In-Depth Notes on Pasture Measurement Techniques

Introduction to Pasture Measurement

• Focus on direct cutting techniques for measuring pasture mass and quality.
• Importance for grazing management and feed budgeting for livestock.

Key Objectives

• Define relevant terminology in pasture measurement.
• Explore methods to measure:
  • Pasture mass
  • Botanical composition
  • Feed quality using direct cutting techniques.

Importance of Measuring Pasture

• Grazing Management: Animals need adequate, quality feed which requires understanding pasture mass and quality.
• Nutritional Value: Knowing the species contribution to pasture quality is crucial for animal health.

Terminology in Pasture Measurement

• Pasture/Sward: Another term for the grassland being measured.
• Dry Matter Basis: Pasture mass is quantified on a dry matter basis to account for moisture variability.
• Visual Estimation Parameters: Includes:
  • Dry matter content
  • Density
  • Height of the pasture

Measurements and Techniques

Fresh Weight and Dry Matter

• Fresh weight is variable due to:
  • Moisture content
  • Species variability (e.g., white clover vs. ryegrass)
• To measure dry matter:
  1. Cut pasture sample to ground level.
  2. Weigh fresh weight.
  3. Dry in an oven at 65-80 degrees Celsius until consistent weight is achieved.
  4. Calculate dry matter percentage using the formula:
     ( ext{Dry Weight} / ext{Fresh Weight}) imes 100

Quadratic Sampling Method

• Quadratic Cuts: Small areas are cut (e.g., 0.1 m²).
• Collect samples and then follow the drying process.
• Measure total herbage mass for accuracy.

Understanding Pasture Production Rate

• Defined as pasture growth rate in ext{kg dry matter / hectare / day}.
• Techniques include:
  • Exclosure: Use cages to measure regrowth over intervals.
  • Measure mass before and after regrowth period, calculating growth rate accordingly.

Measuring Average Pasture Cover

• Average herbage mass across a farm is crucial.
• Measure all paddocks and calculate a weighted average for the entire farm.

Botanical Composition of Pasture

• Measuring species contribution in total pasture mass is essential for understanding nutritional balance.
• Key components for assessment include:
  • Leaf to stem ratio
  • Green to dead material ratio
  • Grass vs. clover/legume ratio

Techniques for Botanical Assessment

• Visual assessments to estimate:
  • Pasture height
  • Density
  • Dry matter content
• Use of quadrats or lawnmowers for physical sampling.
• Consideration of left-over materials and the need to avoid soil or dung in samples.

Measuring Pasture Quality

• Feed Quality Variables:
  • Metabolizable energy (ME)
  • Crude protein content
  • Trace minerals
• Assess quality effects affected by:
  • Age of herbage (older leads to higher dead material percentage)
  • Seasonal variability in composition.

Methods to Measure Quality

• In Vitro Digestibility: Using enzymes to estimate digestibility rates.
• NIRS (Near Infrared Spectroscopy): A quicker method for various quality assessments like ME value.

Summary of Measurement Techniques

• Direct cutting methods provide accurate measurements of pasture mass and composition.
• Required multiple samples across areas for accuracy reflecting pasture variability.
• Key Reading Reference: Focus on chapters in textbooks related to pasture science for deeper understanding.