With regard to horse pasture management and worm parasite burden we are often asked about the effects of the weather and intervention such as harrowing. Harrowing grassland can be very beneficial for the actual grass as it pulls out dead grass making room for healthy new growth, also if the land has deposits of manure on it the droppings are broken up and therefore the rotting process is sped up. However, unless the weather conditions are very favourable, harrowing used horse paddocks will simply help the worm eggs to spread themselves evenly over the entire area harrowed. This could nullify the natural “roughs and lawns” (toilet and grazing areas) that the horses themselves have developed. For harrowing to be really effective, a long period of sunshine combined with no rainfall is required, meaning summer time is the best opportunity to harrow land.
To reduce worm egg burden on the pasture an effective method of dung removal should be employed, baring in mind that an average 500kg horse produces about 10 tonnes of manure per year. Collecting the droppings could be a part of your daily routine but in reality every other day is sufficient and weekly should do the trick in winter if that works better with your weekend activities.
Rotating the pastures is one way of reducing the number of worm larvae on the grass. The larvae are very tough and capable of resisting many things thrown at them, with some surviving years. You can never be sure that old pastures are clean but if you rest them completely you give nature a chance to catch up. There is no set answer to how long you should rest your pastures, but we have to be practical so a good start would be 6 months, and introducing other species on the pasture such as cattle and sheep will help as they will “hoover” up and break the life cycle of the equine parasites.
The British Horse Society (BHS) recommends between 0.4 and 0.8ha (1-2 acres) of pasture for each horse during the summer, but other factors come into play such as the individual needs of the horses and the varied level of grass production. When it comes to just the appearance, over grazed pastures look poor and if the grazing is not good then horses will be ingesting more soil particles and all that they contain thereby increasing the worm burden.
When it comes to young stock, pasture management is even more important. Ideally foals should not be grazed alongside older horses as foals are a major source of pasture contamination and require more regular worming than the adults they share pasture with. If possible, each season a new area should be available for foals that ideally did not have foals on the year before. Try not to use small turn out paddocks for foals as pasture will develop extremely high larval counts but if this is not practical, ensure that droppings are removed each and every day.
Methods such as strip grazing also have a role to play but remember there are many different varieties of grassland and horses thrive on good quality mixed grazing. Weed control is also vital to provide safe grazing, if you are in any doubt contact a professional advisor with regard to fertilising and such things as ragwort treatment and disposal.
Laminitis, obesity and such problems as colic are all things to consider when selecting your grazing plans as they all have a direct correlation to grass intake and should any such issues arise then again seek professional advice to help with your pasture management.
In a nutshell horse owners have to take many factors into consideration to get the best for their stock. We don’t live in a perfect world and there is no single answer to the best pasture management, it is more a case of looking at all the circumstances and formulating a pasture management plan that fits in with the different horses on the land.