Digestive enzyme and alkaline phosphatase activities during the early stages of Silurus soldatovi development

To provide a theoretical basis to improve the survival and growth rate and optimize diet of sheatfish （Silurus soldatovi）, the activities of certain digestive enzymes and alkaline phosphatases were investigated during larval development of one-ten day old individuals. Results indicated that sheatfish larva （～ three days after hatching） had high levels of alkaline protease activity, which peaked at five days old and dipped by eight days old, although the trend was generally upward. Acid protease activity at one-eight days old was low, after which it increased rapidly. Amylase activity reached the highest value at five days old, after which it began to decline. Lipase activity fluctuated markedly and showed two peaks at three-four days old and six-eight days old. Larval digestive enzyme activity and alkaline phosphatase activity were higher when fed live food than when fed an artificial diet. Throughout the early development process, alkaline protease activity was higher than acid protease, alkaline protease and amylase specific activity decreased significantly for eight-day-old transition larvae, while acid protease activity increased rapidly. These results indicate that the changes in digestive enzyme activity were relevant to digestive function conversion during fish larvae development. Alkaline phosphatase activity showed an upward trend over the first ten days of life, which indicated that the gastrointestinal function of sheatfish improved gradually.

Effects of dietary supplementation of probiotic,Clostridium butyricum,on growth performance,immune response,intestinal barrier function,and digestive enzyme activity in broiler chickens challenged with Escherichia coli K88

Background： Colibacillosis caused by enterotoxigenic Escherichia coil （E. coil} results in economic losses in the poultry industry. Antibiotics are usually used to control colibacillosis, however, E. coli has varying degrees of resistance to different antibiotics. Therefore the use of probiotics is becoming accepted as an alternative to antibiotics. In this study, we evaluated the effects of Clostfidium butyricum （C. butyficum） on growth performance, immune response, intestinal barrier function, and digestive enzyme activity in broiler chickens challenged with Eschefichia coli （E. coil） K88. Methods： The chickens were randomly divided into four treatment groups for 28 days. Negative control treatment （NC） consisted of birds fed a basal diet without E. coil K88 challenge and positive control treatment （PC） consisted of birds fed a basal diet and challenged with E. coil K88. C. buO/ricum probiotic treatment （CB） consisted of birds fed a diet containing 2 x 107 cfu C. buO/ricum/kg of diet and challenged with E. coil K88. Colistin sulfate antibiotic treatment （CS） consisted of birds fed a diet containing 20 mg colistin sulfate/kg of diet and challenged with E. coil K88. Results： The body weight （BW） and average day gain （ADG） in the broilers of CB group were higher （P 〈 0.05） than the broilers in the PC group overall except the ADG in the 14-21 d post-challenge. The birds in CB treatment had higher （P 〈 0.05） concentration of tumor necrosis factor-a （TNF-a） at 3 and 7 d post-challenge, and higher （P 〈 0.05） concentration of interleukin-4 （IL-4） at 14 d post-challenge than those in the PC treatment group. The concentration of serum endotoxin in CB birds was lower （P 〈 0.05） at 21 d post-challenge, and the concentrations of serum diamine oxidase in CB birds were lower （P 〈 0.05） at 14 and 21 d post-challenge than in PC birds. Birds in CB treatment group had higher （P 〈 0.05） jejunum villi height than those in PC, NC, or CS treatment at 7, 14, and 21 d post-challenge. In comparison to PC birds, the CB birds had lower （P 〈 0.05） jejunum crypt depth during the whole experiment. The birds in CB or CS treatment group had higher （P 〈 0.05） activities of amylase and protease at 3, 7, and 14 d post-challenge, and higher （P 〈 0.05） activity of lipase at 3, 7 d post-challenge than PC birds.

