Influence of Temperature and Inoculum Density of Fusarium oxysporum f. sp. ciceris on Suppression of Fusarium Wilt of Chickpea by Rhizosphere Bacteria

The effects of temperature and inoculum density of Fusarium oxysporum f. sp. ciceris race 5 on suppression of Fusarium wilt in chickpea (Cicer arietinum) cv. PV 61 by seed and soil treatments with rhizobacteria isolated from the chickpea rhizosphere were studied in a model system. Disease development over a range of temperatures (20, 25, and 30 degrees C) and inoculum densities (25 to 1,000 chlamydospores per gram of soil) was described by the Gompertz model. The Gompertz relative rate of disease progress and final amount of disease increased exponentially and monomolecularly, respectively, with increasing inoculum densities. Disease development was greater at 25 degrees C compared with 20 and 30 degrees C. At 20 and 30 degrees C, disease development was greater at 250 to 1,000 chlamydospores per gram of soil compared with 25 to 100 chlamydospores per gram of soil. At 25 degrees C, increasing inoculum densities of the pathogen did not influence disease. Nineteen Bacillus, Paenibacillus, Pseudomonas, and Stenotrophomonas spp. out of 23 bacterial isolates tested inhibited F. oxysporum f. sp. ciceris in vitro. Pseudomonas fluorescens RGAF 19 and RG 26, which did not inhibit the pathogen, showed the greatest Fusarium wilt suppression. Disease was suppressed only at 20 or 30 degrees C and at inoculum densities below 250 chlamydospores per gram of soil. Bacterial treatments increased the time to initial symptoms, reduced the Gompertz relative rate of disease progress, and reduced the overall amount of disease developed.     

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.     

新母鸡产蛋前后的管理

后备蛋鸡饲养者必须认识到适度生长的时间限制和和提早开产的能力有着越来越大的矛盾。     

Incidence of salmonellae in captive and wild free-living raptorial birds in central Spain

A total of 595 faecal samples from raptorial birds, either captive or free-living, residing in GREFA Wildlife Hospital were bacteriologically examined using various selective media and an Automated Diagnostic Assay System for Salmonella detection. Serotype and phage type of the strains identified as Salmonella was determined. In the captive group, of the 285 samples examined, 21 (7.36%) were positive for Salmonella. Serotyping revealed that most of the individuals were infected by Salmonella serotype Havana. This result suggested that there could be a source of contamination in the Hospital although it could not be established. In the wild free-living group, over 310 samples examined (4.19%) were positive for Salmonella. The Salmonella isolates showed a major variety of serotypes: Enteritidis, Adelaide, Brandenburg, Newport, Typhimurium, Hadar, Saintpaul and Virchow. Most of them are similar to those commonly described in isolates from human and domestic animals. These results indicate that wild birds could be involved in the dissemination of Salmonella in humans or domestic animals or vice versa.     

Season of the year influences testosterone secretion in bulls administered luteinizing honrmone

The objective of the present study was to evaluate the secretion of testosterone (T) in bulls in response to the administration of varying doses of bovine LH (bLH) during the four seasons of the year. Five adult bulls (4 yr of age) were treated with an amount of bLH that was estimated to induce a 5 ng/mL amplitude pulse of LH in blood serum on five consecutive days around the spring equinox, summer solstice, fall equinox, and winter solstice. Five hours after this dose, bulls were treated with bLH in amounts that were estimated to induce a 0.25, 0.5, 1, 2, or 4 ng/mL amplitude LH pulse in blood serum in a Latin square design. Blood samples were collected for 5 h after administration of a dose of bLH that was estimated to induce the 5-ng amplitude LH pulse, and for 3 h after administration of the variable doses of bLH, and were then assayed for concentrations of T. Average concentrations and amplitude of T release after doses of bLH that were estimated to induce the 5-ng amplitude LH pulses were greater during the spring and summer than during the winter (P < 0.05). The area under the release curve (AUC) was greater during the spring than during the winter (P < 0.05). During the 3 h after treatment with the variable doses of bLH, T response was affected by dose (P < 0.001) and season (P < 0.001), but there was no dose x season interaction. Testosterone response increased in a dose-dependent fashion for all variables studied. The greatest average concentrations of T and AUC were observed in the spring compared with the fall and winter (P < 0.05). These data support our working hypothesis that testes of bulls are more responsive in releasing T in response to bLH stimulation in the spring and summer compared with the winter; however, there were no changes in sensitivity of the testes to LH during different seasons of the year as indicated by the lack of a dose of bLH x season interaction.     

