和gbmmr“關于棉、菜粕在牛料中的使用”一文的商榷

yangzhaojun

常看到關于牛料配方的問題，覺得在原料使用方面有些心得，寫出來給大家個思路，請諸君斧正。

進入產奶期的奶牛瘤胃菌群穩定，本質上添加多少棉粕沒有限量，除非影響到整個日糧結構，比如只有棉粕，連玉米或者麥麩都沒有。

需要注意，棉粕不是直接給牛吃的，而是給瘤胃微生物吃的，微生物主要形成菌體蛋白，和棉粕本身有多少氨基酸或者氨基酸是否平衡也沒有本質的關系，除非你認為這些棉粕是過瘤胃的。

不論棉粕或者豆粕，都是微生物的良好的蛋白質來源，甚至于尿素，他們都主要用于菌體蛋白或者纖毛蟲形成的蛋白質，豆粕是否比棉粕更有優勢，不取決于豬的研究結果，盡管豆粕用于豬比棉粕好，單用時更多取決于他們如何提供氮源和硫源，就是氮硫比。

菜粕含有更高的硫蛋白，適當的配合菜粕，比單純的增加豆粕可能效果好的多。

不用擔心是否棉粕或者菜粕是否含有更高的毒素或者抗營養因子，那沒有實際的意義，取決于他們是不是使瘤胃的細菌死掉了或者纖毛蟲死掉了，他們多數都將被降解，能形成的危害可以忽略。

反而生的未經熟化的大豆更有危害，尤其和尿素一起使用時，會導致奶牛的尿素中毒，而棉粕和菜粕是不會的。

用牛的眼光看，不要用豬的眼光看，它們就有了合適的價值！


@@007: 偶的觀點：

    在很大程度上我贊成上文作者gbmmr的觀點。
    但對反芻動物來講，仍然存在蛋白質質量的問題，而不單純是看這種原料能提供氮源的多少，否則我們只用尿素不就可以了嗎，還省很多錢。按照康奈爾凈碳水化合物和凈蛋白質體系，蛋白按其在瘤胃中的降解速度分為A、B、C三部分：
                           A、快速降解蛋白，Kd（降解速率）認為無窮大
                           B、潛在降解蛋白
                           C、不可降解蛋白

    這里牽涉到能氮降解平衡的問題，當能量和蛋白質的降解相匹配時，微生物增殖最快，效率最高。然而能量（碳水化合物）的降解往往滯后于蛋白質，所以我們在做奶牛日糧必須選擇合適降解速率的蛋白質來配合能量的降解，而尿素純粹屬于快速降解蛋白，這也是尿素為何不能多用的原因之一。

   下面列幾種常見蛋白原料的蛋白質組成:

原料	A	B	C	Kd
豆粕	8.7	91.3	0	2.4
菜粕	23.4	69.2	7.4	13.1
棉粕	25.6	55.5	18.9	6.8
亞麻粕	19.3	59.7	21	5.3
花生粕	61.7	36.6	1.7	16.1
DDGS	28.5	63.5	8	3.6

     從上表可以看出，豆粕蛋白中B組分最高，且Kd最小，所以對反芻動物來講，豆粕仍然是最好的蛋白源，我們在做奶牛日糧是很少選用豆粕，那還是因為成本的問題，而且我們不使用豆粕也可以做到瘤胃能氮平衡，從而使奶牛發揮好的生產性能。
    從上表還能看出，花生粕降解速度很快(Kd值很大)，A組分含量也很高，所以做奶牛日糧時要慎重使用。高劑量使用花生粕短期有增奶效果，時間長了，會使奶牛迅速消瘦。
   另外，甜菜粕和棕櫚粕的蛋白質量對奶牛來說也是非常好的，可以考慮在日糧中使用。

建玲

用牛的眼光看，不要用豬的眼光看，它們就有了合適的價值！

李良彬

很棒！！！真正從營養學的角度來解釋，高手！

billy.yu

有沒有關于葵花粕應用的資料啊 ？

矮子

1# yangzhaojun

在yahoo找了一篇Ørskov寫的原文：

Use of the nylon bag technique for protein and energy evaluation and for rumen environment studies in ruminants

E R  Ørskov and W J Shand

International Feed Resource Unit, The Rowett Research Institute,
Greenburn Road, Bucksburn, Aberdeen, AB21 9SB, UK

Abstract
The nylon bag technique is a very robust and powerful tool with which to study several aspects of nutrition in ruminants. It is particularly useful in describing degradation characteristics of protein and roughages and also for rumen environment studies. For each purpose a slightly different approach has to be used. This article explains how this is best achieved.

