E.A. Lantinga

Multiphasic analysis of gas production kinetics for in vitro fermentation of ruminant feeds

Recently developed time-related gas production techniques to quantify the kinetics of ruminant feed fermentation have a high resolution. Consequently, fermentation processes with clearly contrasting gas production kinetics can be identified. Parameterization of the separate processes is possible with a suitable multiphasic model and modelling method. A flexible, empirical, multiphasic model was proposed for parameterization of gas production profiles. This equation was fitted, using a two-step method, to four gas production profiles and the maximum fractional rate of substrate digestion (RM) was calculated for each phase. In the first step, the number of phases and starting values for parameters of the multiphasic model were derived from a combination of either (1) the measured cumulative gas production profile and its first (rate of gas production) and second (change in rate of gas production) derivative or (2) a fitted monophasic curve and the residuals between this curve and the observations. In the second step, the starting values were used to fit di- or triphasic models. Using Approach 1 was complicated by frequent fluctuations in the gas production rate. However, the combined graph of the fitted monophasic curve and residuals (Approach 2) gave good results for every profile. The multiphasic model fitted the profiles well. The robustness of the model declined when the number of phases was increased, underlining the importance of accurate estimations of starting values. It is argued that the model parameters and the calculated RM are useful for feed quality evaluation. The results show that mathematical description of gas production profiles requires a two-step approach and a multiphasic model.

Exploring the potential for improved internal nutrient cycling in dairy farming systems, using an eco-mathematical model

Nutrient management at Dutch dairy farms is changing rapidly from strong reliance on external inputs to more prudent utilization of internal resources. This paper explores opportunities and constraints arising from this shift towards eco-technological management. A mathematical model of inorganic and organic nitrogen (N) flows in a dairy farming system was formulated based on ecological concepts, integrating processes of nutrient input, recycling, immobilization and mineralization. Recycling is defined as the mineralization of N within the year of its incorporation into herbage, which occurs through release from faeces, animal urine and non-harvested biomass. We simulated changes in inorganic and organic N per hectare, and the consequent emission (E), mineralization (M s ) and recycling (R) of N for different initial amounts of inorganic and organic N. Results demonstrate that in the long term, the system evolves to equilibrium amounts of inorganic and organic N, which are strongly determined by the imposed management practices, such as fertilizer input and grassland management. In the short term, moving away from the equilibrium is possible for particular initial amounts of inorganic and organic N. In the equilibrium state, E was reduced by lowering inorganic fertilizer input rate, increasing grassland productivity and improving animal N conversion efficiency, i.e., only by production-related parameters. Only in the short term E was affected by adjustments in quality-related parameters: lower N content, lower digestibility of herbage, reduced degradability of non-harvested biomass and faeces, and parameters determining the functioning of soil biota (degradation rate, efficiency, C/N ratio). Qualityrelated parameters had no effect on internal nutrient cycling in the equilibrium state, because adjustments in M s were completely compensated by changes in R. A comparison of farming systems demonstrated that farming systems can be designed in such a way that improvement of internal nutrient cycling supports the same production with lower inputs and lower emissions.

Analysis of the production stability of mixed grasslands. I. A conceptual framework for the qualification of production stability in grassland ecosystems

