by Joel Bagg, Forage Specialist, Jack Kyle, Pasture Specialist & Melanie Beech, OMAF and MRA
Well managed horse pastures can contribute significant forage to the diet, while providing necessary horse health benefits, fulfilling the horse’s psychological need to graze, and minimizing the risk of poisonous weeds. Too often we see over-grazed horse pastures, filled with weeds and bare patches. A common problem is a lack of enough pasture acres to avoid over grazing. As a general thumb rule, at least 2 – 3 acres per horse is required if you expect pasture to provide all of the necessary forage for the season. Also, horses can be difficult graziers. Horses will typically overgraze some areas of a paddock by biting plants very close to the ground, while leaving other areas relatively untouched. Overgrazing weakens and eventually kills forage plants, and weeds become established in their place. Horses prefer not to graze grass that is too tall. Good management is required to balance the needs of the forage plants with the needs of the horses.
Implementing a system using sacrifice paddocks, rotational grazing and proper maintenance with mowing, harrowing, weed control and fertility management can improve pasture quality, and provide more forage for grazing horses.
A sacrifice paddock is an area where horses are fed hay during conditions that are unsuitable for horses to be turned out on pasture. This includes wet periods, such as spring and fall, where horse hoofs will turn wet pasture soils to mud and destroy plant growth. Sacrifice paddocks should also be used when there is not enough pasture forage available to avoid overgrazing, such as during dry summer months. When pasture growth is limited, it can be rationed by confining horses to a sacrifice paddock for part of the day. This provides horses with a chance to be ‘turned-out’ and get exercise without ruining the pastures. Rather than destroying the whole pasture, damage is limited to the sacrifice paddock. It may seem counter-intuitive, but feeding hay to horses in a sacrifice paddock rather than letting them overgraze actually saves hay in the long run.
A good location for a sacrifice paddock is close to the barn. It may include a run-in shelter, and should be connected to the pasture fields. Water and hay should be provided in sacrifice paddocks. Avoid wasting hay by using a well-designed hay feeder. Research shows that more than half the hay is wasted when fed on the ground. Eaves troughs and proper drainage are extremely important in sacrifice paddock design to minimize mud and health issues, such as thrush. Sand can be added to the surface, and sometimes a crushed stone base and specialized footings around waterers is included.
Rotational grazing is the practise of moving horses from pasture to pasture to allow forage plants time to rest and re-grow. If pasture stands are overgrazed, the leaf area of the grass will be greatly reduced so the plant will not be as able to photosynthesis solar energy into re-growth. Overgrazing will also lower carbohydrate stores in the roots, further limiting re-growth and plant health. Overgrazed, stressed grasses store more sugars as fructans, which can lead to founder or other metabolic diseases in some horses.
Pastures should be about 6 – 8 inches tall before horses are turned in to graze a new paddock. Horses should be removed from paddocks when the pasture stand is grazed to about 3 – 4 inches in height. (If it is predominately bluegrass, 5 – 6 inches at move-in and 2 – 3 at move-out.) Mowing at 4 – 6 inches to remove seed heads and weeds, and harrowing to spread manure piles, should be done shortly after the horses are rotated out of the pasture.
The paddock “rest period” requirements will depend on plant growth. In the spring with rapid growth it might take about 2 – 3 weeks for pastures to re-grow, while in the hot dry summer it may take 4 – 6 weeks or more. A good rotation has 4 paddocks that are rotated on a weekly basis. While this may not be possible on some farms with limited paddocks, keep in mind that some rest and rotation of paddocks is better than none at all.
A number of paddocks will often need to be built in order to implement a rotational grazing system, especially when there are multiple groups of horses. It will be necessary to work within your budget. To reduce high fencing costs, consider whether temporary interior electric fencing can be used to create more paddocks and laneways. Exterior fences and sacrifice paddock fences need to be more substantial.
Where rotational grazing in not practical because of unsufficient paddocks, the success of continuous grazing can be improved by the use of sacrifice paddocks when needed, regular mowing, and having sufficient acreage per horse to avoid overgrazing.
Horses are often turned out on to pastures too early in the spring, resulting in a lot of damage to wet soils and immature pasture plants. This severely reduces the amount of pasture growth available for the rest of the year. Also, early spring grass growth is typically very high in non-structural carbohydrates that can increase risk of colic, laminitis and insulin resistance. Reintroducing spring pasture to horses after winter should be done gradually. When the ground is firm and grass growth is about 6 inches tall, horses can be put on pasture for a brief period of time and then gradually increased.
The mixture of forage species present in a horse pasture quickly adapts to the level of management. There is no perfect forage grass species. In a continuous grazing system with high stocking rates, species that we use for hay, such as timothy, smooth bromegrass, and alfalfa that cannot tolerate frequent, close grazing will weaken and eventually disappear. Bluegrass and white clover tolerate frequent, close grazing, so they tend to become dominant, along with ungrazed weeds. Grass species with a good balance of persistence, yield and palatability in horse pastures include orchardgrass, Kentucky bluegrass and endophyte-free tall fescue.
Kentucky bluegrass is lower yielding and goes dormant during the hot, dry summer, but spreads with rhizomes and creates a turf that is fairly resistant to horse traffic. It is very palatable.
Orchardgrass is a bunchgrass that tillers well (forms new shoots) and can be very productive, but requires clipping in the spring to remove seed heads. Like most grasses except timothy, once the seed head is clipped, subsequent growth is vegetative leaf.
Tall fescue is also used in Ontario horse pastures, especially where overgrazing and traffic damage can be an issue. It can sometimes less palatable, but grows well in the summer and fall. Only recommended endophyte-free tall fescue varieties should be used (www.goforages.ca).
