Horse Forage: New Strains Have Lower Lignin Content

Lignin provides structure to the stems of plants. Fresh forage and hay contains varying amounts of lignin and other structural carbohydrates such as cellulose and hemicellulose. Unlike the other components, however, lignin is indigestible, and for each lignin increase of one percent, overall dry matter digestibility drops by three to four percent.

Plants need structural components to hold them upright so they are exposed to sunlight and stay out of contact with the ground, but forages with higher lignin levels are not as easily digested by horses.

Three new strains of alfalfa (lucerne) have been approved by the USDA’s Animal and Plant Health Inspection Service. These strains offer a significantly lower amount of lignin than the 6 to 8% level found in traditional alfalfa. Two new strains produced by conventional breeding techniques will cut lignin by 7 to 10%. Another strain developed by suppressing a natural plant gene will produce alfalfa that contains 12 to 18% less lignin than common strains.

Plants develop more lignin and therefore become less digestible as they mature. Alfalfa and other forages cut in early growth are usually more digestible than late-cut forage. However, weather may not be ideal for mowing, drying, and baling when the perfect stage of growth occurs. With lower lignin levels, these new alfalfa strains should stretch out the harvest period because more mature plants will not contain the level of lignin found in common strains planted at the same time.