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.     

饲料成分与环境温度对奥尼罗非鱼消化酶活性的影响

取相同生长阶段、体重均匀的雄性奥尼罗非鱼(Oreochromis nilotieus×O.aureus)为研究对象,分别设置不同P／E饲料组与不同水温组进行暂养,共3周。在最后一次投喂后2 h进行取样测定。结果表明,饵料蛋白质水平在20％-40％时,肝胰脏和肠道蛋白酶活性变化差异不显著。胃蛋白酶活性随着饵料蛋白水平上升而减低了22.2％和26.0％(P<0.05)。碳水化合物水平由34％上升到42％和50％,肝胰脏淀粉酶活性分别上升了107.1％和106.6％(P<0.01),肠道淀粉酶活性分别提高了67.1％和39.8％(P<0.01)。脂肪水平由1.5％升高7％,肠道脂肪酶活性没有变化,脂肪水平升高到12.5％,肠道脂肪酶活性降低了25.4％(P<0.01)。在水温17-32℃时,罗非鱼消化酶活性均随环境温度的升高而提高。     

Dietary phytase and protease improved growth and nutrient utilization in tilapia (Oreochromis niloticus × Oreochromis aureus) fed low phosphorus and fishmeal‐free diets

A 10‐week study was conducted to evaluate the effects of supplemental phytase and protease in low phosphorus (LP) and fishmeal‐free diets (FMF) on growth and nutrient utilization of tilapia. Seven isonitrogenous diets were prepared as positive control diet (PC) containing 60 g/kg fishmeal and 18 g/kg monocalcium phosphate (MCP), LP diet (12 g/kg MCP), FMF diet, LP‐FMF diet, and three enzyme diets with phytase (LP + Ph), protease (FMF + Pr), and phytase + protease (LP‐FMF + Ph + Pr) supplementation in LP, FMF and LP‐FMF diets, respectively. Weight gain, nutrient (except Ca) retention and digestibility of LP, FMF and LP‐FMF groups were lower than those of PC group (p < 0.05). Compared to LP, FMF and LP‐FMF groups, the supplementation of phytase, protease and phytase + protease improved WG by 13.2%, 11.1% and 13.0% (p < 0.05). The three enzyme groups showed higher digestibility of protein and P, and higher intestinal villus length than those of LP, FMF and LP‐FMF groups (p < 0.05), respectively. Dietary phytase and Ph + Pr also promoted the retentions of crude protein and P (p < 0.05). The results indicated that the supplementation of phytase in LP diet and protease in FMF diet improved the growth and nutrient utilization, and phytase reduced MCP inclusion in the diet of tilapia.     

Effect of fermented Enteromopha prolifera on the growth performance,digestive enzyme activities and serum non‐specific immunity of red tilapia (Oreochromis mossambicus × Oreochromis niloticus)

This study was conducted to evaluate the effect of dietary inclusion of different levels of fermented macroalga, Enteromorpha prolifera, on the growth performance, digestive enzyme activities and serum non‐specific immunity of red tilapia (Oreochromis mossambicus × Oreochromis niloticus). Fish were fed the control diet or the five diets supplemented with fermented E. prolifera for 7 weeks (diets 1–5 containing 10, 20, 30, 40 and 50 g kg^?1 of fermented E. prolifera respectively). The results showed that the percentage weight gain and specific growth rate (SGR) improved significantly in fish fed diets 3, 4 and 5, and regression analysis showed SGR reached the maximum in fish fed diet containing 37 g kg^?1 fermented E. prolifera, while the feed conversion ratio reduced significantly in fish fed diets 2, 3, 4 and 5, and regression analysis showed it reached its minimum in fish fed diet containing 41 g kg^?1 fermented E. prolifera. The pepsin, erepsin, gastric amylase, intestinal amylase, gastric lipase and intestinal lipase activities in fish fed diets 2, 3 and 4 were higher significantly than the control, with the exception of the pepsin activity in fish fed diet 4. The serum total superoxide dismutase, lysozyme, acid phosphatase and alkaline phosphatase activities enhanced significantly in fish fed diets 3 and 4. In conclusion, fermented E. prolifera had positive effects on the growth performance, digestive enzyme activities and serum non‐specific immunity of red tilapia and the recommended dose of fermented E. prolifera is 37–41 g kg^?1 in the diet of red tilapia.     

