Use of processing to explore the factors affecting the digestion of forage cell walls

The dried herbage of early and late cut lucerne, red clover, Italian and perennial ryegrasses and timothy was offered in the long form or three processed forms at three levels of feeding (20, 30 and 40 g DM/kg LW) to store lambs in two experiments. Faecal output of organic matter and cell walls was determined.The potential digestibility of the cell walls of these feeds was determined in vitro. The depression in the cell wall digestion from this potential, observed in vivo, was related to water soluble carbohydrate content (WSC) and buffering capacity (BC) of the forages, their fineness of grinding (MF) and the level of feeding (LF).Uniform processing altered the chemical composition of all forages and produced a wide range of MF in the different forages.The digestion of the cell content fraction of the diets was not influenced by herbage species, fineness of grinding or level of feeding.The digestion of organic matter and cell wall was depressed by increasing LF and decreasing MF (P < 0.001) and the interaction between herbage species and processing was significant (P < 0.001).WSC and LF were positively correlated (r = +0.706 and +0.611), and BC and MF were negatively correlated (r = ?0.498 and ?0.498), with the depression observed in cell wall digestion.These four parameters, together with their significant interaction terms (WSC × BC), (WSC × LF) and (BC × MF), accounted for 95.1% of the variance observed in the depression of cell wall digestion and provided a basis for a hypothetical model of factors affecting cell wall digestion.     

添加纤维素酶的青贮研究进展

青贮是一种传统的青绿饲料作物的保存方法,在青贮中添加纤维素酶可以增强青贮的效果,促进植物细胞壁的酶解,提高青贮料的消化率,添加纤维素酶的青贮也可用于从植物细胞中提取有价值的天然产物,不仅条件温和,且提取率大大提高,应用在线生产纤维素与青贮发酵耦合能大大降低该工艺的成本,对添加纤维素酶青贮的研究可望促进纤维素资源的转化利用。     

Comparison of laboratory methods for predicting the organic matter digestibility of forages

Seven laboratory methods for predicting organic matter digestibility were tested and compared on 42 samples of grass hay, 56 of silages and 39 of pelleted forages and byproducts. For all samples digestibility in vivo was determined with wethers fed at a maintenance level. The methods investigated were: tabular digestibility coefficients, Weende components, cell wall components, summative equations (Van Soest), true organic matter digestibility in vitro (Van Soest), digestibility in vitro (Tilley and Terry) and nylon bag digestibility.None of the purely chemical procedures nor the tabular digestibility coefficients were sufficiently accurate for a practical prediction of organic matter digestibility. Considerably better results were obtained with methods using living rumen micro-organisms. The best results were obtained with the nylon bag technique, but digestibility in vitro, measured by the two-stage technique, also gave accurate predictions of digestibility.     

Measurement and prediction of digestibility of forage maize in The Netherlands

Results of digestibility trials on fresh and ensiled maize (aerial parts) were analysed and compared with laboratory data.

Digestibility of the organic matter of ears was almost constant at 84–85%. Digestibility of organic matter of stover showed great variation. Variation between animals in apparent digestibility of organic matter was greater for maize diets than for diets based on grass products. Most of the differences between animals were caused by differences in the digestion of cell walls. When the true digestibility of cell contents was assumed to be complete, endogenous excretion was, on average, only 7% with respect to organic matter intake, and seemed dependent on digestibility of organic matter.

Prediction of apparent digestibility was more accurate with digestibility in vitro than with crude fibre, although for maize silage, significant relationships were found between crude fibre content and digestibility of organic matter. Standard deviation of organic matter digestibility between lots of fresh and ensiled maize grown on commercial farms amounted to only about 1.2 –2%. As this was only twice the accuracy of digestibility in vivo with four animals, fixed values will be presented to farmers, possibly corrected for year, hybrid selection and cropping practice.     

