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Medhanie G.A.,University of Guelph | McEwen S.A.,University of Guelph | Weber L.,Lloyd Weber Consulting Services | Sanei B.,Ontario Ministry of Agriculture Food and Rural Affairs | And 5 more authors.
Preventive Veterinary Medicine | Year: 2013

Brachyspira species are frequent colonizers of the gastrointestinal tract in a variety of domestic animals, including birds. In chickens, Brachyspira species are associated with a clinical condition known as avian intestinal spirochetosis (AIS), a disease characterized by chronic diarrhoea, weight loss, low egg production, and faecal-stained eggs. The purpose of this study was to identify risk factors associated with the presence of Brachyspira species in Ontario layer chicken flocks. Pooled faecal samples were collected from 89 flocks from 58 farms between August 2010 and February 2011; 52 flocks were classified as dirty flocks (history of downgrades for dirty eggs) and 37 were classified as clean flocks (no history of downgrades for dirty eggs). A questionnaire related to management, biosecurity practices, and antimicrobial use was administered prior to sample collection. Using real-time polymerase chain reaction; 63.5% of the dirty flocks and 24.3% of the clean flocks were positive for Brachyspira species.A logistic regression model with a random effect for farm showed that the odds of Brachyspira species for flocks≥60 weeks of age were higher than for flocks≤34 weeks (OR=9.3; P=0.014). The odds of Brachyspira species in flocks housed in A-frame cages with manure curtains (OR=20.0; P=0.002) and flocks from multi-age farms (OR=8.5; P=0.001) were higher than for flocks in cage-stacked houses and from single-age farms, respectively. The odds of Brachyspira species for flocks housed in barns≥30 years old was lower than for flocks housed in barns≤14 years old (OR=0.1; P=0.002). The calculated intra-class correlation coefficient was 5.6×10-14; the notably low proportion of variation among farms after the fixed effects were included in the model suggests that the farm-level variable (multi-age farm) included in the final model accounted for most of the farm-to-farm variation in Brachyspira presence. Therefore, it is recommended that strict biosecurity, and between-flock decontamination efforts to reduce the infection pressure, be followed on farms with multiple flocks of different ages to avoid transmission of the bacteria between flocks. © 2012 Elsevier B.V. Source


Dorea F.C.,University of Prince Edward Island | Revie C.W.,University of Prince Edward Island | McEwen B.J.,University of Guelph | McNab W.B.,Ontario Ministry of Agriculture Food and Rural Affairs | And 2 more authors.
Preventive Veterinary Medicine | Year: 2013

The practice of disease surveillance has shifted in the last two decades towards the introduction of systems capable of early detection of disease. Modern biosurveillance systems explore different sources of pre-diagnostic data, such as patient's chief complaint upon emergency visit or laboratory test orders. These sources of data can provide more rapid detection than traditional surveillance based on case confirmation, but are less specific, and therefore their use poses challenges related to the presence of background noise and unlabelled temporal aberrations in historical data. The overall goal of this study was to carry out retrospective analysis using three years of laboratory test submissions to the Animal Health Laboratory in the province of Ontario, Canada, in order to prepare the data for use in syndromic surveillance. Daily cases were grouped into syndromes and counts for each syndrome were monitored on a daily basis when medians were higher than one case per day, and weekly otherwise. Poisson regression accounting for day-of-week and month was able to capture the day-of-week effect with minimal influence from temporal aberrations. Applying Poisson regression in an iterative manner, that removed data points above the predicted 95th percentile of daily counts, allowed for the removal of these aberrations in the absence of labelled outbreaks, while maintaining the day-of-week effect that was present in the original data. This resulted in the construction of time series that represent the baseline patterns over the past three years, free of temporal aberrations. The final method was thus able to remove temporal aberrations while keeping the original explainable effects in the data, did not need a training period free of aberrations, had minimal adjustment to the aberrations present in the raw data, and did not require labelled outbreaks. Moreover, it was readily applicable to the weekly data by substituting Poisson regression with moving 95th percentiles. © 2012 Elsevier B.V. Source


Schaafsma A.,University of Guelph | Limay-Rios V.,University of Guelph | Baute T.,Ontario Ministry of Agriculture Food and Rural Affairs | Smith J.,University of Guelph | Xue Y.,University of Guelph
PLoS ONE | Year: 2015

