University of Veterinary Medicine Hannover
Examination of the hygienic status of selected organic enrichment materials used in pig farming
INAUGURAL-DISSERTATION
in fulfillment of the requirements of the degree of Doctor of Veterinary Medicine
-Doctor medicinae veterinariae- (Dr. med. vet.)
submitted by
Krista Marie Tenbrink geb. Wagner Duisburg
Hannover 2021
Academic supervision: Prof. Dr. med. vet. Nicole Kemper
Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour
University of Veterinary Medicine Hannover
1. Referee: Prof. Dr. med. vet. Nicole Kemper
Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour
University of Veterinary Medicine Hannover
2. Referee: Prof. Dr. med. vet. Madeleine Plötz
Institute for Food Quality and Food Safety University of Veterinary Medicine Hannover
Day of the oral examination: 12.05.2021
This research was financially supported by the Tierseuchenkasse Niedersachsen (Animal Disease Fund Lower Saxony, Germany). Krista Marie Tenbrink was financially supported by a grant from the H. Wilhelm Schaumann Stiftung.
What you do makes a difference, and you have to decide what kind of difference you want to make.
(Jane Goodall)
Index
1. Introduction ... 1
2. Publications ... 7
1) „Examination of the hygienic status of selected organic enrichment materials used in pig farming with special emphasis on pathogenic bacteria” ... 7
2) “Mycotoxin Contamination of Selected Organic Enrichment Materials Used in Pig Farming” ... 9
3. Discussion ... 10
4. Conclusion ... 19
5. Summary ... 20
6. Zusammenfassung ... 22
7. List of publications ... 24
8. References ... 25
9. Acknowledgements ... 32
Introduction 1
1. Introduction
Pigs spend most of their daytime activity with exploratory behaviour, if the housing system allows it (Stolba and Wood-Gush, 1989). However, in modern intensive pig production this behavioural need cannot be fulfilled due to the barren pen environment; thus, the behaviour is redirected to the pen structures and pen mates (Studnitz et al., 2007). This misdirected foraging and exploratory behaviour is the main cause of “two stage” tail biting (Taylor et al., 2010). For this type of tail biting, the provision of enrichment material is both preventive and curative (D’Eath et al., 2014). In addition to posing a threat to animal welfare (D’Eath et al., 2016), impairing the health of the pigs (Sutherland and Tucker, 2011) and adversely affecting food safety (Kritas and Morrison, 2007), tail biting is also an economical problem for farmers, leading to costs of approximately 1.1 to 2 € per pig in tail-docked fattening pigs (De Briyne et al., 2018).
At statutory level, administration of enrichment material is subject to the farm animal welfare legislation of the European Union. Council Directive 2008/120/EC requires pig farmers to provide permanent access to a sufficient quantity of enrichment material to their pigs (European Commission (EC), 2009). The materials stated as examples in this Directive are exclusively organic materials: straw, hay, wood, sawdust, mushroom compost, and peat (EC, 2009). Additionally, according to Commission Recommendation 2016/336/EU (EC, 2016) optimal enrichment for pigs should be edible, chewable, investigable, and manipulable. These requirements can only be fulfilled by organic materials. This is in accordance with studies assessing enrichment materials in their effectiveness and acceptance by pigs (Studnitz et al., 2007). At national level, a recent amendment of the German farm animal welfare legislation (TierSchNutztV, 2021) demands the pig farmers to use enrichment material that is “organic and rich in fibres”, specifying exemplary straw, hay, and sawdust.
Irrespective of the potential of a material to better fulfil the behavioural needs of pigs kept in intensive husbandry systems, the basic prerequisite has to be the safety of the material concerning potential animal health risks (EC, 2009; EC, 2016).
Introduction 2
According to a scientific opinion of the European Food Safety Authority (EFSA, 2014), enrichment materials may pose health risks due to contamination with infectious agents such as Yersinia enterocolitica, Oesophagostomum or mycobacteria, or chemical compounds such as chloramphenicol. Furthermore, a common contamination of materials such as straw are mycotoxins (Nordkvist and Häggblom, 2014). Another possible adverse effect of enrichment material is caused when destructible materials are used in slatted pens. Parts of the material get into the manure system and might induce problems as blockages, leading to decreased hygiene and air quality (EFSA, 2014).
A general bacterial contamination of enrichment material (as measured by total viable count of aerobic mesophilic bacteria) is not necessarily a health risk for pigs, since this laboratory analysis cannot discriminate between pathogenic and apathogenic bacteria. The same applies to the total count of coliform bacteria. High coliform counts indicate fecal contamination of the materials (Teramura et al., 2017), but there are no thresholds or guidance values for coliform contamination in pig husbandry to date. However, according to a study in dairy cows, coliform counts exceeding 106 colony forming units (cfu)/g bedding material may cause mastitis (Kristula et al., 2005). In addition, highly contaminated or polluted material is presumably less attractive as enrichment and might not be effective in controlling tail biting.
Escherichia (E.) coli is both used as a hygienic indicator for fecal contamination (Ghafir et al., 2008) and can induce diseases in pigs, including diarrhea, edema disease, septicemia, polyserositis, mastitis and urinary tract infection (Fairbrother et al., 2019). Thresholds for E. coli are lacking as well, and its pathogenicity depends considerably on the virulence factors of the strain present (Fairbrother et al., 2019).
