June 3, 2015 11:39 AM

Cutting forage at the optimal quality for feed should be managed by more than the calendar.

“First cut alfalfa by a certain day in May or June” (location dependent); “Cut alfalfa stands 28 to 32 days after the prior cut.” These have been the standard rules of thumb for many farmers aiming to achieve dairy quality forage – for years. Passed down from generation to generation, these rules worked at times but both environment and plant genetics have changed. Making the decision of when to cut heavily dictates forage digestibility and quality – in addition to location and environment effects – should be enough to drive us to look outside the primitive calendar for guidance.

Over the last ten years, two research-backed methods, outside of the calendar and counting days, have been developed to accurately monitor forage quality and decide on a harvest timeline. Hand harvesting samples (or scissor clips), which applies to all cuttings and all forage types, was the first method to be consistently used. More recently, the PEAQ (Predictive Equations for Alfalfa Quality) method, which applies to the first cutting of alfalfa only, has also been adopted to assess forage quality. Both approaches offer an RFQ (Relative Feed Quality) value to assess quality and both methods allow us to determine harvest schedule based on quality preferred for feed out, or quality preferred at the point when forage has been harvested and put in the bag, bin or silo. Part one of this forage timeline series will focus on the PEAQ stick assessment.

PEAQ forage assessment

The PEAQ stick utilizes a yardstick-type tool (PEAQ stick) to generate an estimate of Relative Forage Quality, based on plant maturity and plant height. Originally developed at the University of Wisconsin – Madison, this method has been validated across the country. It’s important to note, however, that the PEAQ method applies to first cut only and if assessing an alfalfa-grass stand, the PEAQ method should be set aside for the better option of scissor clipping.

While the PEAQ assessment can only be applied to the first cut of forage, this is typically the best forage crop. Due to a cooler growing environment and above average fiber digestibility, relative to following crops, the first crop is one of the most important to accurately assess and develop a proper cut timeline for optimal animal performance.

Determining cut timeline

The first alfalfa crop harvest should be at PEAQ stick height of 19” - 25” with vegetative or bud alfalfa (or roughly 185 – 215 RFQ) for dairy cattle quality feed. Cutting at this height will yield between 160 and 200 RFQ in the silo because roughly 10 to 15 units are lost during harvest and fermentation.

Knowing the goal when assessing the timeline for cutting, it’s important to know that 5 RFQ points (due to 1 unit of NDF increase) are typically lost each day that alfalfa stands and grows in the field. During warm weather, with adequate sun and moisture, this loss can be greater. During cloudy, cooler days this loss can be less per day.

While the calendar can help guide us in a general sense of when the alfalfa cutting time window is approaching, better options for correctly and accurately assess quality forage exist. Farmers should consider taking the extra steps to properly calculate the timeline that will yield optimal quality for animal performance.

For a demonstration on how to employ the PEAQ stick correctly in the field for an accurate RFV measure, check out the video demonstration below.

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