Fribrg01.doc - From nutrient fluxes in animals to nutrient dynamics and health in animal production systems Jaap van Bruchem Martin W.A Verstegen Seerp

Fribrg01.doc - From nutrient fluxes in animals to nutrient...

This preview shows page 1 out of 21 pages.

You've reached the end of your free preview.

Want to read all 21 pages?

Unformatted text preview: From nutrient fluxes in animals to nutrient dynamics and health in animal production systems Jaap van Bruchem, Martin W.A. Verstegen & Seerp Tamminga Wageningen Institute of Animal Sciences (WIAS), Department of Animal Sciences, Wageningen University and Research Centre, P.O. Box 338, NL 6700 AH Wageningen. Summary Agro-ecosystems can be considered as multi-level nested hierarchies, with cross-level interactions of a nonlinear dynamic character. In a balanced situation, agro-ecosystems are capable to apparently behave as selfregulative ‘closed circuit’ systems. Agro-ecosystems, i.c. animal production systems, comprise the subsystems animal, plant and soil. Nutrient use efficiencies at production system level, at issue in this paper, are found to be primarily related to apparent nutrient uptake from the subsystem soil and the balance between the subsystems, rather than to nutrient use efficiency within the subsystem animal. Moreover, animals as such should be considered open systems, with nutrient use efficiencies determined by type and level of production on the one hand and dietary (net/metabolisable) energy to nutrient ratio on the other. The paper addresses the impact of biological manure quality. The authors argue that manure with a higher C:N ratio as a result of lower-protein and higher-fibre diets could serve a variety of purposes. Organic manure with a surplus value compared to artificial fertiliser could replace a major part of external fertiliser use. So, improving manure quality could be the key solution to effectively reducing nutrient emissions to the environment while maintaining high production levels. Such a change in feeding practice is also supposed to benefit health, of animals and soil as well as of the agro-ecosystem as a whole. The authors emphasize that basic technical research alone, carried out under controlled conditions, cannot provide integral solutions for sustainability issues. Interdisciplinary efforts would be needed, undertaken over longer periods of time. New perspectives may emerge through participatory initiatives involving both farmers and scientists for designing, on-farm testing and implementing novel farming technologies. A plea is made for a more complex (nonlinear) and ecocentric (ecotechnological) type of farm management, supporting the whole agro-ecosystem and approaching problems through precaution, rather than through rational (linear) technical control measures. Under such measures natural systems become harnassed, while the ‘end of pipe’ technologies are expensive and, on the longer run, ineffective. Keywords: biological manure quality, soil biology, nutrient use efficiency, health, complex living systems, nutrient emissions environment, balance, agro-ecosystem, sustainability. General introduction Dutch livestock production has adverse effects on the environment. Domestic animals utilise nutrients, i.c. fats, carbohydrates and proteins, inefficiently, in spite of advanced diet formulation and modern breeding techniques. So, a major part of the nutrients, i.c. nitrogen (N), phosphorus (P) and potassium (K), is excreted in faeces and urine. Therefore, a more responsible nutrient management is urgently needed at various levels of the agro-ecosystem, i.c. at the levels of (1) the region, (2) the farm, (3) the animal, (4) digestion and metabolism, 1 and last but not least of (5) the soil-plant interface. This paper primarily deals with nutrient dynamics at the animal and the agro-ecosystem levels, because the excess nutrient emissions to the environment is the most acute problem to be solved. The key question addressed is: “Why has technical research not been more successful in increasing nutrient use efficiencies at commercial farms?”. This cannot simply be a matter of a poor rate of adoption, because farmers are inclined to adhere to conventional practices. Neither is it a question that the proposed technologies would be unpractical and/or too costly. We mean that at the onset of the new millennium, it is time to face the fact that technical experiments as such, carried out on subsystem level under controlled conditions, cannot solve the sustainability issues. Such experiments cannot represent a complex set of interactive parameters across various temporal and spatial scales. Agricultural research practices often apply inappropriate levels of analysis and integration. One should be aware that research at lower aggregation levels, e.g. productivity of individual plants/animals or even beyond, does not automatically provide sound information on system performance at a higher hierarchical level, e.g. the farm. Each level of hierarchy exhibits its own emergent properties, reflecting higher-order interactions among subsystems, in a multidimensional