Forage Quality

Forages are the foundation upon which nutritionally sound, economical and healthy livestock diets are formulated. The ultimate indicator of forage quality is animal performance such as daily gain, milk production or reproductive performance.

The forage quality of cover crops depends on the species planted, their maturity, as well as environmental conditions. There are several variables that can be measured as indicators of forage quality.  These include lignin, cellulose, and carbohydrates. Lignin is an important plant component that provides strength and defense against stressors. However, it is also responsible for limiting the digestion of plants cell walls. Typically, warm season forages (pearl millet, sorghum) are less digestible than cool season forages (oats, ryegrass, and rye) because they have higher lignin levels. Leaves are more digestible than stems because there is a higher concentration of lignin in stems compared to leaves. Due to their higher leaf to stem ratio, legumes (crimson clover, cowpea) generally have higher nutritional quality than grasses (sudangrass, triticale). However, generalizations about forage quality of warm vs. cool season and legumes vs. grasses are risky, due to the variation in quality within and among plant species.  As plants mature and move into a reproductive stage (seeds), they accumulate cellulose and other complex carbohydrates which are bound together by lignin. Thus, forages become less digestible as they mature resulting in continuous compromise between forage quantity and quality.  Grass/legume mixtures often provide the best solution to this compromise.

Due to this complexity, laboratory approaches have been developed as indicators of the nutritional value of forages. In addition, the nutrient requirement of livestock differs considerably according to species, age, weight, and performance goals. Forage quality plays a critical role to fulfill the nutrient requirements of the different livestock species. The information below gives more details on how to ensure you have the right forage for your livestock, the importance of evaluating forage quality and how to obtain representative samples for analyses.

Information and tips on forage quality most common questions:

Additional Resources

Detailed hay sampling procedures and a lists of hay probes are provided by the National Forage Testing Association: www.foragetesting.org

Contributors:

Dr. Matias Aguerre, Assistant Professor, Clemson University; Dr. Lisa Baxter, Assistant Professor and Forage Extension Specialist, University of Georgia; Philip Brown, Grazinglands Specialist, Georgia Natural Resource Conservation Service, Julia Gaskin, Sustainable Agriculture Coordinator – retired, University of Georgia