Anaerobic digestion of whole-crop winter wheat silage for renewable energy production

With biogas production expanding across Europe in response to renewable energy incentives, a wider variety of crops need to be considered as feedstock. Maize, the most commonly used crop at present, is not ideal in cooler, wetter regions, where higher energy yields per hectare might be achieved with other cereals. Winter wheat is a possible candidate because, under these conditions, it has a good biomass yield, can be ensiled, and can be used as a whole crop material. The results showed that, when harvested at the medium milk stage, the specific methane yield was 0.32 m3 CH4 kg–1 volatile solids added, equal to 73% of the measured calorific value. Using crop yield values for the north of England, a net energy yield of 146–155 GJ ha–1 year–1 could be achieved after taking into account both direct and indirect energy consumption in cultivation, processing through anaerobic digestion, and spreading digestate back to the land. The process showed some limitations, however: the relatively low density of the substrate made it difficult to mix the digester, and there was a buildup of soluble chemical oxygen demand, which represented a loss in methane potential and may also have led to biofoaming. The high nitrogen content of the wheat initially caused problems, but these could be overcome by acclimatization. A combination of these factors is likely to limit the loading that can be applied to the digester when using winter wheat as a substrat

Assessing the accuracy of current near infra-red reflectance spectroscopy analysis for fresh grass-clover mixture silages and development of new equations for this purpose

The purpose of this study was to ascertain whether Near Infra-Red Reflectance Spectroscopy (NIRS) prediction equations calibrated on grass silage samples, could accurately predict the chemical composition of mixed grass-clover silage samples, and furthermore, to develop and calibrate new grass-clover equations should the grass-based equations be insufficiently accurate for these silages. A set of 94 silage samples from mixed grass-clover swards (clover concentration (CC) ranging from 4 to 1000 g/kg as fed; determined manually) were analysed for chemical composition using reference laboratory techniques, in vivo digestible organic matter in the dry matter (DOMD, in sheep), and in situ degradability of dry matter and crude protein (in cows). The same samples were scanned fresh (undried and unmilled, as is standard practice for silage analysis within UK laboratories) using NIRS (at AFBI, Northern Ireland) and grass-based prediction equations applied. Predicted and observed results were compared. Of 15 chemical components that were tested for prediction accuracy, only volatile-corrected dry matter and nitrogen were well predicted (RPD values of 4.9 and 2.4 respectively, with low root mean square errors of prediction (RMSEP)). Neutral detergent fibre and DOMD showed low RPD values, however the predicted and observed datasets had no significant bias between them and were therefore also considered as fit for purpose. Variables with significant bias between predicted and observed datasets that were not considered suitably accurate included crude protein, acid detergent fibre, microbial dry matter yield and the effective degradability of protein. For many components, bias could be attributed at least in part to CC and changes in the fractionation of nutrients present. For some variables such as crude protein, grass-based equations were sufficiently accurate at low CCs but became inaccurate as CC increased, as expected. In response to inadequate prediction accuracy of certain nutrients, new grass-clover equations were calibrated using the obtained spectra. These were validated and results indicated that the grass-clover-based equations outperformed their grass-based counterparts. The adoption of new grass-clover equations, or alternatively, with further development, the use of a CC correction factor to the existing grass-based equations, is recommended for commercial laboratories offering undried and unmilled silage analysis on samples containing clover

Iron Content Of Ramphastid Diets

Volume: 105Start Page: 130End Page: 13

Yield of microbial protein in sheep fed diets differing in protein degradability

Modern protein systems for ruminants require estimates of microbial protein yield relative to the amount of energy fermented in the rumen. In the Metabolizable Protein (MP) System (Webster 1992) this is expressed by the ratio of microbial nitrogen to fermented metabolizable energy (MiN:FME). However uncertainty as to the estimation of MiN yield both in absolute terms and relative to rumen degradable N (RDN) generates further uncertainty as to the efficiency of capture of quickly and slowly degraded N (QDN and SDN). Moreover the MP system assumes no capacity to recapture recycled undegraded N (UDN). This experiment measures increments in excretion of purine derivatives by sheep to explore the effects of varying relative and absolute supply of QDN, SDN and UDN on relationships between FME utilisation and yield of microbial N from the rumen.</jats:p

