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Pasture Management |
Alternative Veterinary Medicine Centre |
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Pasture Management1. HORSES & PONIES (also Donkeys)BackgroundModern horse pastures suffer two common problems. The first is that they are over-grazed by horses, usually without the benefit of other grazing herbivore species during the year. The second is that, in the post-war thrust for home food production, the idea of grassland 'improvement' has been to spread artificial nitrogen on grassland, to use herbicides both to discourage ‘weeds’ and to encourage grass and to reseed with a narrower band of grass species. The main advisory bodies and colleges have inherited their basic culture from this government-led self-sufficiency drive for farm land and, now that farming has declined in the UK and horse-keeping has increased, such organisations are turning to advising horses for their income. Sadly, the policy has not changed, to recognise and to take into account the crucial differences in dietary needs between simple-stomached herbivores, such as the horse on the one hand and ruminant herbivores, such as cattle, on the other. The result is that colleges, advisory bodies and current farming wisdom propose using artificial nitrogen to promote grass growth. It does promote grass growth very well indeed, but at the expense of wholesome nutrition in the case of horses. It can even cause toxic side-effects for horses. Practical ApplicationWhat actually happens is that the rich diversity of plant species, once a feature of traditional grassland, is giving way to a very limited number of species, mostly selected grasses (e.g. ryegrass* - Lolium spp.). This grass is then top-dressed with artificial nitrogen, which displaces the trace mineral cations (e.g. copper, zinc, manganese) from the clay micelles of the soil (this is a known chemical effect). The very next rain washes away those minerals (this is a demonstrable consequence of such management). Furthermore, the soil microflora has been damaged. Yes, the grass looks green. Yes, the grass is thick and lush. It is, however, nutritionally nowhere near in the same league as traditional grass, even ignoring the tragic loss of species diversity and the absence of essential, deep-rooting herbs. The topsoil has been increasingly impoverished over the years, as a result of such short-sighted policies. Knowing the importance of minerals to nutrition and health, we can easily predict what a disaster for the horse this process is. Another important penalty is that non-structural carbohydrates in grass are increased and non-protein nitrogen compounds (both potentially toxic families of compounds) are increased, while important fibre (structural carbohydrate) is decreased, in response to artificial nitrogen application. One clear result of all this, apart from the poor nutrition that ensues, is that ponies (and, to a lesser extent, horses) are much more prone to laminitis, when grazing such 'improved' grassland. Furthermore, Potassium levels in growing grass are increased, while Magnesium levels are decreased. This can result in more excitable, jumpy horses, showing greater anxiety and unpredictable behaviour. Herbicides appear to be very dangerous for horses. We have even had several bad cases of laminitis following application of a common 'livestock safe' herbicide to nettles. The problem appears to occur when horses eat the wilting nettles. Apart from the benefits to botanical and invertebrate biodiversity and to the dependent ecology in general, a variety of herbage in the sward is valuable for grazing horses. Deep-rooting 'weeds' can bring up all-important minerals from deeper soil layers. Dandelions, for example, are very good at this and are very palatable. Nettles are a good 'weed' to have around the edges of the pasture. They act as host to various butterfly species and, when cut, offer wonderful nutrition, including minerals, to horses, being very palatable when wilted. Conserved forage is also subject to similar problems. Hay, haylage and dried grass will vary in suitability for horses, depending upon the management during its growing period. Contrary to current popular belief, horses will fare better on meagre unfertilised traditional pasture than on lush, productive 'modern' or 'improved' pasture. Horses are accomplished fibre-converters and dried-looking pasture in late summer is much more beneficial to them than its luxuriant, well-fertilised counterpart. The AVMC is very willing to advise on grassland management for health and on nutritionally compensating the horse for the ill-effects of the above methods, should the client wish. 2. RUMINANTS Although the grass loses nutritive value (vitamins and minerals), in response to top-dressing with artificial nitrogen, grass bulk production increases. Ruminants are better able to handle the resultant non-structural sugars and non-protein nitrogen compounds than horses, so they become more productive, when grazing this sort of pasture. They become more prone to hypomagnesaemia (grass staggers), however, when the grass responds to fertiliser application. Modern production animals now require massive supplementation with trace minerals, to compensate for the lowered nutritional value of 'improved' grassland, if they are to remain healthy. Relative deficiencies of manganese, zinc, copper, cobalt, iodine and selenium are common and widespread problems. The application of modern chemicals to grassland not only directly depletes the soil of trace minerals and major minerals but it also narrows the species diversity, especially of deep-rooting plants, thus exacerbating the problem. We have seen a cow with rumen atony, which eventually died, following ingestion of sprayed nettles (despite the chemical being labelled 'livestock safe'). See also: Poisonous Plants
(& 'unfriendly' plants) *Italian Ryegrass (Lolium multiflorum) is generally recognised as the highest yielding species but only provides two-year leys. Perennial Ryegrass (Lolium perenne) is a very common and often dominant species in pasture seed mixes. Copyright ©
AVMC - March
2007 |
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