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21st November 2011
- Managing pasture to reduce the risk
The full version of this document can be downloaded from www.rirdc.gov.au
What the report is about
This report explains how environmental conditions can trigger three-fold increases in the sugar, starch and fructan (collectively called non-structural carbohydrates or NSC) content in pasture plants and hay. Horses and ponies consuming pasture excessively rich in NSC can develop laminitis. The owners of horses and ponies prone to laminitis, and feed producers catering to such animals, need to understand how to manage pasture and hay crops to decrease NSC concentration and thus minimise the risk of laminitis. They also need to understand under which conditions pasture or hay NSC content become so dangerous that access for high risk animals should be limited or eliminated. It is important to realise that the success of most pasture improvement programmes is measured against increased meat, fibre and dairy production in farm animals other than horses. Increasing the readily available carbohydrates in pasture and hay is thus a primary focus of modern production based agriculture. However the resultant increased amounts of NSC has made some pastures inappropriate and dangerous for horses and ponies prone to obesity, insulin resistance and laminitis.
Who is the report targeted at?
This report is targeted at the owners of horses and ponies so that they can make informed decisions about pasture management and to more safely feed animals prone to laminitis or obesity. It is written for those horse owners who are prepared to make a serious effort to learn how to grow the 'best' pasture, and seek the 'best' feed to prevent and manage laminitis.
Laminitis is a leading cause of death in horses and makes a significant financial and emotional impact on the horse industry. Recent studies show that insulin alone can induce laminitis in horses and ponies thus implicating as causal factors those dietary carbohydrates that have an insulin stimulating, metabolic impact.
Fermentation of fructan in the equine gut releases laminitis trigger factors and may induce laminitis. High insulin concentration in the blood (hyperinsuliaemia) and fermentation of excess fructan in the hindgut act separately or in concert to trigger laminitis. For detailed knowledge on equine laminitis consult the RIRDC companion volume "Equine Laminitis - Current Concepts" Publication No.08/062.
Most grasses in tropical and sub-tropical regions of Australia are of a type that does not contain fructan. However, they contain high levels of sugar and starch, especially in conditions of intense sunshine, drought or cold stress. Temperate region grasses can contain high levels of all the NSCs (sugar, starch and fructan) especially under intense sunlight accompanied by cold stress or nutrient deficiency.
This booklet aims to provide strategies based on principles of plant science. Grass grown under less stress will have reduced NSC concentrations. The use of a sacrificial area and preservation and re-introduction of native grass pastures that are inherently lower in NSC will decrease the risk of laminitis by reducing NSC intake. Some pasture management practices that minimise pasture NSC also happen to be important features of environmentally friendly, sustainable land stewardship. Grazing horses in wooded areas that limit exposure to sunlight is an easy way to provide low NSC pasture. The planting of trees to provide shade can lower NSC in pasture, whilst controlling erosion and improving hydrology. Some practical methods for minimising pasture NSC are provided, such as timely slashing, proper fertilisation and avoidance of pastures species that have high genetic potential for excess NSC accumulation under stress. Weed control, rotational grazing, appropriate fertilisation and de-stocking of pastures during drought are also discussed as methods to minimise pasture NSC. Laminitic horses will benefit first. Later generations of Australian land owners may benefit as well.
The existing forage science literature is reviewed to provide the reader a better understanding of carbohydrate metabolism in grass. The authors consulted widely with the managers of horse and pony establishments to understand the association between laminitis and the pastures growing in Australia.
When grass is considered 'the enemy' by the owner of a horse with laminitis, the strategy of deliberate overgrazing to limit grass intake, is sometimes adopted. This is misguided and may lead to 'horse sick' pastures that are prone to erosion, soil compaction, degradation of soil fertility, weed infestation and accumulation of parasites. All too often, these tactics fail. The possible reasons for these failures are explained here.
Implications for relevant stakeholders
Traditional graziers are selling off tracts of land near cities as 'lifestyle acreage' for people seeking a more peaceful, rural way of living. These new land owners often acquire horses, donkeys and ponies for recreation or pasture ornamentation. Many receive pasture management advice directed towards maximising NSC production and thus weight gain in cattle and sheep. Future projects directed towards developing sustainable pasture management programmes for lower, rather than higher NSC content in pasture, for the owners of nonathletic, grazing horses would be beneficial. It would lower the incidence of pasture associated laminitis and provide an opportunity to develop environmentally responsible land stewardship. A better understanding of the links between pasture consumption and laminitis will lead to a more unified approach and rational preventive and treatment strategies, by owner, veterinarian and farrier alike.
The lack of affordable, accurate testing for NSC in feed and forage in Australia is a hindrance to horse owners trying to limit sugar, starch and fructan levels in their animal's diet. Implementing appropriate analytical laboratory procedures in Australia for quantification of NSC, would benefit all animal managers. It would help those maximising pasture NSC for improved production animal weight gain, as well as those seeking low pasture NSC to more appropriately feed horses and ponies prone to or already suffering from laminitis. Feed producers catering to horse owners could manage pasture and hay crops to decrease NSC concentration and make them safer for horses and ponies with a risk of laminitis. With appropriate validation and labelling, such laminitis accredited horse feeds may be a profitable business opportunity. Likewise the production of seeds that result in low NSC pasture suitable for laminitis prone horses and ponies may have a niche market. Contained in this report are recommendations enabling horse and pony owners to make informed management decisions on a daily to annual basis. Perhaps in the future, these recommendations can be tested and refined, based on properly conducted scientific studies.
NOTE - This is an extract from the document which can be found and downloaded from www.rirdc.gov.au