尼龙袋技术评定饲料营养价值研究进展

饲料营养价值的准确评价是研究动物营养需要和进行日粮配方的前提和基础。在评定饲料营养价值诸多的方法中,尼龙袋法(技术)(NylonBagTech-nique,NBT)由于和动物的消化过程紧密结合,其测定结果同体内试验具有良好的可比性,且重复性好、操作相对简单,便于大批样品的研究,在评定饲料营养价值(特别是蛋白质和氨基酸营养)方面被广泛采用,有人(Orskov和McDonald,1979;Kristensen等,1982;AFRC,1992;Wilkersonetal.,1995)还提议建立尼龙袋法的饲料养分标准数据库。但是,尼龙袋法由于受试验材料、操作程序、试验动物内环境等诸多因素的影响而造…     

瘤胃尼龙袋法测定10种饲料过瘤胃淀粉量和淀粉瘤胃降解率

以3头安装有永久性瘤胃瘘管的利木赞×鲁西黄牛杂交阉牛为试验动物,采用尼龙袋法对大麦、麸皮、玉米、玉米DDGS、苹果粕、大豆皮、豆粕、苜蓿干草、青贮饲料、羊草等10种饲料原料中淀粉的瘤胃降解率和过瘸胃淀粉含量进行测定.结果表明,10种饲料的过瘤胃淀粉量依次为60.37、17.98、216.23、9.23、14.18、6.13、18.22、8.11、3.78 g/kg和2.77 g/kg;其淀粉瘤胃降解率依次为90.57%、92.32%、64.37%、78.95%、84.18%、86.30%、70.93%、66.43%、72.19%和65.08%.总之,大麦等能量饲料的过瘤胃淀粉含量较高,苜蓿等粗饲料的过瘤胃淀粉含量较低,副产品饲料和蛋白质饲料过瘤胃淀粉含量居中.     

Adaptation of the rumen microbial population to native potato starch degradation determined with the gas production technique and the nylon bag technique

Experiments were conducted to investigate the influence of the adaptation of rumen micro-organisms on the degradation of native potato starch (PS) in the rumen. Cows were fed with rations used for gas production (GP) analysis (dry cows, 1.6% starch) and for the nylon bag (NB) technique (lactating cows, 23% starch, mainly maize starch) and a ration containing 19% native PS (lactating cows). Fermentation characteristics of 13 samples were investigated with the GP technique using rumen fluid from cows fed each of the three rations. The same samples were investigated with the NB technique in the cows obtaining the NB ration and the PS ration. The results showed that the rate of GP was influenced by the source of the rumen fluid. The fermentation rate of PS was considerably enhanced by using rumen fluid adapted to the fermentation of native PS instead of using the other rumen fluids. Incubating in cows fed the PS ration, the rate of PS degradation determined with the NB technique, was higher compared with cows fed other rations. Using the PS ration the observed lag period for PS was shorter. The results show a clear influence of ration on the degradation characteristics of starch, determined with both the GP technique and the NB technique. However, these changes in behaviour did not explain observed differences in amounts of rumen escape PS measured in vivo in animal experiments and in situ, using the NB technique.     

利用瘤胃尼龙袋法评定添加麦芽根的啤酒糟发酵饲料的品质研究

用麦芽根调节啤酒糟的水分含量,配制含水量为50%的发酵原料,进行袋装发酵贮藏,分别在0、30、60、90、120d开袋取样,用瘤胃尼龙袋法研究的结果表明,不同发酵天数的饲料在奶牛瘤胃中DM、OM、NDF的消失率随着样品发酵时间的延长均呈上升的趋势,发酵处理的饲料此3项指标都显著高于未处理饲料,其中发酵120d的饲料效果最好,表明用麦芽根按一定比例调节鲜啤酒糟水分含量后的发酵饲料不仅可以较长时间保存,而且可以改善啤酒糟营养价值。     

The evaluation of the mobile nylon bag technique for determining the apparent protein digestibility in a wide variety of feedstuffs for pigs