The Study on the Effects of Chinese Herbal Mixtures on Growth,Activity of Post-Ruminal Digestive Enzymes and Serum Antioxidant Status of Beef Cattle

Sixteen Limousin×Luxi crossbred beef cattle [（199.4±8.67） kg] were used to evaluate the effects of Chinese herbal mixtures （CHM） on growth, activities of post-ruminal digestive enzymes and serum antioxidant status of beef cattle. Treatments were control （no CHM supplementation） and three formulations of CHM （CHM-A, CHM-B and CHM-C） that were arranged as completely randomized design. The calves were fed in indoor individual feeding barn with total mixed ration for 90 d. The CHM-A, CHM-B, and CHM-C was incorporated into the diet at the level of 20 g kg-1 DM （dry matter） of concentrate. The cattle were weighted at the beginning, at the end and every 15 d between to determine growth rate. Blood sample was taken every 30 d to analyze activities of total superoxide dismutase （T-SOD） and glutathione peroxidase （GSH-PX） and concentration of malondialdehyde （MDA）. The cattle were slaughtered at the end of experiment and chymus samples from various section of the post-ruminal digestive tract were collected to analyze enzymes activities. All cattle had similar average daily gain, but cattle supplemented with CHM-A tended faster growth （P=0.08） compared to the control and other CHM treatments. Supplementation of CHM did not affect pH of chymus in any section of the post-ruminal digestive tract. Activities of pepsin, trypsin, chymotrypsin, and lipase in chymus samples were enhanced （P0.05） to various extents by supplementation of CHM-A, CHM-B, and CHM-C depending on the enzymes and the site of the digestive tract. Amylase activity was increased only by CHM-A and CHM-C from chymus sample collected at the ileum. Supplementation of CHM-A and CHM-B reduced （P0.05） concentration of MDA, but did not affect GSH-PX activity in the serum of cattle throughout the entire experimental period. Cattle supplemented with CHM-B also had higher （P0.05） T-SOD activity in the serum at day 30 and 60 as compared with the control and the other two CHM treatments. Chinese herbal mixtures supplemented at the levels of 20 g kg-1 DM of concentrate increased post-ruminal digestive enzymes activity and enhanced serum antioxidant status. Inclusion of CHM-A and CHM-B in the diet may be favourable for ruminant production.

Responses of Detoxifying, Antioxidant and Digestive Enzyme Activities to Host Shift of Bemisia tabaci (Hemiptera: Aleyrodidae)

The polyphagous B-biotype of Bemisia tabaci （Gennadius） has demonstrated a high capacity to adapt to numerous hosts from diverse plant families. To illustrate induced responses by the host plant, biochemical research on eight plant-insect interaction correlative enzymes, representing detoxifying, antioxidant and digestive pathways, were investigated. Transferring whitefly adults to Zhongmian 23 from the pre-adapted host Zhongmian 41 induced activities of carboxylesterase （by 1.80-fold）, glutathione S-transferase （by 3.79-fold）, proteinase （by 1.62-fold） and amylase （by 2.41-fold） activities, hut decreased polyphenol oxidase （by 1.89-fold） and peroxidase （by 1.88-fold）. However, transferring whitefly adults to the favorite host abutilon from Zhongmian 41 was associated with increased activities of cytochrome P450 monooxygenase （by 1.61-fold） and amylase （by 1.42-fold）, and decreased activities of polyphenol oxidase （by 2.96-fold） and peroxidase （by 2.07-fold）. Our results, together with previous studies, proved that multiple pathways are involved in coping with host shifts by polyphagous herbivores, and the taxonomic status and preference of the host transferred would affect which pathway would be induced. These results would represent a key challenge in developing long-term sustainable insect control strategies.