Botanical composition and extent of lignification affecting digestibility of wheat and oat straw and paspalum hay

Samples of 1 kg of wheat straw, oat straw and paspalum hay were separated manually into botanical fractions, and the three largest fractions of each forage were analysed chemically for cell-wall constituents, silica and nitrogen. Proportions of digested dry matter, cellulose and hemicellulose, and potential digestibility for each of these major botanical fractions were determined when chaffed samples were placed in nylon bags and incubated for 12, 24, 48, 72 and 96 h in the rumen of sheep fed on lucerno. Cross-sections of botanical fractions were stained with safranin and fast green, and proportions of lignified tissue determined by light-microscopy and planimetry.Large differences in dry-matter digestibility between wheat straw and oat straw were attributed to the different proportions of botanical fractions. Within forages, stem was the largest fraction, the most lignified and had the lowest potential digestibility. Proportions of digested dry matter from botanical fractions at 12 h were poorly correlated with lignin content of dry matter (r = 0.25) but at 72 h were negatively correlated with lignin content of dry matter (r = ?0.84, P<0.01) and with proportions of lignified tissue (r = ?0.67, P<0.05) in the respective botanical fractions. Proportions of cellulose and hemicellulose digested at 72 h were strongly correlated with lignin content of cell walls (r = ?0.90, P<0.01; r = ?0.85, P<0.01, respectively). Proportions of lignified tissues were less closely correlated with all measurements of digestibility than were proportions of lignin in cell walls determined chemically. Development of a technique for measuring intensity of lignification might enhance the value of light-microscopy measurements.     

Determination of polyphenol and crude nutrient content and nutrient digestibility of dried and ensiled white and red grape pomace cultivars

The present study aimed to determine the nutrient and energy content of fresh and ensiled grape pomace (GP) from different grape varieties originating from Germany, and to estimate the feed value of dried white, dried red and ensiled white GP by calculating nutrient digestibility and the content of metabolisable energy (ME) and net energy lactation (NEL) measured in sheep as a ruminant model. GP from red cultivars had higher contents of organic matter (OM), crude protein (CP), ether extract (EE), crude fibre (CF), total phenolic contents (TPC) and ME, whereas the concentrations of ash and sugar were lower than from white cultivars. Compared with untreated GP, ensiled GP had increased concentrations of CP (+19%), ether extract (EE; +23%) and CF (+12%) and a higher ME content (+7%) and markedly decreased concentrations of sugar (?99.6%) and TPC (?48%). The concentrations of dry matter, OM and ash were not different between ensiled and fresh GP. Compared with dried GP, ensiled GP had a higher nutrient digestibility (OM, +32%; CP, +43%; CF, +46%; neutral detergent fibre [NDF], +54%; acid detergent fibre [ADF], +69%) and higher energy values (ME, +16%; NEL, +19%). The digestibility of OM, CP, EE and CF and the energy content were higher for dried red than for dried white GP, whereas the digestibility of NDF_OM and ADF_OM was lower for dried red than dried white GP. In conclusion, the results show that both red and white GP are suitable dietary sources for enrichment with TPC. Furthermore, compared with drying ensiling of GP improves the feeding value of GP and is a good possibility of preserving the seasonally produced by-product of winemaking for ruminant feeding.     

Prediction of methane emission from beef cattle using data measured in indirect open-circuit respiration calorimeters

The objectives of the present study were to examine relationships between methane (CH4) output and animal and dietary factors, and to use these relationships to develop prediction equations for CH4 emission from beef cattle. The dataset was obtained from 108 growing-to-finishing beef steers in five studies and CH4 production and energy metabolism data were measured in indirect respiration calorimeter chambers. Dietary forage proportion ranged from 29.5% to 100% (dry matter (DM) basis) and forages included grass silage, fresh grass, dried grass and fodder beet. Linear and multiple regression techniques were used to examine relationships between CH4 emission and animal and dietary variables, with the effects of experiment or forage type removed. Total CH4 emission was positively related to live weight (LW), feeding level and intake of feed (DM and organic matter) and energy (gross energy (GE), digestible energy (DE) and metabolisable energy (ME)) (P < 0.001), while CH4/DM intake (DMI) was negatively related to energy digestibility and ME/GE (P < 0.05 or less). Using LW alone to predict CH4 emission produced a poor relationship when compared to DMI and GE intake (GEI) (R2 = 0.26 v. 0.68 and 0.70 respectively). Adding feeding level, dietary NDF concentration and CP/ME or feeding level, energy digestibility and ME/GE to support LW resulted in a R2 of 0.66 or 0.84. The high R2 (0.84) was similar to that obtained using DMI or GEI together with energy digestibility and ME/GE as predictors. Further inclusion of dietary forage proportion and ADF and NDF concentration to the multiple relationships using GEI as the primary predictor resulted in a R2 of 0.87. These equations were evaluated through internal validation, by developing a range of similar new equations from two-thirds of the present data and then validating these new equations with the remaining one-third of data. The validation indicated that addition of energy digestibility and ME/GE to support LW with feeding level, DMI and GEI considerably increased the prediction accuracy. It is concluded that CH4 emission of beef steers can be accurately predicted from LW plus feeding level, DMI or GEI together with energy digestibility and ME/GE. The dataset was also used to validate a range of prediction equations for CH4 production of cattle published elsewhere.     

