Feed hygiene and related disorders in horses

SECTION C  Applied Nutrition – Feeds

Feed hygiene and related disorders in horses

20 

Josef Kamphues Introduction Diversity/variety of contaminants in feeds for horses Practical evaluation of feed hygiene Microbiological investigations to assess the hygiene status of feedstuffs and bedding material Potential effects of poor feed hygiene on horse health

367 367 369

Other potential contaminants Water quality and hygiene Responsibilities of partners in the feed supply chain Summary References

375 375 376 378 379

370 372

Introduction Energy, nutrient content, digestibility and palatability are the main parameters typically used to describe the nutritive value of ingredients intended for use in animal feeding. Nonetheless, factors related to “feed hygiene” are equally important and should be considered when choosing a feed. Feed hygiene is a very broad term that covers all the measures that are necessary to minimize health risks due to physical, chemical or biological contamination (as described in the EC Regulation on Feed Hygiene No 183/2005) of feeds and feedstuffs. Worldwide there has been increased interest in the potential role feed contamination may play in horse health (Raymond et  al 2000, Buckley et  al 2007, Sacchi et  al 2009). Recent epidemiological studies suggest that it is not uncommon for horse feedstuffs to be of moderate or poor “hygienic quality”, which could predispose to various disorders (Germany: Wolf et  al 2009, Austria: Kaya et  al 2009, Switzerland: Wichert et  al 2008). In 1996, the author developed the first systematic approach to characterize the hygienic status of equine feedstuffs. This was based on the evaluation of various hygiene problems encountered in equine feedstuffs. This work provides the core foundation for this chapter, which has been enriched by more recent published studies that have focused on more specific areas of contamination involving pathogenic fungi, endotoxins and mycotoxins.

Diversity/variety of contaminants in feeds for horses To a greater or lesser extent all feedstuffs (and bedding/ litter material) will be contaminated with a variety of substances and organisms. Depending on the conditions during growth, at harvest, during storage and mixing, etc., as well as the type of feeds and how they are provided to the horse, the level of contamination will vary between years, feed producers, and the people who take care of the horses.

Whilst it is virtually impossible to eradicate contamination, it is important to minimize the load and eliminate those contaminants that are of high risk to the horse. The different types of contaminants that may occur in feeds for horses (and sometimes also in litter and drinking water) are listed in Table 20-1 based on the EU directive, 183/2005. Contamination can occur at any point along the feed supply chain; production, harvesting and storage through to the point of ingestion. Unintentional contamination, for example, may arise from the use of fertilizers, herbicides and pesticides as well as from exposure to pollutants during production and harvesting. Due to adverse environmental or storage conditions in particular, the growth of bacteria, fungi and/or yeasts can result in the formation of a variety of chemical compounds that may cause health effects. Even processing itself can introduce unwanted and potentially toxic contaminants, for example dioxins within natural vitamin E products (Halbert & Archer 2007). Contaminants also can arise from the environment and possibly lead to unintended doping of the equine athlete (Barker 2008, Popot et al 2011). It is not always easy to determine the actual point of entry of certain contaminants and therefore on whom any responsibility should lie in the case of a dispute or adverse event. Good manufacturing, production and handling practices will help to reduce risk, as discussed later and in Chapter 21.

Key Points • Most feedstuffs carry some form of unavoidable natural contamination; the challenge is to minimize any such contamination and the associated risks • Contaminants can be biological (e.g. molds or pests), chemical (e.g. prohibited substances, heavy metals) or physical (e.g. stones, string) in nature; • Contamination can also be present in forage and water, and occur at any point in the supply chain from primary growth to the feed room. • Whilst the horse appears to be able to withstand a certain load (depending on the source), excessive contamination can affect health and performance and should be avoided.

Examples in equine feeds and/or bedding material

1. “Chaff” in uncleaned cereals, “fines” in concentrates 2. Soil/sand in/on hay, straw, beets, carrots 3. Feces and urine of rats, mice (uncovered forage and concentrates)

1. Moths in/on concentrates, cereals 2. Beetles in/on cereals, concentrates, hay, straw 3. Mites in cereals, hay, straw

1. Epiphytic molds (like Fusarium) on cereals 2. Species indicating spoilage (Aspergillus, Mucor) 3. Yeasts on silages, cereals, (wet) concentrates

1. Epiphytic bacteria on cereals (like Flavobacterium) 2. Species indicating spoilage (like Clostridia, Staph.) 3. Pathogenic species like Salmonella, Listeria Leptospira, clostridia

1. Mycotoxins (cereals, grass, maize silage) 2. Endotoxins (from gram-negative bacteria) 3. Exotoxins such as botulism toxin

Dirt / “dust”

Pests / insects

Molds / yeasts

Bacteria

Toxins of micro­organisms

Roughage mainly

Use within the feed mill, confounding accidents, errors

Water

Cross-contamination of concentrates (coccidiostats)

Heavy metals

Rodenticides, insecticides

Fluorine

Ionophores

Concentration in roughage (paddocks without green fodder)

Silage

Bales of hay/straw/silage

Sand/soil

Glass

Threads/ strings

Physical contaminants

Grass but also concentrates

Fertilizer

Chemical contaminants

1.  Ragwort in roughage/hay 2. Autumn crocus in roughage/hay 3. Trisetum flavescens

Poisonous plants

Biological contaminants

Categories and examples of contaminants

Impaired passage of ingesta, intestinal obstruction

Mechanical damage within the GIT

Colic (accumulation of sand)

Sudden death, cardiac and skeletal muscle degeneration, colic, myoglobinuria

Teeth/bone alteration

Depends on type of substances

Depends on type of metal

Depends on kind of fertilizer

1. Mycotoxicosis (effects depending on kind of toxin) 2. Respiratory tract diseases (irritation, sensitization) 3. Intoxication

1. Gastrointestinal dysbiosis (altered flora composition) 2. Gastrointestinal dysbiosis (altered flora composition and activity → gas formation) 3. Diarrhea, abortion (depending on species of bacteria)

1. Gastrointestinal dysbiosis (altered flora composition) 2. Altered composition of intestinal flora/ respiratory problems 3. Mycosis (e.g. guttural pouch mycosis)

1. Reduced feed palatability and lower feed intake 2. Allergic reactions, coughing 3. Signs of colic

1. Impairment of respiratory tract (mechanical irritation) 2. Gastrointestinal disorders (“sand colic”) 3. Exposure to pathogenic bacteria like Salmonella, Leptospira, Listeria

1. Hepatotoxicity 2. Signs of colic (due to colchicin) 3. Calcinosis (blood vessels/kidney)

Potential adverse effect

Art et al 2002 Rollins & Clement 1979

Kamphues et al 1990; Aleman et al 2007; Hughes et al 2009; Dorne et al 2011

Kamphues et al 2009

Liesener et al 2010; Raymond et al 2000, 2005; Sacchi et al 2009; Caloni & Cortinovis 2010, 2011 Snell 1966; Kamphues et al 1991; McGorum et al 1998; Pirie et al 2001, 2003

Traub-Dargatz et al 2000; Sargison 1993; Raymond et al 2000

Gregory & Lacey 1963; Rade et al 1998; Wright et al 2009; Buckley et al 2007; Keller et al 2007; Blomme et al 1998

Kamphues & Reichmuth 2000; Eder et al 2000; Rade et al 1998

Clarke & Madelin 1987; Kirschvink et al 2002; Robinson et al 1996

Kamphues & Meyer 1990; Wolf & Kamphues 2001

References

Table 20-1  Contaminants in Feedstuffs and Bedding Materials for Horses: Examples of Their Occurrence and Veterinary Relevance (According to Kamphues 2007)