The analysis of the intrinsic properties and processes of ecosystems, which regulate the production stability of mixed grasslands, has been complicated by the environmental noise caused by stochastic weather fluctuations. A mathematical framework is presented to deduct the actual, the extrinsic and the intrinsic stability of grassland ecosystems, as defined in the companion paper, from their yield patterns and the environmental patterns during a long time-course. Intrinsically stable grassland ecosystems remain stable when subjected to structured environmental fluctuations, yet are destabilised by stochastic environmental fluctuations. Contrastingly, intrinsically oscillating grassland ecosystems are on average somewhat stabilised by stochastic environmental fluctuations in temperate climates. Structured environmental fluctuations may fully stabilise these systems in continental climates. However, in these climates these ecosystems are destabilised by stochastic environmental fluctuations. As in some cases the actual stability of yields may be higher in intrinsically oscillating systems than in intrinsically stable systems, the stability of yields observed in short-term experiments is a poor reflection of the intrinsic ecosystem properties. Subsequently, this mathematical framework is applied to a number of experimental ecosystems in the Park Grass Experiment (UK) and at the Ossekampen (The Netherlands), which were subjected to various fertiliser and lime applications, and to a regime of either cutting or grazing, respectively. In the Park Grass Experiment, the yields of all plots studied appeared to be extrinsically unstable, with only small differences between fertiliser treatments. However, plots receiving lime showed a higher extrinsic stability than unlined plots. The extrinsic stability of the plot receiving farmyard manure (FYM) was lower than that of the plot receiving an equivalent of mineral nitrogen. Also at the Ossekampen, only small differences arose between the extrinsic stability of plots receiving various fertiliser treatments. Instead, the grassland management of the plots had an overriding effect on these stability levels. Whereas the extrinsic stability of all cut plots was low, all grazed plots were nearly entirely stable. It is argued that the nitrogen dynamics in grassland ecosystems have only a small impact on their extrinsic stability levels, in spite of the predictions by simulation models. Instead, pH-related soil processes and the grassland management play an overriding role in the maintenance of the production stability of mixed grassland. It is conceivable that a large number of other processes, which regulate ecosystem stability, could be identified in other plots and experiments, using the same mathematical framework.

Interpretation of results from on-farm experiments: manure-nitrogen recovery on grassland as affected by manure quality and application technique. 1. An agronomic analysis

This article discusses the outcomes of a re-analysis of a grassland experiment, by locating it within the wider institutional context composed of well-established routines used in agronomic research and the dominant epistemological tradition of agricultural sciences. It is argued that both, research routines and epistemological tradition, are strategic pillars of the reigning socio-technical regime. They contribute to path-dependency, thus reinforcing the uni-lateral development tendency centring on technological solutions that fit within the dominating regime. An important, albeit probably unintended consequence is that promising novelties are obscured within and through research, thus blocking a potentially highly effective road towards sustainability.

Herbage intake and use of outdoor area by organic broilers: effects of vegetation type and shelter addition

The herbage intake and use of outdoor areas by organic broilers were investigated in an experiment laid out in two fields, i.e., a grass-clover pasture and wheat stubble with undersown clover. Each field was divided into two plots, one with and one without extra shelter consisting of camouflaging nets around huts constructed from straw bales where the broilers were housed during the night. Five hundred birds were assigned to each of the four treatment combinations. To analyse the use of outdoor areas with respect to herbage intake, plots were divided into three smaller areas surrounding the night house: P1 (most intensively used area), P2 (intermediate area) and P3 (least intensively used area). The mean daily herbage dry matter intake per broiler between 25 and 80 days of age was 10.7 g, irrespective of vegetation type. The amount of herbage consumed represented up to 7 and 3% of the birds’ daily protein and energy requirements, respectively. When extra shelter was provided, the area of P1 increased, suggesting that some extra protection gave the broilers more confidence to explore further areas of the plots. However, the total frequently-used area (P1+P2) was not affected by the presence of extra shelter, indicating that there was a critical distance (about 20 m in this study) that was seldom surpassed. It is concluded that adding shelter in the field contributes only marginally to a more even distribution of the excreta.

