Ray Smith, PhD, professor and forage extension specialist in the University of Kentucky Department of Plant and Soil Sciences, gave a talk on pasture quality impacts on yearling horses during the second session of UK’s 10th annual Equine Research Showcase Jan. 19. The session highlighted nutrition and pasture topics appropriate for weanling to yearling horses. Presenting sponsors for the event included BET, Kentucky Performance Products, McCauley’s, Merck, Rood & Riddle Equine Hospital and Tribute Equine Nutrition.

With information given from research and observation on farms, Smith covered topics from establishing horse pastures, soil fertility and managing horse pastures. He maintains that that good management mixed with good pastures can lead to quality forage for growing horses, reduced hay and grain feeding and a lovely view.

Beginning with stages of pasture management, Smith introduced the concept of establishing horse pastures. Ideal horse pastures have at least 80% desirable forages and less than 20% undesirable forages.

“In the central Kentucky region, we would count desirable forages for weanlings as tall fescue, Kentucky bluegrass, orchardgrass, white clover and ryegrass,” Smith said, “Less than 20% should include broadleaf weeds, weedy grasses like nimblewill, johnsongrass, foxtail and bare soil.”

Smith explained that the average Kentucky horse pasture is 55% desirable forage, in comparison to the 80% rating that is recommended. To understand why that is, Smith discussed soil fertility and what that means for a pasture.

“The standard recommendation is to sample your soils every two to three years. Ideally, you’ll use a probe you can purchase online or borrow from your county agent, because it takes a cylindrical core of the soil that provides the same amount of topsoil as it does the deeper soil. I recommend going 4 inches deep and 10-20 samples per pasture,” Smith said.

Depending on the results, it is suggested that horse owners and horse farm managers apply the recommended amounts of phosphorus, potassium and lime. If assistance is needed to interpret the recommendations, Smith encouraged the people to contact their county agent or a consultant.

Nitrogen is another essential nutrient for pasture production. Specifically, for Kentucky’s cool season perennial grass pastures, Smith gave nitrogen recommendations of 60 to 80 pounds of urea per acre (30-40 pounds of actual nitrogen) in late September and in late October or double this amount with one application in mid-October. This increases the regrowth of the pasture but doesn’t lead to excess production.

Smith said horse owners and horse farm managers should not try to balance diets by applying fertilizers to fields, for example adding a type of product to increase micronutrient levels in the grass. It’s much easier and more dependable to provide micronutrients through mineral supplementation.

Smith said a question he often gets pertains to overseeding an existing pasture to thicken up the stand. Doing this is possible, but it is important to note that for this to work, there must be some bare soil. Mowing or grazing close before seeding is also important, due to having less competition for the growing seedlings. Planting species that do well in shade, such as orchardgrass, also proves to be beneficial, because as the surrounding growth matures, it still allows the new seedlings to grow. If overseeding is the route that is being taken, Smith suggested to overseed in early September and to watch the depth closely. If planted deeper than ¼ to ½ inch, the seedlings may not emerge from the soil.

Smith encouraged horse farm managers to consider a complete renovation for problem fields. If the pasture has too many weedy species and has proven difficult to recover, it may be necessary to completely start over. Doing this requires removing all competition from existing plants. This can be accomplished with two killing sprays of glyphosate at a high rate in early July and in mid-August or repeated tillage. Then seed perennial mixture to establish the new stand in early September.

When establishing a new pasture, it is important to note that high-quality, improved seed should be used as well as planting enough of it at the right time. Using the best seeding method available and controlling the competition are other ways to promote new growth. Following this, rest is needed for a few months, as it takes six to 12 months for a newly seeded stand to develop a good sod.

Showing diagrams of seedling root growth between types of grass, Smith weighed the options of annual rye, perennial rye, tall fescue and orchardgrass.

“My point here is if you want a quick pasture, annual rye would be the best of these four. But it’s only going to live until the following summer, so it is very short term. Perennial rye grass in our area is another quick establishing pasture but has about a two-year window,” Smith said.

Therefore, he said, for long term perennial pasture, use orchardgrass and Kentucky bluegrass and consider including one of the new novel tall fescue varieties for added durability.

When discussing management of horse pastures, Smith said the goal is to match grazing to seasonal growth.

“Cool season grasses grow best in the spring and the fall, and stocking rates should be reduced during the summer months. There’s a slump in the growth there, sometimes referred to as the summer slump period. For intense summer-only grazing, establish a grass like bermudagrass or even crabgrass. The limitation with crabgrass is that it is an annual grass, so it would have to be seeded every year. We typically don’t recommend either of these in Kentucky because they have a fairly short summer growing season. So, we like to focus on good management of cool season, perennial grasses,” Smith said.

In managing pastures, one of the strongest recommendations from Smith was to look for ways to employ rotational grazing. A video example was provided that showed two orchardgrass plants, one employing rotational grazing and one continuous. The rotational grazed orchardgrass showed significantly more growth after one month, than the plant simulating continuous grazing.

Smith also talked about stocking density, or the average animals per acre for a growing season, and stocking rate, or animals per acre at any one time. For Kentucky, he suggested 2 acres per 1,200 pounds or about 1 acre per yearling (rotationally grazed).

“It’s better to have higher stocking rates and rotational graze than low stocking rates and continuously graze,” Smith said, “Some rest is much better than no rest, particularly with the grazing patterns of horses.”

On mowing management of pastures, Smith suggested mowing when grass seed heads emerge, when weeds are shading out grasses or producing seed, when horses are removed from a pasture or when seeding a pasture.

“When you mow very close, less than 3 inches, it is detrimental to the pasture with the exception of something like bermudagrass, a summer perennial grass. When you start getting higher than 8-10 inches, the quality and palatability is dropping,” Smith said.

Smith also touched on Kentucky 31 tall fescue in the growing horse and its controversial background. He shared that no conclusive data has been found in regard to the negative impacts on growing horses, but with all classes of horses KY-31 tall fescue causes vasoconstriction.

“The take home that I want to make is while it is not a major concern, it could be a concern. The simple solution, if you like the positive attributes of fescue with how strong of a grass it is and how good of a sod it forms, you should consider planting a novel endophyte tall fescue if you do a complete re-establishment,” Smith said.

The novel endophyte types have a beneficial endophyte that helps the grass but doesn’t produce ergovaline. Kentucky 31 does have a toxic endophyte, and that’s where you have the problems with the late term pregnant mares, he said.


Reprinted with permission UK College of Agriculture, Food & Environment