Apparent and true digestibility of the Weende components, cell content and cell wall of ryegrass

For 14 samples of ventilated hay and 6 of fresh grass, digestibility was determined with young wethers. The contribution to the digestibility was calculated for the Weende components (crude protein, crude fibre, nitrogen-free extractives + fat) and for cell content and cell wall (Van Soest) components. For the cell content and crude protein, a hyperbolic relationship, y' = a − b/x between the digestibility coefficient of the components (y') and the percentage component in dry matter (DM, x) can be accepted with a sufficient degree of certainty. This means that the apparent digestibility of the cell content and crude protein increase with increasing concentration. The latter formula can be transformed into a linear regression y = ax − b where y = percentage digestible component in DM, a being an estimate of the true digestibility of the component and b an estimate of the endogenous excretion of the component. From these relationships some important practical conclusions can be drawn. For other dry matter components, such as crude fibre, nitrogen free extractives + fat and cell wall, the relationship between the digestibility coefficient and the percentage of the component in DM cannot be expressed by a simple regression line. The advantages of splitting the digestibility into a contribution from cell content and cell wall components versus splitting into contributions from the Weende components are discussed.By determination of the cell wall and its digestibility in vitro, a very good prediction for the dry matter digestibility of grass can be given, which is of great importance for plant breeding and grassland research.     

Digestion of algae by Stegastes nigricans and Amphiprion akindynos (Pisces: Pomacentridae), with an evaluation of methods used in digestibility studies

An investigation of the digestive physiology of two species of damselfish (family Pomacentridae) was undertaken, comparing a herbivore Stegastes nigricans with an omnivore/ planktivore Amphiprion akindynos . Apparent digestibility of Enteromorpha flexuosa (Chlorophyta) was calculated using both total collection and a range of ash-marker methods. In addition, Van Soest's system of fibre analysis was used to determine the digestibility of algal cell walls. A comparison of total collection methods (comparing food intake v. faeces output) with ash-marker methods showed that the calculated digestibility estimate will depend on the method used. Total dry matter digestibilities varied from 75 to 20% for S. nigricans and from 79 to 15% for A. akindynos . Comparable ranges were obtained for organic matter, cell wall, nitrogen and soluble carbohydrate. Digestibility estimates calculated using total collection methods were larger and less variable than estimates calculated using ash-marker methods. Despite major methodological variation, there was no significant difference in the digestibility of algae between the two species.     

Suitability of cell-wall constituents as predictors of organic matter digestibility in some tropical and subtropical by-products

The van Soest detergent method for determination of cell wall constituents is suggested as a good routine analysis for plant material of high fibre content. The chemical composition of the fibre fraction of 24 tropical and subtropical by-products has been investigated, and simple and multiple correlation coefficients have been calculated between organic matter digestibility in vivo and in vitro, and the contents of different cell wall fractions.The acid detergent fibre (ADF) gave the highest negative correlation with the digestibility of organic material independent from the botanical origin of the sample. The ADF fraction proved superior to the Weende crude fibre as well as to single fractions of the cell walls such as lignin, cutin and silica.The determination of ADF is more convenient, and needs only half the time and half the expenditure required for the Weende crude fibre analysis. There is the additional aspect of health: determination of ADF in the detergent analysis requires no use of asbestos.     

Digestibility, nitrogen excretion, and mean retention time by North American porcupines (Erethizon dorsatum) consuming natural forages

North American porcupines (Erethizon dorsatum) subsist predominantly on low-protein, high-fiber, high-tannin diets. Therefore, we measured the porcupine's ability to digest dry matter, fiber, and protein by conducting digestion trials on eight natural forages and one pelleted ration varying in concentration of fiber, nitrogen, and tannins. On these diets, dry matter intake ranged from 5 to 234 g/kg(0.75)/d and dry matter digestibility ranged from 62% to 96%. Porcupines digested highly lignified fiber better than many large hindgut fermenters and ruminants. The porcupine's ability to digest fiber may be explained, in part, by their lengthy mean retention time of particles (38.43+/-0.56 h). True nitrogen digestibility was 92% for nontannin forages and pellets. Endogenous urinary nitrogen was 205 mg N/kg(0.75)/d, and metabolic fecal nitrogen was 2.8 g N/kg dry matter intake. Porcupines achieved nitrogen balance at relatively low levels of nitrogen intake (346 mg N/kg(0.75)/d). Tannins reduced the porcupines' ability to digest protein. However, the reduction in protein digestion was not predictable from the amount of bovine serum albumin precipitated. Like many herbivores, porcupines may ameliorate the effects of certain tannins in natural forages on protein digestibility through physiological and behavioral adaptations.     

