A simple gas production method using a pressure transducer to determine the fermentation kinetics of ruminant feeds.
TL;DR: Results obtained establish the pressure transducer as a suitable tool for determining the fermentation kinetics of ruminant feeds and ranking them with respect to their in vitro fermentability.
About: This article is published in Animal Feed Science and Technology.The article was published on 1994-08-01. It has received 1524 citations till now.
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TL;DR: The Reading Pressure Technique (RPT) as discussed by the authors is a semi-automated gas production technique based on a pressure transducer interfaced with a PC that allows accumulated head-space gas pressure values to be directly entered into a spreadsheet.
524 citations
TL;DR: In this paper, a flexible, empirical, multiphasic model was proposed for parameterization of gas production profiles and the maximum fractional rate of substrate digestion (RM) was calculated for each phase.
480 citations
TL;DR: A review of the available in vitro gas measuring techniques used for feed evaluation with emphasis on assessing their relative advantages and disadvantages is given in this article, where the authors highlight the potential of gas techniques for tackling some interesting areas of research.
462 citations
TL;DR: The present review examines the micro-ecology of the GIT, with most emphasis on the large intestine as the most important site of fermentative activity, and an attempt is made to clarify the importance of the microfloral activity (i.e. fermentation) in relation to the health of the host.
Abstract: The phasing out of antibiotic compounds as growth promoters from the animal industry means that alternative practices will need to be investigated and the promising ones implemented in the very near future. Fermentation in the gastrointestinal tract (GIT) is being recognized as having important implications for health of the gut and thus of the host animal. Fermentation in single-stomached animals occurs to the largest extent in the large intestine, mainly because of the longer transit time there. The present review examines the micro-ecology of the GIT, with most emphasis on the large intestine as the most important site of fermentative activity, and an attempt is made to clarify the importance of the microfloral activity (i.e. fermentation) in relation to the health of the host. The differences between carbohydrate and protein fermentation are described, particularly in relation to their endproducts. The roles of volatile fatty acids (VFA) and NH3 in terms of their relationship to gut health are then examined. The large intestine has an important function in relation to the development of diarrhoea, particularly in terms of VFA production by fermentation and its role in water absorption. Suggestions are made as to feeds and additives (particularly those which are carbohydrate-based) which could be, or are, added to diets and which could steer the natural microbial population of the GIT. Various methods are described which are used to investigate changes in microbial populations and reasons are given for the importance of measuring the kinetics of fermentation activity as an indicator of microbial activity.
433 citations
Cites methods from "A simple gas production method usin..."
...The method of Theodorou et al. (1994) which measures the kinetics of fermentation, can also be used to assess activity of microbial populations (Williams et al. 2000a)....
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TL;DR: The equations permit the extent of ruminal degradation (hence the supply of microbial protein to the duodenum) to be evaluated, thus linking the gas production technique to animal production.
Abstract: Equations to describe gas production profiles, obtained using manual or automated systems for in vitro fermentation of ruminant feeds, were derived from first principles by considering a simple three-pool scheme. The pools represented were the potentially degradable and undegradable feed fractions, and accumulated gases. The equations derived and investigated mathematically were the generalized Mitscherlich, generalized Michaelis–Menten, Gompertz, and logistic. They were obtained by allowing the fractional rate of degradation to vary with time. The equations permit the extent of ruminal degradation (hence the supply of microbial protein to the duodenum) to be evaluated, thus linking the gas production technique to animal production.
366 citations
References
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TL;DR: A simple technique for the determination in vitro of the dry- or organic-matter digestibility of small (0·5 g) samples of dried forages is described, which involves incubation first with rumen liquor and then with acid pepsin.
Abstract: A simple technique for the determination in vitro of the dry- or organic-matter digestibility of small (0·5 g) samples of dried forages is described. It involves incubation first with rumen liquor and then with acid pepsin. Using 146 samples of grass, clover and lucerne of known in vivo digestibility (Y), the regression equation Y= 0·99 X– 1·01 (S.E. ± 2·31) has been calculated, where X=in vitro dry-matter digestibility. This technique has been used for the study of the digestibilities of plant breeder's material, of the leaf and stem fractions of herbage and of herbage consumed by animals.
6,837 citations
"A simple gas production method usin..." refers methods in this paper
...Of these, the most frequently used is the rumen liquor, acid pepsin in vitro technique of Tilley and Terry (1963)....
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TL;DR: In this paper, a method for estimating the percentage of dietary protein that is degraded by microbial action in the rumen when protein supplement is added to a specified ration is proposed, where the potential degradability, p, is measured by incubating the supplement in artificial-fibre bags and is related to incubation time, t, by the equation p = a+b (1 − e -ct ).