Studies were conducted with four (50 to 70 kg) barrows to evaluate the mobile nylon bag technique (MNBT) for determining the apparent protein digestibility (AD) in a variety of feedstuffs. One-gram samples of each feedstuff, ground through a 1.0-mm mesh screen, were enclosed in nylon bags (25 X 40 mm; 48 microns mesh). Following predigestion (.01 N HCl; 4,000 Folin Intestinal Pepsin Units/liter), four bags of each sample were inserted into each pig via a duodenal T-cannula. The indigested contents were pooled within pig and feedstuff prior to crude protein analysis. The AD of each feedstuff was determined previously with four barrows according to the conventional method (CM), based on a 5-d total collection of feces following a 14-d adaptation period. The following results, AD (%), were obtained with the MNBT (n = 4) and CM (n = 4), respectively. Barley, 70.1 vs 81.2 (P less than .05); corn, 72.3 vs 82.1 (P less than .05); wheat, 79.6 vs 86.4 (P less than .05); corn gluten feed, 73.9 vs 70.9; rice bran, 57.3 vs 57.4; wheat middlings, 70.8 vs 79.4 (P less than .05); soybean meal, 89.9 vs 93.0; a mixture of soybean meal and hulls, 86.9 vs 88.8; coconut expeller, 65.0 vs 69.8; fababeans, 79.5 vs 78.5; peas, 87.6 vs 88.1; meat meal, 83.2 vs 84.0; complete diet (4.3% crude fiber), 76.3 vs 83.6 (P less than .05); and complete diet (13.6% crude fiber), 56.5 vs 55.0.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of undegradable intake protein digestibility of forages using the mobile nylon bag technique

Two experiments were conducted using 2 ruminally and duodenally fistulated steers to determine the digestibility of undegradable intake protein (UIP) of smooth bromegrass (Bromis inermis), birdsfoot trefoil (Lotus coniculatus L.), and heat-treated alfalfa (Medicago sativa) using the mobile nylon bag technique. Undegradable intake protein was determined using neutral detergent insoluble CP at a single in situ incubation time point based on 75% of the total mean retention time estimated from IVDMD plus a 10-h passage lag. In Exp. 1, UIP (% DM) of smooth bromegrass in June and July were 1.82 and 1.71, respectively (P = 0.11). Undegradable intake protein (% DM) of birdsfoot trefoil increased from 1.30 in June to 1.94 in July (P < 0.01). Total tract indigestible protein of smooth brome-grass and birdsfoot trefoil increased in July (P < 0.05). Digestibility of UIP decreased in July for smooth brome-grass (P < 0.01) but tended to increase for birdsfoot trefoil (P = 0.07). In Exp. 2, alfalfa from plots fertilized with low (66 kg of N/ha) or high (200 kg of N/ha) amounts of N were dried to simulate 3 preservation methods: dehydrated (100 degrees C, 10 h), sun-cured (50 degrees C, 15 h), and lyophilized (-50 degrees C, 72 h) alfalfa. Undegradable intake protein (% DM) was estimated as in Exp. 1 and was 3.13, 2.10, and 1.84 for dehydrated, sun-cured, and lyophilized alfalfa, respectively. Total tract indigestible protein (% DM) was increased (P < 0.05) for dehydrated alfalfa (1.66) compared with sun-cured (1.54) or lyophilized (1.57) alfalfa. As a result of greater UIP flow to the lower tract, digestibility (%) of UIP was greater (P < 0.01) for dehydrated (46.4) than for sun-cured (25.6) or lyophilized (14.7) alfalfa. Heat-treated alfalfa samples increased net UIP absorption in the lower tract because 1.47, 0.56, and 0.27 percentage units of UIP (% DM) of dehydrated, sun-cured, and lyophilized alfalfa, respectively, disappeared. Overall, the digestibility of the UIP of these forages was low in the lower tract.     