盐度对奥尼罗非鱼仔稚鱼生长、存活及其消化酶活力的影响

研究了不同盐度对奥尼罗非鱼仔、稚鱼生长、存活和消化酶活力的影响。试验设计2、4、6、8、10和纯净淡水0（对照组）共6个盐度梯度组,仔鱼的初始体重0.0080.001 g。结果表明,不同盐度对奥尼罗非鱼仔、稚鱼生长有显著差异（P0.05）,盐度4和6时,仔、稚鱼的生长速度和绝对增重率最高,分别为0.08 cmd-1和0.033 gd-1;盐度10时较低,只有0.06 cmd-1和0.023 gd-1;仔、稚鱼的肥满度介于3.43~3.81,各组之间差异不显著（P0.05）;盐度0~10时,各组存活率介于92.3%~94.7%,幼鱼所占比例介于66.0%~67.3%,各组之间差异不显著（P0.05）;胃蛋白酶和胰蛋白酶活力随盐度升高而降低,均在盐度0时活力最高,10时最低;脂肪酶和淀粉酶活力在盐度4时达到最高,10时活力最低。根据试验结果,奥尼罗非鱼仔、稚鱼培育的盐度最好控制在4.6左右。     

Quantitative and qualitative studies on bacterial flora of hybrid tilapia (Oreochromis niloticus × O. aureus) cultured in earthen ponds in Saudi Arabia

The bacterial flora of the rearing pond water and sediment as well as the gills and intestine of healthy hybrid tilapia cultured in Saudi Arabia was estimated quantitatively and qualitatively, the isolates being identified at genus or species level. Total viable counts of bacteria (measured as colony‐forming units, cfu) were in the range 5.6 ± 0.8 × 10³ to 2.4 ± 1.2 × 10⁴ cfu mL^?1 in pond water; 9.3 ± 1.1 × 10⁶ to 1.9 ± 1.5 × 10⁸ cfu g^?1 in sediment; 7.1 ± 0.7 × 10⁵ to 8.7 ± 1.1 × 10⁶ cfu g^?1 in the gills of tilapia; and 3.4 ± 1.8 × 10⁶ to 5.8 ± 0.4 × 10⁷ cfu g^?1 in the intestine of tilapia. In total, 15 bacterial genera and 18 species were identified. Pond water and sediment bacteria reflected the bacterial composition in the gills and intestine of tilapia. In contrast to gill bacteria, more diversification was observed in intestinal bacteria. Corynebacterium urealyticum, Shewanella putrefaciens and Aeromonas hydrophila predominated in all samples. In pond water, C. urealyticurn, S. putrefaciens, A. hydrophila, Flavobacterium sp. and Pseudomonas sp. were the most predominant bacterial species (prevalence > 10%), whereas A. hydrophila, C. urealyticum, S. putrefaciens and Escherichia coli were predominant in pond sediment, and C. urealyticum, S. putrefaciens and A. hydrophila were predominant in both the gills and intestine of tilapia.     