Agro-ecological indicators (AEIs) for dairy and mixed farming systems classification: Identifying alternatives for the Cuban livestock sector

Attainment of acceptable levels of land and labor productivity and low external input use is not a mutually exclusive proposition. This study examines characteristics of a range of current specialized dairy farming systems (DFS) and mixed (crop-livestock) farming systems (MFS) in Cuba to determine their efficiency in the process of food and feed production. The central question was whether the favorable results of MFS realized in a small-scale experimental system were also attainable in larger, commercial farms. To this end, we collected data on 93 farms from around the country for a period of 1 year. The farms were classified according to four predictor variables: farm type, years since conversion from DFS to MFS, proportion of land allocated to crops in rotation and farm size. Farms were compared based on 12 pre-selected Agro-Ecological Indicators (AEIs) by using analysis of variance and Tukeys HSD tests. The 12 AEIs were also subjected to a principal components analysis and related to the four predictor variables by reduced-rank regression, also known as redundancy analysis. Three farm types were distinguished: mixed farming experimental (MFe), mixed farming commercial (MFc) and specialized dairy farming (DFS). Total energy output per unit of farm area was on average four to six times higher on the mixed farms than on the specialized dairy farms, while protein output three to four times higher. Milk yield per unit of forage area was highest on MFe (2.4 Mg ha−1 yr−1), followed by MFc (1.7), while it was much lower (0.7) on DFS. The redundancy analysis revealed that MFe did only slightly better than MFc and was most opposite to DFS in terms of AEIs. In conclusion, the previous experimental findings were confirmed nationwide, thus demonstrating the benefits of MFS for agro-ecological performance in Cuba.

Complex agro-ecosystems for food security in a changing climate

Attempts to increase food crop yields by intensifying agricultural systems using high inputs of nonrenewable resources and chemicals frequently lead to de-gradation of natural resources, whereas most technological innovations are not accessible for smallholders that represent the majority of farmers world wide. Alternatively, cocultures consisting of assemblages of plant and animal species can support ecological processes of nutrient cycling and pest control, which may lead to increasing yields and declining susceptibility to extreme weather conditions with increasing complexity of the systems. Here we show that enhancing the complexity of a rice production system by adding combinations of compost, azolla, ducks, and fish resulted in strongly increased grain yields and revenues in a season with extremely adverse weather conditions on East Java, Indonesia. We found that azolla, duck, and fish increased plant nutrient content, tillering and leaf area expansion, and strongly reduced the density of six different pests. In the most complex system comprising all components the highest grain yield was obtained. The net revenues of this system from sales of rice grain, fish, and ducks, after correction for extra costs, were 114% higher than rice cultivation with only compost as fertilizer. These results provide more insight in the agro-ecological processes and demonstrate how complex agricultural systems can contribute to food security in a changing climate. If smallholders can be trained to manage these systems and are supported for initial investments by credits, their livelihoods can be improved while producing in an ecologically benign way.

The influence of feeding strategy on growth and rejection of herbage around dung pats and their decomposition

SUMMARY Fresh cattle dung from four farms with different feeding strategies was used to create artificial dung pats in a continuously grazed pasture in order to compare the rejection of herbage growing around the pats, the effect on undisturbed herbage growth under cages and pat decomposition. The first farm was an extensive organic farm (ORGE) with young steers grazing on a biodiverse sward. The second was an intensive organic farm (ORGI) with dairy cattle grazing on a grass/clover sward during the day and fed low-protein forages indoors. The third dung used was from an integrated farm (INT), where the feeding strategy was aiming for high dung quality by including straw in the diet. The fourth examined dung was from a conventional farm (CONV) aiming for a high milk production per cow, where fertilized grazed grass was the main component of the diet. A human smell test was performed to rank the odour of the four dungs. After 6 weeks of continuous grazing with dairy cattle, herbage yield around INT pats tended to be lowest, whilst undisturbed herbage yield in and around caged INT pats was highest (P<0 . 05). Therefore, it could be concluded that rejection was lowest for INT. The CONV pats gave highest rejection (P<0 . 05). However, herbage yield around the dung pats under grazing showed no significant correlation with both the human smell test and the contents of total-N and sugar in the rejected herbage. The feeding strategy had a significant effect on the decomposition of dung pats under the cages. After 6 weeks, the most liquid and least fibrous dung (CONV) showed highest decomposition (P<0 . 05), whilst decomposition of the most solid and fibrous dung (ORGE) tended to be lowest. However, no relationship was found between the decomposition of dung and the rejection of herbage around the dung pats. When combining a number of parameters determined in the experiment and comparing them using index figures for dung quality in terms of rejection, herbage growth and decomposition, the index figures of ORGI (102) and especially INT (113) were above average (100), while those of ORGE (94) and CONV (90) were below average. The difference between ORGI and INT might be explained by the addition of straw to the diet in the latter. The study showed that there are possibilities to improve dung quality by altering feeding strategy.