体外产气法与尼龙袋法评定粗饲料干物质降解率的相关性分析

为寻求可在实验室条件下简单地评定饲料降解性能的方法,试验以玉米秸秆及不同尿素、石灰比例复合处理的玉米秸秆为发酵底物,对饲料体外产气量和尼龙袋瘤胃干物质降解率作了相关性分析。统计分析表明,体外产气量与体内干物质降解率呈高度正相关,相关系数分别为:对照组0.967、料A0.964、料B0.999和料C0.994。结果证明,在对饲料降解性能及潜在可降解能力作快速、定性判断时,体外产气法可以代替尼龙袋法。     

尼龙袋法评定单胃动物饲料营养价值研究进展

饲料营养价值的准确评价是研究动物营养需要和进行日粮配方的前提和基础。在评定饲料营养价值的方法中,尼龙袋法（Nylon Bag Technique）和动物的消化过程紧密结合,其测定结果同体内试验具有良好的可比性,且重复性好、操作相对简单,便于大批样品的研究,在评定饲料营养价值（特别是蛋白质和氨基酸营养）方面被广泛采用．Orskov和McDonald等还提议建立尼龙袋法的饲料养分标准数据库。     

Determination of the digestibility of lignocellulose material using the bag (nylon bag) method

A trial was performed on wethers to study the digestibility of various lignocellulose materials (LCM) by the nylon bag method. The animals were fed good meadow hay ad lib. with unlimited access to water and mineral lick. The trial showed that LCM digestibility was not influenced by different weights of substrate sample. However, digestibility increased with the time for which the LCM were left to ferment in rumen. Almost 90% or more dry matter of the different substrates (pure sulphate cellulose, barley straw and treated beech sawdust) was digested within 48-hour fermentation in rumen. The situation is similar when the substrates are left to ferment in vitro for 96 hours. The high correlation coefficients calculated from the digestibility values of the substrates in vitro and in vivo testify to this fact. The only exception is untreated beech sawdust in which no such a high correlation was found, mainly owing to its low digestibility. However, this should be verified in other kinds of untreated wood (aspen, maple, ash), but with a higher digestibility. It should be stated that silk with a 50 mu mesh is the best material for the production of the bags.     

An ocular technique for estimating utilization of karoo bushes

A subjective technique for estimating utilization of karoo bushes is evaluated and guidelines for its use are proposed. Taking the average utilization from estimates on 30–40 bushes, 20% differences in utilization could be distinguished as significant ‐ even when different operators were used. Zero and 100% levels of utilization were judged with greater accuracy and precision than intermediate levels. However, if more than 30 bushes are taken per sample the precision and accuracy at all levels is adequate. Acceptable levels of accuracy were obtained with fewer bushes than that required for adequate precision. Using similar sample sizes the ocular‐estimation technique was more precise and more accurate than objective techniques. Furthermore, this technique was far more efficient than any of the objective techniques.     

Evaluation of mobile nylon bag technique for determining apparent ileal digestibilities of protein and amino acids in growing pigs

The mobile nylon bag technique (MNBT) may offer a simple, rapid means for assessing ileal AA digestibility of pig feed ingredients. In the present study, the effects of washing bags recovered from digesta, the amount and fineness of feeds, and feed trypsin inhibitor activity on apparent ileal digestibilities (AID) of CP and AA were determined with the MNBT. Twenty-four ileorectal anastomosed pigs (Yorkshire x Chinese Black barrows, 30 kg initial BW), of which 12 were fitted with duodenal T-cannulas, were used. Not washing the bags recovered from ileal digesta resulted in a reduction (P < 0.05) in apparent ileal digestibilities of CP and AA determined by MNBT. Washing the bags for more than 4 min overestimated (P < 0.05) the apparent ileal digestibilities of CP and AA compared with those determined with the anastomosed pigs. Sample size and fineness of grinding also affected (P < 0.05) apparent ileal digestibilities of CP determined by MNBT. The apparent ileal digestibilities of CP determined by MNBT were reduced (P < 0.05) when sample size exceeded 0.75 g and when feed was ground through screens with a mesh size of more than 1.0 mm. The closest agreement between results obtained by MNBT and a conventional ileal digestibility assay occurred when 0.75 g of feed ground through a 1.0-mm mesh screen was used per bag and bags were washed for 2 min after retrieval from digesta. Further studies are warranted to investigate the use of the mobile nylon bag technique for predicting the ileal digestibilty of AA for feeds containing antinutritional factors.     

