Is Grass Enough for Your Horse?
Hermione Perry MSc Equine Nutritionist
In Britain, the majority of horses have access to plentiful grazing, and as the most cost effective and readily available feed for horses it is easy to understand why many leisure horses are given grass alone, especially during the summer months. However, the horse may appear to be blooming on the outside, but is his paddock really providing him with everything he needs?
Horses evolved as grazing animals and therefore grass has always provided a major part of their diet, but in the wild, horses travel considerable distances to forage and consume a huge variety of herbage. The modern horse kept in an acre paddock, and sometimes even on a ‘starvation’ paddock has a much more restricted diet than his wild counterparts. We may feel that we are providing him with the best possible care, but it is interesting to consider how fit and healthy our native ponies look in the harsh climates in which they live. It is often only when these ponies are removed from their natural habitats that they develop such conditions as laminitis and sweet itch. So are our native ponies actually getting something which the modern horse lacks? And is our modern day pasture really meeting all his needs after all?
We all know that variety is key when giving ourselves a balanced diet, and the same goes for our horses. However, most modern paddocks provide very limited plant species. It is also difficult to calculate the nutrients his grazing is providing as this depends on so many factors. The time of year is obvious, as we all know the grass is richer during the summer than winter, but the season will also alter the mineral and trace element content. The species of grass in the pasture will alter the protein and energy content, and the part of the country and thus the mineral status of the soil affects the mineral content of the grass. How the grass is managed will also affect on its nutritional value. It is also important to consider the horse you are feeding – a youngster or broodmare will have greater needs than an adult, a horse in hard work needs more than an animal at rest etc. Therefore the proportion of your horse’s daily requirements met by his grazing depends not only on the grass he is eating but on his age and lifestyle as well.
Grass Species
In theory, the most fertile pastures can support five, 500kg horses per hectare (approx 2.5 acres) from grazing and conserved forage. Where as a poorly managed paddock may only support one horse. The most productive swords contain at least 30% perennial ryegrass, with rough meadow grass, cocksfoot, timothy and other meadow grasses such as fescue and Yorkshire fog. The proportion of clover depends on the use of nitrogenous fertilizers and grazing pattern but it can be as much as 25%. The stocking density is generally correlated with the amount of ryegrass in the sward. – the greater the concentration of ryegrass the more nutritious the pasture and the more horses it can support.
Time of Year
Within any pasture the nutritional quality varies from area to area and therefore the feeding value of the pasture as a whole depends on the stocking density and the most palatable herbage at any one time. The protein content of pasture is directly correlated with rainfall, and inversely with soil temperature during the growth period. In the UK, the greatest yield of digestible energy and protein occurs during May and June, and from then on this declines particularly from July and August when the grasses flower. Re-growth of succulent leafy material occurs in autumn, but work with sheep suggests that this may be utilized up to 40% less efficiently than spring grass of a similar chemical composition.
The time of year will also affect the mineral content of the grass. A preliminary study performed by Jones, Lax & Holland’s of Dodson & Horrell Ltd showed a significant difference between the mineral content of pasture in the spring (March – June) and the summer (July – September). The aim of the study was to determine whether grass would provide a balanced diet for growing thoroughbreds, and if the season would affect this. They discovered that summer pasture contained considerably less copper, zinc and phosphorus than the growing stock required, which could have serious detrimental effects on musculo-skeletal development if not rectified by a feed or supplement. With the exception of potassium and magnesium neither the spring nor summer pasture provided adequate minerals for growing thoroughbreds.
Vitamins, Minerals & Trace Elements:
In the UK, a calcium deficiency is unlikely among grazing horses even when the ground is poor. In the summer when the ground is parched, the horses will firstly be deprived of water, then energy and protein followed by phosphorus. Horses can become deficient in calcium, phosphorus and magnesium if they are confined to wet, acid soils covered by poor quality grass. Horses seem more resistant to low magnesium than cattle, but a fall in serum magnesium of lactating mares is possible. One of the reasons for low magnesium has been blamed on the increased potassium in the lush herbage which grows in the spring.
The trace element content of grass depends on the trace element content of the soil and it therefore varies naturally across the UK, with clay soils tending to have the highest levels. When waterlogged soils are correctly drained this tends to increase the availability of selenium and zinc but may reduce the availability of iron, manganese, cobalt and molybdenum. Individual trace elements may be deficient or even toxic in some parts of the country. For example, poorly drained soil in Somerset, Ireland and some parts of Devon may lead to copper deficiency which can be identified by loss of pigmentation particularly around the eyes (sometimes known as ‘spectacles’). Soils with a high rainfall, acid pH and water logging often produce selenium-deficient pasture which is sometimes blamed for muscle problems such as azoturia. The Welsh and Scottish borders, north Cornwall and Shropshire are most prone to selenium deficiency. Sandy soil, such as in Newmarket is also selenium deficient. Applying minerals to the soil to correct a trace element deficiency is usually not practical and therefore a targeted supplement is usually the easiest and most cost effective method.
Grass Management
As a horse owner, there are a number of practices you can employ to improve your horse’s pasture.
Harrowing – harrowing grass in the spring will help to aerate the soil and remove dead and matted grass which is clogging up the base of the plants. It is import to help the air to reach the root ball to encourage good grass growth. Harrowing will also spread any droppings which are remaining on the paddock. The benefit this may have on parasite burden is questionable, but spreading the droppings is an effective way of keeping the grass palatable and preventing patches being left due to tainting.
Fertilizers – many horse owners are worried about applying nitrogen as it is associated with the rich pastures needed for dairy cows, and brings concerns of laminitis for horses. However nitrogen is essential as it is vital for healthy plant growth and it is leached out of the soil by heavy rainfall in winter. There are special slow-release fertilizers available for horse specific pastures.
Rolling – particularly when performed after fertilizing will help to push the nitrogen into the soil. It also helps to encourage leaf growth as it gently crushes the growing shoots so that secondary shoots take over. More leaf is produced and combined with the nitrogen this will trigger greater growth earlier in the year.
Topping – horses are fussy grazers and can leave patches which they find unpalatable (particularly if the droppings are not removed). Topping the pasture to a length of 10 – 15 cm will prevent these areas from going to seed and allowing poor quality grasses to take over. If cattle and sheep are kept these animals should be grazed on a rotational basis as they will eat up the areas left by horses and also help to break the worm cycle.
Conclusion
It is difficult to obtain accurate and representative pasture analysis but it is fair to assume that if your horse is having no hard feed or supplements whatsoever it is likely that his diet will not be providing a balance of all the vitamins and minerals. This is particularly crucial for pregnant mares and growing young stock who’s demands for minerals are so much greater. With this in mind, the use of a mineral lick will give you peace of mind that your horse has access to everything he needs. All mineral licks from Brinicombe Equine are manufactured by a unique low-molasses process. This ensures that the Lick is low sugar, non sticky, weatherproof but still extremely palatable. We have a range of licks to suit every horse's needs:
Think Fly Lick - vitamins and minerals combined with our unique fly deterrent
Think Laminitix Lick - vitamins and minerals with targeted nutrients for horses prone to the effects of spring grass
Think Complete Lick - our highest specification vitamins and mineral lick, recommended for all horses including broodmares and youngstock
HerbiLIX Original - The economic broad spectrum lick
HerbiLIX Airways - The economic broad spectrum lick with added eucalyptus, menthol and herbs for clear airways