THE MANAGEMENT OF PASTORAL GRAZING SYSTEMS UNDER BIOLOGICAL AND ENVIRONMENTAL VARIATION

The demand from meat processors that pastoral farmers supply animals a t an agreed time, and to agreed specifications (e.g. carcass weight), requires formal consideration of uncertainty and variability in feed p lanning. This paper develops this theme by deriving the probability di stributions associated with simple feed planning models when pasture g rowth, initial estimated pasture dry, matter and animal growth are reg arded as random variables. It is shown that the probability of achievi ng a goal (e.g. satisfying a contract to deliver animals of a particul ar type at a given time), becomes an important statistic when the key feed planning variables are random. The feed resources required to ach ieve a goal with various degrees of certainty can be calculated, and t his is demonstrated in the paper. The effect of changing variances in feed planning variables on the resources needed to achieve a goal with specified probability is demonstrated with a simple example. The opti ons a farmer has for managing variability (e.g. feeding supplements), are discussed. It is particularly notable that smaller variances in es timates of initial pasture dry matter and pasture growth rate assist f eed planning under variability.