Abstract
Twenty grass accessions were evaluated as annual summer growing forages in subtropical Australia. Eleven were annuals and nine were perennials, but the latter were sown at a higher seeding rate than usual. Grasses were either cut five times throughout the growing season at four weekly intervals or were cut four times with an eight week period before the first cut and with four weekly harvests thereafter. Harvested material was separated into leaf, stem and reproductive heads. In vitro digestibility was measured on the separated components. The two most productive perennial grasses (Chloris gayana cv. Katambora and a Setaria sphacelata×S. splendida hybrid) yielded an average of 11, 000kg/ha with five cuts and 15, 000 with four. However the leaf yield was virtually unchanged at about 6, 000kg/ha. The two most productive annuals, Zulu and Sudax sorghum, averaged 10, 000 and 19, 000kg/ha for the same cutting treatments and leaf yields were 5, 000 and 6, 000kg/ha. Thus less frequent cutting increased yield of stem much more than yield of leaf. The higher stem yields were associated with a depression of 5% in stem digestibility. Digestibility of both leaf and stem was highest at the beginning and end of the growing period. Measurements of plant and tiller density were made after each harvest and were related to changes in yield over the season. The advantages and disadvantages of using either annuals or perennials as annual fodder crops are discussed