environment. Therefore, before starting an in-depth analysis of nutrient dynamics at various hierarchical levels, it should be realised that the concept “sustainability” entails a variety of objectives that must all, at least partly, be achieved simultaneously. A sustainable (healthy) production system should (1) have no adverse side effects on fragile regions elsewhere in the world and not jeopardise the needs of future generations, (2) be socially acceptable and economically viable in the long term, (3) utilise non-renewable resources as efficiently as possible, (4) use restricted amounts of drugs and agro-chemicals, (5) be ecologically compatible, (6) produce wholesome products for human consumption at a fair price, (7) take into account the integrity of the animal, including health and welfare, (8) be compatible from an ethical perspective, and (9) contribute to the viability of a multifunctional rural environment (Van Bruchem, 1998). According to Waltner-Toews (1997), addressing sustainability questions goes to the very heart of how to make intelligent decisions in the midst of the almost unimaginable complexity of living systems (Fig. 1). The classical notion of animal science is merely geared towards sequential analysis at lower aggregation levels, for instance at level L-2 (organs/tissues) or L-3 (molecular genetics). However, agriculture activities take place within a complex set of interactions between culture and nature. Hence, addressing the problems in agriculture needs philosophically grounded integrative methodologies, at aggregation levels L1 (soil-plantanimal system) to L3 (including gamma and other disciplines as well as the place and time domains). An interdisciplinary approach is needed to deal with the full complexity of the phenomena being studied and to bring about an appropriate communication of integrated knowledge. Agricultural scientists in general are fond of “hard systems”: they endorse and practice analytical/rational thinking, seeking solutions for their scientific problems. For example in the case of the postgraduate school WIAS more than 95% of the research is of a technical nature, of which ~75% at aggregation level L-2 or lower. Although models that account for energy and/or nutrient flows provide highly relevant information for evaluating agro-ecosystems (Heitschmidt et al., 1996; Vavra, 1996), they can represent only a tiny part of the complex reality in the field, that also includes emotional, mental and spiritual matters. Agroecosystems must be considered as multilevel nested hierarchies that have a nonlinear dynamic character and result in high levels of complexity. According to Checkland & Scholes (1990), “hard ware” agricultural cycles are embedded in “human activity systems”. Agro-ecoystems are the product of a combination of evolutionary and genetic history, and the priorities of their managers. We mean that the vitality of the agro-ecosystem is seriously threatened by the lack 2 of coherence between ecologically defined hierarchies representing long-term harmonybalance-flexibility-resilience, and the paradigms of managers and governments, characterised by short-term competition-imbalance-rigidity-fragility. Therefore, integrated action is most urgently needed, to avoid the risk of an eventual collapse of the agro-ecosystem and the rural economies (Van Haaften & Van de Vijver, 1996). synthesis plants L -3 L0 animals L1 L3 soil analysis Figure 1. Research focus relative to level of aggregation (L-3 to L3), from analysis and specialisation to interactive synthesis and design (e.g. L-3, molecular genetics or intracellular, L-2 metabolism or organ/tissues; L-1, animal breeding, nutrition or husbandry; L0 animal; L1, soil-plant-animal cycle; L3, representing 33 subsystems/disciplines/stakeholders). This illustrates that solving the excessive nutrient emissions to the environment is not simply a technical issue. It clarifies why recent initiatives aimed at increasing nutrient use efficiencies (NUE) at crop and animal levels have occasionally resulted in even lower NUE at farm level (Van Keulen et al., 1996). When production systems become unbalanced, nutrient use efficiency may decrease due to antagonistic feedback mechanisms between subsystems. On the other hand, in more balanced situations, synergistic effects may emerge and the performance of production systems as a whole may surpass the total of the subsystems. Therefore, understanding the holistic structure of an animal production system as a functionally self-supporting unit, would be a fundamental step towards sound and meaningful animal science research. Living systems exhibit a dissipative nature. They are open systems which depend on continuous flows of energy and nutrients. Driven by solar energy, water and nutrients from the soil and carbon dioxide from the atmosphere are converted into organic compounds. Plants constitute the main link between the above-ground and below-ground compartments of terrestrial agro-ecosystems. Plant biomass is ingested by animals and converted into animal biomass and heat. So, nutrients flow through