Forage Maturity: The Most Important Factor Affecting Forage Quality (and Yield?)

Stan Smith, OSU Extension PA, Fairfield County

Considering the weather Ohio experienced the first two weeks of May this year, the last thing a farmer wants to hear is anyone suggesting that hay needs to be made now . . . and in fact, right now! I realize that most folks who have hay to make also have row crops to plant and care for, and perhaps also have cows to breed, pastures to rotate and any number of other spring time chores. Regardless, you’ve heard it before and will hear it again, young leafy forages are high in protein and total digestible nutrients. And, once those plants begin to make seed heads, quality and digestibility decline quickly.

The ages old argument for not making hay now is that if we wait further into spring the likelihood of it getting rained on decreases while the tonnage is increasing. And, while that may be true, fact is the total digestible dry matter is increasing very little, and it’s likely to soon go down. Saying it another way, while we may get more total tonnage by harvesting at a later date, the TOTAL digestible nutrients that are available to nourish a ruminant actually go up little from this point on, and soon will actually go down. The illustration below from the University of Georgia (UGA) Extension bulletin 1425 Understanding and Improving Forage Quality exhibits just that.

As an illustration of a typical situation, the total yield of bermudagrass increases with maturity, but the amount of digestible dry matter (DM)/acre does not generally increase beyond four-week-old growth. Because of increasing fiber and lignin concentrations, more undigestible DM is produced and lowers the quality. (UGA Extension Bulletin 1425)

While the illustration above examines burmudagrass, all forage crops would react similarly even though perhaps at different rates. Simply put, and again directly from the the UGA publication Understanding and Improving Forage Quality, “Even though more total DM yield accumulates with advancing forage maturity from vegetative to reproductive stage of growth, there is a point where the amount of digestible dry matter harvested per acre (digestible yield) no longer increases.”

While digestible yield is leveling off, soil nutrients continue to be utilized as additional tonnage is created. Delayed harvest not only gains few additional digestible nutrients, but it creates the need for additional harvest and storage costs, causes added soil nutrient removal and in some cases eliminates a cutting from the annual harvest. All this while creating little if any more actual feed!