Energy Evaluation Systems Research Articles

Status and Prospect of the Evaluation of the Global Wave Energy Resource

Background: With the increasingly serious energy and environmental crises and shortages of conventional energy such as coal and oil, humans have been focusing on new energy sources, especially the abundant wave energy resource. Previous researchers have made great contributions to the design of wave energy converters and have also applied for many patents. However, advanced comprehensive wave energy evaluation and application systems are still scarce, which results in the primitive state of wave energy evaluation. Methods: The goal of this work is to overview the status and prospects of the evaluation of global wave energy to find an effective method to evaluate wave energy resources. This study divides the wave energy evaluation into 4 historical periods according to the data source. The future focus for wave energy resource evaluation is also presented in this study. Results: The wave energy evaluation includes 4 periods: the observational wave data period, the satellite-derived wave data period, the hindcast (simulation wave data from a wave model) wave data period and the reanalysis wave data period. In future research, the focus of wave energy evaluation should include the swell energy, the climatic characteristics of the wave energy resource, the characteristics of marine environments, the mid-to-long-term prediction of wave energy, the short-term forecasting of wave energy, and the evaluation of resources at a particular site. Conclusion: A scientific evaluation framework and application system (software) is urgently needed to provide a basis for decisions for the development of wave power generation, desalination and other developments of wave energy and to promote the sustainable development of human society.

Quantification of the main digestive processes in ruminants: the equations involved in the renewed energy and protein feed evaluation systems

The evolution of feeding systems for ruminants towards evaluation of diets in terms of multiple responses requires the updating of the calculation of nutrient supply to the animals to make it more accurate on aggregated units (feed unit, or UF, for energy and protein digestible in the intestine, or PDI, for metabolizable protein) and to allow prediction of absorbed nutrients. The present update of the French system is based on the building and interpretation through meta-analysis of large databases on digestion and nutrition of ruminants. Equations involved in the calculation of UF and PDI have been updated, allowing: (1) prediction of the out flow rate of particles and liquid depending on the level of intake and the proportion of concentrate, and the use of this in the calculation of ruminal digestion of protein and starch from in situ data; (2) the system to take into account the effects of the main factors of digestive interactions (level of intake, proportion of concentrate, rumen protein balance) on organic matter digestibility, energy losses in methane and in urine; (3) more accurate calculation of the energy available in the rumen and the efficiency of its use for the microbial protein synthesis. In this renewed model UF and PDI values of feedstuffs vary depending on diet composition, and intake level. Consequently, standard feed table values can be considered as being only indicative. It is thus possible to predict the nutrient supply on a wider range of diets more accurately and in particular to better integrate energy×protein interactions occurring in the gut.

The development of a model to predict BW gain of growing cattle fed grass silage-based diets

The objective of this meta-analysis was to develop and validate empirical equations predicting BW gain (BWG) and carcass traits of growing cattle from intake and diet composition variables. The modelling was based on treatment mean data from feeding trials in growing cattle, in which the nutrient supply was manipulated by wide ranges of forage and concentrate factors. The final dataset comprised 527 diets in 116 studies. The diets were mainly based on grass silage or grass silage partly or completely replaced by whole-crop silages, hay or straw. The concentrate feeds consisted of cereal grains, fibrous by-products and protein supplements. Mixed model regression analysis with a random study effect was used to develop prediction equations for BWG and carcass traits. The best-fit models included linear and quadratic effects of metabolisable energy (ME) intake per metabolic BW (BW0.75), linear effects of BW0.75, and dietary concentrations of NDF, fat and feed metabolisable protein (MP) as significant variables. Although diet variables had significant effects on BWG, their contribution to improve the model predictions compared with ME intake models was small. Feed MP rather than total MP was included in the final model, since it is less correlated to dietary ME concentration than total MP. None of the quadratic terms of feed variables was significant (P>0.10) when included in the final models. Further, additional feed variables (e.g. silage fermentation products, forage digestibility) did not have significant effects on BWG. For carcass traits, increased ME intake (ME/BW0.75) improved both dressing proportion (P<0.01) and carcass conformation (P<0.001) and increased (P<0.001) carcass fat score. Increased dietary CP concentration had no significant (P>0.10) effect on dressing proportion or carcass conformation score, but it increased (P<0.01) carcass fat score. The current study demonstrated that ME intake per BW0.75 was clearly the most important variable explaining the BWG response in growing cattle. The effect of increased ME supply displayed diminishing responses that could be associated with increased energy concentration of BWG, reduced diet metabolisability (proportion of ME of gross energy) and/or decreased efficiency of ME utilisation for growth with increased intake. Negative effects of increased dietary NDF concentration on BWG were smaller compared to responses that energy evaluation systems predict for energy retention. The present results showed only marginal effects of protein supply on BWG in growing cattle.

