酶制剂在水产养殖上的应用研究概况

饲用酶制剂越来越多地应用于水产养殖中。介绍了酶制剂对水产动物消化机能、生长和饲料转化率、饲料中适宜添加量、内源性酶和养殖环境影响等方面的研究情况。提出了存在的问题及发展方向。     

饲用酶制剂在水产动物中应用的最新研究进展

酶制剂作为一类安全、高效的绿色饲料添加剂,在畜禽类饲料中已得到广泛应用。酶制剂不仅可以在一定程度上缓解国内饲料资源的不足,还可以促进绿色养殖环境的发展。由于酶制剂受热敏性条件制约的原因,其在水产饲料中的应用率较低,但随着一些设备的应用,如多道真空后喷涂等,使液体酶制剂在水产饲料中的广泛应用成为可能。本研究就酶制剂在水产动物上的应用、作用机理和存在的问题进行了综述,并展望了饲用酶制剂在水产饲料中的应用前景,以期为饲用酶制剂的应用提供参考依据。     

饲用酶制剂在水产养殖中的应用

饲用酶能提高饲料转化率,促进动物的生长,降低粪便污染和动物的死亡率,综合提高动物的生产性能,在动物饲料中应用越来越普遍,被认为是一种无残留、无污染、无公害的环保型添加剂。1　饲用酶制剂的作用机制目前,在水生动物饲料中应用的酶制剂主要包括:纤维素酶、β-葡聚糖酶、木聚糖酶、淀粉酶、蛋白酶和植酸酶等。饲料中添加外源性酶制剂的目的主要是提高动物对营养物质的消化率和分解饲料中的抗营养因子,从而促进动物的生长。幼年的水生动物,自身消化系统发育得不完善,内源消化酶分泌不足,在饲料中添加外源性消化酶,可以促进水生动物对…     

对虾消化酶的研究概述

酶制剂作为饲料添加剂,在畜牧业上,国内外很早就对酶制剂的作用机制进行了深入研究。水产饲用酶制剂的研究起步较晚,国内相关研究主要集中在淡水鱼类的饲用酶制剂应用方面。但外源酶制剂对对虾消化酶活性的影响鲜见报道,且主要集中在温度、酸碱度对对虾消化酶活性及不同生长阶段消化酶活性的变化等。     

饲用酶制剂及其在水产业中的研究进展

介绍了饲用酶制剂的种类及其在水产养殖中的功能,综述了近10年来国内研究人员对饲用酶制剂在水产业中应用的研究成果,最后提出了水产饲用酶制剂研究存在的问题及其对策.     

饲用酶制剂的应用研究进展

饲用酶制剂是一种活性蛋白质,作为一种饲料添加剂具有无残留、无污染、对人畜健康没有不良影响等优点。它能够降解动物体内不易消化的植物性饲料,使其营养物质得以充分利用,从而提高饲料消化率,改善了动物的生产性能和产品品质。文章对酶制剂的分类体系、作用机制以及在动物上的应用效果等研究进展作了综述,分析了目前国内酶制剂应用存在的问题对其发展前景进行展望。     

饲用耐高温酶的研究与应用

随着养殖业的迅速发展，酶制剂作为一种高效、安全、无污染、多功能的“绿色”饲料添加剂越来越受到人们的青睐。大量的试验证明，在饲料中添加一定比例的酶制剂可以补充动物体内消化酶的不足，明显提高动物饲料的利用率，促进动物生长，改善生态环境和防治动物疾病等等。目前，大多数饲用酶在饲料中的应用大多以干粉粒的形式在饲料加工调     

