Image‐driven electronic identification keys for invasive plant species in the Netherlands

For several years work has been ongoing to compile information to facilitate the identification of non‐native plants that (potentially) pose a threat to the biodiversity of the ecozone comprising Northern Germany, the Netherlands, Belgium and North‐Western France. Such identification information may also be used for species that are regulated by other countries and are likely to be present as contaminants in commercial exports originating from the Netherlands. This information system comprises a set of interactive image‐driven identification keys for invasive plants at various growth stages for use in a range of different situations: seed contaminants in bird feed, weeds in bonsai plants, seedling identification, identification keys of invasive terrestrial plants and invasive aquatic plants. The advantage of image‐driven identification keys using a multiple entry system lies in limiting misunderstandings in terminology and failure in identification, in the absence of certain characters, as is sometimes the case in dichotomous keys. The interactive keys are linked to the species information in the Q‐bank database, including datasheets, worldwide distribution maps, specimen level information, barcodes of selected species, etc. This information is now available at http://www.q-bank.eu/Plants/     

Modelling worker physical health and societal sustainability at farm level: An application to conventional and organic dairy farming

Farm-level modelling can be used to determine how farming systems and individual farm-management measures influence different sustainability indicators. Until now however, worker physical health and societal sustainability have been lacking in farm models. For this paper, we first selected attributes of physical health (working conditions) and societal sustainability (food safety, animal welfare and health, and landscape quality). Second, possible sustainability indicators for these attributes were identified, and those selected were included in an existing dairy farm LP-model that was subsequently used to analyse possible differences in societal sustainability within and between a conventional and organic dairy farming system. Results for physical health and societal sustainability were similar for conventional and organic dairy farming systems in the basis situation, as well as in the situation where additional management measures were applied to improve societal sustainability, but improved animal welfare did result in the organic system due to prescribed grazing, and due to assumed summer feeding in the conventional system. Results show that additional management measures considerably improved societal sustainability of the conventional as well as the organic system. LP-modelling appeared to be a suitable method for comparing farming systems and determining the effect of management measures on physical health and societal sustainability. The level of societal sustainability is determined mainly by applied management measures, and is related to the particular farming system in only a very limited way. This implies that societal sustainability is mainly dependent on the cost-effectiveness of management measures and on the attitude of the dairy farmer.     

The retention of trace elements on funnel surfaces of sampling equipment for wet deposition

The retention behaviour of heavy metals from wet deposition on funnel surfaces of wet-only collectors was studied. Two groups of elements were distinguished: (i) elements for which the amount retained was proportional to the concentration in the deposition sample, independent of the exposure time: Cd, Cu and most probably also Ni and V; and (ii) elements for which the amount retained increased with exposure time; Fe and Pb. Percentage retention after an exposure time of 14 d ranged from 5 to 13% for group (i) elements to 7 to 18% for group (ii) elements. The difference in behaviour of the elements of group (i) and (ii) might be attributed to the way these metals are present in precipitation samples. Cadmium and Cu are largely dissolved and show corresponding equilibrium behaviour, while Fe and Pb are to a certain extent present in particles in rainwater, which particles accumulate on the funnel surface. The retention of As, Co, Cr and Mn could not be established because their concentrations were below the detection limits.     

‘Plantibodies’: a flexible approach to design resistance against pathogens

Engineering resistance against various diseases and pests is hampered by the lack of suitable genes. To overcome this problem we started a research program aimed at obtaining resistance by transfecting plants with genes encoding monoclonal antibodies against pathogen specific proteins. The idea is that monoclonal antibodies will inhibit the biological activity of molecules that are essential for the pathogenesis. Potato cyst nematodes are chosen as a model and it is thought that monoclonal antibodies are able to block the function of the saliva proteins of this parasite. These proteins are, among others, responsible for the induction of multinucleate transfer cells upon which the nematode feeds. It is well documented that the ability of antibodies to bind molecules is sufficient to inactivate the function of an antigen and in view of the potential of animals to synthesize antibodies to almost any molecular structure, this strategy should be feasible for a wide range of diseases and pests.Antibodies have several desirable features with regard to protein engineering. The antibody (IgG) is a Y-shaped molecule, in which the domains forming the tips of the arms bind to antigen and those forming the stem are responsible for triggering effector functions (Fc fragments) that eliminate the antigen from the animal. Domains carrying the antigen-binding loops (Fv and Fab fragments) can be used separately from the Fc fragments without loss of affinity. The antigen-binding domains can also be endowed with new properties by fusing them to toxins or enzymes. Antibody engineering is also facilitated by the Polymerase Chain Reaction (PCR). A systematic comparison of the nucleotide sequence of more than 100 antibodies revealed that not only the 3-ends, but also the 5-ends of the antibody genes are relatively conserved. We were able to design a small set of primers with restriction sites for forced cloning, which allowed the amplification of genes encoding antibodies specific for the saliva proteins ofGlobodera rostochiensis. Complete heavy and light chain genes as well as single chain Fv fragments (scFv), in which the variable parts of the light (V_L) and heavy chain (V_H) are linked by a peptide, will be transferred to potato plants. A major challenge will be to establish a correct expression of the antibody genes with regard to three dimensional folding, assembly and intracellular location.     

