Grass silage is considered to be asynchronous in the supply of energy and nitrogen to the rumen microbes. It is thought that this contributes towards the reduced quantities and efficiencies of rumen microbial protein synthesis frequently observed in animals feed on such diets (Beever, 1993). Additional energy from carbohydrates may help to ameliorate this situation. A rumen simulated continuous culture (RSCC) system was used to study the influence of supplementation of grass silage with various carbohydrate sources on rumen microbial activity.

The greatest error in formulating rations is due to the inaccuracy of prediction of silage dry matter intake (SDMI). Until recently, predictions have been based on die method of Lewis (1981) which predicts intake from traditional silage analysis :- dry matter (DM), crude protein (CP), digestible organic matter in the dry matter (DOMD) and ammonia N. Recently, the incorporation of new feed characterisation data, obtained from electrometric titration (ET), has unproved predictions (Offer et al., 199S). A 4 year study has yielded data to evaluate alternative methods for the prediction of SDMI using traditional, ET and HPLC data and spectral information obtained by near infra-red reflectance spectroscopy (NIRS) of fresh and dried samples.

The feeding value of grass silage mainly depends on a combination of its intake potential and digestibility. Near infrared reflectance spectroscopy (NIRS) has been successfully used to predict the organic matter digestibility (OMD) of silage (Baker et al., 1994) and Steen et al. (1995) has demonstrated that this technique also offers a much greater potential for the prediction of intake than methods based on wet chemistry. The work reported by Steen et al. (1995) provided a large contemporary sample and data set suitable for exploring the full potential of NIRS for the prediction of both intake and OMD.

Information on the rumen degradation characteristics of various feed fractions including nitrogen (N) and cell walls (CW) is gained largely through the use of the in sacco procedure. While various in vitro techniques have been applied there is an urgent need for the development of rapid methods for predicting aspects of feed degradation. Near infrared reflectance spectroscopy (NIRS) has been widely applied as an accurate and rapid method of analysis. In the present experiment the ability to predict in vitro CW degradability (CWD) characteristics of grass silage (GS) was investigated using NIRS.

The new metabolisable protein system (AFRC, 1992) introduces the requirement to distinguish between the energy in feeds which is fermentable (available for microbial growth) and that which is non-fermentable (available to the host animal; NFE). Fermented forages such as grass silage (GS) may contain substantial amounts of fermentation acids (FA) (volatile fatty acids (VFA) and lactic acid (LA)) and therefore, contain a considerable proportion of NFE. The aim of the present experiment was to investigate the use of near infrared reflectance spectroscopy (NIRS) as a rapid method for predicting the FAs in fresh (undried) GS.

In vitro gas production techniques have been used to nutritionally characterise feedstuffs for ruminants. Consideration of both the soluble and insoluble fractions has recently been shown to be essential for adequate description of cell wall disappearance (Jessop and Herrero, 1996). This study investigates how gas production measurements can be used to predict neutral detergent fibre (NDF) disappearance by correcting for the gas volume produced in the early stages of fermentation from neutral detergent solubles (NDS). The study was carried out using three tropical grasses.

The use of the Pressure Transducer Technique (PTT) to evaluate feed degradation as described by Theodorou et al (1994) recognises the presence of a lag phase (1-2h) after introducing the microbial innocula to the feed under investigation. Previous work has shown that this can be reduced by incubating the microbes with a basal feed for 24h prior to the addition of a test feed. This work considered the effect of the composition of this basal feed.

Four basal mixtures, Grass silage/conc(G), Hay/cone (H), Maize silage/conc: (M), Whole crop wheat/caustic wheat/cone (W) were prepared plus two mixtures based on purified nutrients to give high Starch (St) and high Cellulose (Ce) contents. 20ml strained, homogenised bovine rumen liquor was added to bottles containing 180ml of media and 1.5g DM of each basal mixture. After 24h of vented incubation at 39°C 1g DM of test feed, (either barley grain or straw both milled to 1 mm) was added and gas production measured at decreasing frequencies over the next 72h. Cumulative gas production at 72h were calculated (Table 1).