If a legume is desired to provide nitrogen, only a very small amount of white clover should be used. White clover is very competitive in horse pastures, spreads with stolons, and can take over and dominate other grass species. The grazed leaves of white clover are very high in digestible energy, which can be an issue with high risk laminitis and insulin resistant horses.
Weeds proliferate in overgrazed pastures, so good pasture management (sacrifice paddocks, rotation, mowing, fertility, drainage, etc) goes a long way in controlling weeds. A good working knowledge of common horse pasture weeds is useful. These include annual weeds such as ragweed and wild mustard, biennial weeds such as burdock, and thistles (scotch, nodding and bull thistle), and perennial weeds such as milkweed, Canada thistle, and goldenrod. It is very important that pastures be scouted for weeds that are potentially poisonous to horses, such as poison hemlock, horsetail and buttercup. Refer to “Weed Control In Ontario Horse Pastures” https://fieldcropnews.com/?p=7899 and www.omafra.gov.on.ca/english/livestock/horses/forages.html.
Effective mowing removes seed heads before weeds develop viable seed. This prevents reproduction in species that reproduce only by seed, but is less effective in perennial species that can reproduce by underground roots and rhizomes. Low growing, prostrate weeds are difficult to control by mowing because they can grow and flower below the mowing height.
For pasture herbicide options, refer to the “Guide To Weed Control”, (OMAFRA Publication 75, pp. 165-167, 175-178 www.omafra.gov.on.ca/english/crops/pub75/chapter10.htm). Be sure to consult the product labels for directions, including the period of time to keep livestock out of treated areas.
Broadleaf herbicides, such as 2,4-D, dicamba, and MCPA, can be used to control many broadleaf weeds. However, they will also injure or eliminate broadleaf legumes such as white clover, so they should be limited to straight grass pastures only. Small-boom 12 volt sprayers are commercially available that are suitable for smaller horse paddocks and gates, and can be used with an ATV or small tractor. Ontario farmers must be certified through the Grower Pesticide Safety Course to purchase and use Class 2 and 3 Pesticides on their own farms. For information on certification, refer to www.opep.ca/.
Spot spraying of glyphosate with a back pack sprayer can be done to control thistles, burdock, milkweed, etc. Glyphosate is non-selective, so will also kill desirable forage species. Where larger patches are inadvertently killed with glyphosate, weeds tend to germinate and regrow in these bare areas.
Regular mowing is very important in managing healthy, productive horse pastures. Access to mowing equipment is essential to good horse pasture management. Mowing at a height of 4 – 6 inches is a good strategy to control many weeds, “even out” grass growth, and encourage the tillering of forage grass species to thicken the stand. Mowing should be done a minimum of 2 – 3 times per year. In rotational grazing situations, mowing should be done after each grazing rotation (at the start of the rest period). Horses are selective graziers and graze certain areas more than others, so mowing will even out the forage stand. Horses prefer to graze younger shorter growth and immature plants. They will avoid taller, more mature plants, and also areas where manure and urine are present. As these ungrazed plants mature, they decrease even more in nutrient availability and palatability.
Grass growing around manure in pastures is usually left ungrazed. To eliminate this problem, pastures can be harrowed or dragged at the beginning of the rest period. This spreads the manure more evenly across the pasture. Manure is then broken down by insects and microbes more quickly and nutrients are returned to the soil for plant availability. There are significant agronomic advantages to harrowing, but the practise has become controversial.
A disadvantage of harrowing manure in horse pastures is the potential of increasing the risk of parasite contamination through ingestion of fecal matter. This is becoming more of an issue as internal parasites develop resistance to commercial dewormers. Parasite eggs and larvae can live for a considerable time in manure, soil and plants. Harrowing on hot, dry days at the beginning of the rest period to kill parasites in pastures will reduce the risk. Horses should be kept off pasture for at least a week to reduce the presence of parasites, but longer is better. Consult your veterinarian to discuss a deworming program for internal parasites that includes regular fecal egg counts, strategic selection and use of deworming products, and pasture management.
Soil Testing and Fertilization
Proper fertility improves yield and health of pastures. Taking a representative soil sample and sending it to a lab for analysis helps determine fertilizer requirements. A basic test includes pH, phosphorous (P) and potassium (K) levels. There is not an accurate soil test for nitrogen (N), but N as urea can be applied based on the potential productivity of the stand in split applications (early-spring, June and possibly late-summer). When applying urea, remove horses from the pasture for a few days, or until rainfall. P and K application levels are determined by the soil test results. A list of OMAF accredited soil laboratories can be found at www.omafra.gov.on.ca/english/crops/resource/soillabs.htm .
Pasture Renovation Or Re-establishment
There will be times when pastures will thin and bare ground may start to appear in parts of the field. It may be possible to renovate or rejuvenate a poor pasture without ripping it up and starting over by re-establishment. Simply giving the pasture a rest by removing the horses, fertility and weed management, and mowing may help to some extent. Seeding poor areas with desired pasture species can be done to renovate them. Fall seedings are best done in late-August or early-September. Spring seedings should be done in late-March or April. Using a no-till drill is the best option, but these can sometimes be difficult to use in horse paddocks. Broadcasting can work only if there is good seed-to-soil contact. To prevent seedling damage, it is important to keep horses out of newly seeded pastures until the grasses are well established.
Pasture re-establishment will require a longer rest period that may eliminate horses from grazing that pasture for an entire season. Re-establishing a pasture usually means killing the existing stand and weeds using glyphsate, then reseeding using a no-till drill or tillage and a conventional drill or brillion seeder, and providing broadleaf weed control.
Proper horse pasture management requires more work and attention than just throwing horses out into ‘their fields’ day in and day out. It ultimately provides horse owners with the economic benefits of reduced hay requirements, and healthier horses.