368 Section C  Applied Nutrition – Feeds

Feed hygiene and related disorders in horses

Practical evaluation of feed hygiene In general, there are three main situations that warrant the initiation of a more detailed evaluation of the hygienic quality of a particular feedstuff or ration (Table 20-2). The first steps are to obtain the “history” of the feed through a detailed anamnesis, and then gather data through personal observations and diagnostic activities. Here, it should be

Table 20-2  Typical Situations Requiring a More in-Depth Evaluation of Feed Hygiene 1. Questions from horse owners -  based on observations regarding the quality of   feed batches - regarding shelf-life and the suitability of feeds - regarding the treatment of feeds before feeding 2. Increased frequency of clinical disorders in horses, including - colic - respiratory disorders (e.g. recurrent airway obstruction or “heaves”) - fertility problems (conception rate ↓ / abortions ↑) - poor performance 3. Prophylactic purposes/optimizing feed production and storage - feeding as a part of the whole management - recommendations concerning storage of feeds - control of feed quality before ingredients are used

Chapter

20

emphasized that much of information can be obtained through an intensive and detailed visual appraisal of the feedstuffs in question. It may be necessary to take representative feed samples; these may be retained and appropriately stored as control baseline samples in case further evaluations are required, or directly subjected to chemical and/or microbiological analyses. Table 20-3 presents a summary of the systematic approach to assessment of feed hygiene status. Visual examination enables detection of obvious abnormalities including contamination by dirt, pests and feces of rodents. Careful evaluation of the “fines” may show slight movements, indicating colonization by mites and/or insects (Kamphues 1996). Furthermore the proportion of “fines” in the feed provides an indication of the intensity of cereal cleaning or whether undesired abrasive processes may have occurred during the transport of pelleted concentrates (Kamphues et al 1989). The color of cereals may vary due to superficial contamination (molds/dirt/dust) but also due to genetic varieties (e.g., golden, yellow or black oats), which should not be confused with ergot contamination. In concentrates, the color should also reflect the type and nature of the ingredients (e.g., green due to grass/alfalfa meal) present in the feed. Understanding which feedstuffs are present in the feed can be valuable in other ways; for example, there can be higher risk of contamination by mycotoxins in oats when compared to other cereal grains (Edwards 2009). Two factors might explain this observation; oats are typically harvested later in the year (higher

Table 20-3  A Systematic Approach for Evaluation of the Hygiene Status of Equine Feeds (Progression Through All Steps Increases the Expenditure) Step

Procedure

Relevance (examples)

1

Gather information on the feed by questioning the horse keeper on, e.g. - production/storing/treatment - observations after starting to use the feed - changes in defecation/feces quality

→ label of the feed? → weather at harvest? technical equipment? storing facilities? → reduced palatability? coughing? gastrointestinal disturbances? → watery feces

2

Conduct a thorough visual appraisal (appearance/odor/texture) - feed itself - feed circumstances/surrounding environment, e.g. cleanliness of utensils used, how long any soaked feed is left before feeding etc.

roughage: test DM content by feeling silages: test the smell (nuances of butyrate/alcohol); cereals: appearance of the surface(changes due to smell?) → compare to expected “normal qualities” for that feedstuff/ feed: determine if there is an obvious smell of molds/ yeasts or obvious presence of physical contaminants etc. → note air humidity/temperature/ storage conditions, etc.

3

Take appropriate samples of feeds (and bedding material) - from stored feedstuffs - from offered feedstuffs

ideally should represent the actually offered/ingested feed → may mean taking samples out of the trough! → time between delivery and sampling? → record history of the feed Always label feedstuffs with the batch or delivery number and date delivered.

3.1

Chemical analyses of: • dry matter content • acid content, pH-values (for haylage/silage)

generate objective values and compare to standards

3.2

Microbiological investigations type/kind and counts of bacteria type/kind and counts of molds and yeasts

Signs in horses specific for pathogenic bacteria? → indicative of spoilage/deterioration? see Table 20-6

3.3

Analysis for microbial toxins mycotoxins endotoxins (e.g. lipopolysaccharides)

In specialized laboratories only → related to clinical signs/molds detected → information regarding mass of Gram-negative bacteria

369

370

Section C  Applied Nutrition – Feeds

Table 20-4  Summary of the Main Differences between Silage and Haylage Forage

Target species

Storage form

Date of 1st cut

Typical DM %

Preservation

Silage

Farmed ruminants

Clamp or large, round bales (300–500 kg)

Early May*

18–40

Fermentation (higher acid contents)

Haylage

Equines

Bales: small (25 kg); vacuumpacked large (180–250 kg); round or square, wrapped

Mid June*

55–70

Limited fermentation and preservation (due to higher DM content and pH-values)

*Northern hemisphere

frequency of bad weather) and the husk has a groove on the surface that predisposes it to contamination. Assessment of dry matter (DM), temperature and the pH value of silage and haylage are important when considering suitability for feeding horses (Müller 2005, Müller et al 2011). The feeding of spoiled silages/haylages might result in excessive gas formation in the gastrointestinal tract of horses, resulting in colic. The main differences between silage (typically fed to farm livestock) and haylage (specifically made for horses) are their moisture content, extent of fermentation, date of harvest and nutrient content (Table 20-4). Low DM materials (<40%) require some form of fermentation of the plant sugars to form lactic acid that, in effect, “pickles” the grass. However in higher DM haylages, lower moisture and sugar contents restrict the opportunity for fermentation, and the main method of preservation is excluding air by wrapping or vacuum packing. If there are concerns with respect to the DM content of any feedstuff, it is recommended to send in samples for analysis (Table 20-5). During the careful visual appraisal of hay, straw and silages there is also the need to be carefully checked for the presence of toxic plants or other potentially toxic contaminants (e.g., blister beetles in US-sourced alfalfa [lucerne] products). This chapter cannot do justice to the range of potential poisonous plants but over the last decade several published reports have underlined the clinical relevance of such contaminations (e.g., Kamphues & Meyer 1990, Wolf & Kamphues 2001). Important plant contaminants include Equisetum palustre, Colchicum autumnale, Senecio jacobaea and Hypericum perforatum in hay, as well as Trisetum flavescens, Mercurialis annua and Senecio spp. in silages, and Apera spica venti in straw (the latter is not a toxic plant but its ingestion has been associated with colic; Kamphues & Schad 1992).

Microbiological investigations to assess the hygiene status of feedstuffs and bedding material There is variation in the methods used for microbiological examination of feedstuffs; in particular, methods can vary according to: 1. The pretreatment of the feed (diminution/dilution/

incubation of feed-water suspension).

2. The temperature used for incubation (25 to 45°C). 3. The duration of incubation (2 to 7 days).

Table 20-5  Suggested Quantitative Values Regarding the Dry Matter Content of Equine Feedstuffs Relating to   Aerobic Spoilage Oats/barley/ maize

≥ 88% = very dry < 88 – > 85% = desirable

< 85% = unacceptable

Concentrates

≥ 86% required by feed legislation

< 85% = unacceptable

Hay/straw

≥ 86% = desirable 86 – 85% = insufficient

< 85% = unacceptable

Silages (wilted)

35–50% = normal range

< 30% = unacceptable

Haylage

55–70% = desirable

> 70% = risky

In earlier studies, for example, the cultural investigations were restricted to either thermophilic or thermotolerant species of moulds depending on the temperature used during incubation (Kirschvink et al 2002, Mair & Derksen 2000). Wright et al (2009) have emphasized that there is no correlation between the results (molds, fungal spores) obtained when the temperature during incubation was at either 22°C or 35°C. Accordingly, Raymond et al (2000) have recommended combining different incubation times and temperatures in order to obtain data on the wide spectrum of microorganisms present in feeds (7 days at 25°C: mesophile aerobic bacteria, molds, yeasts; 5 days at 40°C: thermotolerant fungi; 3 days at 55°C: thermophilic Actinomyces). The cost of such intensive analyses has prevented this approach being widely adopted in the field. More than two decades ago, a standardized procedure for microbiological investigations was established for all “official” analyses of feedstuffs in Germany (Schmidt 1991). The intention was (and still is) to generate data on the extent of the “load” of mesophile aerobic microorganisms within feeds, including bacteria, molds and yeasts (divided into normal “epiphytic” and undesirable spoilage inducing organisms). This approach has facilitated the development of knowledge of what can be considered “normal” vs. “abnormal” microbiological contamination, and these parameters have been adopted for use in other countries (Switzerland and Austria). There is good agreement between the “upper normal values” used in Germany with data from other published studies (e.g., Raymond et al 2000, Wright et al 2009) when comparable analytical procedures have

