In Vitro Digestibility of Diallel and Polycross Progenies of Intermediate Wheatgrass

Previous forage plant evaluation by breeders has centered around agronomic factors that determine persistence and forage and seed production with little consideration given to utilization. Forages must be consumed by animals for utilization, so forage quality as it relates to the animal should be an important evaluation factor. Plants and animals function together in determining forage quality. Such plant characters as leafiness, coarseness, height and physiological age are easily observed and deternd.ne quality to a degree. Other components such as digestibility, lignin and protein are just as important, but cannot be determined as easily. Animal acceptance and consumption are also measures of forage quality. The ultimate determination of quality, though, is expressed in the production of utilizable animal product. Forage breeding programs are concerned with large numbers of samples and small quantities of plant material per sample. Using animals to determine quality differences in this situation is not possible. The recent development of in vitro methods has made it practical for the forage breeder to screen selection nurseries on an individual plant basis to determine differences of quality. Such screening is an adequate preliminary step in the development of a forage strain of superior quality. Intermediate wheatgrass was selected for this study because this species is becoming increasingly important as a superior cool-season grass for pasture and hay in the northern Great Plains, Great Basin and Intermountain areas where the annual precipitation is 14 inches or more. The estimated acreages of intermediate wheatgrass for all purposes in South Dakota is about 60, 000 acres. An increase in digestibility of only 5 percent could result in an additional 6!000 tons of utilizable dry matter from this acreage. This research was conducted with the following objectives: 1. To determine if in vitro dry matter digestibility techniques could be used to determine differences in digestibility between genotypes in the screening of intermediate wheatgrass selection nurseries. 2. To determine if certain plant parts of intermediate wheatgrass could be used as adequate predictors of digestibility for the whole plant. 3. To determine the nature of inheritance of in vitro dry matter digestibility within two crossing nurseries of intermediate wheatgrass