Winning the alfalfa game: Does RFQ tell the score?

Posted on June 17, 2020 in Forage Foundations
By Stacy Nichols, Vita Plus dairy technical specialist
The goal of managing alfalfa through harvest should not be to maximize relative feed quality (RFQ).  Instead, it should be to achieve a balance between digestible fiber content and effective fiber.

Historical quality measures
It can be difficult to grow a high-quality alfalfa that also maximizes feed efficiency in lactating cows.  Historically, we have used two key metrics to judge alfalfa quality:

  1. Relative feed value (RFV), which is directly related to the fiber content
  2. Relative feed quality (RFQ), which is related to both fiber content and fiber digestibility

Although RFV and RFQ have merit for a quick evaluation of alfalfa quality, they don’t completely reflect the nutritional quality of alfalfa for the cow.  The challenge with these metrics is they assume a higher value is always better, but that is not always the case.  You can read more about RFQ and its meaning in this Forage Foundations article.

RFQ as a scoreboard
As a dairy nutritionist, when I look at a lab report for alfalfa, my eyes immediately gravitate to RFV and RFQ.  I use those values as a “scoreboard” to tell me if I should get excited for the potential to win, or alert me that I need a new game plan.

Another metric I look at on the lab report is the NDF digestibility (NDFD) and how it compares to the lab averages.  The NDFD relationship to the lab average is like an over/under line in Las Vegas.  In my opinion, NDFD is a more accurate measure of quality than RFQ.  If the NDFD is several points below the lab average, it would be wise not to bet on the RFQ.

In my experience, rations with more than 10% of the dry matter (DM) coming from alfalfa feed better when the RFQ is above 140.  If you’re feeding higher levels of alfalfa (more than 25% of the DM), you won’t see a drastic improvement in performance once RFQ increases above 190.  After this point, RFQ starts failing in many cases because, while it may be higher, the actual digestible fiber content is often lower than what the RFQ value would suggest.

Formulating rations
It is important to understand that your nutritionist is not using RFV, RFQ or NDFD metrics in ration formulation.  After considering the RFV/ RFQ scoreboard and the NDFD over/under line, I look at the nutrient values used for ration formulation, such as:

  • aNDFom (fiber content)
  • uNDF240 (indigestible fiber)
  • Digestible fiber pool size (aNDFom – uNDF240)
  • NDF kd (digestion rate of the digestible fiber pool)

These nutrient values are put into the ration balancing software and allow us to optimize the level of the forage in the ration based on the quality and inventory.

Manage your alfalfa harvest for quality 
Alfalfa should be harvested early- to mid-bud stage.  My advice is always walk and check your fields.  What do the plants look like?  How mature and tall are the plants getting?  My favorite evaluation method is scissor clippings with a quick lab analysis as you get closer to the harvest window.  For first cutting, you can utilize growing degree days (GDD) or a PEAQ stick to help determine quality.

For subsequent cuttings, scissor clippings are the best option to access RFQ and should be done 21 to 23 days post-harvest.  Ask your Vita Plus consultant to set you up with a forage testing lab to have a quick analysis turnaround.

Additionally, do not lose sight of effective fiber in the pursuit of a high RFQ.  This can often result in harvesting short alfalfa plants with lots of leaves, which doesn’t always behave like forage and may often result in decreased feed efficiency due to excessive DM intake without an improvement in milk production.

RFV and RFQ can be useful quality metrics, but maximizing RFQ should not be the main criteria to determine when you should harvest alfalfa.  Instead, focus on setting specific goals for the nutrients used in ration formulation.  Your Vita Plus consultant can help set those goals and put together a plan to address your herd’s forage needs all year long.

Category: Feed quality and nutrition
Forage Foundations
Forage harvesting