Changes of free radicals and digestive enzymes in saliva in cases with deficiency inspleen-yin syndrome

Objective：To explore the nature of deficiency in spleen-yin syndrome,which could provide scientific theoretical support and practical guidance for clinical Traditional Chinese Medicine（TCM）syndrome differentiation based on biology,and had a strong clinical significance.Methods：Serum Cu and Zn were detected by atomic absorption spectrophotometer,serum vitamin E by high performance liquid chromatography,serum vitamin C by 2,4-Dinitrophenylhydrazine Colorimetry,total superoxide dismutase（SOD）and Cu and Zn- SOD by the xanthine oxidase method,and malondialdehyde（MDA）by the 2-thiobarbituric acid method（TBA）.Total antioxidant capacity was detected by a colorimetry kit.Amylase Activity was detected by an automatic biochemical analyzer.Lysozyme was detected by lysozyme detection plate,the diameter of bacteriolysis circle was measured and the corresponding content of lysozyme was obtained from a table of standard curve values.Results： No significant difference in total SOD and Cu,Zn-SOD was found between deficiency in spleen-yin group and normal group.However,such factors in deficiency in kidney-yin group were significantly lower than the other groups（P〈0.05）.The MDA content in both deficiency in spleen-yin group and deficiency in kidney-yin group were significantly higher than that of normal group（P〈0.05）,while the total antioxidant capacity was significantly lower than normal group（P〈0.05）.The vitamin E content in deficiency in kidney-yin group was significantly lower than that in the other two groups（P〈0.05）.No significant difference in the contents of vitamin C,Cu and Zn were observed in these groups.The Zn/Cu level in deficiency in kidney-yin group and the vitamin E level in deficiency in spleen-yin group decreased,but with no significant difference.Amylase activity in unit time in cases with deficiency in spleen-yin was lower than and had significant differences with that in normal cases,and higher than that in cases with deficiency in kidney-yin.The sectional velocity of saliva and the ratio of lysozyme in normal case group were significantly higher than other two groups,while deficiency in the spleen-yin group was significantly higher than the deficiency in kidney-yin group.Conclusion：All the results indicated that the objective pathological mechanism between the deficiency in spleen-yin and deficiency in kidney-yin was different.

Effect of water temperature on digestive enzyme activity and gut mass in sea cucumber Apostichopus japonicus (Selenka),with special reference to aestivation

The effect of water temperature on gut mass and digestive enzyme activity in sea cucumber Apostichopusjaponicus, including relative gut mass （RGM）, amylase, lipase, pepsin and trypsin activities were studied at temperatures of 7, 14, 21, and 28℃ over a period of 40 days. Results show that RGM significantly decreased after 40 days at 21 ℃ and markedly decreased over the whole experiment period at 28℃; however, no significant effect of duration was observed at 7 or 14℃. At 14℃, trypsin activity significantly decreased over 10 and 20 days, then increased; amylase and trypsin activity significantly decreased after 40 days at 28℃. However, no significant effect of duration was found on amylase, pepsin or trypsin activities in the other temperature treatment groups. At 28℃, lipase activity peaked in 20 days and then markedly decreased to a minimum at the end of the experiment. On the other hand, pepsin activity at 28℃ continuously increased over the whole experimental period. Principle component analysis showed that sea cucumbers on day 40 in the 21℃ group and in the previous 20 days in the 28℃ group were in the prophase of aestivation. At 28℃, sea cucumbers aestivated at 30-40 days after the start of the experiment. It is concluded that the effect of temperature on the digestion ofA. japonicus is comparatively weak within a specific range of water temperatures and aestivation behavior is accompanied by significant changes in RGM and digestive enzyme activities.

Effects of Dietary Stachyose on Growth Performance, Digestive Enzyme Activities and Intestinal Morphology of Juvenile Turbot(Scophthalmus maximus L)

