酶制剂在高粱基础型日粮中的研究与应用

高粱是五大谷类作物之一,可作为一种动物饲用的基础型日粮。高粱在动物日粮中主要由淀粉提供能量,但是高粱中存在的一些抗营养因子和蛋白包膜,如植酸、醇溶蛋白等,影响了高粱营养物质的消化利用。本文综述了高粱的营养特性、国内外对高粱的应用与研究现状及酶制剂在高粱基础型日粮中的研究与应用。     

高粱型日粮中提高猪和家禽生产性能的方法

高粱是一种可供食用和饲用的谷物;高粱型日粮通常用作反刍动物、猪和家禽的饲料。高粱在动物日粮中主要用作能量饲料,其能量来自所含有的淀粉。然而,高粱所含能量的利用效率差异较大,这不利于动物生产。高粱中的淀粉颗粒被高粱醇溶蛋白体包裹着,二者又被嵌入高粱胚乳中的谷蛋白基质中。高粱胚乳中蛋白-淀粉的互作可能会限制淀粉的水解和利用率。因此,高粱中的蛋白质/氨基酸消化率通常较其他谷物的低。高粱醇溶蛋白在高粱蛋白质组分中占很大的比重,它很难被动物消化,且缺乏一些必需氨基酸,尤其赖氨酸。高粱中酚类化合物和植酸盐含量比其他谷物的高,它们通过直接或间接结合蛋白质和淀粉来影响消化。正如在本综合中所考虑的那样,为提高猪和家禽对高粱的利用率,研究人员已经对多种饲料加工技术进行了评估。带有坚硬胚乳的高粱品种由于对昆虫有抗性和产量高,在育种方案中也越来越多地受到欢迎。研磨后高粱颗粒大小的减小程度和均匀性对猪和家禽的生长性能有极其重要的作用。高粱极易受热液加工的影响,这种工艺将会显著减低高粱蛋白的体外胃蛋白酶的消化率。因此,进行加热和加湿的蒸汽制粒、蒸汽压片和湿式挤压,会在高粱中产生有害的物理-化学变化,如在高粱醇溶蛋白中形成二硫键。干式挤压法(加工过程中通过摩擦产热)在无须添加水分的情况下,通过淀粉的糊化并破坏高粱的结构可以提高淀粉的消化率。将还原剂与水热工艺结合起来,可以通过裂解二硫键或阻止二硫键的形成,来提高高粱蛋白质的溶解性和消化率。在猪和家禽日粮中添加外源性酶,是一种可以提高单胃动物生产性能的公认方法;同时,由于高粱含有相对较高水平的植酸盐,添加植酸降解酶——植酸酶显得更为合理。包括辐射在内的其他策略在提高高粱营养利用率方面也有应用前景。由于猪和家禽在胃肠道结构和生理特征上的巨大差异,它们对以上的处理工艺会产生不同的反应,尤其在谷物的颗粒大小方面。     

高粱在肉鸡营养中的影响

高粱是世界上第五大粮食作物,年产量大约560万t。高粱型的日粮在肉鸡生长中表现次佳。高粱蛋白质中大部分是高粱溶醇蛋白,其消化率低,缺乏赖氨酸。因此,随着高粱溶醇蛋白比例的增加,必需氨基酸的消化率以及赖氨酸浓度将会下降。在低单宁酸,添加植酸酶的高粱型日粮中,肉鸡表现不好的重要的原因之一可能是高粱溶醇蛋白含量,多变的氨基酸消化率和浓度以及谷物粒度结合不当的加工方法。     