Comparison of mathematical models to describe disappearance curves obtained using the polyester bag technique for incubating feeds in the rumen.

Different nonlinear models were evaluated as candidates to describe ruminal degradation kinetics of forages from data obtained by the incubation of the feeds in the rumen using polyester bags. Nine models were used: segmented model with three straight lines (Mod0); simple Mitscherlich or exponential (Mod1); inverse polynomial (Mod2); compartmental model with two exponential terms (Mod3); generalized Mitscherlich (Mod4); generalized Michaelis-Menten (Mod5); logistic (Mod6); Gompertz (Mod7); and generalized Von Bertalanffy (Mod8). All these models can be represented in the general form D = W + S0 x phi(t), where D is in situ disappearance at incubation time t, W and S0 are positive scalars, and phi is a positive monotonically increasing function unique to each of the models studied. Based on first principles, a general formula for calculating the extent of degradation of feeds in the rumen has been derived that is applicable to all the models. The disappearance curves of different feed components (DM, N, and NDF) of 87 Mediterranean forages (i.e., a total of 261 curves) were fitted to all the models. A comparative study was carried out based on the mathematical, statistical, and biological characteristics of the models. Flexible models that can accommodate both diminishing returns and sigmoidal behavior were more appropriate in describing the curves. A discrete-lag parameter was introduced into Mod0, Mod1, and Mod2 to describe the initial stage of the disappearance curve, and this parameter considerably improved the fit of experimental data. Based on statistical criteria, models Mod1, Mod4, Mod5, and Mod8 were better than the others for most statistical tests and disappearance curves, but differences among these four models were not consistent. The estimates of degradation parameters to quantify the rate (half-life, fractional degradation rate), and extent (undegradable fraction, effective degradability) of ruminal degradation of feeds were also used as a means to discriminate between models, although in most cases all of the models gave similar values of the degradation parameters. In particular, when the extent of degradation was calculated for each forage and feed component, differences between the estimates obtained with the different models were of little nutritional significance for the animal.     

ORIGINAL ARTICLE: Ruminal and total tract phosphorus release from feedstuffs in cattle measured using the mobile nylon bag technique

Phosphorus (P) excretion in manure is a concern for dairy and beef producers. Excess P released into surface water runoff can lead to eutrophication and algal blooms in streams and lakes. One approach to reducing P excretion is to reduce dietary P. Data regarding P release from feedstuffs is limited and more precise formulations based on specific feed P release in the digestive tract may be one way to lower excreted P. In this experiment, the mobile nylon bag technique was used to determine the disappearance of P in corn silage, alfalfa hay, Coastal bermudagrass hay, and Tifton‐85 bermudagrass hay in steers after ruminal (24 h), ruminal + pepsin/HCl (rumen + PHCl), and ruminal + pepsin/HCl + intestinal (rumen + PHCl + I) incubation. Ruminal disappearance of P differed (p < 0.05) between feedstuffs and by site of incubation. Total tract (rumen + PHCl + I) P disappearance for corn silage, alfalfa hay, Coastal bermudagrass hay, and Tifton‐85 bermudagrass hay were 90.6%, 93.7%, 83.8% and 84.0% respectively. The range in P release (approximately 7%) indicates that considering P availability when balancing rations could have a measurable impact on subsequent P excretion from ruminants. More data concerning P availability as affected by other feed ingredients or plant species, maturity, and/or quality are needed to more accurately define P release from ruminant feeds.     