Abstract: A method is proposed for estimating the percentage of dietary protein that is degraded by microbial action in the rumen when protein supplement is added to a specified ration. The potential degradability, p , is measured by incubating the supplement in artificial-fibre bags in the rumen and is related to incubation time, t , by the equation p = a+b (1 – e -ct ). The rate constant k , measuring the passage of the supplement from the rumen to the abomasum, is obtained in a separate experiment in which the supplement is combined with a chromium marker which renders it completely indigestible. The effective percentage degradation, p , of the supplement, allowing for rate of passage, is shown to be p = a +[ bc/(c+k) ] (1- e -(e+k)t ) by time, t , after feeding. As t increases, this tends to the asymptotic value a+bc /( c+k ), which therefore provides an estimate of the degradability of the protein supplement under the specified feeding conditions. The method is illustrated by results obtained with soya-bean meal fed as a supplement to a dried-grass diet for sheep. The incubation measurements showed that 89% of the soya-bean protein disappeared within 24 h and indicated that it was all ultimately degradable with this diet. When the dried grass was given at a restricted level of feeding the allowance for time of retention in the rumen reduced the estimate of final degradability to 71% (69% within 24 h). With ad libitum feeding there was a faster rate of passage and the final degradability was estimated to be 66% (65% within 24 h).
4,552 citations
"A simple gas production method usin..." refers methods in this paper
...…general, we have found that these equations provide a better description of the gas production data generated by the pressure transducer technique than the exponential function advocated by Orskov and McDonald (1979) and McDonald ( 1981 ), as it is capable of describing sigmoidal trends....
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TL;DR: A rapid method for measuring gas production during incubation of feedingstuffs with rumen liquor in vitro was described and gas production in 24 h from 200 mg feed dry matter was well correlated with digestibility of organic matter, determined in vivo with sheep.
Abstract: A rapid method for measuring gas production during incubation of feedingstuffs with rumen liquor in vitro is described. Gas production in 24 h from 200 mg feed dry matter was well correlated with digestibility of organic matter, determined in vivo with sheep. Multiple regression analysis, when it included data from proximate analysis, resulted in an equation ( R = 0·98) for prediction of metabolizable energy content, based on 30 experiments with rations varying in protein and crude fibre content, and 59 other experiments with concentrates. Energy content was in the range of 7·7–13·2 MJ ME/kg D.M. ( ± S.D. = 11·17 ± 1·08). The residual standard deviation of the equation was 0·25 MJ. Gas production was measured in calibrated syringes. The only chemical determinations needed are dry matter, protein and fat. Differences in activity between batches of rumen liquor are corrected by reference to gas production with standard feedingstuffs (hay meal and maize starch).
1,759 citations
TL;DR: In this article, the authors proposed a modification to the formula for effective degradability so that it may remain valid under low values of t for some protein supplements, linseed meal for example.
Abstract: Estimates of the degradability of protein in the rumen are essential for the application of new systems which have been suggested for the evaluation of the protein requirements of ruminants (Agricultural Research Council, 1980). The effective percentage degradability (P) of protein supplements in the rumen is dependent not only on the course of degradation of the protein particles in the rumen, but also on the time distribution of their stay in the rumen, and will decrease if there is an increase in the rate of passage of the particles. It was shown by Orskov & McDonald (1979) that if the percentage protein disappearance (p) from samples incubated for time t is described by the equation and if k is the fractional rate of passage from the rumen, then the effective degradability can be calculated as . The calculation depends on the equation for p remaining valid from t =0 (time of ingestion) until a time when all the particles have passed beyond the rumen. It has been found that for some protein supplements, linseed meal for example, the equation for p does not hold true for low values of t. The present note proposes a modification to the formula for effective degradability so that it may remain valid under these circumstances.
854 citations
"A simple gas production method usin..." refers methods in this paper
...…general, we have found that these equations provide a better description of the gas production data generated by the pressure transducer technique than the exponential function advocated by Orskov and McDonald (1979) and McDonald ( 1981 ), as it is capable of describing sigmoidal trends....
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TL;DR: In this article, an artificial fiber bag technique was evaluated for assessing the proportions of dietary D. M. and N which disappear in the rumen and the most important factor determining the variability in disappearance from bags incubated together was the sample size in relation to bag size.
Abstract: The artificial fibre bag technique was evaluated for assessing the proportions of dietary D. M. and N which disappear in the rumen. The most important factor determining the variability in disappearance from bags incubated together was the sample size in relation to bag size. For incubation of 5 g air dry feed, a bag size of 17 ✗ 9 cm was found to be adequate. There were also variations in substrate disappearance between animals and between days of incubation. It was estimated that three sheep and the measurement of substrate disappearance twice were necessary in order to obtain acceptable repeatability.The technique was found to be satisfactory as a simple and rapid guide for measuring nutrients disappearance in the rumen such as protein degradation and carbohydrate fermentation. It has been used in subsequent work to measure the effect of features of the rumen environment, such as pH and NH3 concentration, on rate of fermentation.
804 citations
"A simple gas production method usin..." refers methods in this paper
...The polyester bag technique has been used for many years to provide estimates of both the rate and extent of disappearance of feed constituents (Quin et al., 1938; Chenost et al., 1970; Mehrez and Orskov, 1977)....
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