Technical note: Comparing 4 techniques for estimating desired grass species composition in horse pastures

Area of Science:

• Pasture Management
• Forage Quality Assessment
• Equine Science

Background:

• Accurate estimation of desirable forage species composition is crucial for managing improved horse pastures.
• Existing methods for species composition estimation lack comparative studies specifically for horse pasture environments.
• Selecting an appropriate and reliable method is essential for effective pasture management and subsequent grazing studies.

Purpose of the Study:

• To evaluate and compare four techniques for estimating desirable forage species composition in cool-season horse pastures.
• To assess methods based on prevalence estimates, repeatability, bias, and practicality.
• To select the most suitable method for use in future equine grazing research.

Main Methods:

• Four techniques were examined: Equine Pasture Evaluation Disc (EPED), Line-Point Intercept with 3 transects of 50 observations (LPI 3-50), LPI with 5 transects of 30 observations (LPI 5-30), and Step Point (StPt).
• Statistical analysis involved a generalized linear-mixed effects model (GLIMMIX) with a logit link to test for differences among species.
• Pairwise comparisons using a paired t-test were conducted for significantly different methods (α = 0.05), with agreement analyzed by grass species.

Main Results:

• Methods showed no significant differences for creeping bentgrass or orchardgrass, but significant differences were found for Kentucky bluegrass, tall fescue, and other species.
• Method repeatability decreased as species prevalence increased. Five out of 30 method pairs exhibited significant bias, with three involving LPI 3-50 and EPED.
• LPI 3-50 and LPI 5-30 agreed perfectly, as did StPt and EPED, indicating interchangeability. LPI 3-50 and EPED were the most dissimilar.

Conclusions:

• Step Point (StPt) and Line-Point Intercept (LPI) methods are interchangeable for assessing horse pasture species composition.
• While StPt and LPI are interchangeable, StPt was selected for its thorough pasture representation and ease of use.
• The findings provide guidance for selecting appropriate methods in equine pasture research and management.