Use of Mycobacterium avium subsp. paratuberculosis specific coding sequences for serodiagnosis of bovine paratuberculosis

In this study, the finished complete genome of Mycobacterium avium subsp. paratuberculosis (Map) was screened for specific coding sequences that could be very valuable in the design of a sensitive and specific Map detection serological assay. Eighty-seven Map-specific sequences were retained. Among these, three candidate antigens have been analysed for their serodiagnostic potential. These antigens were selected on the basis of their putative immunogenicity as predicted by in silico analysis. The antigens were cloned in Escherichia coli, expressed, and purified before testing in an antibody detection ELISA test, using a well characterized panel of 18 and 48 sera from Map infected and uninfected cattle, respectively. Two of these antigens, antigen 6 and MAP1637c, yielded in our conditions a sensitivity of 72% and 82%, respectively, for a specificity of 98%. It is particularly noticeable that, when probed with the same serum panel, the most widely used European paratuberculosis commercial seroassay (Pourquier test) yielded a sensitivity of 72% for a specificity of only 92%.     

以农民经验小组方法评价奶牛饲料的应用价值

采用优劣势分析和配对排序法,分析了玉米秸作为粗饲料饲喂产奶牛的优缺点.奶农采用干玉米秸杆做为饲草资源, 容易得到、饲喂成本低是主要原因,容易贮存制备、提供粗纤维是次要原因;营养价值低、不利于繁殖性能和产奶量提高是制约因素.采用半结构性访谈,以奶农经验小组评价了”种植高-丹草饲养奶牛”和”夏季对奶牛补饲保护性脂肪”在奶牛生产中的适用性.在耕地很少的城市郊区,二者分别居于农民需求程度的第3位和第2位.高-丹草种植,宜早于6月,行距应宽于50 cm.补饲保护性脂肪,使奶牛抗热性增强,产奶量稳定,乳脂率提高明显.     

Colonization strategy of Campylobacter jejuni results in persistent infection of the chicken gut

Although poultry meat is now recognized as the main source of Campylobacter jejuni gastroenteritis, little is known about the strategy used by the bacterium to colonize the chicken intestinal tract. In this study, the mechanism of C. jejuni colonization in chickens was studied using four human and four poultry isolates of C. jejuni. The C. jejuni strains were able to invade chicken primary cecal epithelial crypt cells in a predominantly microtubule-dependent way (five out of eight strains). Invasion of cecal epithelial cells was not accompanied by necrosis or apoptosis in the cell cultures, nor by intestinal inflammation in a cecal loop model. C. jejuni from human origin displayed a similar invasive profile compared to the poultry isolates. Invasiveness of the strains in vitro correlated with the magnitude of spleen colonization in C. jejuni inoculated chicks. The C. jejuni bacteria that invaded the epithelial cells were not able to proliferate intracellularly, but quickly evaded from the cells. In contrast, the C. jejuni strains were capable of replication in chicken intestinal mucus. These findings suggest a novel colonization mechanism by escaping rapid mucosal clearance through short-term epithelial invasion and evasion, combined with fast replication in the mucus.     

Early and temporary quantitative food restriction of broiler chickens. 2. Effects on allometric growth and growth hormone secretion

1. An experiment was conducted with male broiler chickens to investigate the effect of different early food restriction programmes on proportional weights and allometric growth coefficients of carcase parts and on pulsatile growth hormone secretion. 2. At 4 d of age the animals were restricted to 80% or 90% of the ad libitum intake for 4 d or 80% for 8 d. When the restriction was finished, all birds received ad libitum food again. 3. On d 1, 8, 11, 14, 21, 28, 35 and 42, from each group 8 birds were weighed, stunned and killed and the weights of the stomachs, liver, heart, sternum, right thigh, right drumstick, breast and abdominal fat pad were determined. On d 29, 30, 31, 32 serial blood samples of 2 birds from each group were taken to determine the plasma growth hormone (GH) content. 4. Only the most severe restriction resulted in a tendency for the stomachs to mature earlier and the thighs to mature later. No other significant effect on the allometric coefficients could be observed. 5. It is concluded that during the restriction the birds give priority to the development of the supply organs such as the stomach, which are more important during early development at the expense of the demand tissues like breast and thigh. 6. No significant differences concerning the GH secretory parameters could be observed.     