中型褐壳产蛋鸡对饲粮植酸磷的利用率及饲粮钙水平的影响

以植物性饲料原料为主的畜禽饲粮中植酸磷的含量占总磷的60%～80％（Mollaguard,1946;deBolend,1975;Keddy,1982;Graf,1986）。一些早期报道显示,肉鸡对植酸磷的消化利用率仅为10％（Asada等,1969;Abernathy等,1973）。未被消化的植酸磷随粪排出进入环境,从而导致潜在的环境磷污染。鸡对植酸磷利用率受日粮钙、磷水平和鸡年龄的影响,而钙的影响更大一些。高钙饲粮会抑制植酸磷的降解。在实际生产中为了获取最佳生产性能和骨骼的钙化,一般采用较高钙水平的饲粮,这样植酸磷的降解率很低,消化利用率差（Gilles等,1957;Nelson,1976）。Natt（1967）和Bal-lam（1984）报道,饲粮钙水平为1％时肉鸡对植酸磷的降解率比饲粮钙水平为0.85％时低。 Mo-hammed（1991）报道,饲粮钙从1％下降到0.5％时,肉鸡对植酸磷的降解率增加15％。然而近期的一些研究表明,肉鸡对植酸磷利用率为50％（Edwards,1983;Edwards,1993;Mohammed等,1991）。由上可见,关于鸡对植酸磷利用率的研究主要集中于肉鸡上,而关于蛋鸡对植酸磷利用率的研究很少。本研究的目的,是以商品代北京红产蛋鸡为试验动物,以玉米-豆粕型饲粮为基础饲粮,研究中型产蛋鸡对饲粮植酸磷的消化利用率及饲粮钙水平的影响,为蛋鸡生产中合理添加无机磷和钙提供试验依     

植酸酶在肉鸭低非植酸磷水平饲粮中的应用

饲粮中添加植酸酶已经成为降解饲粮中植酸及其盐类从而提高畜禽对磷利用率、节约磷源矿物质饲料和减少磷排放的有效途径,植酸酶广泛应用于畜禽饲粮配制和养殖生产中。相对猪和鸡,植酸酶在肉鸭饲粮中的应用研究较少。因此,本文综述了在低非植酸磷水平饲粮中添加植酸酶对肉鸭生长性能、骨骼发育和养分利用率的影响以及植酸酶活性与饲粮非植酸磷水平之间定量换算关系方面的研究报道,旨在为肉鸭饲粮配制中科学合理使用植酸酶提供技术支撑和理论依据。     

中型褐壳产蛋鸡饲粮非植酸磷适宜水平的研究

用20周龄的商品代北京红开产蛋鸡150只进行饲养试验和磷代谢试验，研究饲粮非植酸磷水平对20－40周龄阶段蛋鸡产蛋性能、蛋及蛋壳品质、血清生化特性和饲粮植酸磷表观消化利用率的影响，进而从多方面综合评价中型褐壳产蛋鸡的饲粮非植酸磷适宜水平，同时测定产蛋鸡对饲粮植酸磷的消化能力。试鸡按完全随机设计以体重随机分为5个处理组，分别喂以含非植酸磷0．20％、0．25％、0．30％、0．35％和0．40％及含钙量均为3．5％的玉米一豆粕型饲粮。饲粮非植酸磷水平对鸡的产蛋率、蛋重、产蛋量、采食量、饲料效率、蛋壳强度、蛋品哈氏单位、蛋形指数、血清白蛋白、球蛋白和碱性磷酸酶（AKP）活性无明显影响（P＞0．18），而对蛋壳厚（P＜0．04）、蛋壳重（P＜0．07）及植酸磷表观消化率（P＜0．05）有显著影响。蛋壳厚、蛋壳强度及蛋壳重 0．20％非植酸磷水平组最大，此时鸡对饲粮植酸磷的表观消化率高达70．5％，但随饲粮非植酸磷水平的增加，上述4项指标均恒定降低，在0．30％－0．40％非植酸磷水平，蛋壳厚（P＜0．04）和蛋壳重（P＜0．07）明显降低，在0．25％和0．40％时植酸磷表观消化率分别比0．20％水平组降低17．7T和21．4个百分点（P＜0．05）。结果表明，北京红中型褐壳产蛋鸡在20－40周龄阶段的饲粮非植酸磷水平以0．20％（实测值为0．23％）为宜；中型褐壳产蛋鸡对饲粮植酸磷有很强的消化能力。     

