MYCOTOXINS

The frequency of mycotoxin contamination of poultry feeds appears to be on the increase globally. This is a serious threat, since complex poultry rations are highly susceptible. As a result, such contamination can seriously affect bird performance. Proper measures are needed to minimise losses.

By Trevor K. Smith, Professor, Department of Animal and Poultry Science, University of Guelph, Ontario, Canada

Do you know that mycotoxins are the second most important issue faced by the animal industry today next to feed cost? This sentiment was expressed by 30 animal industry leaders, representing 15% of world feed production, who recently attended Alltech's President Club.

Mycotoxins are metabolites produced by fungi (moulds) that can infest crops pre-harvest and can continue to flourish under sub-optimal storage conditions. Grains with high moisture content are particularly unstable and prone to mould proliferation and possible mycotoxin production. Excess rainfall at harvest and at key periods during the growing season can be a major promoter of mycotoxin contamination of feedstuffs.

Aspergillus mainly in tropics

The most significant species of mycotoxin-producing fungi that have an impact on poultry production would include Aspergillus and Fusarium. The most significant mycotoxin produced by Aspergillus fungi are the aflatoxins. The fungi that synthesise aflatoxins A. flavus and A. parasiticus are considered to be tropical or semi-tropical moulds that thrive under conditions of high moisture and temperature. The effects of feed-borne aflatoxin on poultry production have been extensively studied and we have a good understanding of the tolerance of various classes of poultry. This is partly due to concern for human health and food safety issues arising from contamination of poultry products with aflatoxin, since aflatoxin is a potent hepatocarcinogen. Analytical techniques for aflatoxin analysis in feeds are very practical due to the small number of different compounds that allow their simultaneous analysis.

Another important mycotoxin is the nephrotoxin ochratoxin A. This compound is produced by Aspergillus ochraceus and Penicillium verrucosum. As with aflatoxin, there is concern that residual ochratoxin A in poultry products could pose a threat to human health due to the possible carcinogenic nature of this compound.

Fusarium in temperate climates

Fusarium fungi flourish in more temperate climates. Our understanding of Fusarium mycotoxicoses in poultry is much less complete than our understanding of aflatoxicosis. This is in part because of the very large number of Fusarium mycotoxins, more than 100 that have been chemically characterised, which makes complete analysis of feedstuffs for Fusarium mycotoxins impractical, if not impossible.

The most commonly recognised Fusarium mycotoxins include the trichothecenes, a large family of structurally-related compounds including deoxynivalenol (DON, vomitoxin), T-2 toxin, nivalenol, diacetoxyscirpenol (DAS) and over 100 others, zearalenone, an oestrogenic compound, fumonisins and fusaric acid.

Analysis in poultry feeds

A major source of error in mycotoxin analysis is inadequate sampling of feedstuffs, with sampling accounting for approx. 82% of the variability in analysis. Proper sampling protocols have been developed and published in an effort to minimise this source of error. However, even with such protocols, error is unavoidable as mycotoxins are not evenly distributed within a batch, but occur in hotspots. Even with correct sampling, as an example, from a 25 t batch of feed, approx. 100 sub-samples should be taken comprising a total of 25 kg. From this a 250 g sub-sample is taken and eventually a 1 g sample analysed. Considering that only 1 g is analysed from 25 t, it is hardly surprising that mycotoxin analysis is not accurate!

Another source of error is the potential presence of different chemical forms of mycotoxins that may escape routine analysis. Attention has been focused on the presence of conjugated forms of mycotoxins that are produced by plants. This may be the result of detoxification of mycotoxins by plant metabolism, and it has been suggested that the presence of conjugated mycotoxins might be used in genetic selection of plant resistance to fungal invasion. Although conjugated forms of dexoynivalenol (DON, vomitoxin) were identified many years ago (1992), little information is available regarding the relative significance of conjugated and free mycotoxins in poultry diets. Schneweis and co-workers identified glucose conjugated zearalenone insamples of wheat. Naturally-contaminated wheat and corn samples from Slovakia have been found to contain glucose-conjugated DON with up to 29% of deoxynivalenol in a glucose conjugated form (2005). More recently, an increase in DON concentrations of up to 88% were found when barley samples from North Dakota were treated with trifluoroacetic acid prior to analysis. Such acid treatment would hydrolyse all different conjugates of DON. Similar acid treatment of different barley samples showed up to 21% of total DON found in conjugated forms. Most recently, even higher levels of bound DON were found in barley and beer using a variety of analytical techniques.