A minimum data set for soil quality assessment of wheat and maize cropping in the highlands of Mexico

The objective was to establish a minimum soil quality dataset for a long-term tillage, residue management and rotation trial for wheat (Triticum aestivum L.) and maize (Zea mays L.) production systems. Based on this soil quality evaluation, sustainable management practices could be selected for transferring technologies to farmers in the region. A long-term experiment was conducted with 16 different crop management practices varying in: (1) rotation (continuous maize or wheat and both phases of the rotation of maize and wheat), (2) tillage (conventional and zero) and (3) crop residue management (full retention or removal for fodder). Superior soil quality was considered to represent the maintenance of high productivity without significant soil or environmental degradation. The pertinent, minimum soil quality data set included the following physical indicators: time-to-pond, aggregate stability, permanent wilting point, and topsoil penetration resistance. Chemical indicators were: soil C, N, K and Zn concentrations, measured in the 0–5 cm topsoil and C, N concentration in 5–20 cm. Multivariate analysis grouped the treatments into clusters: (1) zero tillage with retention of residue, (2) zero tillage with residue removal and (3) conventional tillage. Zero tillage combined with crop residue retention improved chemical and physical conditions of the soil. In contrast, zero tillage with removal of residues, led to high accumulation of Mn in the topsoil, low aggregate stability, high penetration resistance, surface slaking resulting in low time-to-pond values and high runoff. Finally, soil quality under conventional tillage was intermediate (irrespective of residue management), especially reflected in the physical status of the soil. The results provide a strong justification to promote zero tillage technology combined with appropriate residue management to farmers in the volcanic highlands of Central Mexico and other similar regions. The minimum data set and associated tools for careful monitoring and observation, will be essential for evaluating soil quality in farmer's fields.     

Nitrous oxide production of heavy metal contaminated soil

Arsenic (As), lead (Pb), copper (Cu) and zinc (Zn) can be found in large concentrations in mine spills of central and northern Mexico. Interest in these heavy metals has increased recently as they contaminate drinking water and aquifers in large parts of the world and severely affect human health, but little is known about how they affect biological functioning of soil. Soils were sampled in seven locations along a gradient of heavy metal contamination with distance from a mine in San Luis Potosí (Mexico), active since about 1800 AD. C mineralization and N₂O production were monitored in an aerobic incubation experiment. Concentrations of As in the top 0-10 cm soil layer ranged from 8 to 22,992 mg kg⁻¹, from 31 to 1845 mg kg⁻¹ for Pb, from 27 to 1620 mg kg⁻¹ for Cu and from 81 to 4218 mg kg⁻¹ for Zn. There was a significant negative correlation between production rates of CO₂ and concentrations of As, Pb, Cu and Zn, and there was a significant positive correlation with pH, water holding capacity (WHC), total N and soil organic C. There was a significant negative correlation (P<0.05) between production rate of nitrous oxide (N₂O) attributed to nitrification by the inhibition method in soil incubated at 50% WHC and total concentrations of Pb and Zn, and there was a significant positive correlation (P<0.05) with pH and total N content. There was a significant negative correlation (P<0.05) between the production rate of N₂O attributed to denitrification by the inhibition method in soil incubated at 100% WHC and total concentrations of Pb, Cu and Zn, and a significant positive correlation (P<0.01) with pH; there was a significant positive correlation (P<0.05) between the production of N₂O attributed to other processes by the inhibition method and WHC, inorganic C and clay content. A negative value for production rate of N₂O attributed to nitrifier denitrification by the inhibition method was obtained at 100% WHC. The large concentrations of heavy metals in soil inhibited microbial activity and the production rate of N₂O attributed to nitrification by the inhibition method when soil was incubated at 50% WHC and denitrification when soil was incubated at 100% WHC. The inhibitor/suppression technique used appeared to be flawed, as negative values for nitrifier denitrification were obtained and as the production rate of N₂O through denitrification increased when soil was incubated with C₂H₂.     

Effect of Wheat Grain Steaming and Washing on Lipase Activity in Whole Grain Flour

During whole grain flour (WGF) storage, lipase activity causes partial loss of its functionality and the sensory acceptability of products produced from it. The objective of this research was to evaluate the effect of steaming and washing on lipase activity in (fractions of) wheat. Steam treatment conditions were optimized for wheat grains and their bran, shorts, and flour fractions. Lipase activities were determined colorimetrically, as were peroxidase, endoxylanase, and α‐amylase activities. Steaming grains for 180 s effectively inactivated lipase, peroxidase, endoxylanase, and part of the α‐amylase without gelatinizing starch. The work further demonstrated that lipase is mainly, if not only, located in the bran fraction. Separate bran treatment holds promise for obtaining WGF with reduced lipase activity but without altered functional properties. Washing grains did not reduce WGF lipase activity.     

