A study was conducted to estimate variation among laboratories and between manual and automated techniques of measuring pressure on the resulting gas production profiles (GPP). Eight feeds (molassed sugarbeet feed, grass silage, maize silage, soyabean hulls, maize gluten feed, whole crop wheat silage, wheat, glucose) were milled to pass a 1mm screen and sent to three laboratories (ADAS Nutritional Sciences Research Unit, UK; Institute of Grassland and Environmental Research (IGER), UK; Wageningen University, The Netherlands). Each laboratory measured GPP over 144h using standardised procedures with manual pressure transducers (MPT) and automated pressure systems (APS). The APS at ADAS used a pressure transducer and bottles in a shaking water bath, while the APS at Wageningen and IGER used a pressure sensor and bottles held in a stationary rack. Apparent dry matter degradability (ADDM) was estimated at the end of the incubation. GPP were fitted to a modified Michaelis–Menten model assuming a single phase of gas production, and GPP were described in terms of the asymptotic volume of gas produced (A), the time to half A (B), the time of maximum gas production rate (tRMgas) and maximum gas production rate (RMgas). There were effects (P<0.001) of substrate on all parameters. However, MPT produced more (P<0.001) gas, but with longer (P<0.001) B and tRMgas (P<0.05) and lower (P<0.001) RMgas compared to APS. There was no difference between apparatus in ADDM estimates. Interactions occurred between substrate and apparatus, substrate and laboratory, and laboratory and apparatus. However, when mean values for MPT were regressed from the individual laboratories, relationships were good (i.e., adjusted R2=0.827 or higher). Good relationships were also observed with APS, although they were weaker than for MPT (i.e., adjusted R2=0.723 or higher). The relationships between mean MPT and mean APS data were also good (i.e., adjusted R2=0.844 or higher). Data suggest that, although laboratory and method of measuring pressure are sources of variation in GPP estimation, it should be possible using appropriate mathematical models to standardise data among laboratories so that data from one laboratory could be extrapolated to others. This would allow development of a database of GPP data from many diverse feeds.

The preservation of crimped wheat grains by three bacterial inoculants or a chemical additive was compared. Crimped wheat grain [56.8 g dry matter (DM)/kg] was conserved in 1.75-kg plastic bag, mini-silos without treatment, with 4L/tonne of Crimpstore (CS; an additive containing a mixture of ammonium formate, propionate, ethyl benzoate, and benzoate, SAS Kelvin Cave, Ltd., UK) or 1 x 10(5) cfu/g of each of three inoculant additives containing Lactobacillus fermentum (A), Leuconostoc mesenteroides (B), and Lactobacillus buchneri (C). Six replicates were conserved per treatment. Ensiling DM losses, chemical composition, fermentation characteristics, and aerobic stability were measured in the silages after 68 d of ensiling. All the silages were well fermented and remained stable for 84 h after aeration. Subsequently, the rate of deterioration was slowest in crimped grains treated with CS treatment, followed by those treated with inoculant C, while those treated with inoculant A deteriorated most rapidly. Residual water-soluble carbohydrate concentration was higher in crimped grains treated with CS than those treated with the inoculants. Ammonia nitrogen concentrations were lowest in CS-treated crimped grains, followed by inoculants C and A. DM losses were greater in CS-treated crimped grains than in crimped grains treated with inoculants A and C. In vivo digestibility was also measured in Texel-cross lambs fed a grass silage basal diet supplemented with the additive-treated crimped grains or a conventional, lamb finisher concentrate. Dry matter intake and digestibility were unaffected by treatment. In conclusion, bacterial inoculants containing L. buchneri are promising preservatives for crimped wheat grains.

During grazing, it is unclear to what extent rumen conditions cause immediate physical damage to intact, ingested plant cells and whether this coincides with microbial degradation of plant constituents.An in vitro model that included or excluded rumen microorganisms was used to investigate the extent of membrane damage and release of cell constituents from model and forage plants in relation to fermentation parameters.Significant ion release after 2 h indicated that plant cell membranes were intolerant of rumen conditions. Linear release of soluble carbohydrates was observed when timothy grass (Phleum pratense ) was incubated in the presence or absence of rumen fluid for 6 h. Up to 50% of the betanin was released from vacuoles of red beet (Beta vulgaris ) tuber at least 6 h before microbial fermentation had attained maximal rates; 20% of this release was due to nonmicrobial action.We conclude that release of small molecules from ingested, viable plant cells is limited by cell wall porosity. Thus plant structure may influence the colonization and degradation of plant cells by the microbial population.

