February 17, 2016 – New research has shown that tackling antibiotic resistance on only one front is a waste of time because resistant genes are freely crossing environmental.
Analysis of historic soil archives dating back to 1923 has revealed a clear parallel between the appearance of antibiotic resistance in medicine and similar antibiotic resistant genes detected over time in agricultural soils treated with animal manure.
Collected in Denmark – where antibiotics were banned in agriculture from the 1990s for non-therapeutic use – the soil archives provide an 'antibiotic resistance timeline' that reflects resistant genes found in the environment and the evolution of the same types of antibiotic resistance in medicine.
Led by Newcastle University, UK, the study also showed that the repeated use of animal manure and antibiotic substitutes can increase the capacity of soil bacteria to mobilize, or ready themselves, and acquire resistance genes to new antibiotics.
Publishing their findings in the academic journal Scientific Reports, the study's authors say the data highlights the importance of reducing antibiotic use across all sectors if we are to reduce global antibiotic resistance.
"The observed bridge between clinical and agricultural antibiotic resistance means we are not going to solve the resistance problem just by reducing the number of antibiotics we prescribe in our GP clinics,” said lead author David Graham, professor of ecosystems engineering at Newcastle University.
"To reduce the global rise in resistance, we need to reduce use and improve antibiotic stewardship across all sectors. If this is not done, antibiotic resistance from imprudent sectors will cross-contaminate the whole system and we will quickly find ourselves in a situation where our antibiotics are no longer effective."
Antibiotics have been used in medicine since the 1930s, saving millions of lives. Two decades later, they were introduced into agricultural practices and Denmark was among the leaders in employing antibiotics to increase agricultural productivity and animal production.
However, a growing awareness of the antibiotic resistance crisis and continued debate over who and which activities are most responsible led to the EU calling for the use of antibiotics in non-therapeutic settings to be phased out and Denmark led the way.
The Askov Long-Term Experiment station in Denmark was originally set up in 1894 to study the role of animal manure versus inorganic fertilizers on soil fertility.
Analyzing the samples, the team – involving experts from Newcastle University, the University of Strathclyde and Aarhus University – were able to measure the relative abundance of specific β-lactam antibiotic resistant genes, which can confer resistance to a class of antibiotics that are of considerable medical importance.
Prior to 1960, the team found low levels of the genes in both the manured soil and that treated with inorganic fertilizer. However, by the mid 1970s, levels of selected β-lactam genes started to increase in the manured soils, with levels peaking in the mid 1980's. No increase or change was detected in the soil treated with inorganic fertilizer.
"We chose these resistant genes because their appearance and rapid increase in hospitals from 1963 to 1989 is well-documented," explains Professor Graham.
"By comparing the two timelines, we saw the appearance of each specific gene in the soil samples was consistent with the evolution of similar types of resistance in medicine. So the question now is not which came first, clinical or environmental resistance, but what do we do about it?"
Following the ban on non-therapeutic antibiotic use in Danish agriculture, farmers substituted metals for antibiotics, such as copper, and levels of the key β-lactam genes in the manured soils declined rapidly, reaching pre-industrialization levels by 2010.
However, at the same time the team measured a 10-fold rise in Class 1 Integrons. These are gene carrier and exchange molecules – transporters that allow bacteria to readily share genes, including resistance genes.
These findings suggest the application of manure and antibiotic substitutes, such as copper, may be 'priming' the soils, readying them for increased resistance transmission in the future.
"Once antibiotics were banned, operators substituted them with copper which has natural antibiotic properties," explains Professor Graham.
"More research is needed but our findings suggest that by substituting antibiotics for metals such as copper we may have increased the potential for resistance transmission.
"Unless we reduce use and improve stewardship across all sectors – environmental, clinical and agricultural – we don't stand a chance of reducing antibiotic resistance in the future."
In August 2010, British Columbia’s first biodigester began operating in Abbotsford – using, among other substrates, poultry litter. The B.C. government provided $1.5 million to assist in the development of the project (known as “Fraser Valley Biogas”) as a way to go beyond green electricity generation. “B.C.’s Clean Energy Act sets a target to ensure our electricity supply is 93 per cent renewable,” notes Sue Bonnyman, director of generation and regulation electricity policy at B.C.’s Ministry of Energy and Mines. “However, the current low electricity prices, due to B.C.’s very fine hydroelectric system, create challenges for a number of new or renewable technologies.” That’s one reason the province has made it possible for Fraser Valley Biogas to sell “biomethane” to the natural gas company Fortis, instead of using the digester’s biogas to make electricity.
Digester biogas must be “cleaned up” before it’s placed into any natural gas network (the biogas is then known as “biomethane”), and the scrubbing equipment required is costly. “Such a system thus only makes sense at larger-sized projects such as these, of at least one megawatt,” notes Matt Lensink, application manager with PlanET Biogas, the company that built Fraser Valley Biogas. (Another obvious limitation for digesters to sell biomethane is that they must also be located near a natural gas pipeline.) How many tonnes per day of dry or wet manure is required to run a one-megawatt system depends on the type of manure – and the type and amount of off-farm materials.
Fraser Valley Biogas uses liquid dairy cattle manure and solid poultry manure from four nearby farms, as well as a substantial amount of food industry byproduct. As the project is just beginning, Lensink says details are not available about things like how much poultry manure/litter is used per year, what overall percentage of digester feedstock comes from poultry litter, whether it’s placed directly in the digester after barn cleanout, and whether the farmer is compensated for the manure. However, no matter how much or how little manure is used at Fraser Valley Biogas, co-substrates are definitely needed for manure digesters to be economically viable, says CH-4 Biogas Inc. Systems Analyst Claire Allen. CH-Four has created a software program to analyze what amount of a given substrate, such as source-separated organics or fat/oil/grease, is advisable to add to what’s already present in a digester. The company has nine digester systems running in Canada, one in New York State and three more being constructed in Canada; they are all “combined heat & power” (CHP) systems, generating heat and electricity.