Klebsiella pneumoniae is a typical causative agent of mastitis in dairy cows (Jain, 1979) but can also cause septicaemia in piglets and mastitis in sows (Broes et al., 2019). It can be detected in materials such as unused sawdust bedding (Verbist et al., 2011), and unused pelleted corn cobs (Hogan et al., 1990). Pigs are the primary reservoir of Yersinia enterocolitica, the causative agent of one of the most frequent food-borne infections in humans in the EU (Laukkanen-Ninios et al., 2014). However, in pigs, infection with Yersinia enterocolitica is typically asymptomatic (Broes et al., 2019). If the use of bedding material increases or decreases the risk of Yersinia spp.
Introduction 3
prevalence, is disputed in scientific literature (Skjerve et al., 1998; Vilar et al., 2013).
The importance of Salmonella enterica is on the one hand related to its ability to induce clinical disease in pigs, and on the other hand due to its zoonotic character and the risk of infecting humans via pork (Griffith et al., 2019). To prevent salmonellosis in humans, European countries have implemented control programs which penalize a high prevalence of Salmonella enterica. Since feed raw materials are frequently contaminated by Salmonella enterica (EFSA, 2006), enrichment material might also represent a route of introduction into the farm.
Antimicrobial resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) are an increasing problem in human and animal healthcare. It was shown that livestock-associated MRSA can occur on pig farms (EFSA, 2009). In MRSA-positive farms, the pathogen can be detected in the air and soil around the farm (Schulz et al., 2012). Additionally, antibiotic resistant bacteria, as well as the antibiotics themselves, and the respective resistant genes, are found in manure of positive pig herds, applied on fields as organic fertilisers (Chee-Sanford et al., 2009).
Via this route, a contamination of enrichment material grown on these fields is a possible risk. Organisms of the Mycobacterium (M.) avium complex are frequently found in peat (Matlova et al., 2012; Agdestein et al., 2014) and the detection in unused sawdust has been described before (Álvarez et al., 2011). According to Matlova et al. (2005) this contamination can induce infection in pigs when they have contact to the material. The species, that has been studied most extensively, is M.
avium subsp. hominissuis, which causes severe pulmonary and systemic diseases, as well as lymphadenitis in humans (Agdestein et al., 2014) and granulomatous lesions in pigs (Álvarez et al., 2011). Since these lesions cannot be macroscopically distinguished from tuberculous lesion caused by M. tuberculosis complex, carcasses with tuberculous lesions are generally condemned at the slaughterhouse, leading to financial losses for the farmer (Álvarez et al., 2011).
Since moulds are considered ubiquitous (Bryden, 2012), some level of contamination can be expected in the materials. High levels of mould might have a negative impact on health. However, the main relevance of mould contamination is a deterioration of the material minimising its palatability and acceptance, and particularly the formation of mycotoxins (Bryden, 2012). Mycotoxins are secondary metabolites of fungi, and are produced on field or during storage, depending on the involved fungal species
Introduction 4
(Devreese et al., 2013). Thus, the absence of moulds does not necessarily indicate absence of mycotoxins. Mould growth and mycotoxin formation vary depending on various factors such as climatic conditions (Bryden, 2012). Aflatoxin B1, for example, is a typical contaminant of products from tropical or subtropical regions and is produced by Aspergillus parasiticus and Aspergillus flavus (EFSA, 2004b). In contrast, the toxins of Fusarium spp. such as deoxynivalenol, zearalenone and fumonisin are frequently found in feed from central Europe (Gruber-Dorninger et al., 2019). The effects of mycotoxin intake depend on the quantity and variety of the mycotoxins as well as on the age, immune status and stress level of the animals (Morgavi and Riley, 2007; Bryden, 2012). Overall, several thousand secondary metabolites of fungi have been described to date (Bryden, 2012). However, only 400 of them have been identified as toxic to animals (Jard et al., 2011). The analysis was conducted by a liquid chromatography tandem mass spectrometry multi-mycotoxin method which can detect more than 380 mycotoxins and metabolites. The practical relevance based on toxic effects of many of those detectable mycotoxins and metabolites is not understood completely. Thus, analysis in this study focused on mycotoxins regulated by maximum permissible values or guidance values in the EU, namely aflatoxin B1, deoxynivalenol (DON), zearalenone (ZEN), ochratoxin A, and fumonisin B1 and B2 (EC, 2002; EC, 2006). Additionally, these mycotoxins were considered as important because pigs exhibit a particularly high sensitivity to them (Morgavi and Riley, 2007; Meissonnier et al., 2008; Bryden, 2012; Devreese et al., 2013; Gruber-Dorninger et al., 2019).
High levels of DON contamination in feed induce gastrointestinal disorders or feed refusal as well as growth retardation in pigs (Serviento et al., 2018). The mycotoxin ZEN can bind estrogenic receptors causing reproductive disorders (Fink-Gremmels and Malekinejad, 2007). Furthermore, intoxication with ochratoxin A induces mycotoxic nephropathy in pigs while fumonisin B1 causes the porcine pulmonary edema (Devreese et al., 2013). However, clinical cases of mycotoxicoses are relatively rare. Subclinical intoxication due to low level contamination, causing decreased growth performance, reproduction, and impaired immunity, are more relevant (Bryden, 2012). To meet these concerns, the EFSA implemented no- observed-(adverse)-effect levels and lowest-observed-(adverse)-effect levels for
Introduction 5
DON (EFSA, 2017b), fumonisins (EFSA, 2018), ochratoxin A (EFSA, 2004a), and ZEN (EFSA, 2017a).
Another risk regarding mycotoxin ingestion by pigs is a potential carry-over of the respective mycotoxins into pig products for human consumption. DON and ZEN do not play a role as contaminants of animal products, and aflatoxins are predominantly found in milk, but pork is a known source of ochratoxin A, and residues of fumonisins can reach hazardous levels in liver and kidneys of pigs (Voss et al., 2007; Bryden, 2012). A contamination with mycotoxins is common in feed and has also been described for roughage and bedding material before (EFSA, 2004c). However, the relevance of this contamination is discussed controversially, and considered as low in organic enrichment material by the EFSA (2007).