Key words: Rumen, nylon bag, digestibility, degradation characteristics, gas production

Introduction
We have been asked to write a small article relating to the nylon bag technique and interpretations of results. Complications sometimes occur as the technique is used for different purposes, namely protein evaluation, roughage evaluation and evaluation of rumen environments. We would like to treat each one in turn.

Protein evaluation
The dynamic nylon bag procedure was first developed to estimate degradability of protein and for this a formula was developed ( Ørskov and McDonald 1979)

p = a + b (1 - e-ct) (1)

where Ap@ is degradation at time At@ and Aa@,@b@ and Ac@ are constants and Ae@ is the basis of the natural logarithm. The equation was particularly useful since the constants had a biological meaning, Aa@ being the intercept or the immediately soluble fraction, Ab@ the insoluble but rumen degradable fraction, and Ac@ the rate at which the insoluble rumen degradable fraction is degraded. It follows that 100 - (a + b) is the total rumen undegraded fraction. Part of this fraction, depending on the protein source, will be degradable in the small intestine.

Figure 1: Loss of protein from nylon bags at intervals during 72 hours

Let us construct a situation (Figure 1) in which bags are withdrawn at intervals of 2, 4, 8, 16, 24, 48 and 72 hours and the protein disappearance values are 41.5, 49.6, 59.0, 69.5, 74.8, 75.6 and 75.8 then Aa@ = 32.1, Ab@ = 44.0 and Ac@ would be 0.1229 respectively and the residual standard deviation, 0.71. In other words the data fitted the formula well.

The next problem was that since protein supplements consist of small particles which are small enough to leave the rumen, these particles could escape the rumen so that two possibilities existed: an insoluble particle entering the rumen could be degraded, depending on the degradation rate Ac@ or it could flow out, depending on the outflow rate, here denoted as Ak@. In order to describe this we coined the word effective degradability AP@ representing that which was actually degraded in the rumen. This was expressed by:

P = a + b (c/(c + k)) (2)

It can be seen that as Ak@ or outflow rate increases AP@ will, of course, decrease. Let us for example use three values for Ak@ in the equation above namely 0.02, 0.05 and 0.08 which gives effective degradabilities of 69.9, 63.4 and 58.8, respectively.

It must be remembered that this formula should only be used when the feed consists of small particles. For long forage particles it is not applicable, since the time taken to reduce long to small particles by chewing, and microbial disintegration, is not taken into account and this is likely to vary between feeds. For protein supplements therefore it is quite simply the use of formulae 1 and 2.

Roughage evaluation
For several years the 48 hour degradability was used as an approximation to in vivo digestibility and for this it is still used. However, it has since been realised that some of the plant factors affecting consumption of roughages could also be identified by the dynamic nylon bag approach, namely the soluble, the insoluble and fermentable fractions, and the rate at which the insoluble material is fermented. However, here there is a complication which is not so apparent for protein supplements, namely a lag phase when microbes become attached to the fibrous material during which time there is no net disappearance of substrate. In fact, there may even be an increase in weight during the first 2-4 hours. On the other hand the soluble material will disappear rapidly.

There are different ways of dealing with this. In our laboratory we have chosen the following approach. Due to the lag phase, during which time there is no net disappearance of substrate, the Aa@ value in the equation (ie: the extrapolated value) could be negative. As an example, take the situation where samples are removed at 8, 24, 48, 72 and 96 hours after incubation and the typical disappearance values (%) for a roughage are 17.0, 42.1, 51.6, 55.3 and 56.2.