中性植酸酶及其基因工程研究

随着饲料工业和养殖业的迅猛发展，饲料中未被消化利用的植酸磷对环境的污染日益严重，能降解植酸磷的植酸酶(myo-Inositol-hexaphosphate phosphohydrolase，EC3．1．3．8)已成为饲用酶制剂研究的热点。以往植酸酶的研究主要集中在酸性植酸酶上，酸性植酸酶适用于胃pH值呈酸性的单胃动物以及少数鱼类如虹鳟等，但不适用于消化道为中性的淡水鲤科鱼类和畜禽消化道中呈中性的部位。     

加工工艺和酶制剂对肉禽高粱型日粮营养价值的影响

高粱作为一种能量饲料被用于畜禽日粮中,能量主要来自自身所含淀粉。因高粱中存在单宁、植酸等抗营养成分和特殊的淀粉-蛋白结构,影响高粱淀粉和蛋白的营养利用率。饲料生产中通过粉碎、调质、制粒、添加酶制剂等工序,达到破坏高粱特殊结构、提高适口性和营养利用率的目的。文章就加工工艺、酶制剂对高粱型日粮营养价值的影响作一综述,为高粱型日粮在肉禽中的应用提供参考。     

饲喂青贮日本饲用高粱代替青贮玉米对绵羊的生长性能及其主要营养物质消化率的比较研究

试验研究青贮日本饲用高粱与青贮玉米型日粮饲喂绵羊后对其生长性能及主要营养物质消化率的影响。选取体重相近[(47.95±4.49)kg]、12月龄左右的健康陶赛特公羊12只,随机分为2组,分别为对照组和试验组,每组6只,隔栏单独饲养;对照组饲喂青贮玉米1.5 kg,试验组饲喂青贮日本饲用高粱1.5 kg,两组羊的其它饲料及喂量相同;进行为期31 d饲养试验,即饲料转化期10 d,生长性能测定21 d,其中包括6 d的消化性能测定。试验结果表明,在生长性能方面,试验组与对照组相比无显著性差异(P>0.05),但试验组的总增重和平均日增重分别比对照组高10.89%和10.71%;在主要营养物质消化性能方面,各组主要营养物质的摄入量、消化量及消化率之间均无显著差异(P>0.05),但试验组干物质摄入量比对照组提高了3.97%(P>0.05),试验组干物质、有机物、中性洗涤纤维、酸性洗涤纤维、粗蛋白质、钙和磷的消化量和消化率均高于对照组(P>0.05)。在本研究条件下,绵羊饲喂青贮日本饲用高粱饲粮在其生长性能及主要营养物质的消化性能方面与青贮玉米有同等的效果。因此,青贮日本饲用高粱代替青贮玉米饲喂绵羊是可行的。     

褐色中脉（bmr）高粱农艺性状与饲用价值

高粱(Sorghum bicolor)是一种适应性强、抗逆性良好的饲料作物。高粱中褐色中脉（bmr）突变可有效降低木质素含量，提高饲用价值，但bmr突变品系在提高饲用价值的同时降低了农艺性状表现。本研究从牧草品质、农艺性状和饲用价值3方面论述了国外bmr高粱研究概况，并对bmr高粱未来研究方向做了展望，旨在为bmr高粱在我国的研究利用提供参考。     

高粱在畜禽日粮中的应用研究

高粱的抗旱性强，比玉米的生长环境条件更宽广。随着玉米、小麦等能量原料价格的高涨，为了降低成本，提高产品竞争力，很多大型饲料企业开始从国外进口高粱。然而，由于高粱中含有丹宁，与玉米相比，用高梁作为饲料原料降低了非反刍动物对能量和其它养分的消化利用率。文章就目前高粱在非反刍动物营养中的研究应用进行了总结。     

Factors affecting starch digestibility with special emphasis on sorghum and corn

Starch exists inside the endosperm of cereals enmeshed in a protein matrix, which is particularly strong in sorghum and corn. Starch digestibility is affected by the plant species, the extent of starch-protein interaction, the physical form of the granule, inhibitors such as tannins, and the type of starch. Among the cereals, sorghum generally has the lowest starch digestibility. The resistance to digestive action of the hard peripheral endosperm layer is largely responsible for this effect. Processing methods such as steam-flaking and reconstitution are effective in raising sorghum digestibility to near that of corn. Waxy sorghum shows consistently higher feeding value than normal sorghum. Both the starch granules and the protein matrix around them are more digestible in waxy grain. The development of new heterowaxy or waxy sorghum hybrids may further increase sorghum feed efficiency.     