饲料中海洋红酵母对尼罗罗非鱼幼鱼生长性能、消化酶及免疫酶活性的影响

为了研究海洋红酵母(Rhodotorula mucilaginosa)对尼罗罗非鱼(Oreochromis niloticus)幼鱼生长性能、消化酶及免疫酶活性的影响,配制6组饲料,分别为对照组、添加1 gkg-1、2 gkg-1、3 gkg-1、4 gkg-1和5 gkg-1的海洋红酵母组,投喂初始均质量为(5.220.01) g的尼罗罗非鱼,实验56 d。结果显示,与对照组相比,2 gkg-1和4 gkg-1组的饲料系数显著降低(P0.05),1 gkg-1、3 gkg -1和5 gkg-1组则没有显著性差异(P0.05)。5 gkg-1组鱼体粗蛋白含量显著低于1 gkg-1和2 gkg-1组(P0.05),1 gkg-1、3 gkg-1和5 gkg-1组鱼体粗灰分含量显著低于对照组(P0.05)。与对照组相比,1 gkg-1组胃蛋白酶活性显著升高(P0.05),3 gkg-1、4 gkg-1和5 gkg-1组胃蛋白酶活性显著降低(P0.05)。2 gkg-1和3 gkg-1组前肠和中肠淀粉酶和脂肪酶,以及肝脏溶菌酶和一氧化氮合酶活性均显著高于对照组(P0.05)。根据尼罗罗非鱼幼鱼的消化酶和免疫酶活性等指标综合分析得出,海洋红酵母在罗非鱼饲料中的建议添加量为2～3 gkg-1。     

Effect of dietary zinc level on growth,enzyme activity and body trace elements of hybrid tilapia,Oreochromis niloticus × O. aureus,fed soya bean meal‐based diets

A feeding experiment was conducted to determine the dietary zinc (Zn) requirement of hybrid tilapia fed on a diet with soya bean meal as the sole protein source. The quantity of phytic acid in the experimental diet was 15.5 g kg^?1. Juvenile hybrid tilapia were fed on diets containing 31–227 mg Zn kg^?1 in triplicates for 6 weeks. Haematology of the fish was not affected by various dietary Zn levels. Fish fed on a diet containing 31 mg kg^?1 endogenous Zn showed the lowest growth rates, feed utilization, and body and plasma Zn levels. Weight gain (WG), plasma Zn level and superoxide dismutase (SOD) activity increased when a higher quantity of dietary Zn of 127 mg kg^?1 was administered to the experimental fish. Beyond this level, the values of these parameters were relatively stable. On the other hand, within the dietary Zn range tested, whole‐body Zn and ash increased with higher dietary Zn levels. Analysis using a broken‐line model showed that the dietary Zn requirements of hybrid tilapia fed on soya bean meal‐based diets containing 15.5 g kg^?1 endogenous phytic acid were 115, 115 and 105 mg kg^?1 based on WG, whole‐body Zn retention and plasma Zn level, respectively.     

Effects of zinc oxide supported on zeolite on growth performance,intestinal barrier function and digestive enzyme activities of Nile tilapia

A total of 720 Nile tilapia fingerlings were allocated to four treatments and used to investigate the effects of zinc oxide supported on zeolite (Z‐ZnO) on growth performance and intestinal function. The basal diet (control) was not supplemented with zinc and contained 60 mg Zn kg^?1. The other three groups were added 30 mg Zn kg^?1 to the basal diet, in which zinc was supplemented as Z‐ZnO, Z + ZnO (mixture of zeolite and ZnO) or ZnSO₄, respectively. As compared to the control, supplemental Z‐ZnO improved (P < 0.05) specific growth rate, protein efficiency ratio (PER) and survivor ratio; increased (P < 0.05) villus‐height‐to‐crypt‐depth ratio and transepithelial electrical resistance; decreased (P < 0.05) mucosal‐to‐serosal flux of dextran 4 kDa; and improved (P < 0.05) intestinal activities of protease, amylase, lipase and alkaline phosphatase. Fish fed with Z‐ZnO had higher (P < 0.05) specific growth rate and PER, and better intestinal barrier function than those fed with ZnSO₄ or Z + ZnO. The zinc concentrations in whole body and vertebrae were not affected by dietary treatments. The results indicated that Z‐ZnO improved intestinal morphology, barrier function and digestive enzyme activities. Such changes in intestinal health in the presence of Z‐ZnO might contribute to its improvement in growth performance.     

