Growth and utilisation of forage on subtropical dairy farms

Abstract

With deregulation, the focus for dairy production in northern Australia has changed from cow production to improving efficiency to maintain profitability. This requires more effective production and utilisation of forage for greater cost efficiency. This paper summarises the growth of tropical and temperate grass pastures on dairy farms in 2 rainfall environments in south-east Queensland. Fertiliser and feed inputs and milk output were investigated, and forage utilised for milk production was calculated by the reverse application of feeding standards. Growth of tropical grass pastures in summer averaged 100 kg DM/ha/day, with greatest yields at recommended nitrogen inputs. Irrigated annual ryegrass pastures produced 40-50 kg DM/ha/day in winter and over 60 kg DM/ha/day in spring. West Moreton farms (800 mm rainfall) produced 7-10 t DM/ha/year from rain grown tropical grass. Corresponding yields for East Moreton farms (1000 mm rainfall) were 19 t DM/ha/year. Irrigated temperate pastures yielded up to 10 t DM/ha/season in both regions. Pasture utilisation ranged from 20-30% for tropical grass in summer to 70-80% for temperate pasture in winter. Cow requirements exceeded pasture growth in autumn, requiring summer pasture to be carried over. Farm productivity could be increased through improved management of tropical pasture.