Unique to Canada
Fraser Valley Biogas is unique in Canada as an on-farm digester with biomethane being injected into the natural gas network. All others are at municipal sewage plants, landfills or food processing companies. Electrigaz Technologies Inc. president Eric Camirand notes that in Quebec the Ministry of Environment now subsidizes municipal biogas plants up to 66 per cent of capital costs, with the focus on injection of biomethane. Ontario is also looking at this concept; Electrigaz has done several studies for gas companies such as Union and Enbridge on scrubbing biogas and injection biomethane into their networks.
Digesters specifically for poultry litter
Biodigesters that run specifically on poultry manure are being investigated by Anna Crolla, a senior researcher at the Ontario Rural Wastewater Centre (located at the University of Guelph’s Alfred campus). The research project is being funded by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and Natural Resources Canada-Canmet Energy. The anaerobic digestion process applicable to poultry manure is known as dry fermentation, Crolla explains. “It’s a process that can handle substrates with high solids content, greater than 25 per cent, whereas traditional digesters use wet fermentation with slurries containing solids contents lower than 15 per cent.” Dry fermentation is advantageous, Crolla notes, in that a smaller reactor is required compared to that needed for wet fermentation. The amount of effluent wastewater is lower as well, resulting in significantly reduced manure handling costs.
A dry fermentation digester usually consists of boxes into which the substrate is emptied through the use of wheel-loaders. After the boxes are sealed in an airtight fashion, the anaerobic digestion process begins. About three to four weeks later, most of the digested substrates are removed and the boxes are filled again (for higher efficiency, some of the residual fermented material with high concentrations of bacteria is left in the boxes).
However, there are a number of challenges to making dry fermentation of poultry manure work. Crolla explains that when poultry manure (which is rich in nitrogen) is anaerobically digested, the high solids content causes ammonia to accumulate, which slows the digestion down (and production of biogas) down. One way of dealing with this is co-digesting the poultry manure with carbon-rich substrates to increase the C:N ratio, so Crolla is studying how the addition of energy crops works to boost performance of a dry fermentation digester. “The energy crops that we’re studying will include corn silage, corn stover, wheat straw, switchgrass (non-leguminous) and, clover, alfalfa and soybean silages (leguminous),” Crolla notes. She began work on evaluating optimal C:N ratios, pH and moisture content, as well as studying the effects of ammonia accumulation on substrate digestibility, in September 2011.
Bench-scale digesters will be built this coming summer.
Another project in B.C.?
A major developer, builder, owner and operator of electrical power plants fuelled by poultry litter and other agricultural biomass is currently eyeing the Fraser Valley for a possible project. Pennsylvania-based Fibrowatt was founded in 2000 by the management team that built the world’s first three poultry- litter-fuelled power plants in the U.K. in the 1990s. These plants have converted more than seven million tons of poultry litter into more than four million megawatt-hours of electricity (serving about 150,000 homes) and 500,000 tons of ash fertilizer.
In 2007, Fibrowatt built the United States’ first poultry- litter-fuelled (about 50/50 chicken and turkey) power plant in Minnesota, a 55-MW facility that serves about 40,000 homes. The poultry litter is purchased from surrounding farms through long-term contracts and spot purchases, transported in tightly covered trucks and stored at negative pressure to prevent the escape of odours. Inside the power plant, the litter is burned at very high temperatures, heating water in a boiler to produce steam that drives a turbine. A large amount of ash is also produced.
“We sell 90 000 to 100 000 tons of ash a year to a fertilizer company,” says Jim Potter, president and COO of parent company Homeland Renewable Energy Inc. “The rating of the ash is 0-7-7 for NPK, as all the nitrogen in the litter is combusted into N2 gas.” (Note that by-products other than biogas that are created in Canadian digesters are also being used; the effluent is spread on fields, and the solids from the digester tank are used as cattle bedding.)
Will it work in Canada?
Although low electricity prices in B.C. pose a challenge to any Fibrowatt facility moving forward in that province, Potter says, “We hope that people will place a premium on the other services a project such as this can provide. Our plants offer an environmentally responsible and useful outlet for poultry litter in regions that produce more litter than can be utilized for land application. This enhances the sustainability of the poultry industry.” Fibrowatt is also pursuing projects in areas of the U.S. where excess nitrogen and phosphorus is being released into water sources, such as Chesapeake Bay.
Mar. 8, 2012 - Many poultry farmers, most of them with free range or aviary houses, would like to reduce the litter level and improve its quality in their houses.
Jansen Poultry has found a solution and developed a mechanical Litter Removal System.
When using this system:
- Litter level in the house can be kept in check
- Litter is mechanically removed
- Dust and ammonia levels are considerably reduced
How does the system work?
In the walkways of the house, a revolving steel cable with a scraper attached every ± 4m is installed. The back-and-forth movements of the scrapers move the litter to the back of the house.
During the cleaning of the house, the cable with scrapers can be removed so the system does not interfere with the cleaning process.
For more information, please contact your local Jansen Poultry Equipment dealer or http://www.jpe.org/.
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Western Poultry ConferenceMon Feb 27, 2017
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Canada's Food Loss and Waste Forum | Finding solutionsWed Apr 12, 2017