Effects of pretreatment with microbial phytase on phosphorous utilization and growth performance of Nile tilapia (Oreochromis niloticus)

This study was to assess effects of the pretreatment in all‐plant based diets with microbial phytase on phosphorous utilization and growth performance of Nile tilapia (Oreochromis niloticus). Pretreatment trials were conducted using phytase at graded doses to determine the optimal dose of phytase. Available phosphorus (P) levels increased significantly with the increased doses of phytase and the dose of 1000 U kg^?1 was most efficient. Based on the pretreatment trials, plant based diets for Nile tilapia were formulated by pretreating with phytase at 1000 U kg^?1. Experimental diets were supplemented with graded levels of mono calcium phosphate (MCP) at 25, 18.75, 12.5, 6.25 and 0 g kg ^?1 diet. In addition, there were three controls: one phytase control, one inorganic P control and one pretreatment control. The results showed that diets pretreated with phytase gave better growth performance, feed conversion ratio and protein efficiency ratio of Nile tilapia compared with the phytase control diet and pretreatment control diet (P < 0.05). There were no significant differences in growth performance of Nile tilapia between the inorganic control diet and phytase pretreated diets supplemented with MCP at 25, 18.75 and 12.5 g kg^?1 (P > 0.05), which resulted in significantly better performance than those at 6.25 and 0 g kg^?1 (P < 0.05). Dietary interaction effects of phytase were observed for phosphorus retention efficiency and phosphorus load. Apparent digestibility coefficient of P (ADCp) was improved significantly by phytase pretreatment (P < 0.05). No significant difference was detected on ADC of crude protein among all experimental diets (P > 0.05).     

Dietary protein level, microbial phytase, citric acid and their interactions on bone mineralization of Labeo rohita (Hamilton) juveniles

A feeding trial was conducted for 60 days to study the effect of dietary protein, microbial phytase and citric acid on intestinal digesta pH, bone ash and bone mineral contents in Labeo rohita juveniles. Eight experimental diets were prepared in 2 × 2 × 2 factorial arrangement with crude protein levels (25% and 35%), microbial phytase (0 and 500 U kg^?1), and citric acid (0 and 3%). The 25% crude protein level feed was supplemented with phytase (U kg^?1) and citric acid (%) at the level of 0,0 (C₂₅); 500,0 (T₁); 0,3 (T₂); 500,3 (T₃), and 35% crude protein level feed at 0.0 (C₃₅); 500,0 (T₄); 0,3 (T₅) and 500,3(T₆) respectively. One hundred and twenty juveniles of L. rohita (av. wt. 12.61–13.72 g) were distributed randomly in eight treatments, each of with three replicates. Addition of citric acid in the 25% crude protein feed significantly decreased (P<0.001) feed pH with concurrent decrease in intestinal digesta pH (P<0.001) and increased the bone ash content (P<0.05) by 4.6%. An interaction between citric acid and phytase (P<0.05) was also observed for bone ash content. Increasing the dietary protein content from 25% to 35% significantly decreased (P<0.01) bone Zn content by 14.9%, which was more prominent with the addition of citric acid, resulting in significant interaction between protein and citric acid (P<0.05), but the bone Cu content was significantly increased (P<0.01) with increasing dietary protein content. Dietary supplementation of microbial phytase (500 U kg^?1) significantly increased (P<0.05) bone Na, Ca, K, P and Fe contents by 15%, 12.1%, 17.4%, 9.2% and 40.7%, respectively, whereas bone P and Mn content was significantly increased (P<0.05) by addition of citric acid (3%). Addition of phytase to plant‐based diets increased the bioavailability of minerals, thereby increasing bone mineralization. The effect of phytase was increased because of addition of citric acid (3%).     