A 12-week feeding trial was conducted to evaluate the effects of dietary stachyose on the growth performance, digestive enzymes activities and intestinal structures of juvenile turbot(Scophthalmus maximus L). Five isonitrogenous(49.58% crude protein) and isolipidic(10.50% crude lipid) diets were formulated to contain 0(Control), 0.625%(S-0.625), 1.25%(S-1.25), 2.5%(S-2.5) and 5%(S-5) stachyose, respectively. With the increase of stachyose level, the growth performance and feed utilization of turbot, such as the specific growth rate, final mean body weight, weight gain rate and feed efficiency, increased significantly(P < 0.05) and then stabilized. The feed intake of fish fed S-5 was significantly higher(P < 0.05) than that of fish in other groups. The activities of trypsin, intestinal caseinolytic, stomach and intestinal amylase were significantly influenced by stachyose(P < 0.05). The highest values of trypsin and intestinal caseinolytic activities were observed in group S-1.25, while the highest activity of stomach amylase and the lowest activity of intestine amylase were observed in group S-5. No lesion or damage was found on the distal intestine structures of fish from all treatments, while the height of simple folds in the distal intestine was significantly increased(P< 0.05) when 1.25% or 2.5% stachyose was added in the diets. These results indicated that moderate level of stachyose(1.25%) improves the growth performance, feed utilization, digestive enzyme activities and the distal intestine structures of juvenile turbot.

Influence of Probiotics on the Growth and Digestive Enzyme Activity of White Pacific Shrimp (Litopenaeus vannamei)

The influence of Bacillus probiotics on the digestive enzyme activity and the growth of Litopenaeus vannamei were de- termined in this study. The shrimp was treated with five percentages (1.5, 3.0, 4.5, 6.0 and 7.5) of probiotics (Bacillus spp.) supple- mented to the feed and cultured for 45 d. The growth measured as the weight gain at the end of culturing was significantly (P<0.05) higher in probiotic-treated shrimps than that of the control (without receiving probiotics). Activities of protease and amylase, two digestive enzymes of the midgut gland and the intestine were significantly (P<0.05) higher in probiotic-treated shrimp than in the control.

Effect of synbiotics on intestinal microflora and digestive enzyme activities in rats

AIM: To investigate the effect of synbiotics, i.e. probiotics and prebiotics mixture, on the gut microbial ecology and digestive enzyme activities in rats. METHODS: Forty-eight SD rats weighing about 280 g were used in this study. Rats were divided into three groups according to the contents of probiotics and prebiotics mixture in the feed as control, low and high dose groups. The duration of the experiment was 8 wk. RESULTS: Compared with the control group, thefecal Lactobacillus and Bifidobacterium counts were significantly increased and the fecal Coliform organism counts were markedly reduced in the low and high dose groups. Concerning the digestive enzyme activity of jejunum, only lactase activity increased in low dose group. However, significant increase of lipase, lactase, sucrase, and isomaltase activities were observed in high dose group.CONCLUSION: Intake of low and high dosages of probiotics and prebiotics mixture significantly improved the ecosystem of the intestinal tract by increasing the probiotics population and digestive enzyme activities in rats.

Co-localization hypothesis:A mechanism for the intrapancreatic activation of digestive enzymes during the early phases of acute pancreatitis

Acute pancreatitis is generally believed to be a disease in which the pancreas is injured by digestive enzymes that it normally produces. Most of the potentially harmful digestive enzymes produced by pancreatic acinar cells are synthesized and secreted as inactive zymogens which are normally activated only upon entry into the duodenum but, during the early stages of acute pancreatitis, those zymogens become prematurely activated within the pancreas and, presumably, that activation occurs within pancreatic acinar cells. The mechanisms responsible for intracellular activation of digestive enzyme zymogens have not been elucidated with certainty but, according to one widely recognized theory （the ＂co-localization hypothesis＂）, digestive enzyme zymogens are activated by lysosomal hydrolases when the two types of enzymes become co-localized within the same intracellular compartment. This review focuses on the evidence supporting the validity of the m-localization hypothesis as an explanation for digestive enzyme activation during the early stages of pancreatitis. The findings, summarized in this review, support the conclusion that co-localization of lysosomal hydrolases with digestive enzyme zymogens plays a critical role in permitting the intracellular activation of digestive enzymes that leads to acinar cell injury and pancreatitis.