Genetic diversity of rhizobia associated with indigenous legumes in different regions of Flanders (Belgium)

We investigated the diversity of rhizobia isolated from different indigenous legumes in Flanders (Belgium). A total of 3810 bacterial strains were analysed originating from 43 plant species. Based on rep-PCR clustering, 16S rRNA gene and recA gene sequence analysis, these isolates belonged to Bradyrhizobium, Ensifer (Sinorhizobium), Mesorhizobium and Rhizobium. Of the genera encountered, Rhizobium was the most abundant (62%) and especially the species Rhizobiumleguminosarum, followed by Ensifer (19%), Bradyrhizobium (14%) and finally Mesorhizobium (5%). For two rep-clusters only low similarity values with other genera were found for both the 16S rRNA and recA genes, suggesting that these may represent a new genus with close relationship to Rhodopseudomonas and Bradyrhizobium. Primers for the symbiotic genes nodC and nifH were optimized and a phylogenetic sequence analysis revealed the presence of different symbiovars including genistearum, glycinearum, loti, meliloti, officinalis, trifolii and viciae. Moreover, three new nodC types were assigned to strains originating from Ononis, Robinia and Wisteria, respectively. Discriminant and MANOVA analysis confirmed the correlation of symbiosis genes with certain bacterial genera and less with the host plant. Multiple symbiovars can be present within the same host plant, suggesting the promiscuity of these plants. Moreover, the ecoregion did not contribute to the separation of the bacterial endosymbionts. Our results reveal a large diversity of rhizobia associated with indigenous legumes in Flanders. Most of the legumes harboured more than one rhizobial endosymbiont in their root nodules indicating the importance of including sufficient isolates per plant in diversity studies.     

Landscape composition influences roe deer habitat selection at both home range and landscape scales

Understanding how patterns of habitat selection vary in relation to landscape structure is essential to predict ecological responses of species to global change and inform management. We investigated behavioural plasticity in habitat selection of roe deer (Capreolus capreolus) in relation to variable habitat availability across a heterogeneous agricultural landscape at the home range and landscape scales. As expected, woodland was heavily selected, but we found no functional response for this habitat, i.e. no shift in habitat selection with changing habitat availability, possibly due to the presence of hedgerows which were increasingly selected as woodlands were less abundant. Hedgerows may thus function as a substitutable habitat for woodlands by providing roe deer with similar resources. We observed a functional response in the use of hedgerows, implying some degree of landscape complementation between hedgerows and open habitats, which may in part compensate for lower woodland availability. We also expected selection for woodland to be highest at the wider spatial scale, especially when this habitat was limiting. However, our results did not support this hypothesis, but rather indicated a marked influence of habitat composition, as both the availability and distribution of resources conditioned habitat selection. There was no marked between-sex difference in the pattern of habitat selection at either scale or between seasons at the landscape scale, however, within the home range, selection did differ between seasons. We conclude that landscape structure has a marked impact on roe deer habitat selection in agricultural landscapes through processes such as landscape complementation and supplementation.     

Clinical evaluation of the CA530-VET hematology analyzer for use in veterinary practice

BACKGROUND: The CA530-VET is a completely automated impedance cell hematology analyzer, which yields a 16-parameter blood count including a 3-part leukocyte differential. OBJECTIVES: The aim of this study was to examine the operational potential of the CA530-VET and its value for use in veterinary practice. METHODS: The analyzer was tested for blood carry-over, precision, and accuracy. Comparison methods included the CELL-DYN 3500, microhematocrit centrifugation, manual platelet (PLT) counting for feline and equine species, and a 100-cell manual WBC differential. Blood samples for comparison of the methods were obtained from 242 dogs, 166 cats, and 144 horses. RESULTS: The carry-over ratio (K) was 0.28% for RBC, 0.59% for PLT, 0.32% for WBC, and 0.18% for hemoglobin (HGB) concentration. Coefficients of variation (CVs) for within-batch precision and duplicate measurement of blood samples were clearly within the required limits, except for duplicate platelet counts in cats (8.7%) and horses (9.5%). The WBC count was in excellent agreement for dogs and horses and RBC count was in excellent agreement for horses. The accuracy of feline WBC counts was not acceptable, with the exception of values at the high end of the range. RBC counts in dogs and cats, and HGB concentration and MCV in all 3 species were sufficiently accurate. The CA530-VET HCT results were in excellent agreement with microhematocrit results in horses but exceeded the maximum allowed inaccuracy for cats and dogs. In all species, PLT counts established mechanically and manually were not in adequate agreement. Large differences were found between the CA530-VET and the manual differential percentage for lymphocytes and "mid-sized cells" (monocytes and basophilic granulocytes). CONCLUSIONS: The CA530-VET can be considered useful for routine canine, feline, and equine blood cell analyses. It should not be considered accurate, however, for PLT counts, feline total WBC counts in the subnormal and normal range, and leukocyte differentials, except for granulocytes.