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OSU Extension

College of Food, Agricultural, and Environmental Sciences

July 24, 2018 - 8:00am -- Anonymous

Many of us are familiar with the refrain “Don’t Guess, Soil Test”.  With regard to 2018 hay crop quality, we need to take a page from soil testing and say, don’t guess, forage test.  Wet conditions and frequent rainfall events dictated that a lot of first cut dry hay was baled in July. Forage quality is likely to be low.  Will this hay meet the nutrient requirements of those livestock that consume it?  If not, how much additional supplementation is required? Without a forage test, the answers to those important questions are just a guess.  Guessing comes with an economic cost because either under or over feeding and supplementing is expensive.  Mark Landefeld, OSU Extension Educator in Monroe County, recently wrote a very thorough article about forage testing and some of the forage quality measures contained in a forage test result that livestock owners should take a closer look at this year with lower quality hay.  I’m going to excerpt some of Mark’s comments and explanations in this column.  The entire article is available on-line at

Pay attention to the neutral detergent fiber (NDF) number on the forage test.  That number is likely to be higher than normal in many producer’s hay bales because of the over mature condition of the hay. As forage plants mature, cell wall production in the plants increase and NDF content will increase.  As NDF content in a forage increases, dry matter intake decreases because the rate of passage through the rumen decreases. Therefore, with NDF percentages, we can accurately predict forage intake.  The higher the NDF value, the less livestock can physically eat of that forage.

Most mixed grass hay, after heading out, will have NDF values of 65% or greater.  Beef cows can only consume about 1-1.2% of their body weight in NDF/day.   A 1300 lb. beef cow could consume up to 15.6 lbs. of NDF/day on a dry matter (DM) basis.  If our hay is 65% NDF, a 1300 lb. cow can only eat 24 lbs. of this hay on a DM basis or approximately 27 lbs./day as fed.  Without showing all the calculations in this article, feeding this hay results in more than a 2.2 lb. (±14%) deficiency in TDN/day for a superior milking, early lactating cow’s needs. This is why a cow can have a full stomach, but still lose weight.

Ash levels in this year’s hay may be a concern as well. As ash percentage increases, digestible dry matter decreases.  Running equipment over hay, on ground that is wetter than usual, and around wet spots for mowing, tedding and raking has undoubtedly caused dirt/mud to adhere, or splash in some cases, onto the forage that would not normally be there.  Dan Undersander, Forage Agronomist from the University of Wisconsin, explains that ash in forage comes from two sources: internal, e.g. minerals like calcium, magnesium, potassium and phosphorus, and external, e.g. dirt, bedding, sand, etc. The average internal ash content of alfalfa is about 8% and of grasses is about 6%. Additional ash in a hay or silage sample is contamination with dirt, sand, etc.   The issue is that ash can take the place of nutrients such as energy, protein, even some vitamins, on a one to one basis.  Increasing the ash percentage by one percent can potentially decrease digestible nutrient intake by one percent.

Another point to consider this year is going to be heat damage to the forage.  A forage test can tell you if crude protein is lost to heat damage.  This value shows up in the adjusted crude protein percentage in the analysis numbers.   If hay internal temperature reaches 115 to 120°F, a chemical reaction occurs between the protein and carbohydrates present in the forage. This reaction, called the Maillard reaction (often referred to as the browning reaction), is responsible for the characteristic, sweet smelling cured tobacco odor you may notice around your hay bales. While cows seem to like the taste of this type hay, the process denatures proteins making part of them unavailable for digestion by our livestock.  Balance rations using the “Adjusted Crude Protein” rather than the other protein values listed on your forage analysis.

One more item producers may have to deal with this year is mold growth in hay bales. The presence of noticeable mold in stored forages indicates production problems, usually hay baled too wet. Mold and hay quality is a difficult issue because the presence of mold does not necessarily mean that the feed cannot be used.  However, the poor palatability of this hay results in lower intake and animal performance.  In addition, certain mold fungi produce mycotoxins that can harm livestock. This is part of the decision-making problem, since not all molds produce mycotoxins, and the amount produced by those that do is unpredictable.

One final thought; test results are only as good as your sampling method.  Contact the Wayne County Extension office at 330-264-8722 for information on how to take a good forage sample.