Preliminary Results Available from Forage Testing Project

AMES, Iowa -- Thanks to an excess of rainfall this past summer, many producers had difficulty getting hay made in a timely manner, which resulted in over-mature forage. As forages mature, they decrease in both energy and protein, and over-mature forage can lead to long-term negative consequences in the herd, according to Iowa State University (ISU) Extension beef program specialist Denise Schwab.

With this in mind, the Iowa Beef Center requested help and financial assistance from ISU's Leopold Center for Sustainable Agriculture, the Iowa Forage and Grassland Council, and the Southern Iowa Forage and Livestock Committee to initiate a forage testing project, Schwab said.

“As of mid-January, more than 400 samples had been submitted to Dairyland Labs as part of this project, with about 350 of those samples being conventional beef cow hay or corn stalks,” Schwab said. “The test results are important to producers.”

A quick look at the data shows that 13 percent of the samples were below 50 percent total digestible nutrients (TDN) and another 34 percent were between 50 percent and 55 percent TDN.

“While many variables can affect the beef cow’s nutrient requirements, the full feed of these hays would be considered ‘marginal’ to ‘deficient’ in meeting the needs of the average pregnant beef cow during the winter months,” Schwab said. “Another method of looking at forage quality is based on Relative Feed Value (RFV), with 100 being equivalent to full bloom alfalfa hay. Of the hays tested, 78 percent were below 100 RFV, meaning there’s a need for energy supplementation in those diets.”

What do these results mean to the cattle producer?

At the very least, Schwab explained, conventional hay feeding programs may not be providing the required nutrients for late gestation cows, meaning some form of energy supplementation is required.

“If your forages haven't been tested for nutrient content, it's critical that you closely monitor the body condition of your cows. Ideally, each cow would have a body condition score of 6 at calving time to improve the likelihood of her cycling and rebreeding for next year,” she said. “Keep in mind that first cutting hay made in June is likely to be deficient in energy for the gestating beef cow and likely would need significant supplementation.”

If you have questions on winter feeding of the beef cow or are interested in having your forages tested, contact your ISU Extension beef program specialist. Find your specialist online.

The Iowa Beef Center (IBC) was established in 1996 with the goal of supporting the growth and vitality of the state’s beef cattle industry. It comprises faculty and staff from ISU Extension, College of Agriculture and Life Sciences and College of Veterinary Medicine, and works to develop and deliver the latest research-based information regarding the beef cattle industry. For more information about IBC, visit