糠麸营养价值及其发酵饲料在动物生产中的应用

中国的谷物糠麸产量巨大,但未被充分利用,附加值低。小麦麸的粗蛋白质（CP）、粗纤维（CF）含量较高,吸水性较强,易霉变,易被呕吐毒素污染。米糠CP、粗脂肪（EE）含量较高,但易发生酸败。黑麦麸、燕麦麸、高粱糠的CP含量较高,而玉米皮CP、中性洗涤纤维（NDF）、酸性洗涤纤维（ADF）含量较高。糠麸矿物质丰富,还含有多种活性物质。而微生物发酵能够分解有害物质,增加食品、饲料中活性成分。通过微生物发酵能降低糠麸抗营养因子含量,将无法利用、利用率低的成分分解为易消化的小分子物质,提高蛋白质含量及消化率。目前糠麸发酵使用的微生物主要为霉菌、酵母、乳酸菌、芽孢杆菌,少部分使用食用真菌。研究表明,发酵糠麸富含有益代谢产物,能够为动物提供良好的抗氧化剂、益生菌来源,在合理利用糠麸的同时减少抗生素使用。发酵利用糠麸饲料能够达到一物多用,既降低生产成本,又解决废物排放造成的环境污染问题。作者综述了糠麸的营养价值、发酵菌种、发酵前后变化及其发酵饲料在动物生产的应用,以期为发酵糠麸的应用提供一定依据。     

丙酸钙及其在动物生产中的应用

丙酸钙是一种新型饲料添加剂,近年来在饲料生产、动物生产中的应用越来越广泛。作为一种有机酸盐,丙酸钙不仅作为防腐剂,也常常作为酸化剂在饲料工业中应用,对预防疾病与提高动物生产性能发挥了积极的作用。文中综述了丙酸钙的理化性质与功用,对反刍动物产奶量、消化代谢与代谢疾病预防的影响及其在家禽生产中的应用。     

固态发酵豆粕营养价值及其应用研究

固态发酵法是一种切实可行的提高豆粕营养价值的方法。豆粕是畜禽最重要的植物性蛋白源,但其含有的抗营养因子限制了幼龄动物对蛋白质的有效利用。研究结果表明,发酵豆粕对动物的生长性能、消化和免疫功能具有积极的影响。作者就固态发酵豆粕的营养价值研究及其在动物饲养中的应用进行了综述。     

Intestinal function and gut microflora of broiler chickens as influenced by cereal grains and microbial enzyme supplementation

A study was conducted to investigate the effect of the key cereal grains and a microbial enzyme supplement on broiler chicken performance, gut microflora and intestinal function. Ingestion of the barley-based diet was associated with low 28-day body weight, decreased feed intake and high FCR. The supplemental enzyme increased feed intake and weight gain of the chickens on a wheat-based diet. The pH of the gizzard and caecal contents varied with the grain type. Enzyme supplementation reduced ileal viscosity, particularly in birds that received the diet based on wheat. The birds on the barley-based diet had lower ileal digestibility of dry matter, protein and energy than those given maize and sorghum-based diets. The ileal digestibility of starch was increased by enzyme supplementation. Enzyme supplementation increased the number of total anaerobic bacteria in the gizzard of birds fed on sorghum and increased lactobacilli in the gizzard of those fed both sorghum and wheat. The birds fed the sorghum-based diet had the lowest counts of caecal total anaerobic bacteria and lactobacilli. Jejunal villus height and villus:crypt ratio of birds fed the barley-based diet were the lowest when compared with those fed the other diets. Enzyme application induced an increase in villus height and villus:crypt ratio of birds on wheat, crypt depth on barley and a reduction in crypt depth of chickens on the sorghum-based diets. The highest activity of maltase and the lowest activity of sucrase were observed in tissue from birds fed on maize and sorghum-based diets respectively. The differences in the performance of broilers on cereal grains could be explained by changes in intestinal morphology, enzyme activities and gut microflora as well as nutrient digestibility. The improved performance by supplemental enzyme in wheat-fed chickens was associated with beneficial changes in intestinal morphology and digesta viscosity.     