Predicting feed digestibility from NIRS analysis of pig faeces

Digestibility is a key parameter in the evaluation of feeds; however, the measurements on animals require heavy experimental trials, which are hardly feasible when large numbers of determinations are required – for example, in genetic studies. This experiment aimed at investigating the possibility to predict digestibility from NIRS spectra measured on faeces. A total of 196 samples were available from a digestibility experiment investigating the effects of age and genetic background of Large White pigs fed the same diet, rich in fibre (NDF=21.4% DM). Digestibility of dry matter (dDM), organic matter (dOM), nitrogen content (dN), energy (dE) and apparent digestible energy content (ADE) were calculated, as well as total N content of faeces (N). The faeces samples were submitted to reflectance NIRS analysis after freeze-drying and grinding. Calibration errors and validation errors were, respectively, 0.08 and 0.13% DM for total N in faeces, 0.97% and 1.08% for dDM, 0.79% and 1.04% for dOM, 1.04% and 1.47% for dN, 0.87% and 1.12% for dE and 167 and 213 kJ/kg DM for ADE. These results indicate that NIRS can account for digestibility differences due to animal factors, with an acceptable accuracy. NIRS appears to be a promising tool for large-scale evaluations of digestibility. It could also be used for the study of digestibility of different feeds, after appropriate calibration based on a wide range of feed types.     

Prediction of the in vivo digestibility of whole crop wheat from in vitro digestibility,chemical composition,in situ rumen degradability,in vitro gas production and near infrared reflectance spectroscopy

Twenty-six winter wheat forages (cultivars Slepjner, Hussar and Cadenza) harvested at three stages of maturity in each of two years, were conserved with or without Maxgrass additive or with urea (20 or 40 g kg⁻¹ dry matter; DM) in 200 l barrels. The forages were analysed for in vivo digestibility in wethers, chemical composition, in vitro rumen fluid-pepsin digestibility, in vitro neutral detergent-cellulase plus gamannase digestibility (NCGD), in vitro fermentation gas production and in situ rumen degradability. Forages were also scanned using near-infrared reflectance spectroscopy (NIRS) and calibration equations developed for predicting in vivo digestibility. In vivo digestible organic matter content (DOMD) was poorly predicted by cell wall content (r²≤0.19), NCGD (r²≤0.41), rumen fluid DOMD (r²≤0.41), rumen degradability (r²≤0.44) and in vitro gas production (r²≤0.26). Although crude protein content was a better predictor (r²≤0.48), the relationship differed (P<0.05) with the year of harvest of the forages. In contrast, NIRS was a more accurate and consistent predictor of DOMD in vivo (r²=0. 87). This study indicates that traditional laboratory-based feed evaluation techniques are unsuitable for predicting the DOMD of WCW, but that NIRS holds promise. However, as only 26 forages were used to derive the calibration equation, further research is required using large (150) data sets to validate the promise shown by NIRS and enable its adoption by the advisory services.     