The objective of this study was to assess the safety of different types of enrichment materials used in pig farming concerning pathogenic bacteria, moulds, and mycotoxins. Since scientific literature as well as legislation consider organic materials to be superior in comparison to inorganic materials in fulfilling the behavioural needs of the pigs, only organic materials were examined in this study. However, sisal ropes and jute sacks were not considered, because in these materials, the biggest risks presumably derive from contamination with residues, for example mineral oil hydrocarbons, depending on their source (EFSA, 2012). Additionally, in the case of jute sacks, contamination could possibly arise from previous contents during prior use.
The 21 enrichment materials for pigs selected for this study can be divided into four groups: wooden materials, loose straw and hay, compressed straw and hay, and miscellaneous (beet pulp, maize pellets, peat, lick block, lignocellulose litter, maize silage). Eighteen of the materials were commercially available to facilitate a better comparability due to standard processing steps and quality control measures conducted by the producers. Since moisture plays an important role for bacterial and fungal growth (Griffin, 1981) as well as mycotoxin production (Bryden, 2012), the water activity and dry matter (DM) content of the materials were analysed. To assess the aerobic bacterial and mould burden, total viable count, coliform count, and mould count were assessed. However, a high general burden does not necessarily implicate a health risk for pigs, and can be part of the material characteristic, for example in
Introduction 6
case of silages (Orosz et al., 2013). Therefore, the material samples were also tested for the presence of Escherichia coli, Klebsiella species (spp.), Yersinia spp., Salmonella spp., methicillin-resistant Staphylococcus aureus (MRSA), and mycobacteria. Contamination with these pathogenic bacteria can possibly cause infection of the pigs and be a risk for consumption of the meat and other products of affected animals. For the detection of mycotoxins, the materials were analysed by a liquid chromatography tandem mass spectrometry multi-mycotoxin method that is able to detect over 380 mycotoxins and metabolites. However, the assessment of mycotoxin contamination was focused on the six mycotoxins with maximum permissible values or guidance values given by the European Union: aflatoxin B1, deoxynivalenol, zearalenone, ochratoxin A, and fumonisin B1 and B2.
The present study is focused on the question if unused organic materials could be a route of introducing pathogens into farms. It was hypothesised that certain organic enrichment materials can serve as source of pathogenic bacteria or mycotoxins that could cause infection and adverse health effects in pigs, respectively. Finally, based on the results of the analyses, suitable enrichment materials for pigs concerning hygienic risks are recommended. In addition, advise is given regarding materials which potentially pose a health risk and must be monitored when in use.
Publications 7
2. Publications
1) „Examination of the hygienic status of selected organic enrichment materials used in pig farming with special emphasis on pathogenic bacteria”
Krista Marie Wagner, Jochen Schulz, Nicole Kemper
Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, 30173 Hannover, Germany
Porcine Health Management 4, 24, 2018
https://doi.org/10.1186/s40813-018-0100-y
https://porcinehealthmanagement.biomedcentral.com/articles/10.1186/s40813-018- 0100-y
Abstract:
Background: Enrichment materials for pigs, particularly organic materials, are becoming increasingly important in order to reduce abnormal behaviour such as tail biting. However, potential health risks posed by these materials (such as the introduction of pathogens into the herd) have not been sufficiently studied to date.
Therefore, 21 different organic materials used as enrichment materials in pig farming were tested for total viable count of mesophilic bacteria, moulds, coliforms, Escherichia coli, Klebsiella spp., Yersinia spp., Salmonella spp., methicillin-resistant Staphylococcus aureus, and Mycobacterium spp. Additionally, dry matter content and water activity were determined.
Results: The materials differed considerably in their hygienic status. In three materials, no microorganisms were detected. However, the bacterial count in the other materials ranged up to 7.89 log10 cfu/g dry matter (maize silage). The highest coliform and mould counts were found in hay (6.45 and 6.94 log10 cfu/g dry matter, respectively). Important bacteria presenting a risk to human or animal health such as
Publications 8
Escherichia coli, Klebsiella spp., Yersinia spp., Salmonella spp., and methicillin- resistant Staphylococcus aureus were not detected in any of the materials. Hemp straw contained Mycobacterium smegmatis, and peat was contaminated with
Mycobacterium avium and Mycobacterium vulneris.
Conclusions: Most of the tested organic materials are probably not likely to pose a hygienic risk to pigs and are suitable as enrichment material. Nonetheless the detected mycobacteria rule out peat as being a safe and hygienic enrichment material.
Publications 9
2) “Mycotoxin Contamination of Selected Organic Enrichment Materials Used in Pig Farming”
Krista Marie Tenbrink, Jochen Schulz, Nicole Kemper
Institute for Animal Hygiene, Animal Welfare and Farm Animal Behaviour, University of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, 30173 Hannover, Germany
Agriculture 10(11), 565, 2020
https://doi.org/10.3390/agriculture10110565
https://www.mdpi.com/2077-0472/10/11/565/htm
Abstract:
Abnormal behavior, such as tail biting, is a fundamental problem in pig husbandry worldwide, and the application of enrichment materials, particularly organic materials, is one of the most promising preventive and curative measures. However, the potential health risks posed by these materials, such as being an additional source of mycotoxins, have not been sufficiently studied to date. Therefore, 21 different organic enrichment materials were tested for mycotoxin contamination with a liquid chromatography tandem mass spectrometry multi-mycotoxin method. Concerning the legally regulated mycotoxins in the EU, aflatoxin B1 and ochratoxin A were not detected in any of the tested materials. Fumonisin B2 was detected in straw meal made of wheat, rye, and triticale, but the level (0.014 mg/kg) was very low. The level of deoxynivalenol in maize pellets (5.01 mg/kg) and maize silage (2.12 mg/kg) exceeded the guidance value for pig feed. Zearalenone was present at high levels in maize pellets (1.21 mg/kg), hay (0.30 mg/kg), and maize silage (0.25 mg/kg). Maize products showed high levels of mycotoxins presenting a health risk for pigs and cannot be recommended as enrichment material.