This paper describes an automated system that has been developed to measure the production of fermentation gas from ruminant livestock feeds inoculated with rumen fluid. The design of the apparatus and its method of use enables gas production to be determined from fresh, unprocessed plant material, as well as the more commonly used ground, particulate substrates, thus representing a closer simulation of forages consumed in vivo. The system consists of 48×140ml bottles containing 100ml buffered rumen fluid and 1g of test substrate. Gas is produced as a consequence of the fermentation of the substrate. Gas, accumulating in the head-space of bottles, is released automatically, by use of pressure sensitive switches and solenoid valves, when a pre-determined pressure is reached. This prevents any build up of pressure in the fermentation bottle, which can affect the behaviour of the gas and the fermentation process. Gas accumulation profiles are produced as the fermentation proceeds and give information on forage digestibility and fermentation kinetics. In this paper, we describe the principles of the gas production technique and provide examples of how the automated system has been used in the evaluation of forages for ruminants. The results obtained show that the automated system is a useful tool for the determination of fermentation kinetics of ruminant feeds. It is simple to use and is considerably less labour intensive than manual gas measurement techniques.

In vitro cumulative gas production is a means to determine the rate and extent of feed fermentation. However, different apparatus and methods used at different laboratories cause variations in the gas production profiles (GPP) obtained. The objective of this experiment was to determine whether any significant difference between laboratories was observed when the same apparatus and method was used.

Inoculants containing lactic acid bacteria, added to herbage at time of cutting, aid the natural process of fermentation to produce lactic acid during ensilage. This lowers the pH and preserves the silage. It is also claimed that enzyme additives break down polysaccharides in plant cell walls, releasing fermentable sugar to stimulate fermentation and increase the digestibility of the silage. This study was carried out to investigate the effects of inoculants and enzymes on silage fermentation characteristics and gas production during in vitro fermentation.A second cut of perennial ryegrass (Lolium perenne) was mown, chopped to 2 – 4 cm lengths, divided into aliquots and treated at a rate of 10 ml kg-1. The treatments were: 1) control (water), 2) inoculant (Pediococcus pentosaceus, Lactobacillus plantarum and Propionibacter jensenii at 1.6 x 105 cells g-1 herbage) 3) enzyme (xylanase, β-glucanase and amylase, applied at a rate of 0.001 g kg-1 herbage) and 4) inoculant + enzyme.

In vitro gas production techniques are becoming increasingly popular as tools to investigate the food quality for ruminant and monogastric herbivores. They are attractive due to their ability to measure the kinetics of digestion associated with the gut microbial fermentation of foodstuffs. It is therefore important to know and understand what factors affect the volume of gas produced, particularly as they relate to repeatability within or between laboratories. In studies involving gas pressure and volume measurement, the chemical composition of the culture medium, the nature of the microbial population and the type and amount of substrate available for fermentation all have a significant influence on gas accumulation. In this study, the manual pressure transducer technique (PTT) of Theodorou et al. (1994) was used to investigate the effect of head-space pressure on the resultant gas production profiles.

There is contradictory evidence regarding the effect on the gas production (GP) profile of a feed if the incubation medium is shaken during the fermentation. In experiments conducted by Theodorou et al. (personal communication), there was no effect of shaking on the rate of gas production (when the medium was shaken after a recording). However, when buffer solutions (containing no substrate) were continually shaken, there was an effect on the volume of gas produced (Rymer et ai. , 1998). The objectives of this experiment were therefore to determine whether die time of shaking affected the GP profile, and whether there was any significant difference between laboratories in this observation.

Gas production from the in vitro digestion of forage with buffered rumen fluid can be measured and used to determine forage digestibility and fermentation kinetics. Rumen micro-organisms ferment carbohydrate to gases (CO2 and CH4) and volatile fatty acids (VFA). The VFA produced also cause CO2 to be released from the C02-bicarbonate buffer. Theodorou et al. (1994) introduced the principle of measuring gas production by pressure increase using an electronic pressure transducer and sealed gas-tight culture bottles. Gases accumulate in the head space of the culture bottles as fermentation proceeds. The gas is measured and then released at regular intervals throughout the fermentation. This procedure was automated (Davies et al., 1995). The automated pressure evaluation system (APES) has advantages over the manual pressure transducer technique (Theodorou et al., 1994) in that it is less labour intensive and has been shown to be more sensitive to food characteristics (Davies et al., 1995). The APES, used in this work, has been improved to include new switches and a filtering system. It has been used here to determine the fermentation characteristics of various ruminant foods: ryegrass, wheat grain and ryegrass silage.

The survival of Cryptosporidium parvum during ensilage of perennial ryegrass was examined in laboratory silos with herbage prepared in one of three different ways; either untreated, inoculated with a strain of Lactobacillus plantarum or by direct acidification with formic acid. The pH values of all silages initially fell below 4.5, but only formic acid-treated silage remained stable at less than pH 4 after 106 d, with the pH of the untreated and inoculant-treated silages rising to above 6. The formic acid-treated silage had a high lactic acid concentration (109 g kg-1 dry matter (DM)) and low concentrations of propionic and butyric acids after 106 d. However, the untreated and inoculant-treated silages showed an inverse relationship, with low lactic acid concentrations and high concentrations of acetic, propionic and butyric acids. These silages also contained ammonia-N concentrations in excess of 9 g kg-1 DM. In terms of the viability of Cryptosporidium parvum oocysts very few differences were seen after 14 d of ensilage with ca 50% remaining viable, irrespective of treatment and total numbers had declined from the initial level of 5.9 x 10(4) to 1 x 10(4) g(-1) fresh matter. Total oocyst numbers remained approximately the same until the end of the ensiling period, with the percentage of viable oocysts declining to 46, 41 and 32% respectively for formic acid, inoculant and untreated silages. The results are discussed in terms of changes occurring during the silage fermentation, in particular the products which may influence the survival of Cryptosporidium and implications for agricultural practice and the health of silage fed livestock.