Genetic Modification of Herbaceous Plants for Feed and Fuel

Referee: Dr. E. Charles Brummer, Forage Breeding and Genetics, 1204 Agromonomy, Iowa State University, Ames, IA 50011 Much of the research on the genetic modification of herbaceous plant cell walls has been conducted to improve the utilization of forages by ruminant livestock. The rumen of these animals is basically an anaerobic fermentation vat in which the micro flora break down the complex polysaccharides of plant cell walls into simpler compounds that can be further digested and absorbed by the mammalian digestive system. Research on improving the forage digestibility of switchgrass, Panicum virgatum L., and other herbaceous species has demonstrated that genetic improvements can be made in forage quality that can have significant economic value. To meet future energy needs, herbaceous biomass will need to be converted into a liquid fuel, probably ethanol, via conversion technologies still under development. If feedstock quality can be genetically improved, the economics and efficiency of the conversion processes could be significantly enhanced. Improving an agricultural product for improved end product use via genetic modification requires knowledge of desired quality attributes, the relative economic value of the quality parameters in relation to yield, genetic variation for the desired traits, or for molecular breeding, knowledge of genes to suppress or add, and knowledge of any associated negative consequences of genetic manipulation. Because conversion technology is still under development, desirable plant feedstock characteristics have not been completely delineated. Some traits such as cellulose and lignin concentration will undoubtably be important. Once traits that affect biomass feedstock conversion are identified, it will be highly feasible to genetically modify the feedstock quality of herbaceous plants using both conventional and molecular breeding techniques. The use of molecular markers and transformation technology will greatly enhance the capability of breeders to modify the morphologic structure and cell walls of herbaceous species. It will be necessary to monitor gene flow to remnant wild populations of biomass plants and have strategies available to curtail gene flow if it becomes a potential problem. It will also be necessary to monitor plant survival and long-term productivity as affected by these genetic changes to herbaceous species.     

Effect of ambient temperature on nutrient digestibility and nitrogen balance in sheep fed brown-midrib maize silage

The aim of the experiment was to determine the impact of heat stress on nutrient digestibility and nitrogen balance in sheep fed silages differing in fibre quality. The digestibility trial was conducted at three different ambient temperatures (15°C, 25°C and 35°C for 24 h/d). The tested brown-midrib maize (Bm) silage had a higher nutrient digestibility, except for ether extract (EE) and a higher metabolisable energy (ME) content than the control maize (Con) silage. Nitrogen (N) excretion with faeces was higher but N excretion with urine was lower for sheep fed Bm silage, subsequently N balance did not differ between the two silages. Temperature had no effect on nutrient digestibility, except for crude protein (CP), but N excretion with urine was lower at elevated temperatures. A diet by temperature interaction was found for dry matter (DM) and organic matter (OM) digestibility. When the ambient temperature increased from 15°C to 25°C, the DM and OM digestibility increased in animals fed Con silage, but decreased in animals fed Bm silage. Concomitantly, ME estimated from digestible nutrients was higher for Bm than for Con at 15°C, but no differences were found at 25°C and 35°C. Effects of diet by temperature interaction, furthermore, were observed for EE and CP digestibility. Therefore, forage quality has to be considered when feeding heat-stressed animals.     

Effects of inclusion with blue lupins (Lupinus angustifolius) in broiler diets and enzyme supplementation on production performance, digestibility and dietary AME content

An experiment with broiler chickens was conducted to study the effect of inclusion of blue lupins and exogenous enzyme to broiler diets on the apparent metabolisable energy (AME), digestibility and performance. Two basal diets were formulated: a non-lupin diet A based on soya bean meal and maize, and a diet B where parts of soya bean meal and maize were substituted with blue lupin (200 g/kg). The two basal diets were fed either alone or, for diet B in combination with different enzyme preparations (Bio-Feed Plus, lactase, two galactanases (Gal-I and Gal-II)). The experiment was performed in battery cages with 648 male broiler chickens, where eight experimental diets were fed to the chickens from 7 to 21 days of age and weight gain and feed intake were measured during the period. At the end of the experiment, three chickens from each pen were slaughtered and the content from jejunum and ileum was separately collected and pooled and used for measurement on intestinal viscosity. For measurements of the apparent metabolisable energy and the apparent digestibility, excreta were collected at 22–24 days of age and ileal contents collected at 25–26 days from the remaining chickens.

Substitution of soya bean meal and maize with blue lupin depressed weight gain (9%) and feed conversion ratio (12%) significantly. Feed intake of the lupin-based diets was not decreased. The protein in lupin was digested to the same extent as the protein from soya bean meal, the coefficient of ileal apparent digestibility being on average 0.75. However, the high content of the non-starch polysaccharides (NSP; 450 g/kg) in lupin depressed the apparent digestibility of the organic matter by approximately 10%. The AME_n of the non-lupin diet was 14.01 MJ/kg dry matter (DM) compared to a value of 13.11 MJ/kg DM in the lupin control diet. Improvements in the measured parameters were seen with some of the enzymes. Gal-I, and Gal-II in combination with lactase were the most efficient enzymes concerning improvement in AME_n and performance. Weight gain was increased by 3.5–5.5% by addition with these enzymes. Gal-I increased the AME_n significantly to 13.65 MJ/kg, a value not significantly different from the AME_n of the non-lupin diet. There was no effect of addition with the different enzymes on the coefficients of apparent digestibility of organic matter measured in the ileum, whereas addition with Gal-I to the lupin diet increased the apparent digestibility of organic matter over the total tract by 3%. The mode of action of the galactanases has been to hydrolyse the galactan in the NSP cell wall of lupins to galactose and dimers of galactose, which are energy-yielding to poultry. From the results obtained, it can be indicated that Gal-I increased the energy utilisation of the lupin-based diet, confirmed by the improved AME_n content and performance.     