Discussion 10
3. Discussion
Selection of enrichment materials
The enrichment materials were selected based on practical relevance and commercial availability. Straw and hay produced on farm are frequently used as enrichment material, since in this case the farmer does not have to purchase additional material. Hence, it is a simple and often inexpensive material source.
However, the quality and hygiene of straw and hay depend on numerous factors such as weather during growth and harvest, or storage conditions. These pre- and post-harvest conditions are particularly important with regard to the formation of mycotoxins (Bryden, 2012). Therefore, straw and hay produced on farm differ considerably in mycotoxin contents, depending on year and region. Three of the materials tested in this study were produced on a demonstration farm, namely grass hay, wheat straw and maize silage. The contamination level detected in these materials has to be interpreted as a preliminary overview of identifying potential risks, such as high values of ZEN and DON in maize silage. However, these results cannot be transferred to materials produced on other farms or in another year.
Commercially available materials on the other hand are often advertised to be of constant hygiene and quality. Standard procedures and quality control measures are implemented in the manufacturing process of those materials. Thus, a better comparability between different batches of the products can be expected, irrespective of the source of the raw materials and the time of purchase. Nevertheless, the study was limited to one sample of single batches of the 21 materials with substantial differences in the raw materials and material characteristics. Hence, concerning each material, only one producer was tested. The study design did not allow verifying whether the hygiene and quality of commercial products remains constant over time and if it is comparable among different producers from different regions. Due to this single sample design, only descriptive statistical analyses were possible. The study was intended as a pilot study providing first hints to which materials potentially pose risks, and therefore have to be monitored closely or excluded as enrichment materials for pigs.
Discussion 11
Additionally, this study was focused on unused, fresh materials and the potential risk of pathogen and mycotoxin introduction into a farm. Subsequently, the question has to be raised if the organic enrichment materials are favourable growth media for bacteria already present on farm. A study performed with bedding materials and causative organisms of mastitis in dairy cows showed marked differences between the materials in their ability to support the growth of bacteria (Zehner et al., 1986).
Hence, the risk that a material facilitates the growth of pathogenic bacteria in the environment of the pigs has to be considered as well when selecting an optimal enrichment material. However, this consideration was not part of the present study and requires further investigation.
Selection of detection methods
For the determination of bacterial and fungal contamination, conventional cultural methods using commercially available agars and reagents were performed. In the case of Salmonella spp., a pre-enrichment step in accordance with the standard method (ISO, 2007) was added. A prior enrichment enhances the probability to detect the respective microorganism. Escherichia coli, Klebsiella spp., Yersinia spp.
and MRSA were not detected in any of the tested materials. Possibly, an additional enrichment would have shown a low-level contamination that was not detectable with the applied method, particularly since one gram of material was mixed with 50 mL of phosphate-buffered saline comprising a first dilution step. However, these bacteria are frequently found in pig farms and the environment of the pigs (Gürtler et al., 2005;
EFSA, 2009; Bidewell et al., 2018). Thus, the introduction of a small number of bacteria would presumably not alter the hygienic status of the farm and the health of the animals.
Mycobacteria are fastidious microorganisms (Hillemann et al., 2006; Räsänen et al., 2013), so that the analysis for mycobacteria was performed by a specialised external laboratory, the National Reference Centre for Mycobacteria in Germany.
For the detection of mycotoxins, chromatography combined with mass spectrometry was performed. This method is also recommended by the European Commission (EC, 2017) and liquid chromatography coupled with mass spectrometry, which was used in the present study, is prevalently used in recent scientific literature
Discussion 12
(Malachová et al., 2018). The analysis was carried out in a specialised external laboratory according to well documented standard methods (Malachová et al., 2014).
However, taking samples for the analysis for mycotoxins is challenging, since mycotoxins are heterogeneously distributed in the material and form highly contaminated “hot-spots” (Kanora and Maes, 2009). Therefore, samples of ten different locations in the material were taken. For the materials produced on farm, the sampling remained relatively superficial since the hay and straw bales could not be opened, and the sampling of the silage was only possible at the area of the cut surface. The packages of the commercial materials were completely opened, and the samples were taken from different spots of the whole batch. However, the batch size varied depending on the material and could be as small as 10 kg. The study was designed to give first insights into the contamination, but the data cannot be extrapolated to the material types in general.
This study was limited to the analyses for bacteria, moulds, and mycotoxins, omitting a whole group of pathogens, the viruses. Viral diseases such as Porcine Respiratory and Reproductive Syndrome and porcine circovirus diseases are major health concerns in pig farming worldwide (Segalés et al., 2019; Zimmerman et al., 2019).
The materials were not tested for contamination with these common viruses.
Additionally, enrichment material could possibly be a route of introduction for highly contagious epizootic diseases such as African swine fever, when the disease is prevalent in wild boar of the region of material origin. Also, the EFSA warned about parasites on enrichment material (EFSA, 2014) which might compromise the health of pigs. Further research is needed to assess the material hygienic status concerning viral and parasitic contamination.