Performance, digesta characteristics, nutrient flux, plasma composition, and organ weight in pigs as affected by dietary cation anion difference and nonstarch polysaccharide

Two dietary cation anion difference (CAD) levels (-100 and 200 mEq/kg) and two dietary nonstarch polysaccharide (NSP) levels (10 and 15%) were used in a 2 x 2 factorial arrangement in two randomized blocks (trials) to evaluate performance, digesta pH and buffer capacity, apparent digestibility, plasma composition, and organ weight in pigs. Seven pigs with a mean initial weight of 7.5 kg were used in each treatment. Pigs had free access to feed and water during the 3-wk experimental period. At the end of the experiment, all pigs were killed approximately 2.5 h after addition of fresh feed. Liver, kidneys, and small and large intestine were removed and weighed immediately. Gastric and small intestinal (divided into two equal parts) digesta were collected. Dry matter, pH, buffering capacity, viscosity, acid insoluble ash, mineral content (Na+, K+, and Cl-), nitrogen, and gross energy content (only in the second part of the small intestine) of the digesta were measured. An interaction (P < 0.05) between dietary CAD and dietary NSP was observed for feed intake, growth, apparent digestibility of DM and gross energy in the distal small intestine, and chloride in the stomach and duodeno-jejunal part of the small intestine. Increasing dietary NSP content increased apparent digestibility of DM and chloride in the stomach and increased apparent digestibility of DM, chloride, sodium, and potassium in the first part of the small intestine. Lowering dietary CAD levels significantly increased apparent digestibility of DM in the first part of the small intestine and decreased chloride influx in the stomach and the small intestine. No significant differences were found for pH, buffering capacity, and viscosity of digesta, except the buffering capacity in the second part of the small intestine, which was higher (P < 0.05) in the 200 mEq/kg CAD group than in the -100 CAD mEq/ kg group. Plasma urea decreased in the low dietary CAD groups and plasma ammonia increased in the high NSP groups. Large intestine weight was significantly less for the -100 mEq/kg CAD groups than for the 200 mEq/kg CAD groups. In conclusion, the effect of CAD on feed intake and growth in pigs depends on dietary NSP levels.     

Maedi-visna control in sheep II. Half-yearly serological testing with culling of positive ewes and progeny

In 1979 a field trial was started to study the feasibility of maedi-visna control in sheep by half-yearly serological testing (by ELISA) with culling of sero-positive ewes and their progeny. In 13 commercial flocks, with a mean initial incidence of serological reactors of 17%, the sero-positive ewes and all their progeny, those of preceding years included, were culled after each half-yearly test. The percentage of sero-positive sheep decreased gradually and at the end of the second year, at the 5th test, all flocks were sero-negative. Also the 6th and 7th test did not yield sero-positive sheep. At the 8th test, however, 3 sero-positive ewes were detected in one of the flocks. A definite conclusion as to the source of infection could not be drawn. The following flock test was negative. In 2 other commercial flocks, which had a mean initial incidence of sero-positive sheep of 53%, those sero-positive and only their suckling lambs were culled. Here too, a gradual decrease in the incidence of sero-positive sheep was observed at the 2nd and 3rd test, but at the 4th test a sharp increase occurred. The programme was continued and a decrease followed until 0% was reached at the 7th test (end of third year). Age analysis of the sero-positive sheep which caused this peak revealed that the majority had been born before the start of the trial. This suggests that a 'second wave' of sero-positive sheep may be prevented and a quicker result obtained if progeny of preceding years are culled as well.(ABSTRACT TRUNCATED AT 250 WORDS)