The digestive strategy and efficiency of the West Indian manatee, Trichechus manatus

During the winters of 1982/83 and 1983/84, samples of digesta were collected from nine sites along the gastrointestinal tracts of seven West Indian manatees, Trichechus manatus. The voluminous large intestine of the manatee is responsible for considerable water reabsorption, as well as being the major site of organic matter, nitrogen and crude fat digestion. Cellulose digestion occurs primarily in the cecum and anterior portion of the colon in a pattern similar to terrestrial nonruminant herbivores like the horse. Overall digestibility coefficients for organic matter (71%), nitrogen (61%) and crude fat (77%) are comparable to those of terrestrial herbivores. Manatees have one of the highest digestibility coefficients for cellulose (80%) of any known mammalian herbivore. This high efficiency of cellulose digestion is due primarily to an extremely slow rate of passage. In addition, it appears that seagrasses may be more digestible than terrestrial forages, possibly due to their relatively low lignin content.     

Ammonia fiber expansion (AFEX) treatment of eleven different forages: Improvements to fiber digestibility in vitro

With the increased attention to bioenergy and especially cellulosic ethanol, there are concerns regarding potential competition for available land between biofuels and feeds/foods. Ammonia fiber expansion (AFEX), a pretreatment process for cellulosic ethanol, may also be used to improve ruminant digestibility of feedstuffs not traditionally used as forages. Eleven forages – including traditional forages, agricultural residues, and dedicated energy crops – were AFEX treated and digested in vitro with rumen inoculum. AFEX treatment improved 48-h neutral detergent fiber (aNDFom) digestion for several moderately indigestible forages compared to untreated samples, but showed no improvement for highly digestible samples. Of particular interest are corn stover and late-harvest switchgrass, as AFEX treatment improved digestibility by 52% and 128% over untreated material, whereas the improvement was 74% and 70% over conventional ammonia treatment, respectively. The crude protein content of all treated samples increased to more than 100 g/kg dry forage. This research strongly suggests that AFEX-treated feedstuffs can be competitive with traditional forages, and thus offer expanded options for ruminant feeding.     

Organic matter digestibility of condensed tannin-containing Lotus corniculatus and its prediction in vitro using cellulase/hemicellulase enzymes

Three digestion experiments involving cryptorchid weaned lambs were conducted for 14-day periods in the spring, summer and autumn to determine the in vivo digestibility of dry matter (DMD), gross energy (GE), organic matter (OMD), digestible organic matter in the dry matter (DOMD) and estimated metabolisable energy (ME) concentration of Lotus corniculatus L. (birdsfoot trefoil; cv. Grasslands Goldie) at different stages of maturity. The experiments were carried out indoors at Massey University's Riverside farm, in the Wairarapa, North Island, New Zealand. In vivo digestibility samples were then used as standards to investigate if the enzymic in vitro system of [Roughan, P.G., Holland, R., 1977. Predicting in vitro digestiblities of herbages by exhaustive enzymic hydrolysis of cell walls. J. Sci. Food Agric. 28, 1057–1064] could predict OMD and DOMD of condensed tannin (CT)-containing L. corniculatus.Digestibility of L. corniculatus declined as it matured, but the rate of decline was much less than that which occurs for perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture. It was concluded that the in vitro enzymic system of [Roughan, P.G., Holland, R., 1977. Predicting in vitro digestiblities of herbages by exhaustive enzymic hydrolysis of cell walls. J. Sci. Food Agric. 28, 1057–1064] can be used to predict OMD and DOMD of L. corniculatus with a high degree of accuracy, provided a standard curve involving in vivo data generated with L. corniculatus is used. Using a standard curve with in vivo data from perennial ryegrass/white clover pasture led to bias which increased at lower OMD values. Reasons for the differences between L. corniculatus and pasture standard curves are discussed, including possible effects of bound CT.