水产专用酶制剂的特点

随着动物营养研究的深入和现代生物技术的发展，本世纪80年代以来，动物饲料中添加酶制剂已越来越得到重视。关于酶制剂在畜力上的应用已比较普遍，其效果已被广泛认可，但酸制剂在水产养殖中的应用报道不多。由于水产动物本身的营养生理及饲料营养成份与畜禽有很大的差异，在畜尚使用很好的酶制剂，在水产上不一定应用得很好。下面，我们将水产专用酶制剂的特点和在畜禽上使用很好的酶制剂做一探讨。由于各肖饲料为高能量、高纤维、低脂肪、低蛋白饲料，因为牲畜（如牛、马、羊、猪）饲料中添加纤维素分解自（如木聚精辟、p一葡聚精田、纤…     

饲用酶制剂在规模养猪中的应用试验

添加饲用酶制剂不仅能有效地消除饲料抗营养因子和毒素的有害作用,而且能全面促进饲粮养分的分解消化和吸收利用,提高畜禽的生产性能和增进畜禽健康。应用饲用酶制剂有利于开发非常规饲料资源,提高常规饲料的利用率,减少畜禽排泄中有机物、氮和磷的排出量,保护和改善生态环境,提高饲料和规模养猪企业的经济效益。为验证酶制剂在规模养猪中的实际效果,选用120头45日龄的杜大长杂交断奶仔猪分为两组,试验组在对照组日粮的基础上添加华芬酶0.2%,以观察华芬酶在断乳仔猪玉米豆粕型日粮中的饲养效果。试验结果表明:试验组的日增重比对照组提高8.84%;饲料转化率提高9.95%;每公斤增重饲料成本降低9.2%。     

细菌性木聚糖酶在饲料生产中的应用

饲用酶制剂的应用效果现已毋庸置疑，它既能提高饲料的消化率和利用率，提高畜禽及鱼类的生产性能，又能减少畜禽排泄物中的氮、磷含量，减少氮、磷等有机物在水体和土壤中的蓄积，使其免受污染。因而饲用酶制剂作为一类高效、无毒副作用和环保型的“绿色”饲料添加剂，在21世纪将有着十分广阔的应用前景。由于大多数酶制剂会在高温条件下失活而影响其性能发挥，     

The optimum active site of acidic phytase in the gastrointestinal tract of channel catfish (Ictalurus punctatus): in vitro and in vivo studies

This study was conducted to determine the optimum active site of acidic phytase in the gastrointestinal tract of channel catfish. The pH value, acidic phytase activity, resistance of acidic phytase against gastrointestinal protease, substrate availability, and enzymatic reaction products were measured in different gastrointestinal sections of channel catfish, respectively. The results indicated that in the whole gastrointestinal tract, only the pH value of stomach (4.2–4.7) lied in the optimum active pH range of acidic phytase (1.5–5.5). The resistant ability of acidic phytase against proteases in different sections of the gastrointestinal tract was comparable, and the highest activity of phytase was observed in the stomach compared with other gastrointestinal sections. Moreover, the highest concentration of soluble phytic acid as the substrate of phytase was also seen in the stomach. After feeding fish with the diet containing acidic phytase, the residual phytic acid in the stomach was significantly reduced. Correspondingly, the dietary addition of acidic phytase significantly improved the phosphorus absorption in the intestine. In short, this study verified that stomach is the optimum active site for acidic phytase in channel catfish, because it allows higher phytase activity and provides more soluble substrates of phytase than other gastrointestinal sections.     

The Efficacy of a Novel Microbial 6‐Phytase Expressed in Aspergillus oryzae on the Performance and Phosphorus Utilization of Cold‐ and Warm‐Water Fish: Rainbow Trout,Oncorhynchus mykiss,and Nile Tilapia,Oreochromis niloticus