Neonicotinoid insecticides have come under scrutiny for their potential unintended effects on non-target organisms, particularly pollinators in agro-ecosystems. As part of a larger study of neonicotinoid residues associated with maize (corn) production, 76 water samples within or around the perimeter of 18 commercial maize fields and neighbouring apiaries were collected in 5 maize-producing counties of southwestern Ontario. Residues of clothianidin (mean = 2.28, max. = 43.60 ng/mL) and thiamethoxam (mean = 1.12, max. = 16.50 ng/mL) were detected in 100 and 98.7%of the water samples tested, respectively. The concentration of total neonicotinoid residues in water within maize fields increased six-fold during the first five weeks after planting, and returned to pre-plant levels seven weeks after planting. However, concentrations in water sampled from outside the fields were similar throughout the sampling period. Soil samples from the top 5 cm of the soil profile were also collected in these fields before and immediately following planting. The mean total neonicotinoid residue was 4.02 (range 0.07 to 20.30) ng/g, for samples taken before planting, and 9.94 (range 0.53 to 38.98) ng/g, for those taken immediately after planting. Two soil samples collected from within an conservation area contained detectable (0.03 and 0.11 ng/g) concentrations of clothianidin. Of three drifted snow samples taken, the drift stratum containing the most wind-scoured soil had 0.16 and 0.20 ng/mL mainly clothianidin in the melted snow. The concentration was at the limit of detection (0.02 ng/mL) taken across the entire vertical profile. With the exception of one sample, water samples tested had concentrations below those reported to have acute, chronic or sublethal effects to honey bees. Our results suggest that neonicotinoids may move off-target by wind erosion of contaminated soil. These results are informative to risk assessment models for other non-target species in maize agro-ecosytems. © 2015 Schaafsma et al. Source


Papadopoulos A.P.,Agriculture and Agri Food Canada | Yaganza E.S.,Agriculture and Agri Food Canada | Hao X.,Agriculture and Agri Food Canada | Martynenko A.,Agriculture and Agri Food Canada | And 5 more authors.
Acta Horticulturae | Year: 2012

The effects of varying levels of nutrient solution oxygenation on greenhouse tomato (Lycopersicon esculentum L. 'Macarena') was investigated in 2006 and 2007 using rockwool, coir and perlite growing media. In 2006, early marketable and total yields were higher with 75 ppm O2 in the nutrient solution (14.5 kg m-2), than the control (12.8 kg m -2) and compressed air (12.9 kg m-2) treatments, while no significant difference was observed between 20, 30, 35 and 75 ppm. The seasonal yield followed the same trend, i.e. higher values were obtained with 75 ppm O2 (28.9 kg m-2) than with the control (27.1 kg m -2) and compressed air treatments (26.2 kg m-2). The seasonal average weight of marketable fruit was significantly higher with 35 ppm O2 (206 g) than with the control (196 g) and compressed air treatments (194 g). In 2007, in general, the late-season and seasonal marketable yield with all oxygen treatments was either equal to or higher than the control. Except for the 30 ppm treatment, the usual decline in marketable yield across the season was slower with oxygen super-saturated nutrient solution (24-29% between the mid and the last season) than with the control (i.e. a corresponding 40-45% reduction), indicating that oxygen can sustain productivity under ageing stress condition. The 60 ppm O2 treatment resulted in higher total seasonal yield than the control on the rockwool medium. These results suggest that application of nutrient solution oxygenation under certain conditions can improve greenhouse tomato productivity. Differences in climatic conditions may explain partly the differences in crop performance between the two seasons. Source


Guo X.,Agriculture and Agri Food Canada | Hao X.,Agriculture and Agri Food Canada | Khosla S.,Ontario Ministry of Agriculture Food and Rural Affairs | Kumar K.G.S.,Agriculture and Agri Food Canada | And 2 more authors.
Acta Horticulturae | Year: 2016

Inter-lighting, applying supplemental light within crop canopy, has been shown to improve plant vertical light distribution and light use efficiency, with high-pressure sodium (HPS) lamps. However, it is not feasible on vegetables cultivated with the popular twin-row system (narrow row) used in major greenhouse vegetable production area in northern regions because of its high bulb temperature. Lightemitting diodes (LEDs) has low operating temperature and thus is potentially a good fit for inter-lighting. In this study, therefore, the effects of LED inter-lighting on sweet pepper growth, fruit yield and quality, and light and energy use efficiency were investigated in the commercial greenhouse. To optimize the production system with LED inter-lighting, different levels of top HPS lighting were also evaluated in the two experiments. Experiment one evaluated single row of LED inter-lighting module per twin-row (56.8 μmol m-2 s-1) without or with top HPS (78 μmol m-2 s-1). Experiment two evaluated the same LED inter-lighting module without or with the top HPS lamps at greater light intensity (155 μmol m-2 s-1). LED inter-lighting improved plant growth, fruit yield and quality compared to the top HPS treatment. Moreover, LED interlighting significantly increased fruit dry matter content and the content of health promoting compounds in fruits, including total phenolic content, total carotenoid content and antioxidant activities (ferric reducing antioxidant power assay and 2, 2-diphenyl-1-picrylhydrazyl assay), compared with the HPS treatments. As a result of LED inter-lighting more light reached the crop canopy with a higher efficiency of electricity to light conversion and the plants grown with LED inter-lighting and top HPS achieved higher yield and quality than that with the top HPS only in both experiments. Source

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