Regional Ileitis in Pigs Isolation of Campylobacter from Affected Ileal Mucosa

In the last few years special interest has been focused on enteric diseases localized to the lower alimentary tract, especially the ileum of weaned pigs. An increasing frequency of disorders of unknown aetiology described as regional ileitis (Emsbo 1951), necrotic enteritis (Jubb & Kennedy 1970), and intestinal adenomatosis (Rowland et al. 1973) has been reported. The changes include thickening of the ileal mucosa with hypertrophy of the muscular wall. The normal structure of villi is replaced by a proliferation of crypt cells. Necrosis of the mucosa and granulation-tissue proliferation in the submucosa occur in later stages. Regional ileitis in man (Crohn et al. 1932) which is described as a chronic enteric disease with granulomatous inflammatory changes localized to segments of the ileum is also attracting increasing attention in medical research (Liljefors 1972). The lesions are also found in the colon, and the presence of a transmissible agent involved in the aetiology of Crohn''s disease has been discussed on the basis of animal experiments (Cave et al. 1973). The disease in pigs is accompanied by haematological changes, including decreased concentration of total serum protein, albumin, alkaline phosphatase, and zinc (Martinsson et al. 1974, 1976).     

Humoral immune responses to Mycoplasma hyopneumoniae in sows and offspring following an outbreak of mycoplasmosis

Previously healthy sows, seropositive to Mycoplasma hyopneumoniae, developed clinical signs of mycoplasmosis, as well as increasing amounts of antibodies to M. hyopneumoniae during an outbreak of the disease in a herd. During the early phase of the outbreak, young piglets (2 weeks) with maternal antibodies remained healthy while older seronegative piglets (4–7 weeks) developed the disease. The duration of the maternal antibodies to M. hyopneumoniae varied between litters and was related to the amount of antibodies in the serum of the dam. In sows, the level of serum antibodies decreased continuously from 4 weeks ante partum to partus, and the level of antibodies in the whey of colostrum was comparable to that in serum 4 weeks ante partum. After loss of maternal antibodies to M. hyopneumoniae, seropositive animals were not found among piglets younger than 9 weeks. Therefore peripheral blood mononuclear cells (PBMC) were collected from various age categories of piglets in order to measure the ability to produce antibodies to M. hyopneumoniae in vitro. PBMC obtained from piglets aged 1 and 3 weeks produced few antibodies to M. hyopneumoniae. Significantly higher levels of antibodies to M. hyopneumoniae were produced by PBMC obtained from pigs aged 5–9 weeks. Thus, the ability of PBMC to produce antibodies to M. hyopneumoniae in vitro seemed to be age-dependent.     

Grain yield and crop N offtake in response to residual fertilizer N in long‐term field experiments

Organic inputs [e.g. animal manure (AM) and plant residues] contribute directly to the soil organic N pool, whereas mineral N fertilizer contributes indirectly by increasing the return of the crop residues and by microbial immobilization. To evaluate the residual effect of N treatments established in four long‐term (>35 yr) field experiments, we measured the response of barley (grain yield and N offtake at crop maturity) to six rates (0, 30, 60, 90, 120 and 150 kg N/ha) of mineral fertilizer N (N_new) applied in subplots replacing the customary long‐term plot treatments of fertilizer inputs (N_prev). Rates of N_prev above 50–100 kg N/ha had no consistent effect on the soil N content, but this was up to 20% greater than that in unfertilized treatments. Long‐term unfertilized plots should not be used as control to test the residual value of N in modern agriculture with large production potentials. Although the effect of mineral N_prev on grain yield and N offtake could be substituted by N_new within a range of previous inputs, the value of N_prev was not eliminated irrespective of N_new rate. Provided a sufficient supply of plant nutrients other than N, the use‐efficiency of N_new did not change significantly with previous mineral N fertilizer rate. The residual effect of mineral N fertilizer was negligible compared with the residual effect of N from AM and catch crop residues.     

Estimating the dispersal capacity of the rare lichen Cliostomum corrugatum

The objective of this study was to estimate the dispersal rate in an organism assumed to be confined to tree stands with unbroken continuity. We used the lichen-forming ascomycete Cliostomum corrugatum, which is largely confined to old oak stands. Five populations, with pairwise distances ranging from 6.5 to 83 km, were sampled in Östergötland, south-eastern Sweden. DNA sequence data from an intron in the small subunit nuclear ribosomal RNA gene was obtained from 85 samples. Nearly all molecular variance (99.6%) was found within populations and there were no signs of isolation-by-distance. The absolute number of immigrants per population per generation (estimated to 30 years), inferred by Bayesian MCMC, was found to be between 1 and 5. Altogether, evidence suggests abundant gene flow in the history of our sample. A simulation procedure demonstrated that we cannot know whether effective dispersal is ongoing or if it ceased at the time when oaks started to decrease dramatically around 400 years BP. However, a scenario where effective dispersal ceased already at the time when the postglacial reinvasion of oak had reached the region around 6000 years BP is unlikely. Vegetation history suggests that the habitat of C. corrugatum was patchily distributed in the landscape since the early Holocene. Combined with the high dispersal rate estimate, this suggests that the species has been successful at frequently crossing distances of at least several kilometres and possibly that it has primarily been limited by the availability of habitat rather than by dispersal.     

Use of imazapyr against Equisetum arvense on Swedish railway tracks

Since glyphosate has been used extensively for weed control in Swedish railway tracks, common horsetail (Equisetum arvense L), previously relatively rare, has become very common. Glyphosate, although effective against most other weeds found on railway tracks, gives poor control of E. arvense, so that heavy infestation with this weed is now common. Imazapyr (applied as a 250g AE litre(-1) SL, Arsenal) has controlled E. arvense, but is known to be very mobile. Adequate control of the weed requires application of > or = 4 litres ha(-1) of imazapyr SL but environmental factors preclude the use of > 2 litres ha(-1). A suitable strategy was found to be one application of imazapyr SL at 2 litres ha(-1) in each of two successive years but best weed control was obtained by supplementing imazapyr in the first year with glyphosate 360 g AE litre(-1) SL (RoundUp Bio) at 3 litres ha(-1).     

Growth regulation of Scots pine seedlings with different fertilizer compositions and regimes

Scots pine (Pinus sylvestris L.) seedlings were grown in containers filled with peat, using two different fertilizers and three different fertilizer regimes. Seedling shoot and root growth and shoot content of nitrogen, potassium and phosphorus were followed in the nursery and after outplanting in the field. Attempts to regulate growth rate by an exponential nutrient supply were not successful, but the root/shoot ratio was influenced by the fertilization regime. Internal nitrogen concentration was stable only for seedlings with low relative growth rate, while seedlings with high nutrient supply in the nursery showed strong nutrient dilution in the shoot after planting.