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 with the protein it requires. As grasses grow, protein concentration decreases; however, this change is not consistent among grass species or within 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 that are 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 grows, the NDF and ADF concentrations increase, and, similar to protein concentration, this change is not consistent among species or across years.

Visual appraisal of hay can be deceiving. Bromegrass hay with a high number of leaves and relatively few stems may still show stems indicating that the plant had reached the reproductive stage prior to cutting and baling. The reproductive stage, when seed heads are visible, is one of the later stages of plant growth, indicating that a lesser quality hay will be produced. However, bromegrass hay is usually of relatively high quality.

In one nutritive analysis example, even with a high number of leaves, the protein concentration was quite low, at 6.39%. Feed tables list the protein concentration of bromegrass hay at more than 8%, which meets the protein requirements of mid-gestation dry cows; 6% protein does not. Late-gestation and lactating cows will need a protein supplement to meet their protein requirements, which are 9 to 10%.

The NDF concentration of that hay sample was 63%, and the ADF was 41%. This calculated to an estimated TDN of 51%, which is just enough to meet the energy requirements of mid-gestation dry cows. And with the marginal protein concentration in the hay, the cows will need a protein supplement to digest the hay to the calculated TDN potential of 51%.

Visual appraisal of hay is not always adequate for assessing its nutritional value. Even home-grown hay can have a nutritive value very different from what is expected or from forage analyses from previous years. 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 comprise 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. As a reminder, Southwind Extension District has grant funding to cost-share $20 per forage sample. This opportunity is made possible by Bill House Ag Grant Funds from the Community Foundation of Southeast Kansas.

Thank you to the Beef Cattle Institute at Kansas State University for the content in this article. If you have any additional questions or 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 nickell99@ksu.edu. We have a probe in each office and are happy to make field visits to assist our producers!