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Accomplishments and impact from breeding for increased forage nutritional value

Casler, M.D., Vogel, K.P.
Crop science 1999 v.39 no.1 pp. 12
agricultural programs and projects, breeding, forage, plant breeding, genetic improvement, rumen fermentation, digestibility, analytical methods, in vitro digestibility, cultivars, genetic variation, liveweight gain, beef cattle, yields, feed intake, vegetative propagation, biomass production
Despite considerable rhetoric, there were no serious efforts to improve genetically the nutritional value of forage crops until the 1960s when advances in analytical chemistry and rumen fermentation technology allowed breeders to adapt meaningful laboratory techniques for repeatably screening thousands of samples in a short time period. Genetic increases in some measure of digestibility, typically in vitro dry matter digestibility (IVDMD), have been documented in new cultivars of at least seven forage crops, including legumes, cool-season grasses, warm-season grasses, annuals, and perennials. The rate of gain for IVDMD ranges from 8 to 45 g kg-1 cycle-1, which, on a percentage basis (0.7-2.5% yr-1), is similar to long-term gains for grain yield of many cereal crops. In asexually propagated species, in which all genetic variance can be utilized in a single cycle of selection, gains as high as 11.8% cycle-1 have been reported. Generally, gains in IVDMD are repeatable across a wide range of environments and management systems, including on-farm tests. Averaged across species, a 1% increase in IVDMD generally leads to a 3.2% increase in average daily gains of beef cattle (Bos taurus). Because increased IVDMD generally does not decrease forage yield per se, and sometimes occurs with increased forage yield, these gains also translate to improved beef production per hectare. The ability to document increased animal performance associated with breeding for increased forage nutritional value can greatly enhance the value of a new cultivar to forage producers, which can lead to rapid adoption of new cultivars.