Evaluation of Protein Feeds for Dairy Cows

A method is described for the description of feeds and feed mixtures in terms of their ability to provide truly digestible amino nitrogen (N) for cattle. Total basal endogenous N (TEN) loss is assumed to be 0.35g N/kg bodyweight0.75 (Report of A.R.C, Protein Working Group).Feedstuffs are analysed for total N (TN), non-protein N and detergent-insoluble N (neutral detergent, NDIN and acid detergent, ADIN, van Soest, 1982). The disappearance of N is measured from samples incubated in nylon bags in the rumen of dairy cows for 0, 4, 8, 18, 24 and (for forages) 48 hr. Residual N in nylon bags after 18 hr incubation is subjected to 48 hr pepsin digestion to give pepsin-insoluble undegraded dietary N (PSUDN). Digestibility trials are run using three sheep for each test feed and faecal N analysed according to a modification of the method of Mason (1969) into detergent-insoluble faecal N, soluble faecal N and bacterial and endogenous debris N. Urinary N has also been measured since 1983.</jats:p

Effect of heat processing on the nutritive value of mucuna bean (<i>mucun sloanei</i>) for rats

Mucuna bean (Mucuna sloanei, MB) is widely cultivated as a cover crop in a traditional bush fallow system of tropical regions. Despite its protein value and high yield in Nigeria, its use is limited to grazing animals. Its physical-chemical properties may be responsible for under-utilization. Like other legumes, Mucuna bean may contain antinutrients i.e., phenolic compounds which limit their utilization for man and animals. The utilization may be increased by either modifying or removing these compounds using simple processing methods. The following studies were conducted to test the efficacy of using physical-mechanical methods to improve the nutritive value of MB for rats and by implication for other species including human beings.</jats:p

Effect of heat processing on the nutritive value of mucuna bean (<i>mucun sloanei</i>) for rats

Mucuna bean (Mucuna sloanei, MB) is widely cultivated as a cover crop in a traditional bush fallow system of tropical regions. Despite its protein value and high yield in Nigeria, its use is limited to grazing animals. Its physical-chemical properties may be responsible for under-utilization. Like other legumes, Mucuna bean may contain antinutrients i.e., phenolic compounds which limit their utilization for man and animals. The utilization may be increased by either modifying or removing these compounds using simple processing methods. The following studies were conducted to test the efficacy of using physical-mechanical methods to improve the nutritive value of MB for rats and by implication for other species including human beings.</jats:p

4.2 Forage Protein and the Performance and Health of the Dairy Cow

In nutrition, as in any other branch of quantitative applied science, two essential criteria must be met before research findings can be transferred successfully into practice. (1) The fundamental concepts must be essentially sound and (2) the predictions emerging from that conceptually sound system must, in a practical situation, constitute a useful increase in accuracy. The new method proposed by the Agricultural Research Council (ARC, 1980) for expressing protein requirements and the value of feeds for ruminants is undoubtedly an enormous improvement in a conceptual sense on ARC (1965). Indeed, the division of protein inputs into rumen degradable nitrogen (RDN) and undegradable dietary nitrogen (UDN) cannot be faulted since it is the best possible simple description of what happens. Even the decision to retain the concept of crude protein (N x 6.25) and refer therefore to RDP and UDP is harmless. The new ARC protein system therefore fulfils the first criterion for successful practical application. The second criterion can only be fulfilled if ARC (1980) accurately describes both the requirements of animals and the nutritive value of feeds in terms of RDP and UDP. In the case of dairy cows, this is open to considerable doubt.</jats:p