Applying the formula p = a + b (1 - e-ct) gives Aa@ = -7.9, Ab@ = 63.8, Ac@ = 0.0622. RSD = 0.94. Obviously, the solubility cannot be negative. This predicted negative value is due to the lag phase.
Solubility can be determined by different methods such as washing nylon bags, containing the substrate, without incubation in the rumen. This value is called AA@, the value for solubility determined in the laboratory. It is clear that (a + b) represents the asymptote (ie: the maximum potentially fementable material). It is then easy to appreciate that the asymptote (a + b), less the solubility AA@, represents the insoluble but fermentable material. This is called AB@ to distinguish it from Ab@ which is from the mathematical expression. Ac@ is the same as the rate constant generated from the equation. For roughage evaluation therefore the situation is:

A = solubility
B = (a + b) insoluble but fermentable
c = rate constant

From the previous example AA@ was 10.6% thus AB@ = (-7.9 + 63.8) -10.6 = 45.3 and Ac@ is 0.0622. In some trials, multiple regressions using AA@, AB@ and Ac@ have been closely related to feed intake, digestibility and animal performance but more information is required from trials in which both feed intake and degradation characteristics are determined for less conventional feeds such as the leaves from trees and shrubs.

Should incubation periods be different for roughages? Ideally the first bag should be withdrawn only after the lag phase is completed. It is advisable not to withdraw any bags from the rumen before 8 hours. It is essential also that the asymptote is well described (ie: the differences between the losses for the last incubation periods must be small, no more than about 5% of the final value), otherwise the asymptote will be extremely inaccurate and sometimes incubation periods of up to 120 hr are required.

In order to rank the intake potential of the feeds an index value has been derived from regression equations using AA@, AB@ and Ac@ as independent variables to predict intake. The index derived from a number of roughages was:

Index value = A + 0.4*B + 200*c.

These coefficients will be different for different groups of feeds. For cattle in Europe it seems that an index value of about 30 is needed to achieve maintenance energy intake.

The index value of the feed described previously is:

10.6 + 0.4*45.3 + 200*0.0622 = 41.1.

Evaluation of rumen environment
In the above examples it was assumed that the rumen environment was optimal. The substrate is varied and it is assumed that there is an optimal rumen environment. The nylon bag method can also be used to determine the optimal concentration of NH3, S or the optimal pH. In this case the approach is to vary the rumen environment but keep the incubated substrate constant. As standard substrates one can use ground straw, soya bean hulls or other uniform cellulosic substrate. Sometimes it is useful to wash the soluble material out of the substrate as this material will disappear, regardless of the rumen environment.

It must be understood that the rumen environment will not affect AA@ nor the asymptote but it will affect the time taken to reach the asymptote. In other words it is the Ac@ value that will be sensitive to the rumen environment.

The nylon bag technique is a very powerful and robust tool but it is important to understand the purpose for which it is to be used: for evaluating protein supplements or roughages, or for evaluating dietary effects on the rumen environment.

The gas production method
A complementary tool to the nylon bag method is the gas evaluation technique in which substrate is incubated in syringes and the gas produced is measured at intervals of time. The same equation as above [p = a + b (l - e-ct)] can be used and the gas produced at intervals can be used to evaluate feeds. Many comparisons of the two techniques have been published (see Blummel and  rskov 1993). The gas production method can also be used to evaluate antinutritive factors targetting microbes, in so far that complexing agents like polyethylene glycol (PEG) can be added to the substrate and the gas production with and without complexing agents can be used to measure the presence of microbial anti-nutritive factors.
References
Blummel M and Ørskov E R 1993 Comparison of in vitro gas production and nylon bag degradability of roughages in predicting feed intake in cattle. Animal Feed Science and Technology, 40: 109-119.
Makkar H P S, Blummel M and Becker K 1995 Formation of complexes between PVP or PEG and tannins, and their implication in gas production and true digestibility in in vitro techniques. British Journal of Nutrition, 79: 897-913.
Ørskov E R and McDonald I 1979 The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage. Journal of Agricultural Science, Cambridge. 92: 499-503.

