Every summer ranchers cut and bale hay for the winter and don’t think much about it. But the nutritive value of hay is highly variable and not always represented by the visual appraisal of the hay.
The nutritive value of hay is primarily a function of protein concentration and digestibility. The protein in hay is primarily digested by the bacteria in the rumen which are then digested by the animal in the small intestine; thus, providing the animal the protein that it requires. As grasses grow the protein concentration decreases; however, this change in protein concentration is not consistent among species of grasses or for the same species across years.
Digestibility is a function of the fiber concentration in the grass.
There are several types of fiber, but neutral detergent fiber (NDF) and acid detergent fiber (ADF) are two types of fiber related to digestibility. NDF is the total amount of fiber in the plant and ADF is the amount of poorly digested fiber in the plant.
As the total amount of fiber (NDF) increases the digestibility of the grass decreases, and as the amount of ADF increases the digestibility of the grass decreases. From the NDF and ADF concentrations in the hay, we can calculate an estimated digestibility (TDN). As grass grow, the NDF and ADF concentration increases and similar to the protein concentration, this change is not consistent among species or across years.
A “healthy” looking hay bale is not a reliable way to assess its nutritional value.
Even home-grown hay can have nutritive value very different than what is expected or what forage analyses from previous years indicates. A basic forage test that will provide protein, NDF, ADF, and TDN concentrations costs $20 to $40 per sample. One sample from each cutting and each field is adequate, but the sample needs to be comprised of hay from multiple bales.
The best way to sample hay for forage analysis is to use a hay probe on a cordless drill and collect a core from 10% of the bales. The $100 to $200 spent on forage analysis is worth the cost of one open cow from feeding hay that results in thin cows at calving.
The Beef Cattle Institute at Kansas State University contributed information for this article.
If you are interested in testing your hay, give Hunter Nickell, Livestock Production Agent, a call at any of the Southwind Extension District offices or by email at [email protected]