Effect of parenteral and early intrajejunal nutrition on pancreatic digestive enzyme synthesis, storage and discharge in dog models of acute pancreatitis

AIM： To study the effect of early intrajejunal nutrition on enzyme-protein synthesis and secretion during acute pancreatitis. METHODS： Fifteen dogs were randomly divided into parenteral nutrition （n = 7） and early intrajejunal nutrition groups （n = 8）. An acute pancreatitis model was induced by injecting 5% sodium taurocholate and trypsin into the pancreas via the pancreatic duct. Intrajejunal nutrition was delivered with a catheter via a jejunostomy tube after the model was established for 24 h. On d 1 and 7 and at the beginning of nutritional support, radioactive tracing and electron microscopes were used to evaluate the enzyme-protein synthesis in acinar cells, the subcellular fractionation and the change in zymogen granules after 1.85 × 10^6 Bq L-3H phenylalanine was infused at 30, 60, 120, and 180 min. RESULTS： The 3H radioactivity in pancreatic acinar cells reached its peak level at 60 min, and the contents in the early intrajejunal nutrition group were higher than those in the parenteral nutrition group, which were then decreased. The mean number and area of zymogen granules did not show any significant statistical difference in both groups on d i or on d 7 （P 〉 0.05）. CONCLUSION： Early intrajejunal nutrition might be effective in dogs with acute pancreatitis.

Development Study on Some Digestive Enzymes of Takifugu rubripes Larvae and Juvenile

The activities of some digestive enzymes are studied for Takifugu rubripes larvae and juvenile from the first feeding to 27 d after hatching at selected stages of development. The homogenate of whole larvae body is used for enzymatic determination. Activity of acid protease decreases notably during the beginning days after the commencement of completely exogenous feeding and the days before the beginning of the juvenile stage. Alkaline protease specific activity also decreases at metamorphosis. The activities are associated with the morphology of the developing digestive tract. Amylase activity increases before the first feeding, followed by a decreasing and then a rather constant level. Lipase activity remains low during the larvae and juvenile periods. Alkaline phosphatase activity increases gradually. This reflects the development of brush border membranes of enterocytes.

Effect of Different Dietary Protein and Lipid Levels on the Growth,Body Composition,and Intestinal Digestive Enzyme Activities of Juvenile Yellow Drum Nibea albiflora(Richardson)

An 8-week feeding trial was conducted to determine the optimal dietary protein-to-lipid ratio for juvenile Nibea albiflora with an initial weight of(11.76 ± 0.20) g.Nine experimental diets containing different concentrations of protein(40%,47%,or 54%) and lipids(5%,9%,or 13%) in a 3 × 3 factorial experimental design were tested in triplicate groups of fish,while the protein-to-energy(P/E) ratios of the diets varied in the range of 19.74–28.32 mg k J^(-1).Results showed that fish fed diets containing 9% or 13% lipids with 54% protein exhibited significantly higher weight gains and specific growth rates than those fed other diets.The feed conversion rate of fish fed the diet with 40% protein and 5% lipids was significantly poorer than that of fish fed other diets.The protein efficiency rate of fish fed diets with 5% lipids was significantly lower than that of fish fed 9% or 13% lipid diets.Carcass lipid and energy contents were positively correlated with dietary lipid level regardless of protein level.Fish fed a 54% protein diet showed the highest trypsin activity.The intestinal lipase activity of fish fed the diet containing 13% lipids was significantly higher than that of fish fed 5% or 9% lipid diets.These results demonstrate the high protein dietary requirements of N.albiflora.A diet containing 54% protein and 9%–13% lipids with a P/E ratio of 26.2–27.81 mg protein k J^(-1) can be considered optimal for juvenile N.albiflora.

