Evaluation of achievements in breeding forage plants for grazing pastures
The aim of forage crop breeding is to provide crop varieties that increase productivity through improved annual yield, sustained yield in perennial crops, and improved feed value. Breeding is usually carried out in tightly controlled field trials with individual plants or rows. However, correlations between trait values in spaced crop trials and forage plots are often low and non-significant. Trait heritability, a measure of the potential for gains from crop breeding, can be moderate to high for many traits. The highest genetic gains in forage yield measured in small trials range from 6% to 15%. Significant improvements have been achieved each decade, depending on the species. Results from some small-scale grazing trials have shown clear gains in growth performance, but others, particularly dairy cattle, have failed to show an advantage for improved cultivars. Factors contributing to this include aspects of system management, system trial design or breeding objectives, and the evaluation system. The presence of environmental stresses; inadequate statistics and scale-up interactions that limit or dilute trait expression. Some of the factors identified above need to be considered as evaluation systems evolve to respond to changing economic, climatic, and regulatory factors affecting pasture operations.
