innate immune response and disease resistance to Aeromonas hydrophila of juvenile yellow catfish. Six isonitrogenous and isolipidic practical diets were formulated to contain different graded methionine levels ranging from 6.1 to 16.4 g kg^?1 of dry weight. The results indicated that growth performance and feed utilization were significantly influenced by the dietary methionine levels; fish fed the diet containing 6.1 g kg^?1 methionine level had lower specific growth rate, percentage weight gain (PWG), feed efficiency and protein efficiency ratio than those fed the other diets (P < 0.05). Fish fed the diet containing 16.4 g kg^?1 methionine level had lowest protein contents in whole body and muscle among all treatments. Triacylglycerols, cholesterol, aspartate aminotransferase, alanine aminotransferase and haemoglobin (Hb) in plasma or whole blood were significantly affected by dietary methionine levels. Fish fed the diet containing 6.1 g kg^?1 methionine level had higher superoxide dismutase, glutathione peroxidase activities and malondialdehyde values than those fed other diets. Fish fed diets containing 9.7 and 11.8 g kg^?1 methionine levels had higher lysozyme activity, total immune globulin, phagocytic activity and respiratory burst than those fed other diets. The lowest survival after A. hydrophila challenge was observed in fish fed a diet containing 6.1 g kg^?1 methionine. Quadratic regression analysis of PWG against dietary methionine levels indicated that the optimal dietary methionine requirement for the maximum growth of juvenile yellow catfish was estimated to be 11.5 g kg^?1 of the diet in the presence of 4.0 g kg^?1 cystine (corresponding to 23.5 g kg^?1 of dietary protein on a dry weight basis).     

Gonadotropin‐releasing hormone analogue multiple injection potentially accelerated testicular maturation of male yellow catfish (Pelteobagrus fluvidraco,Richardson) in captivity

The potential for accelerating testicular development and final maturation of adult male yellow catfish (Pelteobagrus fluvidraco, Richardson) in captivity was evaluated by using gonadotropin‐releasing hormone analogue (GnRHa) multiple injection, and its possible regulatory mechanism was explored by measurements of luteinizing hormone (LH) and steroid levels. The results showed that GnRHa multiple injection increased gonad‐somatic index (GSI), the sperm count and the milt‐testis index (MTI) and promoted the larvae production by elevated rates of fertilization and hatching, and lowered the rate of deformed larvae. Meanwhile GnRHa treatment decreased the percentages of spermatogonia and spermatocytes, increased the relative sperm density (RSD) and percentages of spermatids and spermatozoa (STZ), suggesting GnRHa treatment could accelerate meiotic division and enhance the formation of spermatids andSTZ. Moreover, pituitary and serum LH, as well as serum T levels were increased after GnRHa multiple injection. Taken together, the present study demonstrated GnRHa multiple injection successfully accelerated the testicular development and maturation of male yellow catfish, which was mediated by the increase in serum LH and T levels that further mediated biological and histological changes of testis. Therefore, GnRHa multiple injection could be a valuable method to induce precocious testicular maturation of adult yellow catfish with gonadal developmental arrest in captivity.