Genetic Engineering for the Improvement of Forage Grass Quality

The forage quality of warm season perennial grasses grown in the Southern States, subtropics, and the tropics is often inadequate and is a major limitation to satisfactory animal performance. Quality improvement of those warm season grasses has been a high priority research objective in breeding programs. Hammond (1987) pointed out that C4 tropical and subtropical grasses generally have lower quality than the C3 temperate grasses. A major problem with those grasses is that they have proportionately higher cell wall constituents than cool season grasses, and this generally correlates negatively to intake (Waldo 1985), digestibility and animal performance (Moore and Mott, 1973; Van Soest, 1978; Morris, 1984). Cell wall digestibility decreases rapidly with increasing maturity and is reduced further by higher growth temperatures as encountered in the south and the tropics (Morris, 1984). It is also well established that forage grass leaves have a much higher digestibility than stems.