Feed energy evaluation for growing pigs.

Pigs require energy for maintenance and productive purposes, and an accurate amount of available energy in feeds should be provided according to their energy requirement. Available energy in feeds for pigs has been characterized as DE, ME, or NE by considering sequential energy losses during digestion and metabolism from GE in feeds. Among these energy values, the NE system has been recognized as providing energy values of ingredients and diets that most closely describes the available energy to animals because it takes the heat increment from digestive utilization and metabolism of feeds into account. However, NE values for diets and individual ingredients are moving targets, and therefore, none of the NE systems are able to accurately predict truly available energy in feeds. The DE or ME values for feeds are important for predicting NE values, but depend on the growth stage of pigs (i.e., BW) due to the different abilities of nutrient digestion, especially for dietary fiber. The NE values are also influenced by both environment that affects NE requirement for maintenance (NEm) and the growth stage of pigs that differs in nutrient utilization (i.e., protein vs. lipid synthesis) in the body. Therefore, the interaction among animals, environment, and feed characteristics should be taken into consideration for advancing feed energy evaluation. A more mechanistic approach has been adopted in Denmark as potential physiological energy (PPE) for feeds, which is based on the theoretical biochemical utilization of energy in feeds for pigs. The PPE values are, therefore, believed to be independent of animals and environment. This review provides an overview over current knowledge on energy utilization and energy evaluation systems in feeds for growing pigs.

Efficiency of energy utilisation and voluntary feed intake in ruminants

Energy requirements of animals are most readily expressed in terms of net energy (NE), while the energy yield of feed is, at least initially, expressed in terms of metabolisable energy (ME). Energy evaluation systems ‘translate’ NE requirements into ME requirements (ME systems) or assign NE values to feeds (NE systems). Efficiency of ME utilisation is higher for maintenance than for production and the NE yield of a feed varies, therefore, with ME intake. In addition, energetic efficiency for maintenance and production is thought to be different for lactating and non-lactating animals and to be affected by diet quality. As a result, there are currently many national energy evaluation systems that are complex, differ in their approach and are, as a result, difficult to compare. As ruminants in most production systems are fed ad libitum, this is also the most appropriate intake level at which to estimate energetic efficiency. Analyses of older as well as more recent data suggest that ad libitum feeding (i) abolishes the effects of diet quality on energetic efficiency (almost) completely, (ii) abolishes the differences between lactating and non-lactating animals (almost) entirely and (iii) results in overall energetic efficiencies that are always close to 0.6. The paper argues that there is now sufficient information to develop an international energy evaluation system for ad libitum fed ruminants. Such a system should (i) unify ME and NE systems, (ii) avoid the systematic bias and large errors that can be associated with current systems (iii) be simpler than current systems and (iv) have as a starting point a constant efficiency of ME utilisation, with a value of around 0.6. The remarkably constant efficiency of ME utilisation in ad libitum fed ruminants could be the result of energetic efficiency as well as feed intake regulation being affected by the same variables or of a direct role of energetic efficiency in feed intake regulation. Models to predict intake on the basis of the latter hypothesis are already available for non-reproducing ruminants but remain to be developed for reproducing animals.

