Forage testing- good investment


The weather so far has year has certainly brought its share of challenges to the farming community.  The constant rains have delayed or prevented the timely planting and harvesting of field crops and hay fields alike.  Most producers have had a number of acres of hay that either got baled a little too wet or got rained on at some point in the curing process leaving the potential for mold and spoilage issues; Some in low lying areas such as bottom land had water sanding on it for several days at a time.  Nearly everyone had some hay land that was well past optimal maturity before the stars aligned to find a window to get it put up in.  All of these things are going to add up to quality issues come feeding time this winter.

Forage testing is one of the cheapest and best investments a livestock producer when it comes to nutrition and their herd.  The test will cost around $20.00 and will give you the information needed to develop a supplement to meet the livestock’s needs.  Like testing anything, useful results only come from a good sampling process.  Always use a hay probe to and take a core sample for your test rather than a simple “grab and go” where you pick a handful from a few bales and call it good.  The core sample should be taken from the round side of a round bale or the end of a square bale, going straight toward the center so you get a good representation of the entire bale.   You will need to probe somewhere between 10 and 20 bales and have a sample that weighs about a pound to get a good representative sample.  Sort hay into “lots” by hay type and harvest window and test each individual lot.

When you get the results back from the lab, you will find two columns listed on the results, one labeled “As fed” and one labeled “Dry Matter”.  The As fed column is exactly that, how the hay was received at the lab and how it will be fed to the livestock.  The dry matter column shows values with the samples dried down and all the moisture removed.  We generally use the “Dry Matter” column for comparing feed stuffs and developing rations because it takes the moisture factor out of the equation.  The “as fed” column is primarily used to look at the moisture in a feedstuff and to determine how much is actually required in a ration.  For dry hay samples, the moisture content should be below 20% for proper storage.  Haylage on the other hand should be between 45 and 60% moisture for proper fermentation and storage. 

Values for several nutrients will be listed under both columns.  Generally the first listed is % Crude Protein.  Crude Protein is a calculated value based off of how much nitrogen is present in the sample.  The amount of nitrogen is multiplied by the conversion factor 6.25 to determine the protein level in the hay tested.  Values can range from as low as 3-4 % for wheat straw or extremely over mature warm season grasses to as high as the mid 20’s for leafy immature legumes such as alfalfa.  In some instances when hay is baled slightly wet, it will heat up and “caramelize” leading to some of the protein being tied up and unavailable for digestion in the animal.  Caramelized hay will have a tobacco like look and a sweet aroma to it and is quite palatable just not all of the protein will be available.  For a little extra, you can get an “available protein” test ran as well to see how badly the protein level has been affected.  It generally takes the hay heating to above 1400 F to cause any problems.

Next you will find values for Acid Detergent Fiber (ADF) and Neutral Detergent Fiber (NDF).  Fiber levels are used to determine the digestibility of forages and how much an animal will be able to consume.  Legumes will typically have less fiber than grasses.  ADF is used mostly to determine the digestibility of the forage; good quality legumes will generally run between the low 20’s and mid 30’s on a percentage basis where grasses will run between the low 30’s and mid 40’s.  NDF is an indicator of how much an animal will be able to hold in their rumen.  NDF levels should range in the 30’s and 40’s and grasses should be in the 50’s and 60’s.  Levels above 70% are will generally not work well without a great deal of supplement.

Total Digestible Nutrients (TDN) represents the total of all digestible protein, carbohydrates and fats in the sample.  TDN is commonly used in beef rations to represent the energy content of the feed.  Levels as high as the mid 60’s can be seen on early cut alfalfa where late cut grasses can be as low as the high 30’s or low 40’s.  Most classes of livestock require levels above 50% to meet their energy requirements. 

Once the test results have been looked at and are understood, the next step is to weigh the information against the requirements of the animal being fed.  When thinking of the cow herd, stage in the production cycle and maturity of the cow are the two most important factors to be considered.  The desired rate of gain determines the needs of young growing cattle.  The enclosed chart shows some nutritional requirement guidelines for several classes of cattle. 

Other factors affecting palatability could be an issue this year as well.  Hay that was rained on or baled wet may have a good deal of spoilage or waste because of mold and storage losses.  It can also get a musty smell leading to some refusal to eat by livestock.  Hay fields that were under standing water for extended periods of time might have a foul taste because of dirt and other contaminates left on it after the water subsided and the field was cut.

Fortunately, there are ways around many of the quality issues we will see with hay because of the rain such as supplementation and ammoniation of poor quality feeds and using molasses or other products to sweeten up foul smelling hay.  We are also fortunate that the rain has brought with it an abundance of grass growth, stalling the need to feed hay.  Cattle prices remain relatively high and grain prices have subsided from the levels seen from a few years ago making it an easier decision to feed your cow herd right to maintain production.

Source: Andy McCorkill, Livestock Specialist