Nutritive value of fermented and amino acid-supplemented malted sorghum sprouts for growing pigs

Two experiments were carried out to determine the effects of diets containing fermented and amino acid (AA)-supplemented malted sorghum sprout (MSP) on performance, nutrient utilisation and feed cost analysis of growing pigs. In experiment 1 (digestibility trial), 12 pigs were individually housed in metabolic crates, equipped with feeding and watering troughs which also allow for separate collection of faeces and urine. Data collection lasted for 7 days during which feed intake and faecal output were weighed, with daily storage of collected faeces at ?4 °C. Four diets, a basal diet, basal plus malted sorghum sprout (B?+?MSP), basal plus fermented malted sorghum sprout (B?+?FMSP) and basal plus amino acids plus malted sorghum sprout (B?+?AA?+?MSP), were tested. Samples of test ingredients, feed and faeces were analysed for their gross energy and proximate compositions. In experiment 2, 18 weaner pigs were used in a completely randomised design for 63 days to determine the performance and cost analysis of feeding malted sorghum sprout at 0, 100 and 200 g/kg in pig’s diet, six pigs per diet with each pig representing a replicate. Daily feed intake and weekly weight gain were determined. The prevailing cost of each feed ingredient was used to compute the feed cost and, subsequently, the feed cost analysis. Results of digestibility trial showed that there was no difference in the utilisation of the chemical constituents of B?+?MSP and B?+?AA?+?MSP diets, which were also similar to the basal diet, except the crude protein (CP) in amino acid-supplemented malted sorghum sprout diet, which was lower compared to the basal diet. B?+?FMSP was lower (P?<?0.05) in the digestibility of dry matter, organic matter and CP compared to the basal diet. The digestible energy (DE) and the fraction of gross energy utilised as DE of each diet also were not affected by fermentation and supplementation with AA. In experiment 2, the levels of MSP used did not affect (P?>?0.05) the performance and feed cost indices measured. It was concluded that MSP can be used in growing pig’s diet, without the need for fermentation and AA supplementation, at 200 g/kg level with no adverse effect on the nutritive value of the diet.     

Predicting intake and digestibility using mathematical models of ruminal function

Intake and digestibility of feeds by ruminants are influenced by characteristics of the feed, animal and feeding situation. Integration of these characteristics in mathematical models is critical to future progress in forage evaluation and optimal formulation of diets for ruminants. The physiological and physical theories of intake regulation can be described by simple mathematical equations. These equations indicate that intake is a linear function of animal characteristics, such as body weight and production level, and a reciprocal function of feed characteristics, such as fill effect and energy content. Theoretical equations were developed to predict intake when the neutral detergent fiber and energy content of the diet and the energy requirements of the animal are known. The theoretical model also can be used to predict the maximum intake that will maintain a given level of animal production by solving the physiological and physical intake equations at their intersection. Psychogenic intake regulation, which is related to the animal's behavioral response to factors not related to physiological or physical characteristics, can be described mathematically as a multiplier. Digestibility can be predicted by summing the contents of ideal nutritive entities in feeds, which have true digestibilities near 100%, subtracting their associated endogenous losses and adding the variable digestible fiber content. Steady-state models indicate fractional rates of digestion and passage can be used to define ideal nutritive entities and predict digestibility over a range of kinetic characteristics. The steady-state solutions are particularly useful in understanding and predicting the depression in digestibility associated with changes in rates of passage at high levels of feed intake.     