柠檬酸对罗非鱼生长、体成分和消化酶活性的影响

研究了饲料中添加不同水平柠檬酸 (0 .1%、0 .2 %、0 .3%、0 .4 % )对奥尼罗非鱼 (Oreochromisniloticus×O .aureus)幼鱼 (初始平均体重约 2 .0g)生长、饲料利用、体成分和消化酶活性的影响。共设 5组试验饲料 ,每一饲料组设 3个重复水族箱 ,每箱随机放鱼 15尾 ,投喂率为 6 % ,自然光周期 ,循环过滤水系统饲养 9周 ,每周称重 1次并相应调节投喂量。结果表明 :随着柠檬酸添加量的增大 ,饲料pH值呈下降趋势 ;添加 0 .2 %柠檬酸的试验组罗非鱼的特定生长率显著高于对照组 (P <0 .0 5 ,LSD多重比较 ,下同 ) ;饲料效率在 0 .3%柠檬酸组显著高于对照组 (P <0 .0 5 ) ;罗非鱼血清葡萄糖含量在0 .4 %组显著低于对照组、0 .1%组和 0 .3%组 (P <0 .0 5 ) ;0 .2 %组和 0 .3%组血清甘油三酯含量最高 ,但组间差异不显著(P >0 .0 5 ) ;全鱼水分、粗蛋白、粗脂肪和灰分含量在组间差异不显著 (P >0 .0 5 ) ;胃蛋白酶、胰蛋白酶和肠蛋白酶活性随柠檬酸添加量增加呈先上升后下降的趋势 ,0 .2 %组的最高 ,但组间差异不显著 (P >0 .0 5 ) ;肝胰脏和肠淀粉酶活性分别在 0 .2 %和 0 .3%组最高 ,组间差异亦不显著 (P >0 .0 5 )。结果提示 ,饲料中适量添加柠檬酸 ,能提高罗非鱼幼鱼消化酶活性 ,提高饲料利用率 ,促进罗非鱼生长     

Dietary calcium requirements of juvenile tilapia, Oreochromis niloticus × O. aureus, reared in fresh water

A feeding experiment was conducted to determine the dietary calcium (Ca) requirement for juvenile hybrid tilapia, Oreochromis niloticus × O. aureus reared in nature water. Purified diet supplemented with 0, 1, 2, 3, 4, 5, 7 and 10 g Ca kg⁻¹ diet providing of 0.6, 1.6, 2.6, 3.7, 4.7, 5.5, 7.5 and 10.7 g Ca kg⁻¹ diet, respectively, were fed to tilapia (mean initial weight: 0.52 ± 0.01 g, n = 3) for 8 weeks. Each diet was fed to three replicate groups of fish in a closed, recirculating fresh water rearing system. The rearing water contained 27.1–33.3 mg L⁻¹ Ca. The tilapia fed the diets supplemented with ≥3.7 g Ca kg⁻¹ had significantly (P < 0.05) higher weight gain, when compared with fish fed the diet with ≤1.6 g Ca kg⁻¹. Fish fed the unsupplemented control showed significantly lower weight gain when compared with the other groups (P < 0.05). Bone Ca concentration was highest in fish fed the diets with ≥4.7 g Ca kg⁻¹, intermediate in fish fed the diet with 2.6 g Ca kg⁻¹ and lowest in fish fed the control diet. Scale Ca concentration was higher in fish fed the diets with ≥3.7 g Ca kg⁻¹ than in fish fed the diets with ≤2.6 g Ca kg⁻¹. Serum alkaline phosphatase activity was 36% increased in fish fed the diets with ≥2.6 g Ca kg⁻¹ than fish fed the diets with <1.6 g Ca kg⁻¹. Analysis by broken‐line regression of weight gain, bone and scale Ca concentrations indicated that the adequate dietary Ca concentration for tilapia in water containing 27.1–33.3 mg Ca L⁻¹ was 3.5, 4.3 and 4.2 g Ca kg⁻¹ diet, respectively, supplied as Ca‐lactate.     

