Effects of clipping frequency, row spacing and nitrogen fertilization in Digitaria eriantha cv. Irene

During the yearly cycles 2000-2001 and 2001-2002 an experiment was conducted with the perennial grass, Digitaria eriantha cv. Irene, at Bahía Blanca (Argentina). In randomized blocks-design with three replications and a 2 x 2 x 3 factorial arrangement of treatments, the factors studied were: 1) cutting frequency: continuous, whenever the plants reached a height of 26-28 cm; and seasonal, with one cutting at the end of spring and of summer; 2) row spacing: 30 and 50 cm; and 3) levels of nitrogen fertilization: 0, 50, and 100 kg/ha. Forage harvested in spring and summer was weighed to determine dry matter yields per season and annual total (MS, kg/ha). Crude protein content (% PC), CP yield (kg/ha), efficiency of N utilization (ENU, kg MS/kg N) and N recovery in forage (% NR) were also determined. Fertilization was the most influential factor in addition to rainfall. Mean total yields of DM with 0, 50, and 100 kg N/ha were, in drier 2000-2001: 1632, 2122, and 2539 kg/ha, and in rainier 2001-2002: 2564, 4474, and 4708 kg/ha, respectively. Mean of CP of both years for the same N levels, were 6.8, 9.0, and 10.7, respectively. Yields of CP were also highest with 100 kg N/ha, but ENU and NR were better with the lower level of N application. These results suggest that N fertilization at a level close to 50 kg/ha is recommendable. Continuous cutting reduced forage yields (P<.05), but gave higher % CP relative to seasonal cutting (P<.05). Row spacing had no consistent effect on these variables, but 30 cm is favored to reduce soil erosion

Experimental neosporosis in bulls: Parasite detection in semen and blood and specific antibody and interferon-gamma responses

Aim To investigate the presence of Neospora caninum in semen and blood, and the development of specific antibody and interferon-gamma (IFN-γ) responses in experimentally infected bulls. Methods Eight bulls were intravenously infected with 108 live N. caninum tachyzoites of NC-1 isolate. The presence of N. caninum in semen and blood was assessed using a nested-PCR procedure. PCR-positive semen samples were bioassayed using a BALB/c nu/nu mouse model. Specific anti-N. caninum antibody and IFN-γ responses were also examined. In parallel, eight seronegative bulls were studied as non-infected controls. All bulls were monitored for 26 weeks. Results All eight experimentally infected bulls showed N. caninum DNA in their semen and/or blood samples at some time during the course of the study. Parasite load in semen ranged from 0.1 to 14.5 parasites/ml (mean 6.0). N. caninum could not be detected in BALB/c nu/nu mice inoculated with PCR-positive semen samples. A significant increase in mean serum specific IgM antibody response to N. caninum was detected between 10 and 28 days post-infection (p.i.). Serum specific IgG, IgG1, and IgG2 antibody levels in experimentally infected bulls were significantly different after 21, 10, and 14 days p.i. as compared to controls, respectively. Specific anti-N. caninum IgG were detected in seminal plasma from infected bulls and values obtained were different from controls after 25 days p.i. Mean specific IFN-γ responses in experimentally infected bulls were significantly higher than controls 3 days p.i. Conclusions This is the first study to report the presence of N. caninum DNA in the semen and blood of experimentally infected bulls. Our observations indicate an intermittent presence of N. caninum in low numbers in semen and associated with chronic stage of the infection. This study is also the first to report the detection of anti-N. caninum IgG in seminal plasma of experimentally infected bulls

Bluetongue Virus Serotype 1 Outbreak in the Basque Country (Northern Spain) 2007–2008. Data Support a Primary Vector Windborne Transport

BACKGROUND: Bluetongue (BT) is a vector-borne disease of ruminants that has expanded its traditional global distribution in the last decade. Recently, BTV-1 emerged in Southern Spain and caused several outbreaks in livestock reaching the north of the country. The aim of this paper was to review the emergence of BTV-1 in the Basque Country (Northern Spain) during 2007 and 2008 analyzing the possibility that infected Culicoides were introduced into Basque Country by winds from the infected areas of Southern Spain. METHODOLOGY/PRINCIPAL FINDINGS: We use a complex HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model to draw wind roses and backward wind trajectories. The analysis of winds showed September 28 to October 2 as the only period for the introduction of infected midges in the Basque Country. These wind trajectories crossed through the areas affected by serotype 1 on those dates in the South of the Iberian Peninsula. Additionally meteorological data, including wind speed and humidity, and altitude along the trajectories showed suitable conditions for Culicoides survival and dispersion. CONCLUSIONS/SIGNIFICANCE: An active infection in medium-long distance regions, wind with suitable speed, altitude and trajectory, and appropriate weather can lead to outbreaks of BTV-1 by transport of Culicoides imicola, not only over the sea (as reported previously) but also over the land. This shows that an additional factor has to be taken into account for the control of the disease which is currently essentially based on the assumption that midges will only spread the virus in a series of short hops. Moreover, the epidemiological and serological data cannot rule out the involvement of other Culicoides species in the spread of the infection, especially at a local level