Feed hygiene and related disorders in horses

been used. It is also necessary to differentiate the results of microbiological analyses according to the reason for the investigation, e.g. some authors have focused on pathogenic fungi (Aspergillus fumigatus, A. niger, A. flavus and Fusarium), ignoring non-pathogenic species of molds, yeasts or bacteria (Buckley et al 2007). As mentioned, all equine feedstuffs are contaminated (predominantly on their surface) by microorganisms that represent the so-called epiphytic flora; counts for bacteria and molds are typically ∼106 colony-forming units (cfu)/g feed and ∼103–104 cfu/g feed, respectively. Normally, the presence of these epiphytes neither harms the plant, seed or feed, nor impacts horse health. However, under certain circumstances (high humidity and temperature, physical damage; e.g., from insect or pest damage) there is opportunity for other undesirable microorganisms to multiply rapidly to the point that epiphytic flora no longer the predominant species (feed spoilage). During this spoilage process, the variety of species present decreases while the number of “spoilage-indicating bacteria (and molds)” increases, reaching values up to 109–1010 cfu/g feed. Concurrently, the smell of the feed changes (putrid/moldy/fusty/ stuffy) and the feed begins to lose its original appearance. At this stage, microbiological analyses can provide useful information regarding the microbial species involved as well as their counts. With extreme spoilage, however, visual appraisal alone will reveal the impact of microbial contamination on the quality of the feed. The contamination of the feed by distinct pathogenic species of bacteria such as Salmonella spp. or Leptospira spp. is a completely different scenario as these microorganisms are not normally present in feeds and these species do not result in typical feed spoilage. Nonetheless, even when present in relatively low levels these organisms can cause clinical illness (e.g., diarrhea and sepsis (Salmonella) or abortion (Leptospira)). Examination of feedstuffs for the presence

Chapter

20

of these pathogenic species is warranted when clinical disease occurs and feed is considered a possible source of the infection. It should also be noted that Clostridium spp. and Listeria spp. are common in the soil. Soil contamination therefore increases the risk of contamination. A visual check or rejection of material that feels “gritty” can help avoid such material. Ash analysis of forages can also provide information on above-average soil contamination. Tables 20-6 and 20-7 provide information on microflora in feeds, including “normal” counts that have been detected in the absence of negative effects on animal health. Even when these values are exceeded, it is not possible to conclude that a particular feed has caused a problem. In general, however, when the “normal values” are exceeded by a factor of 5–10 there should be high suspicion that the feed has contributed to the observed problem. Other methods for estimation of the potential microbiota load of the feed include measurement of structural constituents like ergosterol (from the cell wall of molds and yeasts) or the content of lipopolysaccharides (constituents of the cell wall of Gram-negative bacteria). The advantage of this approach is the detection of the entire cell mass of microorganisms (both dead and alive), and it can also be used for feeds that have been subjected to intensive heat treatment (which will destroy all alive microorganisms) or exposed to other treatments that prevent the use of the culture methods (for further details see Kamphues 1986).

Key Points Systematic evaluation of feed hygiene involves • History taking (including observations on horse health) • Visual and organoleptic assessment of the feed • Chemical analysis • Microbiological analysis

Table 20-6  Characterization of Microorganisms Occurring on Feedstuffs (Analyzed by Microbiological Cultural Techniques: Bucher & Thalmann 2006) Type of microorganisms

Classification

Group no.

Typical species that represent the group number (examples only)

Aerobic bacteria

“Epiphytic” (normal)

1

Indication of spoilage / deterioration

2

Flavobacterium Pseudomonas Bacillus spp. Staphylococcus/ Micrococcus Streptomyces spp.

3 Aerobic molds

Yeasts a

Able to produce bacterial toxins Mycotoxinsa

6

Verticillium Acremonium Fusarium Aureobasidium Aspergillus Penicillium Scopulariopsis Wallemia Mucor spp.

7

All species

Gas producer

“Epiphytic” (normal)

4

Indication of spoilage / deterioration

5

Indicating spoilage

Comments

Different types of mycotoxins are produced by the different mold species.

Mycotoxinsa

Destruents

371

372

Section C  Applied Nutrition – Feeds

Table 20-7  Highest Acceptable Counts of Microorganisms in Typical Feedstuffs for Horses (VDLUFA 2011). The Group Numbers Correspond to Those in Table 20-6. Microorganisms Group number Cereals - oats - barley - maize

Aerobic bacteria ×106 cfu/g 1 50 20 2

Molds ×103 cfu/g

2

3

1 1 0.5

Yeasts ×103 cfu/g

4

5

6

7

0.05 0.05 0.05

200 40 20

50 30 30

2 2 5

200 100 60

By products - bran (wheat) - soybean meal

8 1

1 1

0.1 0.1

50 10

50 20

2 1

80 30

Pelleted feeda

0.5

0.5

0.01

2

6

1

5

Mixed feed

5

0.5

0.1

3

20

5

50

Silages - maize/corn - grass

0.4 0.2

0.2 0.2

0.03 0.01

5 5

5 5

5 5

1000 200

2 2

0.15 0.15

200 200

100 100

5 5

150 400

Roughages - hay - straw

30 100

a

The pelleting process should result in a reduced count of microorganisms.

Potential effects of poor feed hygiene on horse health Feeds and feeding can adversely affect horse health in several ways, as summarized by Meyer & Coenen (2002): • • • • •

an oversupply or deficiency of energy and/or nutrients an unsuitable composition of the whole ration poor feeding methods the intake of toxic constituents from ingredients poor feed hygiene (specific ingredients or the whole ration).

Respiratory system It has long been recognized that poor hygiene status of feed ingredients can adversely affect the health of the respiratory tract in horses. Exposure to dust and its constituents (fine particles of feeds, straw, feces, microorganisms, mites; toxins of microbial origin, chemically active substances like ammonia) is the most important challenge to the respiratory tract (McGorum 1994, McGorum et al 1998, Clarke & Madelin 1987, Kamphues et al 1991, Kamphues & Schulze Becking 1992, Robinson et al 1996, Mair & Derksen 2000, Raymond et al 2000, Pirie et al 2001, Rade & Kamphues 1999, Art et al 2002, Kirschvink et al 2002, Ward & Couetil 2005, Buckley et al 2007, Dunett 2009, Wolf et al 2009, Wichert et al 2008). The concentration and composition of airborne dust in horse stables differ markedly depending on the quality of feeds, method of feeding and type of bedding material (and its hygiene status), environmental conditions and other contributing factors (Fig. 20.1). There are several mechanisms underlying the development of respiratory

disease associated with exposure to airborne dusts (Fig. 20.2).