Amount of enrichment material ingested
Studies and statutory regulations, if they exist, are usually focused on organic materials used either as bedding material or as feed. Enrichment material is provided in considerably smaller quantities than bedding or feed. Therefore, established thresholds and guidance values cannot be adopted unaltered to enrichment material.
However, it is still debated how much enrichment material has to be provided, and it is unknown how much of the material is ingested by individual pigs. There are no
Discussion 13
precise recommendations on the minimal amount of enrichment material per day (EFSA, 2014; Wallgren et al., 2016), and the effective amount of material used in studies varies considerably. About 5 g straw per pig and day showed positive effects (Zonderland et al., 2008), however, pigs were willing to work for up to 1 kg of straw (Studnitz et al., 2007). Pedersen et al. (2014) determined approximately 400 g straw per pig and day as sufficient quantity of material. Additionally, the amount of material consumed or worked for does not equate to the amount ingested by the animal. The animals investigate the material thoroughly leading to material losses, in particular in slatted pens where the material gets into the manure system.
Furthermore, there are presumably large individual differences in the intake of material that are influenced by different factors such as individual preferences or hierarchy in the group. The route of providing the material (for instance on the floor, in a trough, rack, or dispenser) is also important for the number of animals that have stress-free access to the material and consume their preferred amount. Moreover, most studies are focused on comparing different amounts of straw, while comparative data for other materials is scarce. While bacterial contamination might pose a risk by mere contact during the investigative behaviour, the adverse effects of mycotoxins in pigs develop primarily through ingestion of contaminated materials. In conclusion, more studies are needed elucidating the amount of enrichment material ingested to improve the risk assessment.
Use of organic materials as enrichment material
The present study is focused on the hygienic parameters of enrichment materials. As mentioned before, organic materials are more suitable in fulfilling the behavioural needs of pigs. However, not all organic materials are equally suitable. Studies show considerable differences in the acceptance of organic materials, and the ranking of material preferences is not consistent among different studies (Bracke et al., 2006;
Studnitz et al., 2007). The provision of organic enrichment material is labour-intensive and costly. Thus, the farmer expects an obvious improvement of welfare and effectivity in controlling tail biting and other undesirable behaviour. For commonly used materials, such as straw and hay, scientific research regarding welfare effects is
Discussion 14
available, however, for some of the materials included in the present study no data could be found. A comparative study on the acceptance and behavioural effects of the materials of the present study identified as suitable from a hygienic point of view would be desirable.
The wooden materials showed low contamination with both bacteria and mycotoxins;
thus, they would be highly recommended. However, if the behavioural study would show that the pigs are not interested in these materials and do not use them extensively, the provision of the material would not be beneficial, and the materials could not be recommended. Both aspects, the hygiene as well as the acceptance by the pigs, have to be considered in the selection of suitable enrichment materials.
In addition, it is crucial how the enrichment material can be administered to the animals. Administration on the floor of the pen involves rapid soiling of the material and is not feasible with the widely used slatted flooring. If the material is provided in a rack, trough, automat, or adapted holder (as for the compressed straw cylinder), the number of animals having simultaneous access to the material is limited. This might result in competition between the pigs for the enrichment material leading to “sudden- forceful” tail biting (Taylor et al., 2010). The administration route and quantity of material has to be adjusted to the structure of the pen and the number of animals to prevent competitive situations, or else the provision of enrichment might increase tail biting instead of reducing it.
Practical aspects of the material for the farmer
On-farm, the factors influencing the selection of enrichment materials are even more complex. First, the material has to be easily available. In the case of straw and hay, it is potentially even produced on farm. Another aspect are the total costs of the provision of enrichment, which consist of the cost of the material, increased labour, and adequate storage facilities (Tuyttens, 2005). The amount of additional labour depends, among other things, considerably on how the material is provided. Loose straw and hay in a rack have to be refilled frequently (often on a daily basis), while the compressed straw cylinder has to be replaced when consumed which is normally after several weeks. Furthermore, it is important if the material can be checked and refilled from the alley, or if the pens have to be entered. In addition, the material used
Discussion 15
has to be compatible with the manure system which is particularly important when straw is used on slatted flooring (Wallgren et al., 2016; Lahrmann et al., 2018).
However, problems with the manure system when using chopped straw seem to be uncommon, and are possibly rather myth than reality (Wallgren et al., 2016).
Recommendations for suitable organic enrichment materials for pigs The aforementioned considerations are very important for the selection of enrichment materials. However, they were not the focus of this study and need further investigation. The obtained results allow for an evaluation of the hygienic safety of the materials, which is a basic requirement for being used in pig farming.
The wooden materials showed a very low bacterial burden. This might partly be due to the fact that wood, depending on species and climatic conditions, is able to minimise its bacterial contamination (Milling et al., 2005). Additionally, the materials tested in this study were not just blocks of wood, but processed materials such as millings and sawdust. A reduction of bacteria might be attained as a side effect of the production process involving heat. The number of different mycotoxins detected in the wooden materials was also low compared to the other material groups; only wood granulate contained a relatively high number of 29 different mycotoxins. However, none of the six most important and statutory regulated mycotoxins was found in any of the wooden materials. In conclusion, materials made of wood can be recommended as enrichment materials for pigs from a hygienic point of view.