Correct values underestimated

The frequency of bound fumonisin routinely exceeded free fumonisin in samples of European corn and corn-based foods. It is not yet clear if the conjugated forms of mycotoxins are as harmful to poultry as the parent compounds, but it has been shown that some conjugated mycotoxins can be hydrolysed in the digestive tracts of animals.

It must be concluded that until we have a better understanding of the frequency, toxicity and nature of conjugated mycotoxins, current mycotoxin analysis of poultry feeds should often be considered to be an underestimate of correct values. To further complicate matters, there exists a number of different analytical techniques (for example ELISA and HPLC) that vary in accuracy and can be sensitive to interference from some dietary components (such as in DDGS). It should also be noted that typically feeds are only analysed for the presence of certain ‘indicator’ mycotoxins. It is well established that mycotoxins rarely occur in isolation and that mycotoxins, when present in combination, can act synergistically to produce more pronounced detrimental effects in the bird. It is necessary at this time, therefore, to consider mycotoxin analysis of feeds as offering only an approximation of the true hazard posed by the feeding of contaminated materials to poultry.

Effects on performance

A series of studies has been conducted to determine the effects of feeding blends of naturally-contaminated feedstuffs, largely corn and wheat, to different types of poultry. This was done in an effort to mimic conditions seen in commercial poultry production where diets contain multiple vectors of mycotoxin contamination. The mycotoxinsin such diets were determined to be mainly DON with lesser amounts of zearalenone and 15-acetyl DON in addition to fusaric acid. Three different modes of action of the mycotoxins fed were identified: reductions in cellular protein synthesis; reduced immunity; and alterations in brain neurochemistry.

Reductions in cellular protein synthesis result in lesions of the gastrointestinal tract, including necrosis, gizzard erosion, haemorrhaging, and malabsorption of nutrients. Reduced hepatic protein synthesis can decrease utilisation of dietary amino acids resulting in increased uric acid synthesis as amino acids are oxidised for energy purposes.

Many Fusarium mycotoxins, as well as aflatoxin and ochratoxin, have been shown to be immunosuppressive. This results in increased susceptibility todisease, lingering health problems in theflock and possible failure of vaccination programmes. The disease symptoms arising from immunosuppression, moreover, are not symptoms characteristic of mycotoxins. They are only indirectly caused by mycotoxins and this makes certain identification of mycotoxins as the causative agent of reduced flock health very difficult.

Combinations of feed-borne Fusarium mycotoxins are pharmacologically active. This means they have drug-like properties due to their effects on brain neuro-chemistry. The most reproducible effects observed are elevations in brain regional concentrations of serotonin. Such changes alter behaviour, including reductions in feed intake, loss of muscle coordination and increased lethargy. The effects on various types of poultry were as follows:

Broilers

The feeding of a blend of ingredients naturally-contaminated with a combination of Fusarium mycotoxins resulted in reduced growth in the grower phase, elevations in blood uric acid levels, discoloration of breast meat and immunosuppression. Other research also showed changes in brain neurochemistry.

Broiler breeders

The feeding of a similar combination of Fusarium mycotoxin contaminated materials to broiler breeders significantly reduced hatchability due to reduced shell thickness of fertile eggs. Changes in brain neurochemistry were also observed. There were no effects of diet on sperm quality. In a parallel study with broiler breeder pullets, Girgis and co-workers observed immunosuppression.

Laying hens

Laying hens were very sensitive to the feeding of combinations of Fusarium mycotoxins. Egg production and feed efficiency were reduced while major increases in blood uric acid concentrations were seen. The elevations in blood uricacid levels were likely due to a reduction in hepatic fractional protein synthesis rates. Immunosuppression was also observed.

Turkeys

Turkeys were very sensitive to the feeding of high levels of Fusarium mycotoxin-contaminated feeds. Growth rates were significantly reduced even in the starter phase (Table 1) and some indices of immunosuppression were seen. The feeding of lower concentrations of Fusarium mycotoxins also reduced growth rates, elevated blood uric acid levels and caused immunosuppression. This was coupled with morphological changes in the small intestine and changes in brain neurochemistry.

Ducks

Ducks were quite resistant to the feeding of combinations of grains naturally-contaminated with Fusarium mycotoxins. Indices of immunosuppression, however, were observed.