Gastrointestinal tract The role of poor feed hygiene in the etiology of colic and other gastrointestinal tract (GIT) problems has received very little attention. Raymond et al (2000) indicated that GIT disorders in horses could be caused by “moldy forage” but the main health risks were linked to the respiratory tract. In a field survey on feeding practices associated with colic in horses, Hudson et al (2001) observed that “feeding hay from round bales” increased the risk of colic. Nonetheless, more than 30 years ago Meyer (1979) emphasized the important role of feed hygiene in the occurrence of colic, for example: • stimulated gas production in the GIT due to feed contamination by yeasts and other gas-producing microorganisms • substances with antimicrobial properties in moldy feeds (especially roughages) that impair/suppress the GIT flora • imbalances within the normal GIT flora enabling “exogenous microorganisms” (from feed/straw/litter) to colonize the alimentary tract • improper physical form of ingredients due to fine cutting of roughage or ingestion without intensive chewing (for example the grass Apera spica venti as a contaminant in straw). The results of some recent epidemiological studies provide support for the ideas expressed by Meyer (1979), for example Wichert et al (2008), Kaya et al (2009) and Wolf et al (2009). Kaya et al (2009), for example, observed an association between reduced hygiene quality of hay and the

Feed hygiene and related disorders in horses

Chapter

20

Roughages (hay and straw): contamination by sand, by organisms (mites, molds, yeasts, bacteria)

Kind and quality of litter material

Fine particles of roughages/litter material

How is the environment managed? - avoiding/reducing or increasing dust release -

Airborne dust (exposure of the respiratory tract)

How are those materials offered? Any pretreatment like cleaning, soaking, compaction?

Fine particles of the different material itself

Further sources (animal: hair, epithelia, feces particles) air, floor of paddocks, hippodrome, riding hall

Cereals/concentrates (contamination by dirt, pests, mites, moulds; processes of abrasion at storing, transport, offering)

Figure 20.1  Sources of airborne dust that may result in exposure of the respiratory tract.

Infections by pathogens (mycosis/bacterial infection of guttural pouch and upper/lower respiratory tract?)

Physical/chemical irritation of the upper respiratory tract (NH3→NH4OH)→coughing

Dust consisting of finest particles

Sensitization antigenic material from microorganisms/ mites/excreta/feed ingredients (inflammatory responses)

Mechanisms of airborne dust affecting the health of the horse’s respiratory tract

Dust consisting of finest particles

Lipopolysaccharides (inhalation challenge → release of cytokines/neutrophils in tracheobronchial secretion ↑, reduced activity of alveolar macrophages)

Figure 20.2  Mechanisms involved in the development of respiratory disease associated with exposure to airborne dusts.

incidence of colic in a population of horses in Austria. However, in general epidemiological studies on colic have not routinely included assessment of the hygienic quality of the feeds offered. Much more in-depth work is needed in this area.

Mycotoxins Mycotoxins are undesirable substances that occur as secondary metabolites of fungal growth. They are produced by molds to aid their survival either as a defense mechanism

or to help the mold colonize its host. Whilst viable molds have been associated with respiratory irritation and allergy in horses, more recently attention has turned to the potential for mycotoxins to cause adverse health effects. For some mycotoxins, such as fumonisins and aflatoxins, the effects on horses are well known, but for other mycotoxins the level at which any potential negative effect occurs are less clear. As mentioned before, contamination of feeds by certain mycotoxins can be a risk for horses’ health, depending on the mycotoxin and the amount present. Of special interest are fusariotoxins (Johnson et al 1997, Raymond et al 2000, Buckley et al 2004, Liesener et al 2010), but also mycotoxins

373

374

Section C  Applied Nutrition – Feeds

from the ergot family produced by Claviceps spp. or by endophytic molds that occur in some species of grass worldwide (Riet-Correa et al 1988, Copetti et al 2002, Fayrer-Hosken et al 2008) leading to reduced fertility, especially to agalactia (due to prolactin antagonistic effects of the ergotamine-like substances). Table 20-8 gives a short overview on this class of contaminants. Different genera/species of bacteria and molds are able to produce toxins and subsequently release these as contaminants in/on feeds. Today it is possible to detect various toxins that can either lead to general impaired health and wellbeing or to specific diseases which may be associated with fairly pathognomonic signs e.g. equine leukoencephalopathy (ELEM; due to fumonisins) or botulism (due to toxins of Clostridium botulinum). Table 20-8 lists some of the more important toxins. Here it has to be underlined that all Fusarium spp. produce their mycotoxins pre-harvest, while Aspergillus spp. and Penicillium spp. can also produce their toxins post-harvesting (e.g., when storing the feed). For the mycotoxins summarized in Table 20-8 there are some data regarding the levels in feeds that are allowed (max. levels from feed legislation) or that could be tolerated (without adverse effects in horses) in the diet (with 88% DM). • Aflatoxins = max. 0.02 resp. 0.01 mg/kg feed (ingredients/compound feeds) • Ergovaline = 300–500 µg/kg diet lead to clinical symptoms • Fumonisins = NOAEL: 10 µg/kg BW; max.: 5 mg/kg diet • Zearalenone = safety margin: 5 µg/kg BW; max.: 2–3 mg/kg diet • DON = tolerance in horses comparable to pigs (up to 1000 µg/kg diet; based on experiments of Schulz et al 2012).

As expected, the clinical signs that can occur after the ingestion of toxin contaminated feeds can affect the entire animal but there are also some relatively specific tropisms (aflatoxins → liver; fumonisins → white substance of the brain; endotoxins → exposure of the respiratory tract → COB/RAO like symptoms). These need to be taken into consideration by the veterinary practitioner. However, the fact that certain toxins are found in the feed does not necessarily mean that they are associated with the observed clinical signs.

Mycotoxin mitigation Given that mycotoxins are often present in equine feedstuffs complete avoidance is difficult. Although once ingested mechanisms for at least partial detoxification and excretion of the mycotoxins exist, horses do not automatically selfprotect by refusing mycotoxin-contaminated feeds. The use of sound practices in the production and storage of feedstuffs (see Table 20-9) is the main strategy for mitigation of mycotoxin load. Special attention leads to the following established methods: • • • •

Rotation in crop production Selection of mold-resistant varieties Use of efficient fungicides Soil management (plowing instead of cultivating).

In the feed industry there are diverse measures to reduce the mycotoxin load of feeds. One of the most efficient is intensive cleaning of cereals and the prevention of mycotoxin formation during storage (sufficient dryness avoiding higher humidity). Last but not least the horse owner has to ensure suitable storage conditions (including well-known principles like first in – first out).

Table 20-8  Toxins Produced by Microorganisms That Belong to Feed Associated Microbial Contaminants Toxin(s)

Produced by

Occurring in

Effects/remarks

Ergotalcaloids/ ergovaline

Claviceps spp. endophytic molds

Rye (bran), wheat grass (hay)

Prolactin antagonism, abortion (mare’s health!)

Aflatoxins

Aspergillus spp. (A. flavus!)

Different feedstuffs (esp. imported onesa)

Liver disease/dysfunction

Fumonisins

Fusarium spp. (F. moniliforme)

Cereals, especially in corn (byproducts)

Typical: equine leukoencephalomalazia (ELEM)

Zearalenone

Fusarium spp. (F. graminearum)

Cereals, soybean corn byproducts

Estrogenic effects (“endocrine disruptor”)

DON (type B-trichothecene)

Fusarium spp. (F. graminearum)

Wheat, barley; corn byproducts

Feed refusal (in other species: vomitus)

T2/HT2 (type A-trichothecene)b

F. langsethiae F. sporotrichoides

Oats, barley, corn byproducts

GIT: mucosal irritations/alterations

Satratoxine

Stachybotrys spp.

Roughages (straw/hay)

Central/nervous symptoms, salivation/tremor

Botulinum-toxin

Clostridium botulinum

Hay, wilted grass, silages, straw

Paralysis, salivation, sudden death

Endotoxines (lipopolysaccharides)

All Gram-negative bacteria (cell wall)

All feedstuffs (especially in “fines” of hay/ straw)

Changes in body temperature, respiratory diseases (→ COB/ RAO like changes)

a

Feedstuffs imported from subtropical and tropical regions are especially prone to contamination with aflatoxin, but under certain circumstances (high temperature, changes in humidity) Aspergillus spp. may also produce toxins in Europe. See EFSA 2011 b There are also effects on immune system; loss of protection against oxidative damage is discussed too.