Effects of Hanseniaspora opuntiae C21 on the growth and digestive enzyme activity of juvenile sea cucumber Apostichopus japonicas

The effects of a diet containing Hanseniaspora opuntiae C21 on growth and digestive enzyme activity were estimated in juvenile Apostichopus japonicus. Groups of sea cucumbers were fed diets containing H. opuntiae C21 at 0(control), 10 4, 10 5, and 10 6 CFU(colony-forming units)/g feed. Results showed that after 45 d the specific growth rate(SGR) of sea cucumbers fed a C21-supplemented diet at 10 4 CFU/g feed was significantly higher than that of the control( P < 0.05). Intestinal trypsin and lipase activities were significantly enhanced by C21 administration at 10 4 and 10 5 CFU/g feed compared with the control( P < 0.05). After feeding for 23–42 d, C21 was demonstrated by denaturing gradient gel electrophoresis to be present in the intestine of sea cucumbers. In addition, after feeding the C21-supplemented diets for 15 d, the sea cucumbers were switched to an unsupplemented diet and C21 was confirmed to be capable of colonizing the intestine for at least 31 d after cessation of feeding. In conclusion, C21 was shown to successfully colonize the intestine of juvenile A. japonicus via dietary supplementation, and improve growth and digestive enzyme activity.

Effect of dietary genistein on growth performance,digestive enzyme activity,and body composition of Nile tilapia Oreochromis niloticus

An 8-week feeding experiment was performed to evaluate the effect of dietary genistein on growth performance,body composition,and digestive enzymes activity of juvenile Nile tilapia(Oreochromis niloticus).Four isonitrogenous and isoenergetic diets were formulated containing four graded supplements of genistein:0,30,300,and 3 000 μg/g.Each diet was randomly assigned in triplicate to tanks stocked with 15 juvenile tilapia(10.47±1.24 g).The results show that 30 and 300 μg/gdietary genistein had no significant effect on growth performance of Nile tilapia,but the higher level of genistein(3 000 μg/g)significantly depressed the final body weight and specific growth rate.There was no significant difference in survival rate,feed intake,feed efficiency ratio or whole body composition among all dietary treatments.An assay of digestive enzymes showed that the diet containing 3 000 μg/ggenistein decreased stomach and hepatopancreas protease activity,and amylase activity in the liver and intestine,while a dietary level of300 μg/g genistein depressed stomach protease and intestine amylase activities.However,no significant difference in stomach amylase activity was found among dietary treatments.Overall,the results of the present study indicate that a high level of dietary genistein(3 000 μg/g,or above) would significantly reduce the growth of Nile tilapia,partly because of its inhibitory effect on the activity of major digestive enzymes.Accordingly,the detrimental effects of genistein,as found in soybean products,should not be ignored when applied as an alternative ingredient source in aquaculture.

Effects of soybean meal replacement with fermented alfalfa meal on the growth performance,serum antioxidant functions,digestive enzyme activities,and cecal microflora of geese

Fermented forages are important feedstuffs. Bacillus subtilis inoculants are often used to improve the value of forage legume fermentation. The present work was conducted to study the effects of replacing soybean meal with solid-state fermented alfalfa meal（FAM） with B. subtilis ACCC 01746 on growth performance, serum antioxidant and digestive enzyme activities, and cecal microflora in goose. 300 healthy geese with similar body weights were randomly assigned to six treatment groups with five replicates of 10 geese（five males and five females） each. Geese were fed ad libitum for 35 days. Results showed that the geese fed with 4 and 8% FAM exhibited no significant effects on their final body weights（FBW） and average day gain（ADG）（P〉0.05）, whereas 12% or higher FAM caused poor growth of the geese compared with control diet（linear（L）： P〈0.05）. The average daily feed intake（ADFI）（quadratic（Q）： P〈0.05） and feed conversion ratio（FCR）（L： P〈0.05） with 8% or higher supplementation level were higher than those of the control group. The activities of antioxidant enzyme in serum increased, and the level of malondialdehyde（MDA） significantly decreased with increasing dietary FAM level（L： P〈0.05）. However, no significant differences were observed at 8% or lower supplementation level for glutathione peroxidase（GSH-Px） and superoxide dismutase（SOD）（P〉0.05） and at 4% for catalase（CAT） supplementation level compared with the control group. All diets containing FAM increased digestive enzyme activities in geese. However, geese fed diets with 12% FAM supplementation showed the highest trypsin activities in pancreas（Q： P〈0.05）. Supplementation with 12% or higher FAM significantly increased amylase activities in pancreas（L： P〈0.05） and duodenum（L： P〈0.05） compared with the control group. Significant differences were not observed in total anaerobic bacteria between geese fed with FAM and control diets on day 35（P〉0.05）. The numbers of Bifidobacterium and Lactobacillus in the cecum of geese fed with FAM significantly increased（L： P〈0.05）, but no significant effects were found with 4 and 8% FAM supplementation levels compared with the control（P〉0.05）. By contrast, the coliform counts of cecum decreased with increasing inclusion of FAM, but these counts were significantly reduced in geese fed diets with 12% or higher FAM supplementation level（L： P〈0.05）. Collectively, our results indicated that supplementation of the basal geese diet with 8% FAM had no apparent adverse effects on growth performance, serum antioxidant enzyme activities, and digestive parameters and beneficial microbiota.