Minimise contamination

It can be concluded that poultry are sensitive to combinations of feed-borne Fusarium mycotoxins and that the feedingof contaminated materials should be minimised. It appears that the frequency of mycotoxin contamination of poultry feeds is increasing. This may be due in part to adverse weather conditions pre-harvest in many parts of the world arising from global climate change. The complex nature of modern poultry rations including the increasing use of potentially contaminated by-products such as distillers’ dried grains adds to the possibility of toxicological synergy between combinations of mycotoxins, thereby increasing the severity of the response of poultry to contaminated feeds. Many of the adverse effects seen in the studies reviewed above could be prevented by the simultaneous feeding of a polymeric glucomannan mycotoxin adsorbent (Alltech Inc.). The use of an appropriate mycotoxin adsorbent is likely the best short-term strategy available for minimising the adverse effects of feed-borne mycotoxins in poultry feeds. It is hoped that long-term strategies such as improved quality control measures arising from advances in analytical methodology and plant breeding strategies to reduce the susceptibility of plants to fungal invasion will help to minimise mycotoxin challenges to the poultry industries in the future.

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Campylobacter and Salmonella in chicken

The survey showed that campylobacter was present in 65% of the samples of chicken tested. Salmonella was in 6% of samples, 0.5% of these samples contained S. enteritidis and S. typhimurium.

Andrew Wadge, Director of Food Safety at the Food Standards Agency, said: "The continuing low levels of salmonella are encouraging, but it is disappointing that the levels of campylobacter remain high. It is obvious more needs to be done to get these levels down and we need to continue working with poultry producers and retailers to make this happen. Other countries like New Zealand and Denmark have managed to do so; we need to emulate that progress in the UK."

As part of the Agency’s work to reduce levels of campylobacter in UK-produced chicken an international conference on campylobacter is being organised for 2010, where a range of options for tackling the bug will be discussed.

Campylobacter is the most common bacterial cause of food poisoning. It is responsible for around 55,000 cases of illness in the UK every year, and is therefore one of the key organisms the Agency is tackling in order to reduce levels of foodborne illness. Campylobacter can be found on meat, unpasteurised milk, and untreated water; however there is strong evidence that chicken is the most common cause of illness.

The FSA emphasises that while campylobacter is still present in a significant proportion of fresh chicken sold in the UK, cooking chicken properly all the way through will kill the bug, so consumers can avoid the risk of illness.

The UK-wide survey of fresh chicken at retail was carried out between May 2007 and September 2008. During the course of the survey, 3,274 samples were tested for the presence of campylobacter and salmonella.

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Chicken sounds indicate stress

Ongoing research on laying hens has demonstrated that bird vocalizations can serve as reliable indicators of particular forms of stress and that different vocalization patterns can be linked with specific kinds of stressful conditions.

Knowing whether and when specific environmental conditions induce stress is a first step towards reducing stress in the production environment, according to Dr Michael J. Darre, a professor in the Department of Animal Science, University of Connecticut, and a member of The Poultry Science Association (PSA).

"Alleviating stress in commercial flocks of laying hens and broilers is important not only because it improves the overall welfare of the birds, but also because stress is a known enemy of production efficiencies," said Dr Darre. "Research involving the analysis of chicken vocalisations may well provide the answer, because it is non-invasive and provides immediate and accurate feedback on levels and types of bird stress."

The Dolittle Project

Joining Darre in his work on chicken vocalisations is one of his doctoral students, Ebenezer Otu-Nyarko. They are participants in a wider study called the Dolittle Project: Classifying Animal Vocalisations. Funded through the National Science Foundation, the Dolittle Project is the first ever to apply modern speech-processing algorithms to animal vocalisations. The lead investigator of the Dolittle Project is Dr Michael Johnson, a professor in Marquette University's Department of Computer and Electrical Engineering.

Chicken vocalisations as stress indicators

According to Dr Darre, one of the primary initial goals of the work on chickens was to determine if vocalisation patterns were the same for all types of stressors; research has shown that they are not. For example, vocalisation patterns have been found to be different for stress due to handling and stress due to overcrowding.

The analysis was carried out by digitally recording laying chickens' vocalisations under different types of stressful conditions, and then, after removing background noise, analysing the recordings using a modified version of the Hidden Markov Model (HMM) with voice recognition algorithms. The modified HMM is a statistical model developed by Marquette University that represents both the temporal and spectral characteristics of audio signals. When applied to chicken vocalisations, HMM has achieved an overall condition classification accuracy of 74%.

Darre and Otu-Nyarko are also looking at how vocal patterns change from the time chickens hatch until they are adults.

The ultimate goal of their work is to develop a "black box" that can be placed in chicken houses that allows farmers to remotely monitor their birds, notifies the farmers when it detects stress vocalisations, and identifies the type of stress, so that action can be taken immediately.