Feed hygiene and related disorders in horses

Table 20-9  A Guide to the Mitigation or Risk Management Activities That Should Take Place at All Stages of the Feed Supply Chain (See Also Chapter 21) Stage

Activity

Supplier

Inhibition of fungi mitigates mycotoxin formation

Growth

Management of crop production chain (selection of varieties, plowing, residues of former crops, sequence of crops, use of fungicides, insect repelling programs, infection pressure from natural reservoirs, equipment cleaning and maintenance)

Harvest

Conditions at harvest; grain drying to DM content >86%

Storage

Protection against damage in the storage unit. Low moisture environment, controlled free water activity, insect and mite defense. Certain preservatives used in store (e.g. propionic acid) may prevent mold growth

Manufacturer

Good manufacturing practice and HACCP

Distributor of finished goods

Good finished product storage and stock management (e.g. ‘first in first out’, stock rotation). Ingress of moisture from leaks or vermin damage can cause mold growth and potentially lead to mycotoxin formation.

The end user or horse keeper

Correct storage of feedstuffs and stock management; Use by sell by date; Effective pest control and cleaning programs.

Currently, there is no routine procedure available for detoxification of feed; mycotoxin binders are available but they do not reduce the actual load of mycotoxins in feedstuffs. More work is needed to validate their use in the feed for horses. Key Points – Mycotoxins • Mycotoxins are undesirable substances that might occur in feedstuffs for horses, too. • They occur as a consequence of the natural presence of molds. • The presence of a mycotoxin or mycotoxins does not automatically indicate a problem but above certain limits clinical issues may occur. • Valid analytical methods are essential for the evaluation of a feed that might contain a mycotoxin • Limits and/or regulatory guidance are available for certain mycotoxins, although a lot more data is required with respect to the horse • Effective risk reduction strategies exist for mycotoxins, and cover the whole process of sourcing feed, from initial crop growth and harvest to the final feed bucket (see Table 20-9)

Other potential contaminants A number of chemical contaminants also may pose risk of feed-associated intoxication. These can be naturally

Chapter

20

occurring, such as morphine due to the inclusion of morphine-producing poppies (see Chapter 21), or due to cross-contamination. The most important substances with respect to cross-contamination are coccidiostats, which are used worldwide as feed additives in complete diets for poultry, rabbits and ruminants. Therefore special risk occur when such feeds are made in the same facilities as the equine feed. Similarly, several substances within the ionophore group are used as growth promoters in different species of food producing animals (not allowed in Europe). Therefore, it is not surprising that severe intoxications of horses have occurred globally due to accidental cross-contamination. Questions should always be asked when a typical equine concentrate is contaminated by pellets of a different color, size, diameter and/or texture. The typical effects of ionophore intoxication in horses are myodegeneration, pain, massive colic, ataxia, sweating, red colored urine and recumbency (Kamphues et al 1990, Aleman et al 2007, Hughes et al 2009). The toxicity of ionophores in horses varies in the order salinomycin > narasin > monensin > lasalocid. The spectrum of contaminants also includes substances that can enter the feed (grass, silage, hay) through soil contamination. Worldwide, there are areas (and rivers) in which soils and sediments contain high levels of heavy metals (e.g., Pb, Cd, Hg, As). Horses at pasture or fed silages or hay produced in those regions therefore may be at risk for heavy metal intoxication (Casteel 2001, Palacios et al 2002, Liu 2003). Analyses of blood and further substrates (like hair) – in addition to feed analyses – are recommended to clarify suspicious cases, with some reference data available (Hoff et al 1998). Sporadic cases of clinical illness also may be encountered due to other less common contaminants (e.g., accidental contamination by fertilizers, rodenticides or pesticides). A potential concern about alfalfa produced in parts of the US is the presence of blister beetles that contain the cytotoxin cantharidin. As little as 4–6 g of dried beetles may be fatal to a horse (Jones 2006). Blister beetles tend to swarm as they feed on alfalfa flowers and therefore large numbers may be sporadically incorporated in baled hay. First cut hay is almost always free of blister beetles because the insects overwinter as subadults and do not emerge until late May or early June in the south-western US. Similarly, the last cut of hay is often safe because it is harvested after the time during which the adult insects are active.

Water quality and hygiene Drinking water should be clear, palatable and free of micro­organisms and chemical contaminants. Changes in physical appearance of the water or a decrease in water intake are indications to evaluate of water quality. Contamination of the water source (e.g., parts of straw, feeds, feces and/or urine) is not uncommon and is usually obvious. However, reduced water intake or complete refusal may be caused by contaminants and/or constituents that are not detectable by visual appraisal. Under these circumstances it is recommended to take a sample of water for assessment of microbiological and physiochemical composition. For example, high iron content can result in lower palatability, while ground water with “naturally” high sulfate content may lead to watery feces (due to osmotic effects) and high

375

376

Section C  Applied Nutrition – Feeds

concentrations of nitrite can result in methemoglobinemia. Under some environmental conditions hygienic deterioration of the water supply can occur, especially when a large supply is maintained for only a small number of horses, e.g. growth of algae (favored by light) and/or microorganisms (favored by temperature). This reiterates the need for water supplies to be checked daily and replenished on a regular basis. Some recommended values (Kamphues et al 2007) regarding the physicochemical quality of drinking water are summarized in Table 20-10 (also see Chapter 4). These values are used as “official” data for the quality of water for food producing animals in Germany. Regarding the microbial contamination of drinking water for animals, the same quality criteria as for human beings should be applied: • • • •

aerobic total viable count: max. 1000 cfu/ml (37°C) aerobic total viable count: max. 10000 cfu/ml (20°C) free from E. coli and coliform bacteria (in 10 ml) free from salmonellae and Campylobacter (in 100 ml)

Note that evaluation of the physicochemical parameters summarized in Table 20-10 is usually not necessary if horses are provided water from a public supply intended for human consumption. However, testing is indicated if the water comes from a “private” source (e.g., well, spring, creek or pond). In rare instances, microbial contamination may be caused by the formation of biofilms in water pipes.

Key Points – Water • The quantity and quality of water supply should be evaluated regularly (in fields, header tanks in stables and water bowls) • If concerned about water quality, both chemical and microbiological parameters should be assessed

Responsibilities of partners in the feed supply chain The principles of feed legislation are to avoid any adverse effects on animal health; to minimize risk to feed quality; and to protect the consumer and the environment. The term “consumer protection” also includes aspects of economic interests (avoiding deception) and transparency (information on feed quality by labelling). With respect to animal health, it is not permissible to produce, sell or offer feeds that are capable of adversely affecting animal wellbeing. Based on the EC regulation no. 183/2005, however, the primary responsibility for feed safety rests with the feed business operator. Table 20-11 summarizes the specific obligations for people who are engaged in feed production and feeding. The feed producer is responsible for feed quality (including hygiene) up until the point of delivery and/or until the “best before date” – providing the consumer has ensured appropriate conditions for feed storage. The consumer has the right to receive an “unspoiled feed” (and obviously massive infestation by mites or high counts of

Table 20-10  Recommended Physicochemical Composition of Drinking Water for Horses (Modified According to Kamphues et al 2007) Parameter

Recommended values for drinking water

Comments (possible effects/dysfunctions due to divergent values)

pH-value

> 5 and < 9

Corrosions in the ductwork

electrical conductivity (µS/cm)

< 3000

Higher values: diarrhea might occur, palatability ↓

soluble salts, total (g/l)

< 2.5

oxidability (mg/l)

< 15

Measurement of burden with oxidizable substances

Ca2+ (mg/l)

< 500

Calcination; technical dysfunctions

Fe (mg/l)

<3

Palatability ↓, technical dysfunctions, biofilm formation possible

Na+/ K+/ Cl− (mg/l)

< 500

Indicator for contamination (excreta, urine)

NO3− (mg/l)

< 200

Formation of methemoglobin; consider total intake (feed!)