Effect of freezing goat milk samples on recovery of intramammary bacterial pathogens

With the aim of evaluating the effect of freezing goat milk samples on recovery of intramammary pathogens, 1200 milk samples from udder halves with subclinical intramammary infection were studied. Samples (20 ml) were frozen at -20 and at -80 degrees C. Thawing was carried out at room temperature at 7, 14, 21, 28, 58, 118, 178, 236 and 730 days after collection and bacteriological analyses were carried out to determine the number of colony forming units/ml (CFU/ml). Mixed model statistical analysis showed that bacterial group, temperature of storage, interaction of bacterial group and temperature of storage and the interaction of bacterial group, time and temperature of storage were statistically significant effects. For coagulase negative staphylococci (CNS), least squares means of log CFU/ml recovered at -20 and -80 degrees C were not different. Nevertheless, for Gram negative bacilli (GNB) a significant decrease was detected in samples frozen at -20 vs. -80 degrees C. At both temperatures and at different times of storage, significant increases were detected between log CFU/ml of CNS and values on day zero. At -20 degrees C, a significant decrease in GNB recovery was detected between freezing days zero and 730. This difference was not detected when goat milk samples infected by GNB were frozen at -80 degrees C. The results show that frozen milk samples can be useful in goat subclinical mastitis control programs.     

Effects of administration of antimicrobials in feed on growth rate and feed efficiency of pigs in multisite production systems

OBJECTIVE: To evaluate effect of various regimens for administration of antimicrobials in feed on growth rate and feed efficiency (feed/gain) of pigs in multisite production systems. DESIGN: Controlled trial. ANIMALS: 24,099 growing pigs in 3 multisite production systems. PROCEDURE: 10 trials involving various regimens for administration of antimicrobials in feed were evaluated. Trial 1 compared effects of 2 antimicrobial regimens on finishing pig performance. Trials 2 through 10 compared growth rate and feed efficiency of nursery and finishing pigs given antimicrobials in feed with values for control pigs not given antimicrobials. RESULTS: In trial 1, no significant differences were observed between the 2 antimicrobial regimens. In the remaining trials, growth rate of nursery pigs fed antimicrobials was significantly improved, compared with growth rate of control pigs. However, growth rate of finishing pigs and feed efficiency of nursery and finishing pigs were not significantly improved by adding antimicrobials to the feed. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that use of antimicrobials in the feed to promote growth should be limited to the nursery phase in multisite pig production systems. Use of antimicrobials in the feed of finishing pigs should be limited to therapeutic applications in which a diagnosis of bacterial infection susceptible to the antimicrobial to be used has been confirmed.     

Yield loss in chickpeas in relation to development of fusarium wilt epidemics

ABSTRACT Development of 108 epidemics of Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris were studied on cvs. P-2245 and PV-61 in field microplots artificially infested with races 0 and 5 of F. oxysporum f. sp. ciceris in 1986 to 1989. Disease progression data were fitted to the Richards model using nonlinear regression. The shape parameter was influenced primarily by date of sowing and, to a lesser extent, by chick-pea cultivars and races of F. oxysporum f. sp. ciceris. Fusarium wilt reduced chickpea yield by decreasing both seed yield and seed weight. These effects were related to sowing date, chickpea cultivar, and virulence of the prevalent F. oxysporum f. sp. ciceris race. Regression models were developed to relate chickpea yield to Fusarium wilt disease intensity with the following independent variables: time to initial symptoms (t(is)), time to inflection point (t(ip)) of the disease intensity index (DII) progress curve, final DII (DII(final)), standardized area under DII progress curve (SAUDPC), and the Richards weighted mean absolute rate of disease progression (rho). Irrespective of the chickpea cultivar x pathogen race combination, the absolute and relative seed yields decreased primarily by delayed sowing. The relative seed yield increased with the delay in t(is) and t(ip) and decreased with increasing DII(final), SAUDPC, and rho. A response surface as developed in which seed yield loss decreased in a linear relationship with the delay in t(is) and increased exponentially with the increase of rho.