Forage nutritive value of modern alfalfa cultivars

Genetically engineered, reduced lignin (RL) alfalfa (Medicago sativa L.) cultivars have been developed for enhanced forage nutritive value. Research is needed to quantify the differences in forage nutritive value among conventionally bred cultivars marketed as high in nutritive value (HNV) and RL cultivars. The objective was to evaluate forage nutritive value and yield differences in HNV and RL cultivar groups compared with control cultivars. Research was conducted in the seeding and following years in New York and Minnesota, with sampling over multiple days within three harvest seasons. Annual yield was similar among control, HNV, and RL cultivars. Relative to the control and HNV cultivars, lignin was 12.5% lower and neutral detergent fiber digestibility (NDFD) was 5% higher for RL cultivars. Reduced lignin cultivars had higher relative forage quality (RFQ) than control and HNV cultivars for five of six site/season combinations. Within harvest seasons, lignin, acid detergent fiber (ADF), and neutral detergent fiber (NDF) increased, whereas crude protein (CP), NDFD, RFQ, and milk production decreased with increasing growing degree-days. Growing degree-day responses were similar across cultivar market groups, with the exception of ADF, NDF, RFQ, and milk during the establishment year in Minnesota, where the rates of decrease in RFQ through time were lower for RL than for control and HNV. Overall, RL cultivars had improved forage nutritive value that persisted with maturity within cutting seasons. Control and HNV cultivars did not consistently differ in nutritive value. Growers can select cultivars for improved nutritive value without concern about compromising forage yield.