Growth performance,digestive enzyme activities and serum nonspecific immunity of the red tilapia(Oreochromis mossambicus×Oreochromis niloticus)feddiets supplemented with ultrafine powder of Enteromopha prolifera

The present study evaluated ef fects of ultrafine powder of the green macroalgae E nteromopha prolifera as dietary supplement on growth performance, digestive enzyme activities and serum nonspecific immune responses of the red tilapia(O reochromis mossambicus × Oreochromis niloticus). The red tilapia were fed five diets supplemented with different levels of E. prolifera ultrafine powder as well as a control diet containing no E. prolifera for seven weeks(Diets 0–6 contained 0(control), 10, 20, 30, 40 and 50 g/kg of E. prolifera ultrafine powder, respectively). The results showed that diets supplemented with E. prolifera ultrafine powder generally improved growth, immunity and digestive enzyme activities of the red tilapia. In particular, the fish fed the diet incorporated 50 g/kg (5%) E. prolifera ultrafine powder(Diet 5) achieved the highest percentage weight gain, specific growth rate and the condition factor(increased by 15.4%, 8.0% and 5.7%, respectively when compared to the control). Feeding the diet also led to significantly increases( P <0.05) in serum nonspecific immune responses, including total superoxide dismutase, acid phosphatase, alkaline phosphatase, lysozyme activities and serum total protein(increased by 19.4%, 48.1%, 29.5%, 30.3% and 8.7%, respectively) as well as digestive enzyme activities of erepsin, gastric amylase, gastric lipase, pepsin, intestinal amylase and gastric lipase(increased by 15.7%, 33.3%, 16.3%, 21.3%, 52.3% and 28.2%, respectively) than those of the control. Based on these results, it is recommended that the inclusion level of E. prolifera ultrafine powder in the diet of the red tilapia should be 50 g/kg(or 5%).

Effect of digestive enzymes and pH on variation of bioavailability of green tea during simulated in vitro gastrointestinal digestion

To exam ine the effect of digestive attributes such as digestive enzymes and pH on changes in phenolic compound content and antioxidant activity during digestion,the bioavailability of green tea infusion was investigated using a simulated in vitro gastrointestinal digestion model.The total polyphenol content(TPC)decreased to 65%–70%throughout the mimicked normal digestion(MD)compared to the initial value.The total flavonoid content(TFC)decreased to approximately 25%after starting the gastric stage(pH 1.2);however,it regained to approximately 60%in the intestinal stage(pH 6.8).The mimicked digestive condition without digestive enzymes(WOE),which followed only the pH conditions of MD,showed significantly lower TPC and TFC values than MD.The percentage of antioxidant activity based on the initial values indexed by DPPH,ABTS,and FRAP gradually declined from approximately 60%at the gastric stage to approximately 40%at the final digestion stage.Meanwhile,the percentage of residual MIC was around 50%at the gastric stage.However,it gradually increased at the intestinal stage.The significantly lower antioxidant activity showed for WOE than MD throughout the simulated digestion.This study demonstrated that digestive enzymes and pH play a crucial role in the bioavailability of green tea infusion.