无鱼粉饲料中添加磷和植酸酶对奥尼罗非鱼生长性能及体成分的影响

奥尼罗非鱼(Oreochromis niloticus×O.aureus)幼鱼的初始体重约5.0 g,试验共设5组饲料,以全鱼粉饲料为对照组(D0),以豆粕和花生粕完全替代鱼粉为试验组,其中两组为不补充磷酸二氢钙的情况下不添加植酸酶(D1)和添加植酸酶(D2),另两组为在补充磷酸二氢钙的情况下不添加植酸酶(D3)和添加植酸酶(D4)。每一饲料组设3个重复,每箱养鱼30尾,在流水系统中饲养,表观饱食投喂,投喂率为5%~6%。饲养实验周期为8周。试验结果表明,添加磷组(D3、D4)和全鱼粉组(D0)的特定生长率和饲料系数在组间差异不显著(P>0.05),但显著高于不添加磷组(D1、D2)(P<0.05);磷的表观消化率在添加植酸酶组(D2、D4)均显著高于不添加植酸酶(D1、D3),但与全鱼粉组(D0)差异不显著;鱼体粗蛋白含量在不添加磷和植酸酶组(D1)显著低于其他4组;体粗脂肪含量在不添加磷(D1、D2)组显著高于其他组;体灰分含量由高到低依次为全鱼粉组(D0)、添加磷和植酸酶组(D4)、添加磷不添加植酸酶组(D3)、不添加磷添加植酸酶组(D2)和不添加磷不添加植酸酶组(D1),且两两组间差异显著;体钙、磷、镁、锌含量和脱脂骨灰分、钙、磷含量在全鱼粉组(D0)最高。不添加磷组(D1、D2)血清磷含量显著低于其他3组,而血清碱性磷酸酶活性显著地高。试验结果说明,无鱼粉饲料中补充磷可保持奥尼罗非鱼幼鱼生长率,饲料利用和全鱼可食部分营养成分含量;同时添加植酸酶,能显著提高饲料中磷的利用率,促进磷、锌和镁在鱼体内沉积,并有进一步提高奥尼罗非鱼幼鱼生长和饲料利用的趋势。[中国水产科学,2006,13(1):112-118]     

Effects of Cu2+-exchanged montmorillonite on intestinal microflora, digestibility and digestive enzyme activities of Nile tilapia

A total of 360 Nile tilapia at an average initial body weight of 3.9 g were randomly allocated to four treatments, each of which had three replicates of 30 fish per tank and used to investigate the effects of Cu²⁺‐exchanged montmorillonite (Cu‐MMT) on intestinal microflora, digestibility and digestive enzyme activities. The dietary treatments were: (i) basal diet, (ii) basal diet + 1.5 g kg^?1 MMT; (iii) basal diet + 30 mg kg^?1 copper as CuSO₄ (equivalent to the copper in the Cu‐MMT treatment group), or (iv) basal diet + 1.5 g kg^?1 Cu‐MMT. The results showed that supplementation with Cu‐MMT significantly improved growth performance as compared with the control and fish fed with Cu‐MMT had higher growth performance than those fed with MMT or CuSO₄. Supplementation with Cu‐MMT reduced (P < 0.05) the total intestinal aerobic bacterial counts and affected the composition of intestinal microflora with Aeromonas, Vibrio, Pseudomonas, Flavobacterium, Acinetobacter, Alcaligence, Enterobacteriaceae decreasing as compared with the control. Addition of MMT improved (P < 0.05) the apparent digestibility of dry matter and crude protein, and the activities of intestinal amylase, lipase, and alkaline phosphatase as compared with the control. Addition of Cu‐MMT improved (P < 0.05) the apparent digestibilities of dry matter, crude protein, ether extract, and crude ash, and the activities of total protease, amylase, lipase, and alkaline phosphatase as compared with the control. While supplementation with CuSO₄ had no (P > 0.05) effect on intestinal microflora, digestibility, and digestive enzyme activities the results showed that Cu‐MMT exhibited antibacterial activity in vivo resulting in a positive effect on digestive enzyme activities, and then promoted the digestion and absorption of dietary nutrition.     

Type of dietary fibre (soluble versus insoluble) influences digestion, faeces characteristics and faecal waste production in Nile tilapia (Oreochromis niloticus L.)