Toward a new practical energy evaluation system for dairy cows

Energy evaluation systems translate an animal’s net energy (NE) requirements into feed metabolisable energy requirements (MER). The Feed into Milk (FiM) project (Agnew RE, Yan T, France J, Kebreab E and Thomas C 2004. Energy requirement and supply. In Feed into Milk. A new applied feeding system for dairy cows (ed. C Thomas), pp. 11–20. Nottingham University Press, Nottingham, UK) proposed a new system to predict MER of dairy cows that is, in contrast to previous energy evaluation systems for cattle, independent of feed quality. The FiM system shares this characteristic with an energy evaluation system for ad libitum-fed cattle proposed in 1994 by Tolkamp and Ketelaars (T&K). The FiM system requires nine parameters to translate requirements for NE into MER for dairy cows, while the T&K system for cattle requires only two for the same purpose. This paper analyses the contribution of each of the parameters to the final MER predictions, the differences in MER prediction between the two systems and the underlying causes of these differences. The systems differ considerably in their estimates of the NE that is required for maintenance and in their (implicit) assumptions about the partial efficiency of ME utilisation for lactation. The T&K system is based on a constant partial efficiency of ME utilisation, but in the FiM system this efficiency changes with milk yield (MY) and shows a sharp discontinuity that is at odds with the underlying biology. These are the two main causes of the differences in MER predictions. Nevertheless, over a range of MYs between 10 and 40 kg, and for cows maintaining, gaining or losing weight, the MER predictions of the two systems are very similar with maximum differences of up to ±2% only. FiM predictions of MER are systematically higher than T&K predictions for cows with very low and very high MY. It is concluded that the FiM system could reduce parameter requirements with negligible effects on MER predictions. The combination of a very high maintenance NE parameter and a curvilinear model with two subsequent corrections leads to internal inconsistencies in the FiM system. The T&K system is much simpler but it might benefit from including more recent information for the estimation of its parameters.

Comparison of energy evaluation systems and a mechanistic model for milk production by dairy cattle offered fresh grass-based diets

Grass-based diets are of increasing social-economic importance in dairy cattle farming, but their low supply of glucogenic nutrients may limit the production of milk. Current evaluation systems that assess the energy supply and requirements are based on metabolisable energy (ME) or net energy (NE). These systems do not consider the characteristics of the energy delivering nutrients. In contrast, mechanistic models take into account the site of digestion, the type of nutrient absorbed and the type of nutrient required for production of milk constituents, and may therefore give a better prediction of supply and requirement of nutrients. The objective of the present study is to compare the ability of three energy evaluation systems, viz. the Dutch NE system, the agricultural and food research council (AFRC) ME system, and the feed into milk (FIM) ME system, and of a mechanistic model based on Dijkstra et al. [Simulation of digestion in cattle fed sugar cane: prediction of nutrient supply for milk production with locally available supplements. J. Agric. Sci., Cambridge 127, 247–60] and Mills et al. [A mechanistic model of whole-tract digestion and methanogenesis in the lactating dairy cow: model development, evaluation and application. J. Anim. Sci. 79, 1584–97] to predict the feed value of grass-based diets for milk production. The dataset for evaluation consists of 41 treatments of grass-based diets (at least 0.75 g ryegrass/g diet on DM basis). For each model, the predicted energy or nutrient supply, based on observed intake, was compared with predicted requirement based on observed performance. Assessment of the error of energy or nutrient supply relative to requirement is made by calculation of mean square prediction error (MSPE) and by concordance correlation coefficient (CCC). All energy evaluation systems predicted energy requirement to be lower (6–11%) than energy supply. The root MSPE (expressed as a proportion of the supply) was lowest for the mechanistic model (0.061), followed by the Dutch NE system (0.082), FIM ME system (0.097) and AFRC ME system (0.118). For the energy evaluation systems, the error due to overall bias of prediction dominated the MSPE, whereas for the mechanistic model, proportionally 0.76 of MSPE was due to random variation. CCC analysis confirmed the higher accuracy and precision of the mechanistic model compared with energy evaluation systems. The error of prediction was positively related to grass protein content for the Dutch NE system, and was also positively related to grass DMI level for all models. In conclusion, current energy evaluation systems overestimate energy supply relative to energy requirement on grass-based diets for dairy cattle. The mechanistic model predicted glucogenic nutrients to limit performance of dairy cattle on grass-based diets, and proved to be more accurate and precise than the energy systems. The mechanistic model could be improved by allowing glucose maintenance and utilization requirements parameters to be variable.