the system while energy gradually dissipates in the form of heat (Phillipson, 1966). Animals, at a macro as well as a micro scale, can be considered open subsystems that produce waste. However, what is waste for one species, is feed for another. Waste products, i.c. excrements, along with plant detritus and animal biomass, are utilised by decomposers, i.e. bacteria and fungi, and their predators, e.g. protozoa, nematodes and micro-arthropods (Hassink et al., 1994). These predator-prey interactions are in turn controlled by higher level predators, e.g. centipedes, beetles and 3 spiders. A second pathway of decomposition is formed by decomposers that ingest the organic matter, such as enchytraeids, millipedes, isopods and earthworms, and their predators, such as small mammals and birds. In undisturbed ecosystems, processes of mineralisation and immobilisation are tightly connected with plant growth. From an ecological point of view, it appears that the greater the biomass and complexity of the food web are, the less nutrients are lost from that system, the more tightly nutrients are recycled from retained forms and back again (Brussaard et al., 1997). Beyond their basal equilibrium, agro-ecosystems are able to maintain a higher-level stable equilibrium/organisation, balanced by a matrix of feedback regulation mechanisms. They form, so to speak, “islands of order in seas of disorder” (Capra, 1996). Unlike the situation in modern high-tech farms, the level of self-organisation and robustness of such agro-ecosystems increases with biodiversity. Problem statement and experimental approach Nutrient use efficiencies in Dutch livestock farming, with its high external inputs of feed and fertiliser, are extremely low (Boons-Prins et al., 1996). Consequently, the nutrient emissions are unacceptably high, leading amongst others to acidification and eutrofication of the environment. This paper primarily focuses on the low use efficiency of nitrogen (N); the most volatile nutrient among the macro-nutrients. Overall N losses in Dutch agriculture, amounting to 350 kg.ha-1, cause nitrate leaching and volatilisation of ammonia, N2O and NOx, at levels exceeding the present and future European standards. With highly digestible and protein rich diets, as recommended and widely applied in practice, the C:N ratio in manure is considerably lower than in soil organic matter (6-7 vs 10). The N in “low C:N ratio” manure is quickly mineralised, so that such manure largely bypasses the soil food web. Moreover, low C:N ratio manure may contain significant amounts of phytotoxic components, e.g. phenolic and aromatic compounds, which may have a harmful effect on soil biota and soil health, and the functioning of the rhizosphere (Parr et al., 1997). Our comprehensive hypothesis is that it is feasible to counteract this negative cascade of events by feeding lower-protein diets. This would significantly reduce urinary N excretion. If associated with diets somewhat higher in fibre, the amount of organic matter in faeces would increase, while an additional part of the urinary N excretion would be shifted to the faeces. This would lead to an increased C:N ratio of the manure, which would result in reduced ammonia emission and nitrate leaching. Furthermore, dietary fibre is known to have a “preserving health” effect, as a substrate for short-chain fatty acids. The latter have been associated with the maintenance of a healthy colonic mucosa and the maturation and differentiation of the animals’ immune system (Ewing & Cole, 1994). Thus, we mean that with lower-protein and higher-fibre diets we would arrive at ecologically sustainable production systems, in which the produced manure is a valuable fertilising source, that has surplus value compared with chemical fertiliser. To test the hypothesis, a “learning to adapt to complex living systems” approach has been adopted. Long-term experiments in an integrated/interactive context have started, amongst others in co-operation with the Friesian environmental dairy farmers’ co-operatives VEL & VANLA. The analyses elaborate on nutrient dynamics in the soil-plant-animal system, to identify whether manure with a higher C:N ratio benefits apparent nutrient (in this case N) recovery from the soil and other complex indicators of agro-ecosystem health. The impact of allegedly risky interventions is evaluated at prototype experimental farms of Wageningen UR. Nutrient use efficiencies in Dutch agriculture 4 The external inputs, related to livestock farming in the Netherlands, are significantly higher than elsewhere in the world. Dutch farmlands comprise approximately 2 million hectares of cultivated soil, consisting of heavy clay, loam, sand or peat soils. An area of highquality loamy and sandy soils, i.c. 0.7 million hectares, is used for arable and/or mixed farming. An area of 1.0 million hectares on heavy clay is used for specialised dairy farming largely based on perennial grasslands. In poor quality rain fed sandy regions, i.c. 0.3 million hectares, fodder crops are predominant, i.c. grass and silage maize. Traditionally, in the latter