利用体外培养法建立饲料营养成分与瘤胃丙酸产量的回归模型

根据美国康乃尔净碳水化合物和蛋白质体系 (CNCPS) ,分析测定了 4类 2 4种饲料的营养成分 ,利用体外批次培养技术测定了它们在体外培养一定时间后的丙酸产量 ,并由此建立了饲料中产丙酸的营养成分和瘤胃丙酸产量的回归方程     

瘤胃淀粉消化率及消化动力学的研究方法评述

文章探讨了研究瘤胃淀粉消化率及消化动力学的方法存在的缺陷。淀粉消化位点及该位点的消化率对反刍动物从消化道吸收养分的数量和形式具有重大影响。通过皱胃或十二指肠瘘管收集的食糜样品缺乏代表性,而双相指示剂法也不能完全解决这个问题。原位法被广泛应用于瘤胃淀粉消化速率的测定,但关于从尼龙袋中消失的物质被发酵的假设仍有待商酌。并且,原位法一次函数的假设也受到质疑,说明根据消化动力学参数估计瘤胃淀粉消化率的模型需要完善。体外法以反应体系中淀粉消失率或产气量为基础来评估淀粉消化速率,其重要前提是淀粉消化速率不能受反应体系限制。     

人工瘤胃发酵调控技术研究进展

~~人工瘤胃发酵调控技术研究进展$安徽农业大学@吴宏忠!邮编:230036 $安徽农业大学@张伟力!邮编:230036 $中国科技大学@胡真虎 $中国科技大学@余汗清     

Effect of diet composition and feeding pattern on the prececal digestibility of starches from diverse botanical origins measured with the mobile nylon bag technique in horses

This trial was conducted to determine the extent of prececal starch digestibility depending on the botanical origin of starch and on diet characteristics (i.e., composition and feeding pattern). The prececal disappearance of six substrates (oats, barley, corn, horse bean, potato, and wheat) was measured in four cannulated horses fed (as-fed basis) 11.8 g/kg BW of a high-fiber (HF) or high-starch (HS) pelleted feed and 10.0 g/kg BW of meadow hay using the mobile bag technique (MBT). The daily feeding pattern was either three meals (two meals of pellets and one meal of hay) or five meals (three meals of pellets and two meals of hay). The experimental procedure was a 2 x 2 factorial arrangement tested in a Latin square design. After 2 wk of adaptation to the diet, collections were made on 5 d. Thirty nylon bags, composed of five bags of each substrate, were intubated to each horse during the ingestion of the morning meal. Bags were collected in the cecum, using a magnet, at 9 h postintubation. In spite of strong interindividual differences, approximately 80% of the intubated bags were collected. On average, the mean retention time of the bags was 6.2 h (+/-0.17). Regardless of the feeding pattern, the transit of the bags was faster when the fiber content of the diet was higher (P = 0.003). Likewise, regardless of the meal composition, transit was also faster when the ration was split into five daily meals (P = 0.001). The DM disappearance, corrected with particulate losses (DMD(c)), differed depending on the substrate tested (33.5, 57.1, 63.8, 67.7, 78.6, and 86.2% for potato, horse bean, oats, barley, corn, and wheat, respectively; P = 0.001). The DMD(c) of corn, barley, and potato was higher when HS was fed (P = 0.020); regardless of the substrate, DMD(c) was higher with five daily meals (P = 0.001). The starch disappearance (StarchD(c)) was different depending on the substrate (P = 0.001; 36.1, 71.2, 86.6, 89.2, 99.0, and 99.7% for potato, horse bean, barley, corn, wheat, and oats, respectively). Whatever the substrate, StarchD(c) was higher when HS was fed (P = 0.007), but it was not affected by the feeding pattern of the diet. Although passage rate was modified and feed intake was different, the botanical origin of starch was the main factor that affected prececal starch disappearance in horses.     

A technique for sampling total rumen contents in sheep

The paper describes the manufacture of an easily removable large rumen fistula closure for sheep and a restraining cradle which is used when sampling total rumen contents. Eight sheep have been fitted with the fistula and have been used regularly for nine months. The technique is rapid and simple and the closure is more reliable than other types which are often removed accidentally.