"This kind of monitoring would help reduce overall stress in flocks and be a great step forward in improving the welfare of commercial bird flocks. This in turn would benefit farmers, and ultimately the consumer, via improved egg-laying and meat output due to the known benefits that accrue from keeping chickens in a lower-stress environment," said Dr Darre.

Source: Poultry Science Association (PSA)

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Indonesian chicken gene resistant to bird flu

At least 62% of chickens indigenous to Indonesia are resistant to bird flu, thanks to a "Mx" gene in their body, the Indonesian Institute of Science (LIPI) revealed.

“Genetically, the indigenous chickens [to Indonesia] have a gene that is immune to avian influenza,” said head of the institute Umar Anggara Jenie, in an exposé of a biological study she gave at the Cibinong Sciences Center in Bogor, West Java, reports the Jakarta Post.

Sri Sulandari, a gene researcher at the institute’s biological research centre who studied the genes of indigenous chickens, said her institute carried out the first ever gene study focusing on how humans coped when contracting the virus and on the vaccination process. “Few have looked into the genetic side to see how chickens themselves have a natural resistance to bird flu. The indigenous chickens’ ability to resist avian influenza varies according to the strength of the antivirus genes in their body,” Sri said.

Recent evidence indicated the Mx gene was associated with chicken resistance or susceptibility to highly pathogenic bird flu. Sri says that Indonesia’s varied population of indigenous chickens is a mine of information on the Mx gene and how resistant each breed of chicken is to bird flu. She went on to say that if there is a bird flu epidemic in a certain region, it is unwise to simply cull indigenous breeds, as we may lose crucial information on the Mx gene.

Based on samples taken from 1,872 indigenous chickens of various breeds, the institute rated the dark-colored Cemani chicken the most resistant to the virus and the green forest chicken the most susceptible.

Source: The Jakarta Post

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Flies spread drug-resistant bacteria in poultry

Researchers at the Johns Hopkins Bloomberg School of Public Health in Baltimore, US, found evidence that houseflies collected near broiler poultry operations may contribute to the dispersion of drug-resistant bacteria and thus increase the potential for human exposure to drug-resistant bacteria.

The findings demonstrate another potential link between industrial food animal production and exposures to antibiotic resistant pathogens.

Previous studies have linked antibiotic use in poultry production to antibiotic resistant bacteria in farm workers, consumer poultry products and the environment surrounding confined poultry operations, as well as releases from poultry transport.

Vectors

“Flies are well-known vectors of disease and have been implicated in the spread of various viral and bacterial infections affecting humans, including enteric fever, cholera, salmonellosis, campylobacteriosis and shigellosis,” said lead author Jay Graham, PhD, who conducted the study as a research fellow with Bloomberg School’s Center for a Livable Future.

"Our study found similarities in the antibiotic-resistant bacteria in both the flies and poultry litter we sampled. The evidence is another example of the risks associated with the inadequate treatment of animal wastes."

“Although we did not directly quantify the contribution of flies to human exposure, our results suggest that flies in intensive production areas could efficiently spread resistant organisms over large distances,” said Ellen Silbergeld, PhD, senior author of the study and professor in the Bloomberg School of Public Health’s Department of Environmental Health Sciences.

Flies and samples

Graham and his colleagues collected flies and samples of poultry litter from poultry houses along the Delmarva Peninsula - a coastal region shared by Maryland, Delaware and Virginia, which has one of the highest densities of broiler chickens per acre in the US.

The analysis by the research team isolated antibiotic-resistant enterococci and staphylococci bacteria from both flies and litter. The bacteria isolated from flies had very similar resistance characteristics and resistance genes to bacteria found in the poultry litter.

Flies have ready access to both stored poultry waste and to poultry houses. A study by researchers in Denmark estimated that as many as 30,000 flies could enter a poultry house over the course of six week period.

Confined animal feeding operations

According to Robert Lawrence, MD, director of the Center for a Livable Future, confined animal feeding operations – where thousands of animals are crowded together and are fed antibiotics for growth promotion – create the perfect environment for selection of bacteria that are resistant to antibiotics.

“Antimicrobials are among the most important developments of the twentieth century in managing infectious diseases in people."

"We can’t afford to squander them by using them as growth promoters in industrial food animal production. The increase in antibiotic-resistant bacteria is a major threat to the health of the public, and policymakers should quickly phase out and ban the use of antimicrobials for non-therapeutic use in food animal production,” said Lawrence.

The study is published in the April 2009 issue of Science of the Total Environment.

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