Influence of nutrition level on digestibility in high yielding cows and effects on energy evaluation systems.

The objective of the study was to determine the effect of nutrition level (NL, multiples of maintenance energy requirement) on the digestibility of nutrients for dairy cows regarding the energy supply of the animal. The digestion of nutrients and energy was investigated in two trials using lactating dairy cows. The NL varied from 2.7 to 5.0 using diets similar composition. In addition, sheep were given the same feed with a NL of 1.4. Digestibility of dry matter (DM) and all specific measures of dietary components declined significantly as NL increased. Digestibility of energy decreased by 4.1% for each increase in NL. The metabolizable energy, the ability to metabolize energy (metabolizable energy/gross energy), and the content of net energy for lactation (NE(L)) per kilogram of DM intake were calculated for NL from 1 to 6 on the basis of these relationships and as well as the gross energy, methane energy, and urine energy. Accordingly the NEL content declined by 0.11 MJ/kg of DM intake or 1.6% as the NL increased by one unit. It means that the NE(L) requirement above the maintenance requirement increased by 0.07 MJ of NE(L) per kilogram of fat-corrected milk, if the NL increased by one unit.

Digestive and Metabolic Utilization of Feed Energy in Swine: Application to Energy Evaluation Systems

Noblet, J. 2000. Digestive and metabolic utilization of feed energy in swine: Application to energy evaluation systems. J. Appl. Anim. Res., 17: 113–132. Feeds can be attributed different energy values according to, first, the step considered in energy utilization (DE: digestible energy, ME: metabolisable energy and NE: net energy) and, second, the method used for estimation at each step. This paper reviews some of the most important dietary (chemical composition) and animal (body weight) factors which affect digestive and metabolic utilization of energy by pigs. Available results show that energy digestibility is negatively affected by dietary fibre (DF) content of the diet and is increased with pig body weight, the negative effect of DF is reduced in heavier pigs, so that most feeds should be attributed at least two different DE values, one for growing-finishing pigs and other for mature pigs (reproductive sows). Metabolic utilization of energy is highly related to diet chemical composition with higher efficiencies for ME provided by fat or starch. The hierarchy between feeds is then dependent on the energy system, with a clear preference for NE systems which are the best predictors of the “true” energy value of feeds and of performance of pigs. The available NE systems are also compared. Further improvements of energy systems for pigs are discussed.

Commission on Horse Production

1. Background • with regard to genetic aspects of horse production major topics covered included genetic base of Horse production in Europe has played an imperformance, reproduction and health, breeding portant and variable role in agriculture over the last programmes, performance testing, estimating 50 years. In the early 50s horse populations were breeding values, inbreeding and population size. largest and horses were mainly used providing draft • With regard to environmental aspects of horse power for agriculture and forestry. Thereafter the production subjects covered included nutrition of number of horses decreased since fewer draught sport horses, nutritional value of feed, protein and horses were needed and in many populations breedenergy evaluation systems, biotechnical aspects in ing goals were adapted for sport horses. Nowadays, reproduction, and management aspects of horses. in most European countries horse populations have • Also organisational aspects relating to registering increased in numbers particularly over the last ten and identifying horses were covered. years and are dominated by sport horses, such as • Recently, more attention has been given to probriding horses, race horses, and cart horses. Neverthelems relating to behaviour of horses, to physiless in some countries horses are kept for meat and ology in training, exercising and performing milk production and other special markets. Parallel horses, and to education of horse owners and with the great changes in size and function of many users. horse populations public and scientific attention given to horses has steadily increased. Following the great variety of horse populations in Europe, the Commission on Horse Production has always looked closely into the situation of horse 2. The commission’s policy production of each individual member country of EAAP. Also, several activities in cooperation beFollowing the mandate of the Commissions as tween scientific groups interested in horses have led defined by the Statutes of the EAAP with regard to to recommendations widely accepted in Europe, such improving the conditions of animal production and as the Energy and Protein Evaluation Systems of its organisation, the Horse Commission focused on Feed for Horses. Recently, the Horse Commission genetic and environmental aspects in horse productestablished a working group for identifying systems ion either by itself or in close cooperation with the of performance testing and evaluating horses within discipline-oriented Commissions. In more detail, and across European countries.

