Penetration resistance and root growth of oats in tilled and untilled loess soil

Penetration resistance, bulk density, soil water content and root growth of oats were intensively studied in a tilled and an untilled grey brown podzolic loess soil. Bulk density and penetration resistance were higher in the top layer of the untilled soil compared with the tilled soil. In the latter, however, a traffic pan existed in the 25–30 cm soil layer which had higher bulk density and penetration resistance than any layer of the untilled soil. Above the traffic pan, rooting density (cm root length per cm³ of soil) was higher but below the pan it was lower than at the same depth in the untilled soil. Root growth was linearly related to penetration resistance. The limiting penetration resistance for root growth was 3.6 MPa in the tilled Ap-horizon but 4.6-5.1 MPa in the untilled Ap-horizon and in the subsoil of both tillage treatments. This difference in the soil strength-root growth relationship is explained by the build up of a continuous pore system in untilled soil, created by earthworms and the roots from preceding crops. These biopores, which occupy < 1% of the soil volume, can be utilized by roots of subsequent crops as passages of comparatively low soil strength. The channeling of bulk soil may counteract the possible root restricting effect of an increased soil strength which is frequently observed in the zero tillage system.     

Field efficacy of a combined use of Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae vaccines in growing pigs

The effectiveness of simultaneous administration of commercial Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae vaccines was tested in an indoor commercial piggery which had experienced continuing respiratory-disease problems confirmed as due to both of these pathogens. Piglets were randomly assigned in equal numbers to vaccination and control groups, and each vaccine was administered at a separate site to assigned piglets at two and four weeks of age. Live weight of vaccinates immediately prior to slaughter was 2.49 kg higher (p = 0.04) than for controls at equal mean slaughter age of 132 days. Average daily gain (ADG) from 16 weeks to slaughter of vaccinates was also significantly higher (33 g/day) than in controls (p = 0.05). Daily gain was not significantly different in younger age groups. Active enzootic pneumonia lesions were more likely in control than in vaccinated pigs. There were no significant differences between vaccination groups with regard to severity of pleurisy or presence of pleuropneumonia lesions at slaughter. Log-linear modelling was used to test the statistical association between vaccination, enzootic pneumonia lesions, pleurisy lesions and pleuropneumonia lesions. It showed a reduction in the severity of enzootic pneumonia lesions for vaccinated pigs, and the presence of pleuropneumonia lesions increased the likelihood of pleurisy lesions. No other association was significant, and no evidence of synergy between the vaccines in influencing lesion severity for pleuropneumonia was detected (within the limitations set by the trial design).     

Clinical Anesthesia and Analgesia in Fish

Fish have become a popular experimental model and companion animal, and are also farmed and caught for food. Thus, surgical and invasive procedures in this animal group are common, and this review will focus on the anesthesia and analgesia of fish. A variety of anesthetic agents are commonly applied to fish via immersion. Correct dosing can result in effective anesthesia for acute procedures as well as loss of consciousness for surgical interventions. Dose and anesthetic agent vary between species of fish and are further confounded by a variety of physiological parameters (e.g., body weight, physiological stress) as well as environmental conditions (e.g., water temperature). Combination anesthesia, where 2 anesthetic agents are used, has been effective for fish but is not routinely used because of a lack of experimental validation. Analgesia is a relatively underexplored issue in regards to fish medicine. However, recent studies have investigated opioid agents, nonsteroidal antiinflammatory drugs, and local anesthetics to determine their efficacy in minimizing pain and discomfort. The opioid morphine and the local anesthetic lidocaine do have significant effectiveness in reducing pain-related responses in rainbow trout (Oncorhynchus mykiss). Studies aimed at developing reliable analgesic protocols should explore a wide range of analgesic drug classes in several fish species.     