The efficacy and tolerance of a novel microbial 6‐phytase were investigated in rainbow trout, Oncorhynchus mykiss, and Nile tilapia, Oreochromis niloticus. Reference diets were sufficient in available phosphorus (P). The test diet limiting in available P was supplemented with phytase at 500, 1000, or 2000 phytase units/kg feed. The enzyme was effective in increasing total P apparent digestibility coefficient in relation to increasing the dose of phytase in rainbow trout and Nile tilapia. Zinc apparent digestibility improved in relation to phytase supplementation in rainbow trout. P release due to phytase supplementation ranged from 0.06 to 0.18% P/kg feed in rainbow trout and from 0.13 to 0.26% P/kg feed in Nile tilapia. A 58‐d performance trial was conducted to evaluate tolerance of fish to phytase supplementation. Dietary treatments consisted of a basal diet without phytase or supplemented with 2000 and 200,000 phytase units/kg feed. Results indicate that this novel microbial 6‐phytase is well tolerated by fish. Significant improvements for growth as well as feed conversion ratio were observed when the phytase was fed at 2000 phytase units/kg feed. This phytase is proven efficient in releasing P from phytate and could be added when plants are used for fish meal replacement in diets for salmonid and omnivorous fish.     

植酸酶对金鳟粪磷及水环境中磷含量的影响

通过喷涂和预处理两种方法将不同浓度植酸酶添加到豆粕型金鳟(Oncorhynchus mykissW albaum)饲料中,研究了植酸酶对金鳟粪磷及养殖水环境中磷含量的影响。金鳟粪磷分析结果显示,喷涂法添加植酸酶,对照组中粪磷含量最高,其他各试验组较对照组差异显著(P<0.05),但500~2000 U/kg组中粪磷含量差异显著(P<0.05),2500~6000 U/kg组中粪磷含量无显著差异(P(0.05);预处理法添加植酸酶,对照组粪磷含量最高,其他各试验组粪磷含量较对照组降低显著(P<0.05),但添加植酸酶的各试验组之间差异不显著(P(0.05)。通过水中磷含量试分析结果显示,无论是喷涂法添加植酸酶还是预处理法添加植酸酶,各试验组水体总磷含量分别较其对照组差异不显著(P(0.05),各试验组的活性磷含量均未检出。实验结果表明,金鳟饲料中添加植酸酶可以降低粪磷含量,对养殖生产过程中控制磷的排放,减少磷污染具有重要的意义。     

Use of Microbial Phytase in Channel Catfish Ictalurus punctatus Diets to Improve Utilization of Phytate Phosphorus1

A 10-wk feeding trial was conducted in the laboratory during which channel catfish Ictalurus punctatus (average initial weight: 6.5 g/fish) were fed five practical diets containing either 0, 500, 1,000, 2,000, or 4,000 units of microbial phytase/kg diet. Fish fed diets containing 500 or more units of microbial phytase/kg consumed more feed and gained more weight than fish fed the basal diet without supplemental phytase. Feed conversion ratios (FCR) did not differ among treatments except the FCR for fish fed 1,000 units of microbial phytase/kg diet was lower than that of fish fed no supplemental phytase. Fish survival was not different among treatments. Contrast analysis showed that weight gain, feed consumption, bone ash, and bone phosphorus were higher and feed conversion ratio was lower for fish fed diets supplemented with phytase as compared to fish fed no supplemental phytase. The concentration of fecal phosphorus decreased linearly as phytase supplementation increased. Results from this study demonstrate that microbial phytase is effective in improving bioavailability of phytate phosphorus to channel catfish, which may eventually lead to a reduction in the amount of supplemental phosphorus added to commercial channel catfish feeds.     

Effects of phytase pretreatment of soybean meal and phytase-sprayed in diets on growth, apparent digestibility coefficient and nutrient excretion of rainbow trout (Oncorhynchus mykiss Walbaum)