文中第一個公式的a指快速溶解部分，b指不溶解但在瘤胃可降解部分，c指不溶解但在瘤胃可降解部分的降解速率，p應是某個培養時間的降解率。

文中第二個公式的k指外流速率，P指有效降解率。

粗飼料評定的ABC與第一個公式的相同。

對LZ列出的Kd，以前見過，沒有查詢，不便評論。

原文提出“用牛的眼光看，不要用豬的眼光看，它們就有了合適的價值！”，根據文章的內容，只能說用低中產奶牛的眼光看，用棉菜粕替代全部或大部豆粕可能可行。但是用豬的眼光看更為可行，如果有無腺體棉粕或雙低菜粕，只需添加合成限制性氨基酸，肉豬生長與豆粕日糧基本相同。如果是普通棉粕，添加亞鐵脫毒，然后添加合成限制性氨基酸；對于普通菜粕，只要脫毒，就能和棉粕一樣使用，用棉菜粕替代全部或大部豆粕飼喂肉豬可能可行。說明一下，非瘤胃保護限制性氨基酸對奶牛產奶量沒有任何效果。

歡迎同行們評論！！！

矮子

E R  Ørskov 不被識別，只好申明英文為E R Orskov。

呵呵！！！

yangzhaojun

請參見NRC奶牛營養需要，Kd是潛在降解組分B的降解速度，而Kp是外流速度。

mzscym

在國內，采用亞硫酸鐵來脫毒理論是可行的，但是在生產中難以推廣使用，從國內外相關研究進展來看，當前只有通過育種能降低棉酚的含量，但是從植物的天然防御特性來看，通過育種降低了棉酚，結果卻導致了一些對棉花生長有害的害蟲快速生長，使棉花的生產效益下降，所以這些低棉酚品種未能在全世界大面積推廣。如果全部采用未脫毒棉粕替代豆粕，結果會導致飼料消失率下降，導致瘤胃內VFA總量降低，該方面可以參照國外相關文獻。
理論而言,瘤胃微生物有脫毒功能，但并非能對全部的棉酚降解，目前這種脫毒是由瘤胃微生物本身功能所致，還是因棉酚與瘤胃中游離蛋白結合所致，還有很大爭議。個人認為，過多的棉酚仍可以影響反芻動物的肝臟代謝與奶牛的繁殖性能，并通過影響瘤胃微生物生理與代謝來影響整體瘤胃發酵，進而對宿主生理產生有害作用。所以建議在奶牛的飼料最好不要全部使用棉粕作為蛋白原料，而應添加適量豆粕。這樣無論從動物福利與動物生產效益來看，對奶牛自身皆是有益的。

矮子

請參見NRC奶牛營養需要，Kd是潛在降解組分B的降解速度，而Kp是外流速度。
yangzhaojun 發表于 2009-2-9 08:43

In the 2001 dairy NRC, feed protein supply is divided into two fractions: rumen degraded protein (RDP) and rumen undegraded protein (RUP). Rumen degraded protein supplies microbial needs. However, rumen microbes require non-protein N (ammonia, amino acids, peptides,) as “building blocks” of microbial protein (MCP). The extent of MCP synthesis in the rumen depends on a number of factors including level of feed intake, digestion rate (Kd) of diet components in the rumen, and passage rate (Kp) of digesta from the rumen. In the absence of a more reliable analytical method, the NRC subcommittee chose to use three fractions (A, B, C) derived indirectly from rumen incubation of in situ bags to derive RDP and RUP supplied by feed ingredients (kg/d):
RDP = A + B × [Kd/(Kd + Kp)]RUP = B × [Kp/(Kd + Kp)] + CWhere A is the amount (kg/d) of N presumably readily available to microbes, B is the amount of N that is available by degradation (at a rate = Kd) and C is the amount of N unavailable for microbial growth.

Kd指瘤胃內日糧組分降解速率，Kp指瘤胃食糜外流速率，A指微生物可利用N的數量（kg/d），B指可降解N的數量，C指不能用于微生物生長N的數量。

臨時筆譯，不知是否得當，望拍磚。

呵呵！！！

yangzhaojun

A是假定可以被微生物很容易地利用的N的數量。哈哈！是假定。