The term 'fermentable metabolisable energy' (AFRC, 1992) has been criticised as an index of the supply of fermentable energy to the rumen because it has not been measured directly, is insensitive to rumen outflow rate and assumes fermentation of some nutrients which bypass the rumen (Newbold, 1994). One alternative is to describe the content of fermentable energy in terms of the amount of gas evolved during fermentation by ruminal microorganisms. The automated pressure transducer technique of Davies et al. (1995) has been applied to individual concentrate feedstuffs to provide an alternative database of fermentable energy content (Baughan et al., unpublished).

Theodorou et al. (1994) using a manual pressure transducer technique observed a linear response to substrate concentration (cone.) in gas production (GP; ml absolute) whilst lag time and rate of GP values remained constant. This experiment investigated the effect of increasing the cone, of maize starch (S) and milled (1mm) dried grass (DG) on the GP profile using an automated GP technique (Cone 1994).

Either 0.1, 0.25, 0.5, 1.0 or 2.0 g of S or DG were weighed into 250 ml bottles and pre-soaked with anaerobic buffer (85 ml). The bottles were connected to a data logger/pressure tranducer unit and gassed with carbon dioxide. Incubation (39°C) started ∽16 h later when strained rumen fluid was injected into each bottle (15 ml) and a data logger initiated. When GP had ceased the final pH of each bottle was measured and 25 ml of 1M H3PO4 added to stop further enzymic activity. DG bottles were filtered to determine organic matter (OM) residue and hence OM degraded (OMD).

During the past twenty years the in vitro, two-stage digestibility method of Tilley and Terry (1963) has been widely used to predict the in vivo digestible organic matter content (DOMD) of forage dry matter. Recently in vitro gas production methods have attracted considerable research interest because of their potential to simulate the fermentation kinetics of forages in the rumen. However the potential of gas production methods to assess DOMD, as well as fermentation kinetics, has not been reported.

It is generally believed that ruminants are better able to degrade highly fibrous feeds than equines. To determine if this is due to differences between the microflora of the rumen and the equine hind-gut, oatfeed (OF), naked oats (NO), soya hulls (SH) and unmolassed sugar beet pulp (SB) were incubated with inocula prepared from bovine rumen digesta or equine caecal digesta.

OF, NO, SH, and SB were ground to pass through a 1 mm mesh screen and incubated for 72 hours, at 39°C with inocula prepared from either rumen (R) or caecal (C) digesta. Rumen digesta was obtained from three hay-fed, ruminally - fistulated Hereford x Friesian steers, and caecal digesta from three hay-fed, caecally -fistulated, Welsh-cross ponies. Gas production throughout the incubation was measured using the pressure transducer technique (Theodorou et al, 1994). After the incubation, VFA production was measured and residue weights were calculated for each feedstuff.

Several studies have shown high correlations between in vtvo and in vitro degradation of fibrous feeds when preparations from either rumen fluid or ruminant faeces have been used as the inocula for the in vitro studies (El Shaer et al., 1987; Akhter et al., 1994 & 1995; Harris et al., 1995). Use of an inoculum prepared from faecal material is attractive, for unlike that obtained from rumen fluid, it precludes the need to prepare and maintain fistulated donor animals. This study investigated the use of pony faeces, as an alternative to pony caecal digesta, as a source of micro-organisms for in vitro feed degradability studies.

The chemical composition of tropical forages is generally more complex than that of temperate forages, yet the need for simple methods to predict nutritive value is greater. Near Infrared Reflectance (NIR) spectra could provide a possible solution. NIR has been used to predict both in vitro and in vivo digestibility (Murray, 1993). Direct calibration with in vivo parameters is ideal, but factors such as different types of forages, animals and management conditions have to be taken into consideration. The gas production technique, which may be considered as an in vitro counterpart of the dacron bag technique, provides information relating to the fermentable fractions and kinetics of a forage and these parameters can be related to the NIR spectra. The aim of this study was to investigate the relationship between NIR spectra and cumulative gas production and derived parameters in tree leaves.