Rainbow trout were fed a diet containing phytase-sprayed and phytase-pretreated soybean meal with different phytase levels. The single factor random block design was used to analyze the effects on rainbow trout of dietary phytase supplementation on growth performance, nutritional ingredient digestibility and nutrient excretion. After 90 days, the results showed that feed conversion ratio (FCR) and protein efficiency ratio (PER) were significantly improved and specific growth rate (SGR) was not affected by spraying phytase, but SGR, FCR and PER were not significantly improved by phytase pretreatment. A digestibility trial conducted after the feeding trial showed that apparent digestibility coefficient (ADC) of diet protein and minerals was increased with phytase supplementation. However, there was a negative effect of phytase on the ADC of lipid. The excretion experiment showed that the supplementation of phytase resulted in decreased nutrient excretion in feces, but lipid excretion was slightly increased with phytase supplementation. In addition, the results of P excretion and ADC of P analyzed by t-test showed that phytase pre-treatment method should be a more rational method than the spraying method. The results of SGR, ADC of P and P excretion analyzed by quadratic regression indicated that 2,000–3,000 U/kg levels by the spraying method could be a rational range of phytase supplementation, and about 1,000 U/kg should be an optimal level by the pretreatment method. Thus, use of phytase in rainbow trout feeds can have economic and environmental benefits.     

Apparent digestibility of nutrients in grass carp (Ctenopharyngodon idellus) diet supplemented with graded levels of neutral phytase using pretreatment and spraying methods

The effects of supplemental graded levels of neutral phytase using pretreatment and spraying methods on the apparent digestibility coefficients (ADCs) of protein, minerals and amino acids were investigated in grass carp (Ctenopharyngodon idellus) (mean weight, 20.92 ± 1.04 g). Seven experimental diets were prepared as: no‐phytase supplementation (control), pretreatment with phytase dose of 500 U (PP500), 1000 U (PP1000) and 1500 U (PP1500) per kg diet. With spraying method, the phytase was added to feed at the same three grades, namely 500 U (PS500), 1000 U (PS1000) and 1500 U (PS1500) per kg diet. After an 8‐week feeding trial, addition of phytase improved the crude protein, crude lipid, dry matter, ash, phosphorus and calcium digestibilities in comparison with the control, especially in the diets where phytase addition level was above 1000 U kg^?1 (P < 0.05). Phytase supplementation, both the pretreatment and spraying, significantly enhanced the ADCs of essential amino acid (EAA) and non‐essential amino acid. The ADCs of the nutrients were significantly influenced by phytase supplementation methods, supplementation levels and interaction of methods and levels. Based on the results, supplemental dietary phytase, regardless of application methodology, improved the ADCs of nutrients in grass carp, and the pretreatment mode of phytase application was more effective than spraying at the same phytase level. We suggest that the optimal level of phytase pretreatment is 1000 U kg^?1 diet, and the best addition level of phytase spraying is 1500 U kg^?1 diet or more phytase is required for spraying.     

Supplemental graded levels of neutral phytase using pretreatment and spraying methods in the diet of grass carp,Ctenopharyngodon idellus

A feeding trial was conducted for 8 weeks to evaluate the effects of graded levels of neutral phytase supplementation using pretreatment or spraying method on growth performance, body composition, bone mineral content and serum biochemical parameter in grass carp, Ctenopharyngodon idellus. A control diet without phytase was added and six additional diets were arranged as a 2 × 3 factorial with two methods (pretreatment or spraying) and three levels of phytase (500, 1000 or 1500 U kg^?1). The results showed that supplemental phytase at different levels in the diet and with different application methods all improved weight gain, specific growth rate and protein efficiency ratio of grass carp (P < 0.05). The feed conversion ratio in phytase‐supplemented groups was lower than the control. Dietary phytase addition reduced the lipid content in the whole body of grass carp. Phytase supplementation with different method increased ash and mineral (P, Ca, Mg and Zn) contents in whole‐body and vertebra (P < 0.05). The increase in these mineral contents was also observed in the serum. Based on the results, we may conclude that: 1) supplemental dietary phytase, regardless of the application methodology, improved the growth performance and nutrient utilization in grass carp; 2) the pretreatment mode of phytase application was more effective than spraying at the same phytase level.     

