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Measuring forage yield and quality
Understanding both the quantity (yield) and quality (nutritional value) of forage is crucial for accurate feed planning, cost control and nutrient management. While nutrient recommendations for silage and grazing are often based on ‘target yields’, accurate measuring gives a much clearer picture.
Yield and quality data help farmers:
- Make sure inputs match crop demand, avoiding both over- and under-application
- Target reseeding or soil improvement where swards are underperforming
- Balance rations to meet livestock nutritional needs
- Identify feed shortfalls early and plan extra feeding if needed
Forage is highly valued on farm, but barriers to accurate measurement may include time, labour and equipment. However, investing in your forage measurement can improve livestock performance, environmental compliance and financial sustainability.
Measuring forage and the importance of getting it right
Over- or underestimating forage availability or quality will have an impact on the management choices made when feeding out.
Listed below are common forage analysis values and the potential impacts.
- Definition: Fresh/dry weight per field/ha
- Overestimation: Feed shortage risk, unexpected costs, high supplementary feed prices
- Underestimation: Surplus forage may go to waste or miss a chance to sell
Note: Overestimation means the value is less than you were expecting, and underestimation means the value is more than you were expecting.
- Definition: The proportion of DM in forage
- Overestimation: May lead to poor fermentation, low pH, intake issues
- Underestimation: Overfeeding and possible aerobic spoilage
Note: Overestimation means the value is less than you were expecting, and underestimation means the value is more than you were expecting.
- Definition: Energy available to animal
- Overestimation: Poor growth/milk yield due to energy shortfall
- Underestimation: Unnecessary supplement costs or risk of overfeeding
Note: Overestimation means the value is less than you were expecting, and underestimation means the value is more than you were expecting.
- Definition: Protein content from nitrogen
- Overestimation: Reduced rumen function if below 10%
- Underestimation: Risk of excessive excretion, inefficient use
Note: Overestimation means the value is less than you were expecting, and underestimation means the value is more than you were expecting.
- Definition: Fibre content affecting digestibility and intake
- Overestimation: Missed opportunities for higher intake
- Underestimation: Poor intake and performance
Note: Overestimation means the value is less than you were expecting, and underestimation means the value is more than you were expecting.
- Definition: Primary source of energy, needed for fermentation
- Overestimation: Risk of poor fermentation and pit losses
- Underestimation: Better preservation and intake if optimal. Too high may increase fermentation rate
Note: Overestimation means the value is less than you were expecting, and underestimation means the value is more than you were expecting.
- Definition: Digestibility indicator
- Overestimation: Growth or milk yield below target
- Underestimation: Overfeeding risk
Note: Overestimation means the value is less than you were expecting, and underestimation means the value is more than you were expecting.
- Definition: Mineral and oil content
- Overestimation: Low digestibility and performance
- Underestimation: High ash can mean soil contamination
Note: Overestimation means the value is less than you were expecting, and underestimation means the value is more than you were expecting.
- Definition: Indicators of fermentation risk
- Overestimation: Insufficient nitrogen can reduce yield/protein content
- Underestimation: High levels reduce fermentation quality
Note: Overestimation means the value is less than you were expecting, and underestimation means the value is more than you were expecting.
Current practices and limitations in yield measurement
Most conserved forage yield is not directly measured unless a forage harvester with calibrated yield monitoring is used.
Common methods (e.g. weighbridge, swath weighing, bale counting) are labour intensive. Even yield monitors need accurate calibration and uniform swathing for reliable data.
Knowing forage DM content will help you to more accurately measure yield.
DM can be assessed by:
- Sampling grass before cutting and drying it on farm
- Sending fresh samples to a laboratory for analysis
- Collecting samples during harvest from trailers or clamps
Sampling before cutting is uncommon, as cutting decisions are influenced more by factors such as:
- Target silage quality (linked to grass maturity)
- Weather forecasts
- Contractor availability
- Nitrogen usage
- Ground conditions
- Existing silage reserves
Learn how to measure yield accurately and explore the methods available
Measuring grass quality with forage analysis
Undertaking forage analysis before cutting can enhance feed planning by:
- Enabling accurate estimation of forage stocks
- Informing decisions on additive use
- Helping avoid under- or overestimating feed values
- Improving ration formulation and livestock performance
Because grass varies across a paddock, a single sample from one point in a paddock is often not a good representation. When sampling:
- Cut at a similar height to your target residual
- Take multiple samples in a W-shape across the paddock
- Avoid areas such as poached patches or gateways that don’t fairly represent the average cover
Find out how to sample grass before cutting for silage
Once you have sampled your forage, find companies that will offer forage testing services.
Understanding forage analysis results
The nutritional quality of grass and silage is assessed by analysing DM, ME, CP and other metrics.
These results show how the forage may influence livestock performance, silage fermentation and the quantity of supplementary feed required.
Visit our webpage on understanding forage analysis
Your nutritional adviser or a representative from your forage-testing company can also help explain your results.