Changes of visceral properties and digestive enzymes in the herbivorous marine teleost Siganus canaliculatus fed on different diets

The rabbitfish Siganus canaliculatus is one of the few cultured herbivorous marine teleosts. To better understand the digestive physiology of this fish and provide data for designing formulated feed using macroalgae as an ingredient, the changes of visceral properties and digestive enzyme activities were investigated after the juveniles were fed on different types of food including raw fish（RF）, formulated diet（FD） or macroalgae Enteromorpha prolifra（EP） and Gracilaria lemaneiformis（GL） for eight weeks. The results showed that the hepatosomatic and viscerosomatic indices in the RF and FD groups, as well as the relative intestine length（RIL） in the EP and GL groups, were significantly higher than those in other groups. Additionally, differences in the histological structure of the liver and anterior intestine were also observed among different dietary groups. The hepatic nuclei were displaced to the periphery by lipid inclusions in fish fed RF. The highest levels of mucosal folds were found in the anterior intestines of fish fed macroalgae. Digestive enzyme activity profiles showed obvious fluctuations in the first three weeks, and then leveled off in the following weeks. The levels of protease, lipase and α-amylase in the alimentary tract showed changes related to the levels of dietary protein, lipid and carbohydrate, respectively.Although macroalgae significantly inhibited the activity of protease in the stomach, it increased RIL and the number of mucosal folds in the anterior intestine so as to compensate for the influences on protease activities in the stomach. This study suggests that the digestive tract of rabbitfish can well adapt to different diets, and needs about three weeks to physiologically acclimatize to the nutritional status, thus implying that rabbitfish are somewhat omnivorous.

Effect of Using Baker＇s Yeast and Exogenous Digestive Enzymes as Growth Promoters on Growth, Feed Utilization and Hematological Indices of Nile tilapia, Oreochromis niloticus Fingerlings

The present study was conducted to evaluate the effect of baker yeast, Saccharomyces cerevisiae （SC） and exogenous digestive enzymes （pepsin, papain and a-amylase, EDE） dietary supplementation on growth performance, feed utilization and hematological indices of Nile tilapia, Oreochromis niloticus fingerlings. A total of 630 Nile tilapia fingerlings with an average body weight of 26.4 ± 0.2 g were divided in the seven experimental net-pen treatments （three replicates each）. The experiment was conducted for 119 days. Seven isonitrogenous （26.50%） digestible protein and isocaloric （13.40 MJ kgl） digestible energy experimental diets were formulated. The control diet had no SC and EDE added. Diets 2-3 each contained SC at levels of 2 and 4 g 100 g diet-t, respectively, while diets 4-5 each contained EDE at levels of （0.64, 1.28, 0.16） and （1.28, 2.56, 0.32） g 100 gdiefI of pepsin, papain and a-amylase, respectively. Diet 6 contained mixture of SC and EDE at levels of 1 g yeast and 0.32, 0.64, 0.08 g of pepsin, papain and a-amylase, respectively 100 gdiet1 and diet D7 contained 2 g yeast and 0.64, 1.28, 0.16 g of pepsin, papain and a-amylase, respectively 100 g dietl. Growth performance and feed utilization efficiency of Nile tilapia were significantly （P 〈 0.05） higher in all treatments receiving SC and/or EDE supplemented-diets than the control diet which suggests that the addition of SC and EDE enhanced the growth performance. Red blood cells counts, hematocrit and hemoglobin were significantly （P 〈 0.05） highest in all treatments receiving mixture of SC and EDE supplemented-diets （D6 ＋ D7）. The same trend was observed for total plasma protein and total plasma globulin levels. The results of present study suggested that Nile tilapia fingerlings fed diets containing the mixture of I g yeast, SC and 0.32, 0.64, 0.08 g of pepsin, papain and a-amylase, respectively 100 gdiet^-1, for 119 days had enhanced growth performance, diet utilization efficiency and hematological indices.