Evaluation of feedstuffs and pig diets. Energy or nutrient‐based evaluation systems? I. limitations of present energy evaluation systems

The present energy evaluation systems of pig feeds are described and evaluated with reference to their scientific basis and practical performance. The different energy evaluation systems are assessed with regard to (i) the definitions and determinations of nutrient fractions in the feed, (ii) the methods for determination of digestible nutrient fractions, (iii) the expression of energy value, (iv) the methods for determination of specific energy coefficients for the different nutrient fractions, and (v) the adequacy of using energy as the sole property in the feed value. It is concluded that present feed evaluation might generally be imprecise due to limitations in the principles of current energy evaluation systems, which oversimplify the nutritional value of the feed and ignore variations in the actual values.

The energetic value of nonstarch polysaccharides in relation to physical activity in group-housed, growing pigs.

The dose response effect of dietary nonstarch polysaccharide (NSP) content on physical activity in relation to metabolic rate in pigs was studied. Twelve clusters of 14 pigs (50-kg castrated males) were fed one of four diets, similar in composition, except for the starch and NSP content. The difference in starch and NSP ratio was created by exchanging sugar beet pulp silage (SBPS) for tapioca. On a DM basis, diets contained 0, 5, 10, or 15% SBPS. Pigs were housed in groups and fed at 2.5 times the maintenance energy requirements. Nitrogen and energy balances were measured per cluster during a 7-d experimental period, which was preceded by a 2-wk adaptation period. Dietary composition did not affect ADG. Metabolizability decreased with increasing dietary SBPS content (P < .01). Heat production as well as energy retention were unaffected by the exchange of starch for NSP (P > .1). However, dietary composition affected energy expenditure on physical activity (P < .10). Pigs were more quiet when dietary NSP content increased. Based on heat production data and on apparent digestibility of crude protein, crude fat, and NSP, the estimated net energy value of fermented NSP was 14.8 kJ/g. This relatively high energy value of fermented NSP was mainly related to the lowered energy expenditure for physical activity, 3.9 kJ/g of fermented NSP. The present study demonstrated that the lower energetic utilization of fermented NSP compared with that of starch can be fully compensated in pigs by reducing their physical activity. Thus, energy evaluation systems should account for systematic dietary influences on physical activity.

The relationship of cell wall content and cell wall degradation rates measured in situ to digestibility depression of forages given to wether sheep

The fractional rate of digestion as compared with the rate of passage can determine the extent of digestion in the digestive tract and the amount of potentially digestible matter escaping digestion (Van Soest, 1982). The lower the rate of digestion or the higher the rate of passage, the more nutrients escape digestion. The effect of rate of passage is higher for food components with slow rates of digestion such as neutral-detergent fibre (NDF) (Mertens, 1985). Increasing feeding level is associated with higher rate of passage, lower residence time in the rumen and decreased digestibility of nutrients. Digestibility depression is considered in several energy evaluation systems (van Es et al., 1978; Moe, 1981; Agricultural and Food Research Council, 1993 etc.) although most of the systems use a standard percentage discounting energy value, regardless of foods or nutrient components. Studies (Tyrell and Moe, 1975) showed that digestibility depression is higher for cell wall than cell solubles, whilst El Khidir and Thomsen (1983) reported that digestibility depression of cell walls was responsible for proportionately 0-7 of the observed decrease in digestibility. Mertens (1985) reported that energy discount factors can be related to NDF content and total digestible nitrogen value of foods. Ørskov (1996) recommended prediction of food potential of both energy value and intake from degradation characteristics.