NO2− (mg/l)

< 30

Methemo globinemia

SO4 (mg/l)

< 500

Laxative effect/diarrhea

NH4− (mg/l)

<3

Indicator for contamination

As (mg/l)

< 0.05

Disturbance of health, performance ↓

Cd (mg/l)

< 0.02

Residues in the food chain

Cu (mg/l)

<2

Consider total intake (feed!)

F (mg/l)

< 1.5

Teeth/bone disorders

Hg (mg/l)

< 0.003

General disorders (intoxication)

Mn (mg/l)

<4

Precipitates in the distribution system, biofilm formation possible

Pb (mg/l)

< 0.1

Residues in the food chain

Zn (mg/l)

<5

Mucosal alterations

−

molds undeniably indicates spoilage). On the other hand, if the consumer has not stored the feed appropriately before feeding, the actual problem may be attributed to himself rather than to the producer. The gathering of objective data (e.g., mold counts, pictures, retained feed samples) is important when the hygienic quality of a feed

Feed hygiene and related disorders in horses

Chapter

20

Table 20-11  Legislative Aspects in the Feed Supply Chain Addressed to

Examples of obligations that are described in detail

European legislation

“Primary production” (= producing feeds on farms)

• measures of feed hygiene → minimizing biological, chemical and physical contamination Good Agricultural Practice – to protect against contamination arising from air, water, fertilizer, plant protection products, veterinary drugs, waste – to keep clean all things that will come in contact with feeds, use clean water – to control measures regarding mycotoxins/heavy metals/correct use of veterinary products

EC No. 183/2005

“Feed business operators” (feed industry)

• continuous control of facilities/equipment, feed quality, storage and transport – Use of HACCP to identify and control hazards – ingredient and finished product quality specifications – in focus: cross-contamination – good storage conditions → to avoid spoilage/ deterioration – pest control system • regarding feed trading/marketing – labelling of feeds/diets – botanical purity (mostly 95 %) – moisture content (< 14 %) – composition (listed ingredients)

EC 183/2005

• general obligations like “prohibited to offer feeds that could harm the animal” – clean feeding equipment/correct storage – feed/bedding material → not to become moldy – water: appropriate quality – person: ability, knowledge, competence

EC No. 183/2005

“Farmer/owner of animals” (people who feed horses)

ANNEX II

ANNEX II

EC No. 767/2009

ANNEX III

Table 20-12  Main Hygiene Risks of Feedstuffs Frequently Used in Horse Nutrition Feed type

Common problems

Evaluation

Cereals

1. mycotoxin development in the field 2. improper cleaning 3. infestation by mites

1. See Table 20-8 2. sieving: determine the “fraction of fines” 3. presence of mites: “honey like smell”, “moving” dust, evaluation with a magnifier (10–20×) 4. appearance (gray), moldy smell, etc.

4. contamination of the cereal surface by molds/bacteria 5. delay of drying after the harvest

5. microbiological analyses (type and counts of microorganisms); mycotoxin testing.

Molassed products

Higher contamination by yeasts

Nuances of alcohol

Concentrates (pelleted products)

Prolonged storing leads to secondary spoilage due to increased moisture content (molds/ yeasts)

Texture (particles adhering together, swelling); the smell has moldy nuances

Hay/straw

Insufficient dry matter at harvestinga

Test the texture at harvesting/ storing → may feel clammy

Storing → contamination by molds (spores), pests

Release of dust (mainly consisting of fungal spores) when “plumping up” the roughage

Cross-contamination of prohibited substances/ drugs through ingestion of contaminated roughage (urine in particular)

Care and proper stable hygiene in particular for competing and racing animals

Haylage/Wilted grass silage

Aerobic deterioration via punctured or split packaging due to yeasts’ activity → secondary: growth of molds/bacteria

May detect slightly increased temperature, also test the smell, issues if has moldy/dump nuances

Corn silage

Elevated counts of yeasts (aerobe deterioration) Vermin damage

Alcohol nuances in the smell

a

High load of fungal spores mainly occurs when roughage is baled at a dry matter content of 75% or even lower (Séguin et al 2010).

377

378

Section C  Applied Nutrition – Feeds

Table 20-13  Examples of Key Circumstances and Conditions Enabling Spoilage of Feed and How They May Be Controlled Factor/aspect

Relevance/effects

Comments

Harvesting - Moisture - Cleaning

Supports microbial growth Reduces dirt/dust

Promotes outdoor deterioration of feeds Only dry cereals can be cleaned effectively Weeks regarding pests, days for molds, hours regarding yeasts/bacteria Most problems occur with high temperature at a high air humidity

- Preserving agents

Time related increase in risk of contamination Risk level influenced by storage conditions including moisture and temperature (but also the presence of pests etc.) Use of propionic acid

Feed processing - Intact/crushed - Pelleted/ unpelleted

Crushing → substrate availability↑ Pressure/heat: microorganisms ↓

Finely ground: highest susceptibility In general cooked products have the highest hygiene status – but can be contaminated for example during the production process if pipes etc. are not fully cleaned and pockets of old feed remain.

Soaked feeds may help to avoid spread of dust but depending on environmental conditions need to be made and consumed quickly Feeding from the floor may have some advantages regarding the respiratory tract but increases the risk of ingestion of sand/ earth

Other potential ways to prevent a high content of fines/dust include choice of source material, techniques for separating dust prior to bagging or feeding etc.

Storage - Time - Conditions

Offering the feed - Dry/weta

- At the floor

Certain “mold inhibitors” can help to reduce the growth of molds but may not always be effective or without their own risks.

Avoid by using well maintained feeding utensils such as troughs.

a

In horses with recurrent airway obstruction and other inflammatory airway diseases, the soaking or steaming of hay, use of hay cobs instead of hay, and pellets instead of grains is very important.

is in dispute. A clear understanding of expected norms for required quality parameters as well as “shelf life” is also paramount. The expiration date or best before date differs markedly between feedstuffs. Problems can occur in particular when ingredients have a moisture content >14% and simultaneously a high availability of sugar and starch due to cracking/grinding/cutting. Silage/haylage (where high moisture content will allow microbial growth and activity) can undergo a process of secondary fermentation within hours (at high external temperatures) or within 2–5 days (winter), thus the time that they need to be used after the opening of the package or bale is limited. Finally Tables 20-12 and 20-13 summarize the key reasons why feed becomes contaminated and provide some suggestions how to prevent the occurrence of such contaminants.

Summary In the feeding management of horses careful attention needs to be paid to the hygienic quality of feeds and bedding material. Infestation by mites and contamination by molds (hay, straw, cereals, and complete feeds) are

relatively common, while contamination by yeasts (silage, haylage, molassed oats, sometimes concentrates) or bacteria (especially in oats) is less common. Aside from the adverse effects of these contaminants on nutritive value and palatability, there is a risk of provoking digestive disorders. As well as the potential adverse effects of the living microorganisms, the toxins produced by bacteria (e.g., Clostridium botulinum) or by different species of molds (mycotoxins produced by Claviceps purpurea, Acremonium, Fusarium, Aspergillus, and Penicillium) can cause adverse reactions in the horse. Dusty feedstuffs (especially roughage) expose the respiratory tract to mites, infectious micro­organisms and toxins (e.g., lipopolysaccharides) and contribute to the pathogenesis of inflammatory airway diseases in horses. Chemical contaminants (e.g., coccidiostats, fertilizer, heavy metals) or physical contaminants (most commonly sand/soil) should not be ignored; similarly the quality of drinking water should be evaluated when feed-related problems are suspected. Optimizing the conditions of feed production and storage (including straw as bedding material) is essential for horses health and performance. The application of sound hygiene practices in feed production and storage as well as feeding can help to minimize feed hygiene-related problems.

