Observational study of factors associated with nursery pig performance

The objective of this study was to determine the association between body weight of pigs at 7 wk of age, specific management factors, and previous body weight. Among 3736 pigs from 8 commercial farms, greater 7-wk weight was associated with greater birth weight (P = 0.001), greater weaning weight (P = 0.001), and earlier age at weaning (P = 0.001). Farms with the earliest average weaning age had the highest health status. Farms with later weaning ages tended to use nurse sows for light-weight pigs. Pigs from farms using all-in/all-out management in the nursery had greater 7-wk weights (P = 0.01). The total mortality and culling rate during the nursery phase (weaning to approximately 7 wk of age) was 6.8%. Higher losses were observed among pigs with low weaning weights (< 4.1 kg) compared with those with higher weaning weights. More of the variation due to 7-wk weight was due to individual sow rather than to farm of origin.     

Evaluation of Natural Chemical Compounds Against Root-lesion and Root-knot Nematodes and Side-effects on the Infectivity of Arbuscular Mycorrhizal Fungi

The survival of two species of plant parasitic nematodes: the root-lesion nematode Pratylenchus brachyurus, and the root-knot nematode Meloidogyne javanica, was evaluated in saturated atmospheres of 12 natural chemical compounds. The infectivity of two isolates of arbuscular mycorrhizal fungi: Glomus mosseae and Glomus intraradices, under identical experimental conditions, was also determined. All the compounds tested exerted a highly significant control against M. javanica and among them, benzaldehyde, salicilaldehyde, borneol, p-anisaldehyde and cinnamaldehyde caused a mortality rate above 50% over P. brachyurus. The infectivity of G. intraradices was inhibited by cinnamaldehyde, salicilaldehyde, thymol, carvacrol, p-anisaldehyde, and benzaldehyde, while only cinnamaldehyde and thymol significantly inhibited mycorrhizal colonization by G. mosseae.     

Effect of early infection on pathotype frequencies in barley powdery mildew (Blumeria graminis f.sp. hordei) populations in field plots

A field experiment with barley powdery mildew ( Blumeria graminis f.sp. hordei ) was designed in order to study how the time of arrival of inoculum in the field influenced pathotype frequencies in the resulting populations. Three isolates belonging to pathotypes that were absent or rare in the local aerial inoculum were used to inoculate field plots of winter barley cv. Plaisant. Two successive inoculations with different combinations of the three isolates were performed with an approximately two-generation delay, and frequencies of inoculated pathotypes were assessed four and nine generations after the first inoculation. Pathotypes of the first inoculated isolates generally persisted throughout the period of sampling; this is described as an 'early arrival' effect. During the epidemics the inoculated isolates were not replaced by isolates from the natural airborne inoculum. Pathotype frequencies depended mainly on the time of arrival of inoculum in the plot, but frequencies also depended on the isolate that had been inoculated. The most frequent isolate, GL1, belonged to the clonal lineage dominant in powdery mildew populations on winter barley in the north of France. These results confirmed that the composition of a powdery mildew population in a field is largely determined by the composition of the initial inoculum.     

Threshold values for chemical control of powdery mildew (Erysiphe cruciferarum) on Brussels sprouts

To establish control thresholds for chemical control of powdery mildew (Erysiphe cruciferarum) on Brussels sprouts, mildew intensity on leaves and buds was observed on the cultivars Lunet, Tardis and Asgard during three years in unsprayed plots. Mildew infection on the leaves was observed from late August onwards, increasing to moderate or high levels. In one year light infestation of the buds was observed, but no reduction in quality occurred. These preliminary results indicate, that from late August onwards the following levels of leaf injury by powdery mildew can be tolerated: T=5+0.42^*(Julian date — 235), in which T is the tolerable leaf injury in percentage leaf area covered. When sampling the crop to assess powdery mildew infection, care must be taken that leaves are sampled from all stem positions, as top leaves tend to be much less infected.     

