OPTIMISING FEED SUPPLY, REPRODUCTIVE EFFICENCY AND PROGENY GROWTH TO MEET MARKET SPECIFICATIONS. 3. EFFIECENT USE OF PASTURE

摘要

Pasture feed availability for grazing cattle in the Mediterranean environment of Western Australia varies between excess high quality green feed in spring to low quantity and quality in autumn. Along with this variation in quantity and quality of pasture energy supply, the breeders’ energy requirements throughout the year vary with their liveweight and physiological status. The aim of this experiment was to compare the year-round energy supply of metabolisable energy from pasture with the energy demand of a cow-calf breeding unit, calving either in autumn or winter (Read et al. 2004; Tudor et al. 2004). Pasture growth rates were calculated from regular pasture assessments as well as utilising data from the remote sensing program (CSIRO 2004). Energy supply from green feed was calculated using daily pasture growth rates and metabolisable energy values calculated from in vitro digestibility analysis. Dry feed energy supply was estimated from feed consumption based on feed on offer and feed quality.Energy requirement of the cows were determined using a generalised liveweight cycle model (breeders varying from 450 to 600 kg annually, and calves growing to 270 kg by 6 months and 350 kg by 9 months). Livestock requirements were estimated from the body weight changes and feed test quality data (AFRC 1993).