Agriculture and Agri-Food Canada

About: Agriculture and Agri-Food Canada is a facility organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Population & Soil water. The organization has 10921 authors who have published 21332 publications receiving 748193 citations. The organization is also known as: Department of Agriculture and Agri-Food.

Impacts of climate change on indirect human exposure to pathogens and chemicals from agriculture.

Abstract: ObjectiveClimate change is likely to affect the nature of pathogens and chemicals in the environment and their fate and transport. Future risks of pathogens and chemicals could therefore be very di...

Quality control of CarboEurope flux data – Part 2: Inter-comparison of eddy-covariance software

Abstract: As part of the quality assurance and quality control activities within the CarboEurope-IP network, a comparison of eddy-covariance software was conducted For four five-day datasets, CO2 flux estimates were calculated by seven commonly used software packages to assess the uncertainty of CO2 flux estimates due to differences in post-processing The datasets originated from different sites representing different commonly applied instrumentation and different canopy structures to cover a wide range of realistic conditions Data preparation, coordinate rotation and the implementation of the correction for high frequency spectral losses were identified as crucial processing steps leading to significant discrepancies in the CO2 flux results The overall comparison indicated a good although not yet perfect agreement among the different software within 5–10% difference for 30-min CO2 flux values Conceptually different ideas about the selection and application of processing steps were a main reason for the differences in the CO2 flux estimates observed A balance should be aspired between scientific freedom on the one hand, in order to advance methodical issues, and standardisation of procedures on the other hand, in order to obtain comparable fluxes for multi-site synthesis studies

Phylogenetic relationships between Bacillus species and related genera inferred from comparison of 3' end 16S rDNA and 5' end 16S-23S ITS nucleotide sequences.

Abstract: The nucleotide sequences of the 3' end of the 16S rDNA and the 16S-23S internal transcribed spacer (ITS) of 40 Bacillaceae species were determined. These included 21 Bacillus, 9 Paenibacillus, 6 Brevibacillus, 2 Geobacillus, 1 Marinibacillus and 1 Virgibacillus species. Comparative sequence analysis of a 220 bp region covering a highly conserved 150 bp sequence located at the 3' end of the 16S rRNA coding region and a conserved 70 bp sequence located at the 5' end of the 16S-23S ITS of the 40 species and six sequences available in GenBank were used to infer the phylogenetic relationships between all 46 taxa. When a maximal distance (D(max), where D refers to the number of nucleotide substitutions per site) of 0.31 was introduced as a threshold to determine groupings, 10 phylogenetically distinct clusters were revealed. Twenty-six Bacillus species were separated in seven groups (I, II, III, IV, V, VI and X), but Bacillus circulans remained ungrouped. All six Brevibacillus species under study were in Group VII. The nine Paenibacillus species fell into two distinct groups (VIII and IX). Species with D(max) values within 0.05 were considered to be very closely related. These were Bacillus psychrophilus and Bacillus psychrosaccharolyticus in Group II; 'Bacillus maroccanus' and Bacillus simplex in Group II; Bacillus amyloliquefaciens, Bacillus atrophaeus, Bacillus mojavensis and Bacillus subtilis in Group VI; Bacillus fusiformis and Bacillus sphaericus in Group VI; Brevibacillus brevis and Brevibacillus formosus in Group VII; Paenibacillus gordonae and Paenibacillus validus in Group VIII; and Bacillus anthracis, Bacillus cereus, Bacillus mycoides and Bacillus thuringiensis in Group X. The phylogenetic classification presented here is, in general, in agreement with current classifications based on phenotypic and molecular data. Our findings suggest, however, that in some cases, further divisions or, conversely, further groupings might be warranted. Should current classifications be re-examined in the light of our results, D(max) values of 0.31 and 0.05, as exemplified here, may prove useful threshold values for the grouping of Bacillaceae into taxa akin to genera and species, respectively. These D(max) thresholds may also reveal, in a different way, bacterial species for which further characterization might be warranted for proper classification and/or reassignment.

The fate of nitrogen in agroecosystems: An illustration using Canadian estimates

Abstract: Agroecosystems rely on inputs of nitrogen (N) to sustain productivity. But added N can leak into adjacent environments, affecting the health of other ecosystems and their inhabitants. Worries about global warming have cast further attention on the N cycle in farmlands because farms are a main source of N2O, and because carbon sequestration, proposed to help reduce CO2 loads, requires a build-up of N. Our objective was to estimate, as an illustrative example, the net N balance of Canadian agroecosystems in 1996 and then infer some hypotheses about the routes of N loss, their magnitude, and ways of reducing them. We defined agroecosystems as all agricultural lands in Canada including soil to 1 m depth and all biota, except humans. Only net flows of N across those boundaries were counted in our balance – all others represent internal cycling. Based on our estimates, about 2.35 Tg N entered Canadian agroecosystems from biological fixation, fertilizers, and atmospheric deposition (excluding re-deposited NH3). In the same year, about 1.03 Tg N were exported in crop products and 0.19 Tg were exported in animals and animal products. Consequently, N inputs exceed exports in products by about 1.13 Tg, a surplus that is either accumulating in agroecosystems or lost to the environment. Because potential soil organic matter gains can account for only a small part of the surplus N, most is probably lost to air or groundwater. Our finding, that N losses amount to almost half of N added, concurs with field experiments that show crop recovery of added N in a given year is often not more than 60%. Better management may reduce the fraction lost somewhat but, because N in ecosystems eventually cycles back to N2, substantive gains in efficiency may not come easily. As well as trying to reduce losses, research might also focus on steering losses directly to N2, away from more harmful intermediates. If some of the `missing N' can be assimilated into organic matter, agricultural soils in Canada may need little added N to achieve C sequestration targets.

Phytogenic Compounds as Alternatives to In-Feed Antibiotics: Potentials and Challenges in Application

Abstract: This article summarizes current experimental knowledge on the efficacy, possible mechanisms and feasibility in the application of phytogenic products as feed additives for food-producing animals. Phytogenic compounds comprise a wide range of plant-derived natural bioactive compounds and essential oils are a major group. Numerous studies have demonstrated that phytogenic compounds have a variety of functions, including antimicrobial/antiviral, antioxidative and anti-inflammation effects and improvement in the palatability of feed and gut development/health. However, the mechanisms underlying their functions are still largely unclear. In the past, there has been a lack of consistency in the results from both laboratory and field studies, largely due to the varied composition of products, dosages, purities and growing conditions of animals used. The minimal inhibitory concentration (MIC) of phytogenic compounds required for controlling enteric pathogens may not guarantee the best feed intake, balanced immunity of animals and cost-effectiveness in animal production. The lipophilic nature of photogenic compounds also presents a challenge in effective delivery to the animal gut and this can partially be resolved by microencapsulation and combination with other compounds (synergistic effect). Interestingly, the effects of photogenic compounds on anti-inflammation, gut chemosensing and possible disruption of bacterial quorum sensing could explain a certain number of studies with different animal species for the better production performance of animals that have received phytogenic feed additives. It is obvious that phytogenic compounds have good potential as an alternative to antibiotics in feed for food animal production and the combination of different phytogenic compounds appears to be an approach to improve the efficacy and safety of phytogenic compounds in the application. It is our expectation that the recent development of high-throughput and “omics” technologies can significantly advance the studies on the mechanisms underlying phytogenic compounds’ functions and, therefore, guide the effective use of the compounds.