Feed hygiene and related disorders in horses

Acknowledgments The author gratefully acknowledges the contributions of Ms. Ruth Bishop and Professor Manfred Coenen in the preparation of the mycotoxin part of this chapter.

References Aleman, M., Magdesian, K.G., Peterson, T.S., et al., 2007. Salinomycin toxicosis in horses. JAVMA 230 (12), 1822–1826. Art, T., McGorum, B.C., Lekeux, P., 2002. Environmental control of respiratory disease. In: Lekeux, P. (Ed.), Equine Respiratory Diseases. International Veterinary Information Service (www.ivis.org), Ithaca, NY. Barker, S.A., 2008. Drug contamination of the equine racetrack environment: A preliminary examination. J Vet Pharmacol Therap 31 (5), 466–471. Blomme, E., Del Piero, F., La Perle, K.M.D., et al., 1998. Aspergillosis in horses: a review. Equine Vet Educ 10 (2), 86–93. Bucher, E., Thalmann, A., 2006. Mikrobiologische Untersuchung von Futtermitteln (Microbiological examination of feeds – orientation values to assess soundness). Feed Magazine/Kraftfutter, 2006 (6), 16–23. Buckley, T., Pickard, J., Murphy, R., et al., 2004. Concentration of different mycotoxins in feed and straw on 6 Irish racehorse farms. Proc. International Society for Animal Hygiene, Saint Malo, 447, http://www. isah-soc.org/documents/2004/Buckley.pdf. Buckley, T., Creighton, A., Fogarty, U., 2007. Analysis of Canadian and Irish forage, oats and commercially available equine concentrate feed for pathogenic fungi and mycotoxins. Irish Vet J 60 (4), 231–236. Caloni, F., Cortinovis, C., 2010. Effects of fusariotoxins in the equine species. The Vet J 186, 157–161. Caloni, F., Cortinovis, C., 2011. Toxicological effects of aflatoxins in horses. The Vet J 188, 270–273. Casteel, S.W., 2001. Metal Toxicosis in Horses. In: The Veterinary Clinics of North America: Equine Pract 17 (3), 517–527. Clarke, A.F., Madelin, T., 1987. Technique for assessing respiratory health hazards from hay and other source materials. Equine Vet J 19 (5), 442–447. Copetti, M.V., Santurio, J.M., Boeck, A.A.P., et al., 2002. Agalactia in mares fed with grain contaminated with Claviceps purpurea. Mycopathologia 154, 199–200. Dorne, J.L., Fernández-Cruz, M.L., Bertelsen, U., et al., 2011. Risk assessment of coccidostatics during feed cross-contamination: Animal and human health aspects. Toxicol Appl Pharmaco Jan 6. [Epub ahead of print]. Dunnett, C.E., 2009. The importance of diet and feeding practices in the development of common health issues in the horse. In: Briese, A., Clauß, M., Hartung, J., Springorum, A., Brno, T.E.U. (Eds.), Proceedings of the XIV ISAH Congress 2009, pp. 1063–1067. Eder, C., Crameri, R., Mayer, C., et al., 2000. Allergen-specific IgE levels against crude mould and storage mite extracts and recombinant mould allergens in sera from horses affected with chronic bronchitis. Vet Immunol Immunopathol 73, 241–253. Edwards, S., 2009. Investigation of Fusarium mycotoxins in UK barley and oat production. Report on Joint FSA/HGCA project, CO4033 and CO4034 HGCA 2706,UK. EFSA, 2011. Scientific Opinion on the risks for animal and public health related to the presence of T-2 and HT-2 Toxin in food and feed. EFSA Panel on Contaminants in the Food Chain (CONTAM). EFSA Journal 2011 9 (12), 2481. Fayrer-Hosken, R., Heusner, G., Hill, N., et al., 2008. Review on effects of fescue grass ergot alkaloids in the horse and preliminary study on effects of fescue grass ergot alkaloid in the stallion. J Equine Vet Sci 28 (11), 666–671. Gregory, P.H., Lacey, M.E., 1963. Mycological examination of dust from mouldy hay associated with farmer’s lung disease. J Gen Microbiol 30, 75–88. Halbert, M.K., Archer, J.C., 2007. Dioxin and Furan contamination of deodorizer distillates and natural vitamin E supplements. J Food Comp Anal 20, 506–514. Hoff, B., Boermans, H.J., Baird, J.D., 1998. Retrospective study of toxic metal analyses requested at a veterinary diagnostic toxicology laboratory in Ontario (1990–1995). Can Vet J 39, 39. Hudson, J.M., Cohen, N.D., Gibbs, P.G., et al., 2001. Feeding practices associated with colic in horses. JAVMA 219, 1419–1425. Hughes, K.J., Hoffmann, K.L., Hodgson, D.R., 2009. Long-term assessment of horses and ponies post exposure to monensin sodium in commercial feed. Equine Vet J 41 (1), 47–52. Johnson, P.J., Casteel, S.W., Messer, N.T., 1997. Effect of feeding deoxynivalenol (vomitoxin)-contaminated barley to horses. J Vet Diagn Invest 9, 219–221. Jones, S.L., 2006. Disorders of the large intestine causing diarrhoea. In: Proceedings of North American Veterinary Conference, Vol 20, pp. 124–127.