The physico‐chemical properties of nutrients influence the physical characteristics of faeces and thus may affect waste removal efficiency. The aim of this study is to assess the effect of type of non‐starch polysaccharide (NSP) on digesta viscosity, faeces recovery and nutrient digestibility in Nile tilapia. Insoluble (cellulose) and soluble (guar gum) NSPs were included separately and combined at a level of 8%, thereby formulating four experimental diets. The diets were assigned to 16 tanks with 35 fish each, with four replicates for each diet. Cellulose inclusion did not influence digesta viscosity, growth and digestibility of protein and starch and tended to increase faeces recovery (P=0.06). Guar gum inclusion increased digesta viscosity and reduced the growth and digestibility of protein, fat and starch (P<0.01). Faeces recovery was reduced by 42% in diets containing guar gum. There were interaction effects (P<0.05) between cellulose and guar gum for the growth and feed conversion ratio, indicating that cellulose alleviated the negative impact of guar gum. In conclusion, dietary soluble NSPs increase organic matter load in the culture system through a reduction in faeces recovery and nutrient digestibility, whereas insoluble NSPs improve the removal efficiency of particles by increasing faeces recovery.     

Effects of temperature and feed processing on protease activity and dietary protease on growths of white shrimp,Litopenaeus vannamei,and tilapia,Oreochromis niloticus × O. aureus

Effects of temperature and processing on the stability of a commercial protease were assessed in an in vitro trial followed by growth trials with white shrimp and tilapia. Results showed that the protease has a high heat stability against pelleting, and it could hydrolyse dietary proteins during feed processing. In Exp. 2, white shrimp (3.3 g) fed low fish meal (FM) diet (LFD) with protease addition had similar growth to that fed high fish meal diet, and both had higher weight gain (WG) and lower feed conversion ratio (FCR) than that fed LFD without protease addition (P < 0.05). In Exp. 3, compressed (CD) or extruded (ED) diets containing 30 g kg^?1 or 90 g kg^?1 FM were supplemented with or without protease and then fed to tilapia (1.7 g) for 8 weeks. WG was improved and FCR decreased (P < 0.05) by the supplementation of protease in 30 g kg^?1 FMCD, but not in 90 g kg^?1 FMCD and ED diets when compared to those diets without protease supplementation. The digestibility trial with CD indicated the improved apparent digestibilities of dry matter and crude protein by dietary protease in 30 g kg^?1 FMCD, but not in 90 g kg^?1 FMCD. Results above showed that the protease has a high heat stability and the supplementation of protease in CD with low FM level can improve the growth of shrimp and tilapia.     

Effect of phytic acid on growth and nitrogen retention in tilapia Oreochromis niloticus L.

Two experiments were conducted to determine the effect of phytic acid on nitrogen retention in tilapia (Oreochromis niloticus). The first experiment utilized graded levels of soybean meal (SBM) with or without hydrolysis of phytic acid. The second experiment utilized diets containing graded levels of purified phytic acid. In the first experiment, weight gain was inversely related to SBM inclusion beyond 250 g kg^?1 of the crude protein (CP). Broken‐line and quadratic models were applied to the growth data. The models suggest limiting inclusion to 380 and 170 g kg^?1 CP for untreated and phytase treated SBM, respectively. The two SBM treatments exhibited similar trends in efficiency parameters. However, significant differences (P < 0.05) within treatments appeared when phytase treated SBM surpassed 250 g kg^?1 CP, but not until 750 g kg^?1 CP with untreated SBM. At similar rates of SBM incorporation, apparent net protein utilizations with untreated SBM were significantly higher beyond 250 g kg^?1 CP (P < 0.05). In the second experiment, phytic acid did not affect efficiency parameters until the concentration was twice that in diets incorporating SBM as 1000 g kg^?1 CP in a 330 g kg^?1 CP diet. Phytic acid does not reduce nitrogen retention in tilapia, and its removal from SBM may decrease nitrogen retention.