In Mongolia animal performance is very much dependent on the quality and quantity of natural grassland available, since certain pastoral animals may obtain as much as 98% of their annual intake from pasture. There have been few studies to date on either in vivo or in vitro degradation of native Mongolian pastures. This paper seeks to investigate the degradation characteristics of native pastures from 2 regions in Mongolia, high mountain and forest steppe. It also investigates the relationship between the in vitro gas production technique and the in sacco technique.

The in situ procedure is used to describe the kinetics of feed degradation in the rumen. However, recent ring tests (Madsen and Hvelplund, 1994; Wilkerson et al, 1995) and reviews (Huntington and Givens, 199S) highlighted the need for standardisation of the in situ procedure. Wilkerson et al. (1995) concluded that the rinsing procedure post rumen-incubation should be standardised and Hyslop (1991) reported that wash severity could have a considerably effect on zero time losses of distiller's dark grains. This experiment determined the effect of post rumen incubation wash severity on dry matter (DM) disappearance (DMdis) in situ in two studies.

In dacron bag methodology an important measurement is the wash value component. This component is assumed to be wholly degrabable and forms a major proportion of effective degradability calculations (Cockburn et al., 1993). Grinding of feeds with a high content of solubles or fine particles may result in high initial wash-out values and may affect feed degradability adversely. An experiment, was conducted to assess the effect of grinding on dry matter (DM) degradation of maize and wheat, using the in situ dacron bag technique.

One of the factors that determines the nutritive value of fishmeal as a protein concentrate for ruminants is its ruminal degradability, which varies with processing methods. It is possible that this variation could be related to the chemical modification of the amino acids/protein or to the change in protein solubility during the industrial processing. The objective of this work was to examine the effect of heat treatment of fishmeal on its ruminal degradability, protein solubility and the oxidation state of methionine.

Little information is available on the dry matter degradability of whole-crop cereals and their components (Hill and Leaver 1994). In this experiment, the in sacco degradability of the DM of four cereal crops was determined, and the effect of physical alteration of whole-crops and their component parts was investigated.

Winter sown crops of wheat (var.Riband) and barley (var.Marinka) and spring sown crops of wheat (var.Axona) and barley (var.Tyne) were cut at the “hard dough” stage of crop maturity and preserved with urea at 40 g kgDM-1 in plastic silos. The in sacco DM degradability of samples of these crops was determined in two fistulated dairy cows (Jerseys, mean liveweight 450 kg) using the method of Paine, Crawshaw and Barber (1982). The cows were fed alfalfa cubes (16% protein) and meadow grass hay, each at 3 kg d-1, and had continuous access to water.

The importance of feedstuff evaluation as part of ration formulation is recognised by UK farmers, with the number of silage samples analysed increasing annually. These can be undertaken by the UK advisory services or feed companies, with several commercial laboratories offering similar services. However, as discussed by Beever [1993], there is concern over the authenticity of some estimates of feeding value, in relation to the analytical techniques used, the lack of agreed standardised procedures, and the apparent variation in results which exists between laboratories. This study examined the extent of this variation when 2 maize silage samples were independently analysed by 9 different laboratories, and compared laboratory based estimates of metabolisable energy [ME] contents with those derived by feeding the same diets to lactating cows.

One approach for effective use of dietary protein in ruminant feeding is to protect it from microbial degradation in the rumen. There has been that sodium hydroxide treatment reduces the degradation of soybean meal (SBM) protein in the rumen. This experiment was to investigate the effects of treating SBM with different concentrations and quantities of NaOH on the microbial fermentation and enzymatic digestion of the treated SBM.