In the loose straw and hay materials, the quantities of bacteria in general (as total viable count), of coliform bacteria, and of moulds were overall the highest in the study. However, as in all other materials, E. coli, Klebsiella spp., Yersinia spp., Salmonella spp., and MRSA were not detected. Due to a lack of specific thresholds for total viable count, coliforms and moulds, a concluding assessment remains difficult. All of the materials, except for alfalfa hay, were close to or even exceeded the coliform level potentially causing mastitis according to Kristula et al. (2005).
Furthermore, the hemp straw contained Mycobacterium smegmatis, a saprophytic inhabitant of soil and water, which rarely induces diseases in humans (Howard and Byrd, 2000). This contamination is considered to be negligible because M.
Discussion 16
smegmatis is frequently found in the environment, and human infections are uncommon.
The number of mycotoxins were high in loose straw and hay products, ranging from 23 to 54 different toxins. Aflatoxin B1 and ochratoxin A were not detected in any of the materials in this study. However, the only detection of fumonisins were 0.014 mg/kg fumonisin B2 in straw meal made of wheat, rye, and triticale. Since this level of contamination is multiple times lower than even the no-observed-adverse-effect level (EFSA, 2018), the straw meal does not pose any risk of fumonisin intoxication for the pigs.
Regarding DON contamination, all products were below the guidance value (EC, 2006). However, the EFSA did not establish an exact lowest-observed-adverse-effect level but states a range of 0.35-13 mg DON/kg feed (EFSA, 2017b). Thus, the straw meal made of wheat, rye and triticale which contained 0.503 mg DON/kg might induce chronic adverse effects in pigs when given over a longer period. The grass hay produced on the demonstration farm showed a ZEN contamination of 0.30 mg/kg, which exceeds the guidance value for piglets and gilts (0.1 mg/kg) as well as for sows and fattening pigs (0.25 mg/kg) (EC, 2006). As mentioned before, enrichment material is presumably ingested in considerably lower amounts than feed.
However, feed might be contaminated as well, and the overall contamination must be considered. Depending on the contamination in feed, the straw meal and grass hay should not be used as enrichment material for pigs, particularly not in piglets and gilts.
The compressed straw and hay materials showed medium total viable counts and, except for the miscanthus cylinder, neither coliforms nor moulds were detected. The reason for this neglectable contamination is presumably the production process of the materials. In contrast to loose straw and hay, the compressed material is exposed to heat, pressure, and shear forces which should eliminate bacterial and fungal contamination. The higher levels of bacteria and moulds in the miscanthus cylinder can be explained by the lower level of compression of the material. Thus, it can be expected that less pressure, heat, and shear forces were used during the production of the miscanthus cylinder. As in the loose straw and hay, the number of different
Discussion 17
mycotoxins in the compressed materials was high, ranging from 29 to 57. However, DON was only detected in the compressed straw cylinder (0.036 mg/kg), and a low- level ZEN contamination of 0.002 mg/kg and 0.011 mg/kg was found in the straw pellets and miscanthus cylinder, respectively. Therefore, compressed straw and hay products can be considered as hygienic enrichment material.
The “miscellaneous” group included materials varying considerably in their raw materials and material characteristics. Thus, they also differed considerably in their hygienic status. The sugar beet pulp and lignocellulose litter were free of any detectable bacterial and mould contamination. Once again, the production process of the materials is the presumable reason for this. Coliforms were found in none of the materials of the “miscellaneous” group, and moulds were only detected in low numbers in peat and maize silage. The overall bacterial contamination was high in peat and particularly in maize silage with the highest count of the study (7.89 log10
cfu/g). This bacterial count is higher than in a previous study, but lower than the counts seven days after exposure to air detected in the same study (Liu et al., 2013).
Since the maize silage samples were retrieved from the cut surface, the material had contact to air for an unknown period of time, which might have facilitated the growth of bacteria. However, since no pathogenic bacteria were detected, the values of the total viable count should not be overrated.
Several non-pathogenic microorganisms are involved in the formation of peat (Trckova et al., 2005); thus, the relatively high overall counts might be part of the material characteristics. In contrast, the detection of mycobacteria was alarming.
Mycobacterium vulneris belongs to the M. avium complex (Rindi and Garzelli, 2014) and can cause human diseases (Matlova et al., 2012). The four subspecies of M.
avium differ in their host species and pathogenicity (Rindi and Garzelli, 2014) with M.
avium subsp. hominissuis being a frequent contaminant of peat (Matlova et al., 2012;
Agdestein et al., 2014). The infection of pigs causes granulomatous lesions resulting in carcass condemnation at the slaughterhouse. Hence, the use of peat as enrichment material for pigs cannot be recommended.
The mycotoxin contamination differed considerably amongst the materials, as well.
Maize products (pellets and silage) contained 64 and 56 different mycotoxins,
Discussion 18
respectively, while the other materials ranged between 16 and 34. The DON and ZEN levels of the materials without maize were very low (up to 0.002 mg/kg). Even though no (maize pellets) or only low (maize silage) mould counts were detected in the maize products, they were heavily contaminated with mycotoxins. A DON contamination of 5.0 and 2.1 mg/kg was detected in the maize pellets and silage, respectively, which is above the guidance value for complementary and complete feedingstuffs for pigs of 0.9 mg/kg (EC, 2006). Regarding the maize pellets, even acute adverse effects such as vomiting might be possible (EFSA, 2017b).
Furthermore, both materials exceeded the guidance value for ZEN for piglets and gilts, while the pellets also exceeded the guidance value for sows and fattening pigs and the silage reached this value (EC, 2006).
Enrichment materials should fulfil the same requirements as feed regarding hygiene and quality. In conclusion, peat should not be used as enrichment material for pigs due to the risk of M. avium contamination, and maize products pose a significant risk of mycotoxin contamination and cannot be recommended, either. This study proved, that enrichment material can be a potential source of pathogens and mycotoxins;
thus, a regular monitoring of the material in use is highly recommended.