Variation in virulence of Cryphonectria hypovirus 1 in Macedonia

We investigated variation in virulence of Cryphonectria hypovirus 1 (CHV‐1) to the chestnut blight fungus, Cryphonectria parasitica, in Macedonia by inoculating chestnut stems in the field. We inoculated trees with two isolates of C. parasitica, each infected with one of five isolates of CHV‐1, four of which were the same for both fungal isolates. Two virus isolates, [Sk28] and [Sk47], were significantly more virulent than the others when compared in the same fungal host isolates, as measured by reduced canker growth and increased callus formation. Mycelial growth rate in vitro was weakly correlated to canker growth or callus formation and is therefore not a reliable predictor for virulence. We found significant fungus × virus interactions for canker growth and callus formation, which seems due mainly to one virus isolate. Significant interactions were not expected because the two fungal host isolates are members of the same clone that is dominant in Macedonia and most of southeastern Europe. Phenotypic variation for response to viruses, therefore, is greater than variation revealed by the genetic markers used to define clones. More than half of the trees inoculated with virus‐free controls were dead within 2 years, and the 30% still alive after 5 years had cankers with extensive callus formation, indicating that natural virus transmission had occurred after inoculation. In contrast, only 2% of the trees inoculated with virus‐infected isolates were dead after 5 years. Hypoviruses naturally occurring in Macedonia reduce canker development and tree mortality similarly to those in other parts of southern Europe, and therefore, may have good potential for biological control of chestnut blight.     

Arbuscular mycorrhizal fungal association in Asteraceae plants growing in the arid lands of Saudi Arabia

The present research was undertaken to explor the possibility of arbuscular mycorrhizal(AM) association with Asteraceae plants in the arid lands of Saudi Arabia(Al-Ghat, Buraydah, Thumamah and Huraymila). AM fungal colonization in the roots, spore numbers in the rhizosphere soil, fungal species diversity and correlation between AM properties and soil properties were determined. The highest colonization was in Conyza bonariensis(65%) from Al-Ghat, Anthemis cotula(52%) from Buraydah and C. bonariensis(53%) from Thumamah. The lowest was in Vernonia schimperi(41%) from Al-Ghat, Pulicaria undulata(25%) from Buraydah, Acanthospermum hispidum(34%) from Thumamah, Asteriscus graveolens(22%) and V. schimperi(22%) from Huraymila. Vesicular and arbuscular colonization were also presented in all plant species examined. The number of spores were 112–207 in Al-Ghat, 113–133 in Buraydah, 87–148 in Thumamah and 107–158 in Huraymila. Funneliformis mosseae, Glomus etunicatum, G. fasciculatum and G. aggregatum were identified. Relative frequency of AM fungal species varied widely and was irrespective of location and plant species. Diversity index varied with the rhizosphere soils of different plant species at various locations. Soil properties varied with locations and no distinct correlations were observed among the soil properties, root colonization and the number of spores. The results of the present study specified the association of AM fungi in different plants of Asteraceae and its significance in the ecological functioning of annual plants in the punitive environments of the rangelands in Saudi Arabia.     

Antibacterial activity of Salvia tomentosa essential oil.

The essential oil of Salvia tomentosa aerial parts, consisting of 1,8-cineol (17%), beta-caryophyllene (11%), cyclofenchene (10%) and delta-cadinene (6%), was screened for its antimicrobial activity. The essential oil remarkably inhibited the growth of tested Gram-positive and Gram-negative bacteria except for Pseudomonas aeruginosa.     

鸭非特异性细胞免疫发生的研究

实验利用鸭全血中单核细胞,粒细胞,血栓细胞及自然杀伤细胞对酵母细胞非特异性细胞毒性作用,检测了１５日龄鸭胚到１１２日龄鸭非特异性细胞免疫的发生。实验结果表明,鸭胚孵出前１周的２２日龄到孵出后３日龄是鸭非特异性细胞免疫的发生期;３￣１１２日龄鸭在正常的生理状态下非特异性细胞免疫水平没有明显的变化。     

Adhesive fimbriae produced in vivo by Escherichia coli O139:K12(B):H1 associated with enterotoxaemia in pigs

Two strains of E. coli O139:K12 (B):H1 were compared in vitro and in the intestinal environment. Both strains colonized the small intestines of experimentally inoculated pigs and exhibited in vivo a similar relationship to the microvillus border as enterotoxigenic E. coli (ETEC). Strain 107/86 grown on blood agar expressed numerous long flexible non-haemagglutinating fimbriae which were antigenically distinct from the known fimbriae of porcine ETEC. It adhered in vitro to porcine enterocyte brush border fragments. Strain 124/76 grown on blood agar was devoid of fimbriae and did not adhere to brush border fragments. However, fimbriae morphologically and antigenically indistinguishable from those of strain 107/86 were detected in the intestinal environment by direct immunofluorescence and by immuno electron microscopy.