Factors affecting nutrient digestibility in rainbow trout (Oncorhynchus mykiss) fed a plant protein–based diet supplemented with microbial phytase

Factors influencing apparent digestibility coefficient (ADC) of nutrients from a plant protein–based diet supplemented with microbial phytase were investigated in a series of experiments with rainbow trout (Oncorhynchus mykiss). The influence of phytase level, water temperature, feed particle size and addition of a protease/non‐starch polysaccharidase (PNSP) enzyme cocktail were tested in a phytase‐supplemented (2000 FTU kg^?1) diet. Finally, the influence of Ca/P ratio, addition of 1,25‐hydroxycholeocalciferol, or inclusion of lactic acid (LA) in diets with and without phytase was evaluated. Addition of microbial phytase improved ADC of dry matter (DM), protein, ash and minerals (P, Ca, Mg, Fe and Zn) (P < 0.05). Reducing feed particle size potentiated the effect of phytase on P and ash ADC, as did the addition of a PNSP enzyme cocktail; the latter also significantly improved DM ADC in both control and phytase‐supplemented diets. Increasing the Ca/P ratio reduced the effect of phytase on P and ash ADC. Addition of 1,25‐dihydroxycholecalciferol and LA had no effect on DM, P and ash ADC in control diets and tended to reduce the phytase‐induced increase in P ADC.     

Microbial Phytase Can Replace Inorganic Phosphorus Supplements in Channel Catfish Ictalurus punctatus Diets1

Abstract.– Juvenile channel catfish Ictalurus punctatus (initial weight: 6.8 g/fish) were fed four practical diets containing 0, 250, 500, and 750 units of microbial phytase/kg and a diet containing 1% feed grade dicalcium phosphate (but no microbial phytase) under laboratory conditions for 12 wk. Fish fed the diets containing 250 units of microbial phytase/kg and above consumed more feed, gained more weight, and had a lower feed conversion ratio (FCR) in comparison to fish fed the basal diet containing no microbial phytase. Fish fed the diet containing dicalcium phosphate had intermediate weight gain and feed conversion ratio as compared to fish fed the basal diet and diets containing microbial phytase. Bone ash and phosphorus concentrations were lower for fish fed the basal diet than for fish fed other diets. No differences in weight gain, feed consumption, FCR, bone ash and bone phosphorus were observed among fish fed the diets containing various levels of microbial phytase. Fish fed the diet containing dicalcium phosphate had a lower bone phosphorus concentration than fish fed diets containing microbial phytase. Fecal phosphorus concentrations were lower for fish fed the diets containing microbial phytase than for fish fed the basal diet and the diet containing dicalcium phosphate. Results from the present study indicated that addition of 250 units of microbial phytase/kg to practical diets can effectively improve bioavailability of phytate phosphorus to channel catfish and may possibly eliminate the use of an inorganic phosphorus supplement in channel catfish diets. However, these data must be verified in trials conducted in ponds, prior to recommending removal of supplemental phosphorus from channel catfish diets.     

Dietary phytase supplementation and the utilisation of phosphorus by Atlantic salmon (Salmo salar L.) fed a canola-meal-based diet

The effect of phytase supplementation to a canola-meal-based diet on phosphorus utilisation in Atlantic salmon was studied in a two-by-two factorial design. Diets were prepared without phytase or inorganic phosphorus supplementation, with phytase, with supplemental inorganic phosphorus and with both phytase and supplemental inorganic phosphorus. Available phosphorus was set below requirement and the total phosphorus set to meet requirements for salmonids. After 12 weeks, there were no significant differences in survival, feed intake and weight gain between diets. There was an interaction effect between supplements on bone ash, bone phosphorus and whole-body phosphorus so that adding phytase, inorganic phosphorus, or both resulted in significantly (P<0.05) higher values for these parameters. An interaction effect was also observed for phosphorus digestibility, phosphorus retention efficiency and phosphorus load. Phosphorus digestibility and retention efficiency were significantly (P<0.05) higher, and phosphorus load was significantly (P<0.05) lower in fish fed the phytase supplemented diet compared with diets containing supplemental inorganic phosphorus. In conclusion, phytase increased phosphorus availability, therefore reducing the need to add inorganic phosphorus and reducing phosphorus waste from plant-meal-based diets for Atlantic salmon.