Comparison of energy evaluation systems for dairy cow feeds

Abstract Nine energy evaluation systems were compared on the basis of results from 51 milk production trials and 261 diets. The nine systems evaluated were the fattening feed unit used in Finland (FU F ), the feed unit used in Denmark (FU D ), the metabolizable energies used in the UK (ME MAFF , ME ARC ) and Sweden (ME SW ), the net energy in lactation used in the Netherlands and Norway (NEL NL ), France (NEL FR ) and the USA (NEL US ) and the net energy in fattening from Rostock (NEF RO ). Energy values for feedstuffs were calculated using the same digestibility coefficients in each system. Energy supply ( S ), requirements ( R ) and the S / R ratio were calculated using the treatment means. The accuracy of the systems was studied through the one-way analysis of variance with the trial as a classifier. Small residual variance (MSE) in the S / R ratio indicated that a system accurately predicted the differences in the productive values of the diets within the trial. The relation between estimated and observed milk yield was studied through regression analysis. The MSE of the S / R ratio was smallest in ME MAFF and NEL NL . The regression coefficient between the estimated and observed milk yields was closest to one and the intercept closest to zero in ME MAFF and in NEL NL . It is concluded that with Finnish dairy cow diets, ME MAFF is the most accurate of the feed evaluation systems examined; the next best are NEL NL and NEL US .

Energy evaluation systems for pig diets: a review

Different energy values are given to a given feed according, firstly, to the considered step of energy utilization by the pig (digestible (DE), metabolizable (ME) or net (NE) energy) and, secondly, to the prediction method used for each step. The aspects developed in the first part of this review relate to the effects of chemical composition of the diet and animal factors such as physiological stage or body weight, and also the interactions between diet and animal, on digestive and metabolic utilization of energy. In a second part, the available DE, ME and NE systems when applied to diets or ingredients are presented. In the third part, the different energy systems (firstly DE vs. ME vs. NE, and secondly the NE systems) are compared in terms of advantages, limits and applicability for each of them. The comparison indicates that the hierarchy between diets and, more clearly, between ingredients is markedly dependent on the energy system. The composition of diets (ingredients and chemical characteristics) resulting from least-cost formulation is also affected by the energy system. The last part of the review considers the validity of the different energy systems or their ability to predict pig performance. From this review, it is clear that more emphasis should be given to, firstly, study digestive interactions and, secondly, improve the methods (chemical, physical, in vitro, …) used for (rapid) prediction of energy values of pig feeds.

Digestible, metabolizable and net energy values of 13 feedstuffs for growing pigs: effect of energy system

Digestible (DE), metabolizable (ME) and net (NE) energy values and digestible nutrient contents of 17 complex diets were measured in 45 kg growing boars. Values for DE and ME were estimated from collection of faeces, urine and measurement of methane production, while NE was obtained from energy balances carried out in respiration chambers. Diets were prepared from 13 ingredients (wheat, barley, maize, tapioca, sweet potatoes, soyabean meal, rapeseed meal, sunflower meal, peas, maize distillers grains, maize gluten feed, cane molasses and animal fat), the inclusion levels of all ingredients being independent. The DE, ME, NE and digestible nutrients contents of ingredients were then calculated by regression of nutritive values of diets on levels of inclusions of ingredients. Digestibility of energy of diets was negatively affected by their neutral detergent fibre (NDF) content (−1.1% per 1% NDF). Digestibility of fat increased curvilinearly with dietary fat content. Energy evaluation systems (DE versus ME versus NE) affected the hierarchy between the tested ingredients: when the energy content of wheat was considered as 100, the energy values of soyabean meal, tapioca and animal fat were 101, 98 and 184 on a DE basis, 97, 99 and 187 on a ME basis and 66, 106 and 241 on a NE basis. The correspondence between measured NE of ingredients and NE values which can be calculated from available NE systems varied according to the system. The study indicates that the tabular DE content or nutrient digestibility coefficients of fibre or fat rich ingredients are overestimated when they are included in complex diets. The results emphasize the necessity for estimating energy values of pig feeds, and especially ingredients, on a NE basis. In addition, more attention should be paid to digestive interactions occurring with changes in feeding level or digestive capacity of the pigs, especially with complex diets.