regions, large scale specialised pig and poultry operations are concentrated. In arable and animal farming as a whole, nutrient use efficiencies are low, for N and P respectively 22 and 31 percent only (Boons-Prins et al., 1996). Table 1 shows external inputs of N and P in chemical fertiliser and concentrates in proportion to the outputs of N and P in products, i.c. milk, meat and egg. About 55 percent of the N surplus can be attributed to dairy farming, primarily caused by the excessive use of fertiliser. Approximately 65 percent of the P surplus is related to intensive animal production, i.c. pigs and poultry husbandry. These operations are predominantly driven by use of feedstuffs imported from abroad, exceeding the natural carrying capacity of the agro-ecosystem. The table also shows desired reductions in external inputs and wanted increases in internal nutrient use efficiencies (NUE). Table 1. N and P balances cq use efficiencies in Dutch agriculture (Boons-Prins et al., 1996). ================================================================= millennium end 2nd projection onset 3rd N P N P -------------------------------------------------------------------------------------------------------------Concentrates 190 35 150 28 kg.ha-1 Minerals 8 kg.ha-1 Fertiliser 220 20 80 kg.ha-1 Miscellaneous 35 2 10 kg.ha-1 Products 100 20 100 20 kg.ha-1 Surplus 345 20 140 8 kg.ha-1 Use efficiency 22 31 42 71 % ================================================================= According to national legislation, by 2003 the “annual losses per hectare” should be reduced to 140 kilograms of N (180 kg for grassland and 100 kg for arable land) and 8.7 kilograms of P (i.e. 20 kg of P2O5), respectively. To achieve these reductions at system level, overall increases in NUE are needed from 22% to 42% for N and from 31% to 71% for P. According to Van Bruchem & Tamminga (1997), maintaining arable/animal crop production is most sensitive to the apparent nutrient uptake efficiency from the soil (Sensitivity Coefficients 94% and 84%, for N and P, respectively), while the N loss is most sensitive to chemical fertiliser use (SC 62%) and the P surplus to the importation of feedstuffs (SC 60%). Nutrient use efficiency at animal level is, in second position to the soil, highly relevant for production (SCN 60%, SCP 58%), but hardly effective for decreasing nutrient emissions to the environment (SCN 17%, SCP 23%). At “APMinderhoudhoeve”, a 45/55 dairy/arable prototype farm in Swifterbant (52o32’ N, 5o40’ E), it is currently shown that in regions suitable for mixed farming, N and P use efficiencies (i.e. nutrients in products in proportion to nutrients in external inputs) of almost 5 100 percent may be achieved (Van Bruchem et al., 1999a). So, low external input and high productive (LEI-HP), apparently “closed circuit” farming systems seem within reach. Following this strategy, nutrient emissions to the environment could be drastically reduced while the current high levels of production could be maintained. As is shown below, an integrated soil-plant-animal approach is expected to lead to new perspectives for specialised dairy farming and, potentially, for pig/poultry production systems as well. There is an urgent need for a paradigm shift, calling on for considering animal manure a valuable source for biological soil fertility instead of considering manure a waste to be disposed of off-farm. This paper focuses on N as the nutrient for which long-term sustainable management is most urgently needed, because of the assumed negative impact of nitrogenous compounds on the biological quality of manure (phytotoxic compounds: ammonia, cyanide, biogenic amines, e.g. putrescine and cadaverine, phenolic compounds, e.g. indole, p-cresol and skatole) and animal health and welfare (e.g. with respect to lameness and stress) (Ewing & Cole, 1994). Moreover, their malodorous side effects, and solubility in water (e.g. nitrate) or volatilisation (e.g. ammonia, N2O, NOx) cause various adverse effects in ground and surface water and in the atmosphere. Farming Systems Analysis In the framework of a dairy farmers’ initiated project aimed at reducing N emissions to ecologically justified levels, an appraisal was made of ~90 dairy farming operations, united in two Friesian environmental co-operatives, respectively VEL in Eastermâr (Oostermeer) and VANLA in Achtkarspelen (approximate locations 53o15’ N, 6o10’ E). For each individual farm, the N flows (kg.ha-1) were assessed in (I) the external inputs of fertiliser and concentrates, (II) in homegrown forage and (III) in the outputs of milk and meat. A summary is presented in Table 2, with Nmanure approximated as Nfeed (i.e. Nforage plus Nconcentrates) minus Nproducts. The following N use efficiencies (NUE) were assessed: (1) NUEanimal, including dry cattle and young stock, as Nproducts over Nfeed, (2) NUEsoil as Nforage over Nfertiliser plus Nmanure, and (3) Nfarm as Nproducts over Nfer...
View Full Document

  • Spring '14
  • ALANNASCHEPARTZ
  • The Land, Manure, NUEsoil, Jaap van Bruchem

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes