Why High-Quality Pasture is Essential for Raising Top-grade Yearlings

During the session of the University of Kentucky’s 10th annual Equine Research Showcase, Ray Smith, PhD, a professor and forage extension specialist in the Department of Plant and Soil Sciences, delivered an enlightening presentation on the influence of pasture quality on yearling horses. This session primarily focused on nutrition and pasture management for weanling to yearling horses, with sponsorship from BET, Kentucky Performance Products, McCauley’s, Merck, Rood & Riddle Equine Hospital, and Tribute Equine Nutrition.

Drawing from both research and practical farm observations, Smith elaborated on the establishment of horse pastures, soil fertility, and effective pasture management. He emphasised that well-managed pastures combined with optimal pasture conditions can result in high-quality forage for young horses, reduce the need for supplemental hay and grain, and enhance the visual appeal of the landscape.

The Basics of Pasture Management and Soil Fertility

Smith began by discussing the fundamentals of pasture management, introducing the concept of establishing horse pastures with a desired composition of at least 80% favourable forages and less than 20% undesirable forages. He noted that in central Kentucky, desirable forages for weanlings include tall fescue, Kentucky bluegrass, orchardgrass, white clover, and ryegrass, while undesirable components should consist of less than 20% of broadleaf weeds, weedy grasses like nimblewill, johnsongrass, foxtail, and bare soil. Smith pointed out that the typical Kentucky horse pasture contains only about 55% desirable forage, compared to the recommended 80%, and explored the implications of soil fertility on pasture quality.

Smith recommended soil sampling every two to three years using a cylindrical soil probe to obtain a representative core of both topsoil and deeper soil layers. He advised taking samples 4 inches deep and collecting 10-20 samples per pasture. Based on the soil test results, horse owners and farm managers should apply the recommended amounts of phosphorus, potassium, and lime. For assistance with interpreting soil test recommendations, Smith suggested consulting a county agent or a soil consultant.

Nitrogen is a vital nutrient for pasture productivity, particularly for Kentucky’s cool-season perennial grass pastures. Smith recommended applying 60 to 80 pounds of urea per acre (equivalent to 30-40 pounds of actual nitrogen) in late September and late October, or doubling this amount with a single application in mid-October to promote pasture regrowth without excessive production. He cautioned against trying to balance horse diets by adding fertilisers to fields, advocating instead for providing micronutrients through mineral supplementation.

Overseeding and Complete Pasture Renovation

Smith addressed the topic of overseeding existing pastures to increase plant density, stating the importance of having some bare soil for this method to be effective. He recommended mowing or grazing closely before seeding to reduce competition for new seedlings and suggested planting shade-tolerant species like orchardgrass. Overseeding should be done in early September, and the planting depth should be monitored closely to ensure it is no deeper than ¼ to ½ inch to facilitate seedling emergence.

For pastures with significant weed problems or poor recovery, Smith recommended considering a complete renovation. This involves eliminating existing plant competition with two applications of glyphosate in early July and mid-August or through repeated tillage, followed by seeding a perennial mixture in early September to establish a new pasture stand. Using high-quality, improved seed, planting at the appropriate time, employing the best seeding methods, and controlling competition are critical steps in promoting new growth. Newly seeded stands require a rest period of six to twelve months to develop a robust sod.

Smith compared the root growth of various grass types, including annual rye, perennial rye, tall fescue, and orchardgrass, noting that annual rye is ideal for quick pasture establishment but is short-lived, whereas perennial rye grass offers a two-year window. For long-term perennial pastures, Smith recommended using orchardgrass, Kentucky bluegrass, and novel tall fescue varieties for added durability.

Seasonal Grazing and Mowing Strategies

In discussing pasture management, Smith stressed the importance of matching grazing to seasonal growth patterns, noting that cool-season grasses thrive in spring and fall, with reduced growth in summer. He advised considering grasses like bermudagrass or crabgrass for intense summer grazing but noted their limitations in Kentucky’s climate. Smith strongly advocated for rotational grazing, showing a video that demonstrated the superior growth of orchardgrass under rotational grazing compared to continuous grazing.

Smith also addressed stocking density, suggesting a guideline of 2 acres per 1,200 pounds or about 1 acre per yearling (rotationally grazed) for Kentucky. He highlighted that higher stocking rates with rotational grazing are preferable to lower rates with continuous grazing, as some rest periods are beneficial, particularly given horses' grazing patterns.

Regarding mowing, Smith recommended mowing when grass seed heads appear, when weeds shade out grasses or produce seed, when horses are removed from a pasture, or when seeding. He cautioned that mowing very close, less than 3 inches, can harm the pasture, except for certain grasses like bermudagrass. Conversely, allowing grass to grow taller than 8-10 inches reduces its quality and palatability.

Smith also touched on the controversial topic of Kentucky 31 tall fescue and its impact on growing horses, noting the lack of conclusive data on negative effects but highlighting the potential for vasoconstriction in all classes of horses. He suggested considering novel endophyte tall fescue varieties that provide the benefits of traditional fescue without producing harmful ergovaline.

By implementing these strategies, horse farm managers can significantly improve pasture quality and forage production, ultimately enhancing the health and growth of young horses.