GIS technology applied to environmental control energy analysis: An example

Energy is an important factor in the economics of agricultural building. Environmental and management variables induce spatial and temporal variation in energy need. Coupling a climate database and agricultural building energy model to a geographical information system makes it possible to estimate areal and peak energy needs for temperature and humidity control. The application of the GIS technology is demonstrated in this paper by using a greenhouse energy model as an example. Manyfold differences in greenhouse energy need between diverse sites demonstrated the need to invest in developing easy to use energy evaluation systems.

Feed energy evaluation systems and current research on dietary fat for pigs in europe report of the 1991 braude scholarship study tour

Dietary energy is the major factor influencing the cost of pig feed and consequently pig meat production. Therefore, precise estimation of the energy value of feedstuffs is particularly important. The 1991 Braude Scholarship was used to finance a visit to a number of research establishments based in the Netherlands, Denmark, Germany, Switzerland and France to compare their systems of energy evaluation, to investigate the energy-yielding ingredients included in pig diets in these countries and to learn of current research concerning these areas, specifically on the digestibility of fats.

Evaluation of various types of forest biomass and wood processing residues as feed for ruminants

Eight digestibility trials were performed with rams to evaluate the nutritive values of energy willow leaves (Salix Aqualica), whole short rotation trees (S. Aquatica, S. dasyclados), forest biomass, consisting of branches, foliage and browses, entire hardwood, hydrolysed birch tree pulp and dissolving pulp. The chemical composition of the materials varied according to the leaf-to-wood ratio and the degree of hydrolysis of the pulp. The leaves had high protein contents and low crude fibre contents but remarkably high contents of acid detergent fibre (ADF). The materials containing wood had a high crude fibre content, 41—54 %, as had also both pulps, 44—75 %, but the ADF content was on average 17.4 %-units higher than the content of crude fibre. The lignin content was high in the wood-containing materials (29—34 %) and also high in one of the leaf pulps. The digestibilities of the leaf pulps varied considerably, from 42 to 61 % for DM. The forest biomass had organic matter OM digestibility varying from 20 to 39 %. The digestibility was affected by the ratio of foliage to wood in the material. Hydrolysed wood pulp had poor digestibility, 38 % for OM, but the digestibility of dissolving pulp was comparable to that of good quality roughage, 75 %. The leaf pulps and dissolving pulp had FU values of 0.48—0.69/kg DM. Forest biomass and hydrolysed birch pulp had low values, 0.22—0.34 FU/kg DM. Various energy evaluation systems were compared in the feed value calculations. The fibre correction system gave very low values. Tree foliage and cellulosic wastes with a low lignin content can be utilized as ruminant feed but the possibilities of disposing in this way of cellulosic wastes with high lignocellulosic contents are very limited.

Tests of 6 energy evaluation systems for dairy cows

The ability of 6 energy systems for accurate animal performance prediction was studied by means of 992 individual results from 40 feed intake trials with dairy cows. The systems are: starch equivalent system (SE), net energy fat system for ruminants (EFr), feed unit for milk production — The Netherlands and Belgium (VEM), feed unit for milk production — France (UFL), metabolizable energy system (ME), net energy lactating cows (NE 1). The results demonstrate that the more recent systems as VEM, UFL, ME and NE 1 are better than the SE system. The EFr system is more accurate than the SE system, but seems less accurate than the others. For all systems, except for UFL, recorded performances were on an average lower than predicted. In the UFL system, energy value of roughages seems to be underestimated. Accuracy of the systems decreases when the level of over- or underfeeding increases, which suggests that standards for body weight change may be improved.