Explorative research into quality of slurry manure from dairy farms with different feeding strategies

To assess cattle slurry manure quality in relation to feeding strategy, a field experiment and a bio-assay were carried out with slurries from four dairy farming systems that used diets differing in protein content and digestibility. Several quality aspects were evaluated. In the field experiment the effects of slurry manure type on herbage rejection by grazing heifers and herbage yield on undisturbed plots under cages were studied for a grass monoculture and a grass/clover mixture. The bio-assay, consisting of a cress (Lepidium sativum L.) seed germination test, was used to study differences in phytotoxicity between the slurry types. After five weeks of undisturbed growth at equal amounts of applied inorganic nitrogen (N), the herbage yields differed statistically for the different slurries. This was probably due to immobilization of N in the case of the two slurries from farming systems in which straw was fed and used as bedding material. Herbage rejection by grazing animals was significantly shown for all slurry types and was significantly and positively correlated with the NH3/NH4 + -N content of the slurry. The slurries showed large differences in phytotoxicity to seeds and seedlings in the bio-assay. Ammonia and electric conductivity appeared to be the most important slurry parameters with inhibiting effects. The slurries with a high C/N ratio showed lowest phytotoxicity. Phytotoxicity in the cress seed germination test did not account for reduced herbage yields in the field experiment. On the contrary, when the slur- ries were ranked according to their phytotoxicity the order was the same as the ranking on the basis of undisturbed herbage yield. It was concluded that there is a need for other laboratory tests that show greater resemblance with what is observed in the field to assess slurry quality.

Chemical composition of lamina and sheath of Lolium perenne as affected by herbage management

The quality of grass in terms of form and relative amounts of energy and protein affects both animal production per unit of intake and nitrogen (N) utilization. Quality can be manipulated by herbage management and choice of cultivar. The effects of N application rate (0, 90 or 390 kg N ha1 year1), duration of regrowth period (23, 45, or 67 weeks), and cutting height (8 or 12 cm) on the mass fractions of nitrogen (N), water-soluble carbohydrates (WSC), neutral detergent fibre (NDF), acid detergent fibre (ADF), lignin and ash in lamina and sheath material of a high-sugar (Aberdart) and a low-sugar (Respect) perennial ryegrass (Lolium perenne) cultivar, were studied in a factorial field experiment during four seasons in 2002 and 2003. Expressing NDF and ADF mass fractions in g per kg WSC-free dry matter (DM) increased the consistency of treatment effects. The high-sugar cultivar had generally higher WSC mass fractions than the low-sugar cultivar, especially during the late season. Moreover, the relative difference in WSC mass fraction between the two cultivars tended to be higher for the lamina material than for the sheath material, which suggests that the high-sugar trait may be more important under grazing conditions, when lamina forms the bulk of the intake, than under mowing regimes. Longer regrowth periods and lower N application rates increased WSC mass fractions and decreased N mass fractions; interactions between regrowth period and N application rate were highly significant. The mass fractions of NDF and ADF were much less influenced. The NDF mass fraction in terms of g per kg WSC-free DM tended to be higher at lower N application rates and at longer regrowth periods. The effect of cutting height on herbage chemical composition was unclear. In conclusion, high-sugar cultivars, N application rate and length of the regrowth period are important tools for manipulating herbage quality.