Conclusion 19
4. Conclusion
The provision of enrichment material is particularly important for the welfare of pigs of all ages, and the use of organic materials is mandatory to fulfil their behavioural needs. However, organic materials can be contaminated by pathogens or mycotoxins, thus being a hazard to the animal’s health. Concerning pathogenic bacteria, all studied materials, except for peat, were suitable as enrichment for pigs.
The detected mycobacteria in peat pose a risk for the health of pigs and humans, resulting in condemnations at the slaughterhouse. Administration of peat is risky and not recommended for pig farming. Regarding the contamination with mycotoxins, grass hay and straw meal made of wheat, rye and triticale showed increased levels of ZEN and DON, respectively, and should only be combined with feed with low-level contamination. The maize pellets and maize silage contained high amounts of DON and ZEN and cannot be recommended as enrichment for pigs in general. Whether all of the tested hygienic materials are suitable from an ethological point of view, and whether viruses and parasites pose a risk, requires further investigation.
Summary 20
5. Summary
Krista Marie Tenbrink (2021)
„Examination of the hygienic status of selected organic enrichment materials used in pig farming”
Tail biting is a major problem in pig husbandry compromising animal welfare, health, food safety, and profit for the farmer. A preventive as well as curative measure is the provision of enrichment material. Legislation and scientific literature recommend organic enrichment materials. However, organic enrichment material might pose health risks in terms of contamination. The aim of this study was to assess the safety of different types of commonly used organic enrichment materials concerning pathogenic bacteria, moulds and mycotoxins. Based on the results of the analyses, suitable enrichment materials for pigs concerning hygienic risks are recommended.
Twenty-one different organic materials were tested in this study. Analyses for overall bacterial contamination (as total viable count), coliform count, mould count, Escherichia coli, Klebsiella spp., Yersinia spp., Salmonella spp., methicillin-resistant Staphylococcus aureus, and Mycobacteria spp. were conducted. To assess the mycotoxin contamination a liquid chromatography tandem mass spectrometry multi- mycotoxin method was performed.
The detected contamination differed widely between the materials. Escherichia coli, Klebsiella spp., Yersinia spp., Salmonella spp., and methicillin-resistant Staphylococcus aureus were not detected in any of the materials. Additionally, aflatoxin B1 and ochratoxin A were not present. Fumonisins were only detected in one sample. Wooden materials showed a very low bacterial and fungal burden, and deoxynivalenol (DON) and zearalenone (ZEN) were not detected. In loose straw and hay materials the bacterial and fungal contamination was overall the highest in the study. Straw meal made of wheat, rye, and triticale showed elevated levels of DON, while the grass hay exceeded the guidance value for ZEN contamination.
Compressed straw and hay materials had a low contamination with bacteria, moulds and mycotoxins. The “miscellaneous” group included materials varying considerably
Summary 21
in their raw materials and material characteristics. The sugar beet pulp and lignocellulose litter were free of any detectable bacterial and mould contamination.
The total bacterial contamination was high in peat and particularly in maize silage with the highest count of the study. The detection of Mycobacterium avium in peat was alarming. The infection of pigs with Mycobacterium avium subsp. hominissuis causes granulomatous lesions resulting in carcass condemnation at the slaughterhouse. DON and ZEN levels in materials without maize were very low.
However, the DON level in the maize pellets and maize silage exceeded the guidance value for pig feed and the pellets might even induce acute adverse health effects. Furthermore, both maize products exceeded or reached the guidance value for ZEN.
The provision of enrichment material is particularly important for animal welfare of pigs. However, organic materials can be contaminated by pathogens or mycotoxins, thus being a hazard to the animal’s health. Concerning pathogenic bacteria, all materials, except for peat, were suitable as enrichment for pigs. Administration of peat is risky and not recommended for pig farming. Regarding the contamination with mycotoxins, grass hay and straw meal made of wheat, rye and triticale showed increased levels of ZEN and DON, respectively, and should only be combined with feed with low-level contamination. The maize pellets and maize silage contained high amounts of DON and ZEN and cannot be recommended as enrichment for pigs in general. Whether all of the tested hygienic materials are suitable from an ethological point of view and whether viruses and parasites pose a risk, requires further investigation.
Zusammenfassung 22
6. Zusammenfassung
Krista Marie Tenbrink (2021)
“Untersuchung des hygienischen Status ausgewählter organischer Beschäftigungsmaterialien in der Schweinehaltung ”
Schwanzbeißen ist ein bedeutendes Problem in der Schweinehaltung und beeinträchtigt das Tierwohl, die Gesundheit der Tiere, die Lebensmittelsicherheit und den Gewinn des Landwirtes. Die Gabe von Beschäftigungsmaterial wirkt dabei sowohl präventiv als auch kurativ. Die Gesetzgebung und die wissenschaftliche Literatur empfehlen die Verwendung organischer Materialien. Allerdings können diese Materialien aufgrund von Kontaminationen auch ein Gesundheitsrisiko darstellen. Ziel der vorliegenden Studie war es, die Sicherheit verschiedener üblicher organischer Beschäftigungsmaterialien in Bezug auf pathogene Bakterien, Schimmelpilze und Mykotoxine zu bewerten. Basierend auf den Ergebnissen sollen hygienisch geeignete Beschäftigungsmaterialien für Schweine empfohlen werden.