In vitro methods which can be used to predict the nutritive value of feedstuflfs for livestock are attractive in terms of both speed and economy. The in vitro pressure transducer technique (PTT) whereby the gas evolved during the in vitro fermentation of feedstuffs in rumen fluid is quantified by a pressure transducer, has been used to predict the nutritive value of ruminant feedstuffs. Here the potential for the PTT in predicting the digestible energy contents of eight feedstuffs varying in non-starch polysaccharide (NSP) content fed to growing pigs, was investigated.

A novel greenhouse based soil tilting table apparatus was used to investigate the potential for movement of the protozoan pathogen Cryptosporidium parvum both through and across a low permeability soil following the application of contaminated livestock waste to land. Soil blocks supported at an angle of 7.5% by the soil table were inoculated at one end with oocyst seeded slurry and subsequently irrigated at regular intervals over a 70-day period. Movement of the pathogen in runoff was demonstrated for at least 21 days and in one case in excess of 70 days from the time of inoculation. Water was also lost following percolation down through the soil profile and significant numbers of oocysts were also lost via this route, average numbers leached decreasing from 8.36±0.56×106 at day 1 to 2.27±0.73×104 at day 70. At the end of the study cores were removed from the soil blocks to determine the location of oocysts remaining within the soil. Numbers decreased down through the soil profile and as the distance from the point of inoculation increased so that 70 cm from the point of inoculation no oocysts could be detected in the soil at any depth. This implies that oocysts contained in runoff stay in the aqueous phase and do not precipitate out onto the soil surface, suggesting that even if the distances travelled are increased there may still be a significant pollution threat.

The potential for transfer of the protozoan pathogen Cryptosporidium parvum through soil to land drains and, subsequently, water courses following the application of livestock waste to land was monitored in the laboratory using simulated rainfall and intact soil cores. Following irrigation over a 21-day period, Cryptosporidium parvum oocysts applied to the surface of soil cores (initial inoculum concentration 1×108 oocysts core−1) were detected, albeit in low numbers, in the leachates from clay loam and silty loam soils but not in that from a loamy sand soil. Variations in leaching patterns were recorded between replicate cores. At the end of the study soil cores were destructively sampled to establish the location of oocysts remaining within the soil. Distribution within cores was similar in all three soil types. The majority (72.8+-5.2%) of oocysts were found in the top 2 cm of soil, with numbers decreasing with increasing depth to 13.2±2.8%, 8.39±1.4%, and 5.36±1.4% at depths of 10, 20, and 30 cm, respectively.

Tolerance of anaerobic fungi in the faeces and rumen digesta of cattle to drying in air at approx. 20-degrees-C or 39-degrees-C was investigated. Anaerobic fungi were able to survive in dried faeces, but no significant survival was observed in digesta collected from five different regions of the rumen. Anaerobic fungi in faeces also survived when samples were dried in the presence of rumen digesta. When dried in the presence of sterile faeces, however, anaerobic fungi in rumen digesta failed to survive the drying process. The most plausible explanation for these results is that, during passage from the rumen to the rectum, anaerobic fungi undergo a transition to a dormant form resistant to air-drying.

The total biomass of Chlorella pyrenoidosa (two strains) Chlamydomas reinhardtii. Euglena gracilis. Anabaena flos-aquae and Plectonenema boryanum was determined after the algae were grown in waters from Sylvan, Pleasant and Pidgeon Lakes (all in northeastern Indiana) that had been supplemented with 0.1, 1 or 10% sewage effluents (Indianapolis and Crawsfordsville, Indiana). Biomass was found not to be significantly decreased when the total phosphorus was reduced by alkaline treatment from 7.20-3.50 mg l−1 (50 per cent reduction) for the Crawfordsville effluents. In another series of experiments Chlorella pyrenoidosa was grown in Sugar Creek water (west central Indiana) to which had been added 0.1. 1 or 10% sewage effluents that originated from a motel treatment system. Reactive sewage phosphorus was reduced from 15.4 to 7.44 mg l−1 (57 per cent reduction) by supplying the motel with non-phosphorus cleaning products. No significant reduction in algal growth was observed. Only when effluents were advanced treated so that reactive phosphorus levels were below 1.2 mg l−1 (92 per cent reduction) was algal growth significantly decreased.