Toxin Binders & Why Your Horse Needs Them
TOXIN BINDERS & WHY YOUR HORSES NEED THEM
Why do your horses need a Toxin Binder?
There has been considerable research conducted in relation to pasture related mycotoxin effects in livestock but very little with regard to horses. Due to this gap in available research, we can only draw from the information that is known about mycotoxicity in other livestock and use a proactive approach to ensure the likely effects of these toxic substances on our horses are eliminated or minimized as much as possible.
In this section, we will explore the symptoms seen in other livestock, the causes, and treatment options for our equine partners.
Facial Eczema is well-known in sheep particularly, due to the severe it's effects on the health of the animal. Cattle can also be affected by FE but it is not officially recognized in horses as Facial Eczema but similarities do exist.
What is fairly common knowledge these days among horse owners is "Grass Staggers". In some countries, this is known as "Drunken Horse Disease".
Some of the many symptoms of mycotoxicity show as:
- Mild to severe staggering,
- Falling over and the horse is unable to rise,
- Overly reactive to noise,
- Flinchy skin and irritation when touched
- Photosensitivity in the form of constantly seeking shade
- Photosensitive skin reactions such as mud fever
Rye Grass Seed Head
Ryegrass staggers is caused by the presence of Neotyphodium lolii in perennial ryegrass (Lolium perenne) and fescue toxicosis by the presence of N. coenophialum in tall fescue (Festuca arundinacea). N. lolii produces at least three major groups of toxins: tremorgenic indole diterpenoids such as paxilline and lolitrem B; ergopeptine alkaloids such as ergovaline and the herbivorous insect repellent compound peramine. N. coenophialum does not produce significant amounts of the tremorgenic toxins but does produce the ergot alkaloids, peramine and high levels of lolines. Other grassendophyte associations cause a number of other well known problems including sleepy grass syndrome (302 Towers – MYCOTOXIN POISONING IN GRAZING LIVESTOCK (USA) (Petroski et al., 1992), drunken horse disease (China) (Miles et al., 1996), and less well-defined problems associated with livestock consuming grasses native to Australia, New Zealand and South America (Cheeke, 1995; Miles et al., 1995a,b, 1998).
Paspalum staggers, although once common when many pastures were paspalum-dominant, is an almost forgotten problem of sheep and cattle grazing tropical or subtropical Paspalum spp. which have been allowed to flower, and the inflorescence has been infected with Claviceps paspali (Lacey, 1991). Paspalum staggers is caused by indole diterpenoid tremorgens, known as paspalinine and paspalitrems A-C, that are structurally related to paxilline and the lolitrems and, as might be expected, the symptoms of paspalum staggers are very similar to those of ryegrass staggers.
Fusarium species which are known to produce the oestrogenic compound, zearalenone, are common in pastures throughout New Zealand (di Menna et al., 1987), and relatively high concentrations of zearalenone (0.5-5 mg/kg pasture dry matter) may be found in the autumn months (February-May), coinciding with the sheep mating season (Sprosen et al., 1995). Zearalenone intakes exceeding 1 mg per day adversely affect reproduction in sheep, the effects becoming more severe at higher intakes and/or longer periods of exposure (Smith et al., 1990a, 1992a). Other details are given by Smith & Morris (2006). Ingestion of zearalenone-contaminated pastures can be readily detected by analysing urine for the presence of the metabolites, α- and β- zearalenol, which increase in concentration in
proportion to the amount of toxin ingested. Analysis of urine samples from throughout New Zealand suggest that more than forty percent of sheep flocks are exposed to sufficient zearalenone to reduce ovulation rates, and thence lamb birth rates, causing significant production losses in affected flocks (Sprosen et al., 1995).
OTHER PROBLEMS POSSIBLY CAUSED BY MYCOTOXINS
There are a number of other animal health and production problems which may be caused by mycotoxins. Before they are accepted as being mycotoxicoses, confirmation is required that not only are toxin-producing fungi present but also that sufficient toxin is produced and consumed by the animals to cause an intoxication. Furthermore dosing the toxin should cause the same symptoms and pathology as observed in field outbreaks of the disease.
(i) Zearalenone and cattle infertility problems High concentrations of zearalenone in pasture, and of zearalenol in urine and blood, have been found in herds with poor reproductive performance (Sprosen & Towers, 1995). However, as the samples were collected in January or February, when veterinary examination revealed low pregnancy rates, some months after mating in spring (October, November), the data do not necessarily reflect a cause and effect relationship between high zearalenol levels in the blood and the fertility problems. Indeed, given that pasture zearalenone levels are generally low when cattle are mated, it seems that a direct effect on ovulation rates, similar to that found in sheep, is unlikely unless cattle are exceptionally sensitive to zearalenone.
(ii) Autumn ill-thrift
Many Fusarium species found in pasture produce not only zearalenone but also a wide range of trichothecene mycotoxins known to be toxic to animals (Lauren et al., 1992). Autumn ill-thrift occurs during the same season as high zearalenone and Fusarium levels are found. The possibility that Fusarium produce trichothecenes in sufficient quantity to affect animal health and performance has been investigated using ELISA assays for deoxy-nivalenol (DON) and nivalenol (NIV), two trichothecenes commonly produced by New Zealand isolates. Litherland et al. (2004) found that on every occasion (10 out of 70 pasture analyses) when NIV and DON levels were above 0.8 mg/kg dry matter, both calves and lambs grew more slowly than expected from the quality and quantity of the pasture available. However preliminary studies dosing lambs with extracts of Fusarium cultures containing DON or NIV suggest that pasture concentrations of these toxins would need to be much higher (i.e. 10-50 mg/kg dry matter) before they would affect the health or growth of ruminant animals (Odriozola, 1996). A cause and effect relationship has not been established and an alternative explanation might be that the high DON and NIV levels are merely markers for the presence of an unidentified, but more potent, toxin.
(iii) Kikuyu grass poisoning
Ill-thrift, illness and death amongst sheep and cattle grazing kikuyu pastures have been reported occasionally for many years. The aetiology Proceedings of the New Zealand Society of Animal Production 2006, Vol 66 303 of the disease has never been resolved but the striking similarities between kikuyu poisoning of cattle and the clinical and pathology findings after dosing cultures of toxin-producing strains of Myrothecium verrucaria and M. roridum to cattle and sheep have been noted (di Menna & Mortimer, 1971; Martinovich et al., 1972). However, the toxins have never been isolated from pasture in any quantity and the intermittent occurrence of the disease has hindered research so that a cause and effect relationship has not been established.
There are a number of strategies for preventing mycotoxicoses:
1. preventing or reducing toxin intakes,
2. protecting the animal against ingested
3. breeding more resistant animals.