Aspects of Pasture
Contrast this feral horse's dry living environment - and his subsequent blooming good health with the photo below of a domestic horse on an 'improved' grass paddock in a much wetter environemnt.
Photo of feral horse - Nancy Florence Pine Nut Wild Horses
Overgrazed grass as in the above photo, is unsuitable for any horse.
This is grass at a great stage of growth, however unless managed, the quantity consumed can become an issue.
Drought breaking rains create the conditions for very dangerous grass. The cracks in the ground allow oxygen into the soil so when it rains, the microbial populations explode resulting in very high potassium and nitrate levels in the resulting grass shoots.
‘Myco’ is the Greek word for fungus so myco-toxins are ‘poisons or chemicals produced by fungi’.
Fungi or moulds produce myco-toxins when they are stressed by weather and moisture levels. Invisible and insidious, they are produced by endophytes inside the rye-grass and tall fescue.
Some are prolific in humid or tropical conditions, others become a problem in Autumn and spring.
The presence of mould does not necessarily mean the presence of mycotoxins but the trouble is you have no way of knowing.
It is known there are at least 500 different moulds out there producing hundreds of different myco-toxins. Many more are yet to be isolated and identified.
Everyone knows about the Lolitrem B which causes the staggers in late summer and autumn, but more harmful is Ergovaline which can exert a vaso-constricting effect. When blood vessels constrict, blood flow is slowed or blocked. When the blood supply is constricted to the skin you get heat stress because it inhibits cooling of their core body temperature.
When blood supply to the uterus occurs it may cause abortion, to the intestine it can cause necrosis and terminal colic.
Can mycotoxins be picked up in blood tests?
Some myco-toxins can be identified in blood tests, you need to specify which myco-toxin you are looking for. Interestingly so far, horses exhibiting symptoms of staggers who have been specifically blood-tested for the presence of Lolitrem B have all tested negative.
What about low or zero-endophyte rye-grasses?
No strain of rye-grass, even those with the endophytes removed, will ever be suitable for horses because of all the other undesirable characteristics.
The equine species has a digestive system designed to derive nutrition from a continuous throughput of relatively low nutrient density, high fibre forage. They have the opposite requirements to production livestock who are ruminants designed to consume plants at a less mature, higher nutrient density stage of growth for rapid weight gain and milk production.
2. Stage of Growth
3. Mineral Imbalances
4. Crude Protein and Nitrogen
5. Sugars and Starches
6. Fluorescing Pigments
7. Hormonally Active Compounds
Unsuitable species of grass are Cool Season grasses which include all strains of Rye-grass, Clovers and Tall Fescue, whether endophyte free or not. They have a propensity for rapid growth and are inherently high in potassium, crude protein, sugars and starches.
Also UNSUITABLE are the Warm Season HIGH oxalate grasses like Buffel and Setaria. Other species of oxalate grasses can work as long as their oxalate properties are addressed with properly formulated calcium supplement is fed. Link to Australia Oxalate Grasses & Big Head XtraCal.au
The vast majority of grasses ARE suitable for horses when grazed at a mature stage of growth. See Grass Seed Mixes and where to buy them in NZ
Clovers are NEVER suitable for horses and need to be actively eliminated from any pasture sward. These include all varieties and Birdsfoot Trefoil. See Article Clover and Nitrogen
Broadleaf varieties: Plantain, Cardillo Centro Envirogro V8 Stylo and others like Cat’s Ear and CapeWeed which are classed as ‘weeds’ should also be eliminated. While a few plants here and there pose no problem, when they take over the land under certain conditions they cause health issues for our horses.
Stage of Growth
This is influenced by soil, season, weather, fertilisers and grazing pressure.
Be aware that ANY species of grass becomes UNsuitable when:
grown on fertilised soils
grazed at a young stage of growth, particularly after a drought-breaking rain
stressed by frost, drought or over-grazing
riddled with clover, cape-weed, plantain, too many herbs
These directly affect
Electrolyte homeostasis, hormones and metabolism
Nerves and muscles and therefore co-ordination and scope of movement
Brain function, eyesight and behaviour
Growth including skeletal development
Duration of useful life and longevity
All aspects of reproduction
Crude Protein and Nitrogen
Ruminant animals are able to convert nitrogen into ammonia, which can then be utilized by the bacteria in the rumen, for synthesis of amino acids.
Horses CANNOT utilize nitrogen in this way because they don’t have a rumen or the enzymes necessary for this process.
Nitrates still need to be excreted – however, the process of excreting excess nitrates (anions) robs the horse of precious calcium and magnesium (cations) which is a major contributor to horses becoming ‘Grass Affected’.
Horses in their natural habitat thrive on plants growing on unfertile land.
Sugars, Starches & Fructans
While clovers and lucerne store their sugars as starch which is easily digestible, all varieties of rye-grass store their sugars as fructans which horses cannot digest.
High production grasses, which include all strains of rye grass, tall fescue, and even Timothy and Cocksfoot (Orchard grass) can become high in sugars while they are in growth mode.
As grass matures, it becomes higher in fibre as the sugars (non-structural carbohydrates) are converted to structural carbohydrates. This makes it infinitely more suitable for horses. Mature grass is past the soft green and leafy stage and is stalky and hardened off.
These are the pigments present in all grasses but much more so in the dark green ones such as rye-grasses, clovers, lucerne, St John’s Wort, Buttercup and plantain. They give these plants their darker green colour. These pigments fluoresce, are activated by light, and are known to cause photophobia and photosensitisation.
This is the true cause of ‘mud-fever’ AND ‘sunburn’.
When you remove these plants from the horse’s diet these conditions go away and do not recur.
See Skin Conditions
Hormonally Active Compounds
Phyto-estrogens are plant estrogens. When consumed by livestock they can exert potent ESTROGENIC activity thereby seriously hampering reproductive performance.
Red and subterranean clovers, and to a lesser extent, white clover, have a high phyto-estrogen content. Animals grazing pastures containing these clovers can develop fertility and other health problems.