Chapter

20

Kamphues, J., 1986. Lipopolysaccharides in feedstuffs – potential relevance, assessment and amounts. Übers Tierernährg 14, 131–156. Kamphues, J., 1996. Risk of feedstuffs loaded by mites, moulds, bacteria and/ or toxins in horses. Pferdeheilkd 12, 326–332. Kamphues, J., 2007. Futtermittelhygiene: Charakterisierung, Einflüsse und Bedeutung (Hygiene of feeds and feeding – characterization, influences and relevance). Landbauforschung Völkenrode, Sonderheft 306, 41–55. Kamphues, J., Meyer, H., 1990. Meadow saffron (Colchicum autumnale) in hay and colic in horses. Tierärztl Prax 18, 273–275. Kamphues, J., Reichmuth, C., 2000. Vorratsschädlinge in Futtermitteln. Potentielle Schadorganismen und Stoffe in Futtermitteln sowie in tierischen Fäkalien. Sachstandsbericht, 4. Mitteilung, DFG, Wiley-VCH, Weinheim, pp. 238–284. Kamphues, J., Schad, D., 1992. Verstopfungskoliken bei Pferden nach Fütterung von Windhalm-(Apera spica venti)-Heu. Proceedings of the 1st European Conference on Equine Nutrition, Pferdeheilkd (special edition) Hannover, pp. 213–215. Kamphues, J., Schulze Becking, M., 1992. Milben in Futtermitteln – Vorkommen Effekte und Bewertung (mites in feedstuffs – prevalence, effects and judgement). Übers Tierernährg 20, 1–38. Kamphues, J., Amtsberg, G., Klarmann, D., 1989. Feinanteile und Staub in Futtermitteln – quantitative und qualitative (Pilze, Bakterien und LPS) Aspekte. (Fines and dust in feedstuffs – quantitative and qualitative (moulds, bacteria and LPS) aspects. Berl Münch Tierärztl Wschr 102, 418–421. Kamphues, J., Meyer, H., Liebler, E.M., et al., 1990. Clinical signs in horses after ingestion of feedstuffs containing ionophores. Dtsch tierärztl Wschr 97, 537–539. Kamphues, J., Fimmen, H., Küstermann, S., et al., 1991. Lipopolysaccharides in feedstuffs for horses. Equine Vet Sci 11, 131–156. Kamphues, J., Böhm, R., Flachowsky, G., et al., 2007. Empfehlungen zur Beurteilung der hygienischen Qualität von Tränkwasser für Lebensmittel liefernde Tiere unter Berücksichtigung der gegebenen rechtlichen Rahmenbedingungen (Recommendations for evaluating the hygienic quality of drinking water for food producing animals in accordance with current regulatory framework). Landbauforschung Völkenrode 3 (57), 255–272. Kamphues, J., Coenen, M., Iben, C., et al., 2009. Supplemente zu Vorlesungen und Übungen in der Tierernährung, 11, überarbeitete Auflage. Verlag M.&H. Schaper, Hannover. Kaya, G., Sommerfeld-Stur, I., Iben, C., 2009. Risk factors of colic in horses in Austria. J Anim Physiol Anim Nutr 93, 339–349. Keller, K.M., Queiroz, B.D., Keller, L.A.M., et al., 2007. The Mycobiota and Toxicity of Equine Feeds. Vet Res Commun 31, 1037–1045. Kirschvink, N., Di Silvestro, F., Sbaï, I., et al., 2002. The use of cardboard bedding material as part of an environmental control regime for heavesaffected horses: in vitro assessment of airborne dust and aeroallergen concentration and in vivo effects on lung function. Vet J 163, 319–325. Liesener, K., Curtui, V., Dietrich, R., et al., 2010. Mycotoxins in horse feed. Mycotox Res 26, 23–30. Liu, Z.P., 2003. Lead poisoning combined with cadmium in sheep and horses in the vincinity ferrous metal smelters. Sci Total Environ 309, 117–126. Mair, T.S., Derksen, F.J., 2000. Chronic obstructive pulmonary disease: a review. Equine Vet Educ 12 (1), 35–44. McGorum, B., 1994. Differential diagnosis of chronic coughing in the horse. In Practice 16, 55–60. McGorum, B.C., Ellison, J., Cullen, R.T., 1998. Total and respirable airborne dust endotoxin concentrations in three equine management systems. Equine Vet J 30, 430–434. Meyer, H., 1979. Bedeutung von Futter und Fütterung bei Koliken des Pferdes. Tierärztl Prax 7, 221–227. Meyer, H, Coenen, M, 2002. Pferdefütterung 4. erw. und aktualisierte Aufl., Parey, Berlin. Müller, C.E., 2005. Fermentation patterns of small-bale silage and haylage produced as a feed for horses. Grass and Forage Science 60 (2), 109–118. Müller, C.E., Hultén, C., Gröndahl, G., 2011. Assessment of hygienic quality of haylage fed to healthy horses. Grass and Forage Sci 66 (4), 453–463. Palacios, H., Iribarren, I., Olalla, M.J., et al., 2002. Lead poisoning of horses in the vincinty of a battery recycling plant. Sci. Total Environ 290, 81–89. Pirie, R.S., Dixon, P.M., Collie, D.D.S., et al., 2001. Pulmonary and systemic effects of inhaled endotoxin in control and heaves horses. Equine Vet J 33 (3), 311–318. Pirie, R.S., Collie, D.D.S., Dixon, P.M., et al., 2003. Inhaled endotoxin and organic dust particulates have synergetic proinflammatory effects in equine heaves (organic dust-induced asthma). Clin Exp Allergy 33, 676–683. Popot, M.A., Garcia, P., Bonnaire, Y., 2011. Doping control in horses: housing conditions and oral recycling of flunixin by ingestion of contaminated straw. J Vet Pharmacol Therap 34, 612–614. Rade, C., Kamphues, J., 1999. Zur Bedeutung von Futter und Fütterung für die Gesundheit des Atmungstraktes von Tieren sowie von Menschen in der Tierbetreuung (Effects of feeds and feeding on the health of the respiratory tract in animals and people handling animals). Übers Tierernährg 27, 65–121.

379

380

Section C  Applied Nutrition – Feeds Rade, C., Koch, W., Leibold, W., et al., 1998. Antibodies against moulds and mites in sera of young horses experimentally exposed to those agents via oral and inhalative challenge. J Anim Physiol Anim Nutr 80, 239–245. Raymond, S.L., Smith, T.K., Swamy, H.V.L.N., 2005. Effects of feeding a blend of grains naturally contaminated with Fusarium mycotoxins on feed intake, metabolism, and indices of athletic performance of exercised horses. J Anim Sci 83, 1267–1273. Raymond, S.L., Heiskanen, M., Smith, T.K., et al., 2000. An investigation of the concentrations of selected Fusarium mycotoxins and the degree of mold contamination of field-dried hay. J Equine Vet Sci 20 (10), 618–621. Riet-Correa, F., Mendez, M.C., Schild, A.L., et al., 1988. Agalactica, reproductive problems and neonatal mortality in horses associated with the investigation of Claviceps purpurea. Aust Vet J 65 (6), 192–193. Robinson, N.E., Derksen, F.J., Olszewski, M.A., et al., 1996. The pathogenesis of chronic obstructive pulmonary disease of horses. Br Vet J 152, 283–306. Rollins, J.B., Clement, T.H., 1979. Observations on incidence of equine colic in a private practice. Equine Pract 1, 39–43. Sacchi, C., Gonzalez, H.H.L., Broggi, L.E., et al., 2009. Fungal contamination and mycotoxin natural occurrence in oats for race horses feeding in Argentina. Anim Feed Sci Technol 152, 330–335. Sargison, N., 1993. Health hazards associated with the feeding of big sale silage. In Practice 15, 291–297. Schmidt, H.L., 1991. Mikrobiologische Richtwerte für die Futtermittelbeurteilung. VII. Int. Kongr. Tierhygiene III, 923–928. Schulz, A., Döll, S., Dänicke, S., et al., 2012. Effects of a deoxynivalenol (DON) contaminated wheat on feed intake and health status in horses. Proc Soc Nutr Physiol 21, 66.

Séguin, V., Lemauviel-Lavenant, S., Garon, D., et al., 2010. Effect of agricultural and environmental factors on the hay characteristics involved in equine respiratory disease. Agriculture, Ecosystems and Environment 135 (3), 206–215. Snell, J.D., 1966. Effects of inhaled endotoxin. J Lab Clin Med 67, 624–632. Traub-Dargatz, J.L., Garber, L.P., Fedorka-Cray, P.J., et al., 2000. Fecal shedding of Salmonella spp. by horses in the United States during 1998 and 1999 and detection of Salmonella spp. in grain and concentrate sources on equine operations. JAVMA 217 (2), 226–230. VDLUFA, 2011. Verfahrensweise zur mikrobiologischen Qualitätsbeurteilung Methodenbuch III, 8. Erg. 2011, VDLUFA-Verlag, Darmstadt. Ward, P., Couetil, L., 2005. Climatic and aeroallergen risk factors for chronic obstructive pulmonary disease in horses. AJVR 66 (5), 818–824. Wichert, B., Nater, S., Wittenbrink, M.M., et al., 2008. Judgement of hygienic quality of roughage in horse stables in Switzerland. J Anim Physiol Anim Nutr 92 (4), 432–437. Wolf, P., Kamphues, J., 2001. Vergiftungen beim Pferd (Horses – have they been poisoned?). Übers Tierernährg 29, 188–197. Wolf, P., Kloetzer, P., Paulus, C., et al., 2009. A survey on the hygienic standard of feeds for horses and its implication for environmental conditions and animal health. In: Briese, A., Clauß, M., Hartung, J., Springorum, A. (Eds.), Proceedings of the XIV ISAH Congress 2009, 1087–1090, Publisher: Tribun EU, Gorkeho 41, Brno, CZ. Wright, R.G., Bebbington, A.M., Boland, G.J., 2009. Assessment of methodologies to quantify respirable fungal spores in hay for horses. J Equine Vet Sci 29 (5), 402–403.