Einundzwanzig verschiedene organische Materialien wurden untersucht. Dabei wurde die allgemeine bakterielle Belastung (mittels Gesamtkeimzahlbestimmung) bestimmt, sowie auf coliforme Keime, Schimmelpilze, Escherichia coli, Klebsiellen, Yersinien, Salmonellen, Methicillin-resistente Staphylococcus aureus und Mykobakterien untersucht. Für den Nachweis von Mykotoxinen wurde eine Multi- Mykotoxin Methode mittels Flüssigchromatographie mit Massenspektrometrie- Kopplung durchgeführt.
Die nachgewiesene Belastung unterschied sich zwischen den Materialien stark.
Escherichia coli, Klebsiellen, Yersinien, Salmonellen und Methicillin-resistente Staphylococcus aureus konnten in keinem Material nachgewiesen werden. Des Weiteren gab es keinen Nachweis von Aflatoxin B1 und Ochratoxin A. Fumonisine wurden nur in einer Probe gefunden. Die Holzmaterialien zeigten eine sehr geringe Belastung mit Bakterien und Pilzen. Desoxynivalenol (DON) und Zearalenon (ZEN) konnten nicht nachgewiesen werden. In den Materialien aus losem Stroh und Heu war die Kontamination mit Bakterien und Pilzen insgesamt am höchsten. Strohmehl
Zusammenfassung 23
aus Weizen, Roggen und Triticale zeigte erhöhte DON-Werte, während das Heu aus Gras die Richtwerte für ZEN überschritt. Gepresste Stroh- und Heumaterialien waren nur gering mit Bakterien, Pilzen und Mykotoxinen kontaminiert. Die „Sonstiges“- Gruppe enthielt Materialien, die sich stark in ihren Ausgangsmaterialien und Eigenschaften unterscheiden. Zuckerrübenschnitzel und Einstreu aus Lignocellulose waren frei von nachweisbaren Kontaminationen mit Bakterien und Schimmelpilzen.
Die allgemeine bakterielle Belastung war in Torf und insbesondere in der Maissilage hoch, letztere hatte den höchsten Wert der Studie. Der Nachweis von Mycobacterium avium war alarmierend. Die Infektion von Schweinen mit Mycobacterium avium subsp. hominissuis verursacht granulomatöse Läsionen, die zu Schlachtkörperverwürfen führen. Die Gehalte von DON und ZEN in Materialien ohne Mais waren sehr gering. Im Gegensatz dazu überschritten die DON-Werte in den Maispellets und der Maissilage jedoch den Richtwert für Schweinefutter und die Pellets könnten sogar negative, akute Auswirkungen auf die Gesundheit verursachen. Zusätzlich überschritten bzw. erreichten beide Materialien den ZEN- Richtwert.
Die Gabe von Beschäftigungsmaterial ist sehr wichtig für das Tierwohl in der Schweinhaltung. Organische Materialien können jedoch durch Pathogene oder Mykotoxine kontaminiert sein und dadurch die Gesundheit der Tiere gefährden. In Bezug auf pathogene Bakterien waren alle Materialien außer Torf als Beschäftigungsmaterial für Schweine geeignet. Die Gabe von Torf ist riskant und kann für die Schweinehaltung nicht empfohlen werden. Im Hinblick auf Mykotoxine zeigte Heu aus Gras erhöhte Gehalte von ZEN und Strohmehl aus Weizen, Roggen und Triticale erhöhte Gehalte von DON. Daher sollten diese Materialien nur mit Futter kombiniert werden, das eine geringe Belastung aufweist. Die Maispellets und Maissilage enthielten hohe Mengen DON und ZEN und können allgemein nicht als Beschäftigungsmaterial für Schweine empfohlen werden. Ob die untersuchten hygienischen Materialien auch aus ethologischer Sicht geeignet sind und ob Viren und Parasiten ein Risiko darstellen können, erfordert weitere Untersuchungen.
List of publications 24
7. List of publications
Besides the publications included, the following papers have been published in connection with this thesis:
Wagner, K., Schulz, J., Kemper, N., 2015. Hygienische Bewertung von Beschäftigungsmaterial beim Schwein. In: Deutsche Veterinärmedizinische Gesellschaft e. V. (DVG) (Eds.): Tagungsband DVG-Vet-Congress, 2. Tagung der DVG-Fachgruppe Umwelt- und Tierhygiene, Biosecurity – Emissionen – Tiergerechtheit: Ein Widerspruch? Berlin, 12.-15.11.2015, pp. 28-30, ISBN 978-3-86345-275-9.
Wagner, K., Sagkob, S., Kemper, N., 2016. Hygienische Bewertung von organischem Beschäftigungsmaterial. In: Qualitätsprüfungen und Projekte in der Tierhaltung, Jahresbericht 2015/2016, Landwirtschaftskammer Niedersachsen, pp. 96-98.
Wagner, K., Schulz, J., Kemper, N., 2016. Organic enrichment material in pig farming: A hygienic risk? In: IPVS (Eds.): Proceedings of the 24th International Pig Veterinary Society Congress, 8th European Symposium of Porcine Health Management, Dublin, Ireland, 07.-10.06.16, p. 142.
Wagner, K. M., Schulz, J., Kemper, N., 2017. Hygienic status of organic enrichment materials in pig production. In: Proceedings of the XVIII ISAH Congress in Mazatlan, Sinaloa, Mexico, 19.03.-23.03.2017, pp. 735-741.
Wagner, K. M., Schulz, J., Kemper, N., 2017. Organic enrichment material in pig husbandry: any risk for animal health? In: Book of abstracts of the 68th Annual Meeting of the European Federation of Animal Science Tallinn, Estonia, 28.08.-01.09.2017, p. 109.
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