Dry Matter Intake and Apparent Digestibility of Nutrients in the Ration of Mangalarga Marchador Weanling Horses Fed Sorghum Silage Versus Grass Hay

In central Brazil, there are two well-defined climatic periods, the rain and the dry season, the latter being marked by massive forage shortages in pastures. In this context, forage conservation such as making hay and silage for herbivores is imperative during the dry season. Grass hay is most commonly used for horses, but sorghum silage is often used for ruminants. The objective was to compare the nutrient digestibility, fecal production, and dry matter intake (DMI) of sorghum silage (Sorghum bicolor l. Moench CV. BRS 655) to that of vaquero hay (Cynodon CV. 90160 CD × CV. Mirage). Twelve Mangalarga Marchador fillies (8 months of age) were divided into two groups: S (sorghum silage, n = 6) and F (vaquero hay, n = 6). The ration was formulated to supply 3.0% body weight in dry matter (DM) per day, with a forage:concentrate ratio of 50:50 on a DM basis. The concentrate used was a corn-based ration formulated to meet or exceed requirements for growth when fed at 1.5% body weight DM to young horses. The animals were housed in individual stalls (3 × 3m) for a period of 25 days, with 21 days for adaptation, followed by 4 days of total collection of feces. During the collection period, an external marker of digestibility, Purified and Enriched Lignin (LIPE), was added to the concentrate as an external marker to determine the apparent digestibility coefficients of DM, crude protein, gross energy, neutral detergent fiber, acid detergent fiber, hemicelluloses, and cellulose. The forage DMI was calculated by subtracting the quantity supplied at each meal minus the amount of forage that was not eaten by the next meal (orts). The measures of digestibility of the sorghum silage were not different (P > .05) from that of vaquero hay. However, DMI of the sorghum silage was lower (P < .05) than the vaquero hay and may be of concern if fed for prolonged periods of time and not supplemented with carefully balanced concentrates. Purified and Enriched Lignin can be used as a marker for evaluation of digestibility of nutrients in weanling horses.     

Invited review: Amino acid bioavailability and digestibility in pig feed ingredients: terminology and application

In this review, the terminology that is used to describe the bioavailability and ileal digestibility of AA in pig feed ingredients is defined. Aspects of the methodology to establish bioavailability and ileal digestibility values also are discussed, and recommendations about the use of these values are provided. Two main factors can contribute to differences between bioavailability and ileal digestibility of AA. First, some AA, such as Lys, may be absorbed in chemical complexes that preclude their use for metabolism. Second, fermentation in the upper gut may result in a net loss or gain of AA to the animal. In addition, dietary effects on the efficiency of using bioavailable AA intake for tissue growth or milk production should be considered and may be attributed to endogenous AA losses in the hindgut and the metabolic costs associated with endogenous gut protein synthesis and losses. Ileal digestibility values may be expressed as apparent ileal digestibility (AID), standardized ileal digestibility (SID), or true ileal digestibility (TID). These terms are used to specify how ileal endogenous AA losses are reflected in digestibility values. Ileal endogenous AA losses may be separated into basal losses, which are not influenced by feed ingredient composition, and specific losses, which are induced by feed ingredient characteristics such as levels and types of fiber and antinutritional factors. Values for AID are established when total ileal outflow of AA (i.e., the sum of endogenous losses and nondigested dietary AA) is related to dietary AA intake. A concern with the use of AID values is that these are not additive in mixtures of feed ingredients. This concern may be overcome by correcting AID values for defined basal endogenous losses of AA, which yields SID values. Furthermore, if the AID values are corrected for basal and specific endogenous losses, then values for TID are calculated. However, reliable procedures to routinely measure specific endogenous losses are not yet available. It is recommended that basal ileal endogenous losses of AA should be measured in digestibility experiments using a defined protein-free diet and that these losses are reported with observed AID and SID values. It is suggested that SID values should be used for feed formulation, at least until more information on TID values becomes available.