Field evaluation of the single intradermal cervical tuberculin test and the interferon-gamma assay for detection and eradication of bovine tuberculosis in Spain

A field comparison of the interferon-gamma (IFN-gamma) assay and the single intradermal cervical tuberculin (SICT) test for the diagnosis of bovine tuberculosis was conducted. A total of 1136 cattle belonging to 85 herds placed in 'Castilla y León' (northwestern Spain) were chosen, and 21 of these herds were subjected to the diagnostic assays two or three times at intervals of at least 4 months. All the animals positive to any of the tests were slaughtered and tuberculosis was confirmed by culture isolation method (CIM) and further identification by means of PCR. Only 10.6% of cattle reacted with the bovine PPD in the SICT test, a percentage that increased to 12.8% in the IFN-gamma assay. The sensitivity of the IFN-gamma assay compared to CIM was shown to be higher (84.9%) than that of the SICT test (80.2%), but the combination of both tests offered the highest sensitivity (92.9%). The number of false positive reactors (those animals in which CIM was negative) was considerably higher for the IFN-gamma assay than for the SICT test and, conversely, the number of false negative animals (M. bovis isolation but negative immunological result) was higher for the skin test than for the interferon assay. In the herds tested twice, tuberculosis was eradicated after the second cycle of testing in 50%, and in 75% after the third cycle in herds tested three times. The combination of these two techniques instead of separately seems, therefore, to be useful in eradication programmes against bovine tuberculosis.     

Postpartum anestrus in dairy cattle--a review

In modern high-yielding dairy herds fertility is of major economic importance. In order to gain maximum profit, calving intervals should not exceed 365 days. The achievement of a 365-day calving interval requires an early resumption of ovarian activity, an excellent oestrus detection, and a high first-service conception rate. Especially the inability to detect oestrus and to mate the cows by 60 to 80 days after calving is a common problem among dairy farmers nowadays. In this article a review is given about the occurrence, causes, treatment and prevention of post-partum anoestrus in dairy cows.     

Quantification of Mycelium of Botrytis spp. and the Antagonist Ulocladium atrum in Necrotic Leaf Tissue of Cyclamen and Lily by Fluorescence Microscopy and Image Analysis

ABSTRACT A technique was developed to localize and quantify the internal mycelial colonization of necrotic leaf tissue of cyclamen (Cyclamen persicum) or lily (Lilium) by pathogenic Botrytis spp. and the antagonist Ulocladium atrum. This technique allows investigation of competitive substrate colonization by both fungi, which is a key process for biological control of Botrytis spp. by U. atrum. A combination of differential fluorescent labeling and image analysis was applied on cryostat sections of necrotic leaf tissue. Botrytis mycelium was labeled specifically by indirect immunofluorescence using a monoclonal antibody specific for Botrytis spp. And an antimouse fluorescein conjugate. Wheat germ agglutinin conjugated to the fluorochrome TRITC was used to label mycelium of both fungi. Image analysis was used to measure the relative surface area of the cryostat section covered by fluorescing hyphae of Botrytis spp. and by fluorescing hyphae of both fungi. A mathematical conversion was derived and used to calculate the relative mycelial volume of each fungal species in the necrotic tissue based on the measured relative surface areas. Temporal aspects of substrate colonization were studied in a short time series. An analysis of components of variance provided insight into spatial colonization patterns for the fungal species involved and allowed the design of efficient sampling strategies for future experiments.     

Liver pathology and immune response in experimental Fasciola hepatica infections of goats

The relationship between the immune response and the pathogenesis of the disease was studied in different primary and secondary experimental Fasciola hepatica infections of goats. The establishment of the infection, measured as percentage of recovered flukes at the necropsy, was similar in primarily and secondarily infected animals (between 19.7% and 24.3%), but the hepatic damage was much more severe in secondarily infected goats, as revealed by the levels of serum hepatic enzymes GGT and LDH. Primary infection evolves to chronic fasciolosis that did not induce the development of resistance, since goats were highly susceptible to secondary infection, showing severe acute and chronic hepatic lesions that led to the death of some animals in each group. The immune response to the infection was proved by the production of specific IgG antibodies to ESP of F. hepatica and the involvement of CD3+ T lymphocytes and lambda IgG+ plasma cells in the hepatic infiltrate. Secondary infection did not induce any difference in either IgG response or in the cellular composition of the infiltrate of hepatic lesions, although this was much more extended. However, neither antibodies nor cell-mediated response were protective: there was no correlation between IgG levels and fluke burden and there was no evidence of cell-mediated killing of the parasite. This suggests the existence of some immune evasion mechanisms in goat infection with F. hepatica. The parasite may depress the local inflammatory and immune response, as suggested by the scarcity of CD3+ T cells in the infiltrate surrounding acute migratory tunnels. Moreover, in secondary infected goats can be suspected an immunological damage of the liver, since a very severe infiltrate of immune cells replaced wide areas of hepatic parenchyma and an immune-mediated damage of hepatocytes could occur.