Diurnal Variation in Forage Nutrient Composition of Mixed Cool-Season Grass, Crabgrass, and Bermudagrass Pastures.

This study investigates the nutritional composition and diurnal variations in carbohydrates of warm-season grasses compared to cool-season grasses, with an emphasis on their suitability as low-carb pasture forages.

Study Approach

• This research focused on two warm-season grasses, specifically ‘Quick-N-Big’ crabgrass (CRB) and ‘Wrangler’ bermudagrass (BER), in comparison to mixed cool-season grass (CSG), inclusive of ‘Inavale’ orchardgrass, ‘Tower’ tall fescue, and ‘Argyle’ Kentucky bluegrass.
• The grass samples were collected every 4 hours over a period of 3 days when each species had reached the boot stage of maturity – a growth stage just before the emergence of a seed head.

Key Findings

• The research found that the Digestible Energy (the amount of energy that can be absorbed by the body) was highest for the CSG variety and lowest for BER grass.
• The Crude Protein (a measure of protein content) was found to be lowest for the CSG variety, while the Neutral Detergent Fiber (a measure of plant cell wall constituents, indicative of the forage quality) was highest in the case of BER grass.
• The Non-Structural Carbohydrates (readily digestible carbohydrates) were found in greater amounts in the CSG as compared to the warm season grasses.
• The concentrations of NSC were found to be highest in the afternoon and evening and lowest in the early morning, with these variations being most evident in the CSG variety when compared to warm-season grasses.

Implications of the Study

• The results of this study provide crucial information about the nutritional composition of CRB and BER grasses. The low levels of non-structural carbohydrates content hint at their potential as pasture forages for animals, especially horses, in situations where the intake of these carbohydrates needs to be controlled.
• The research also supports the recommendation to restrict grazing to early morning hours as a strategy to limit the intake of non-structural carbohydrates, especially in areas with CSG pastures.