Wheat forage quality: significance, genetic and genomic advances, knowledge gaps, and future directions

Winter wheat is grown worldwide primarily for grain, yet it also serves as an important cool-season forage, supporting livestock production when other feed is scarce. Wheat can be utilized as grazed pasture or harvested as hay, silage, and straw, and is widely used as dual-purpose (forage + grain) and double-cropping systems. During vegetative growth, wheat forage is highly palatable and nutritive, typically containing 20-30% crude protein (CP), and >80% digestibility, supporting rapid liveweight gains in beef cattle. However, forage quality is highly dynamic: as wheat matures, CP and energy decline, while neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin increase, reducing intake potential and digestibility. Forage quality is also affected by moisture, fertilization, and wheat class. At comparable developmental stages, winter and spring wheat generally show little inherent differences in forage quality, indicating that maturity and management are the major determinants of quality. This review synthesizes current knowledge on wheat forage in dual-purpose and grazing systems, emphasizing dry matter, CP, NDF, ADF, acid detergent lignin, relative feed value, and relative forage quality as key indicators of biomass, nutritive value, intake potential, and digestibility. We further assess developmental shifts in these traits and their consequences on livestock intake, animal performance, and grazing management, together with forage evaluation methods such as near-infrared reflectance spectroscopy. We also examine genetic and genomic approaches for improving forage traits. Wheat breeding has historically prioritized grain yield and straw characteristics, genomic dissection of forage quality remains limited. Nevertheless, recent genome-wide association, QTL mapping, and genomic selection studies targeting water-soluble carbohydrates, fiber fractions, and digestibility-related traits highlight promising avenues for improvement. Overall, wheat forage can provide exceptionally valuable winter feed resources, but its quality is governed by strong developmental, environmental, and genetic effects. Improved screening methods and breeding targets, such as combining high protein and energy with agronomic resilience, are needed to exploit wheat's dual-purpose potential. This review integrates agronomic, animal nutrition, and genetic perspectives to guide future research and breeding of high-quality forage wheat.