Trigger points can be established for key times of the year (calendar dates) when the prospect of achieving good levels of feed is assessed compared to long term records. If the prospect of receiving future pasture growth is considered to be high or low based on long-term records, then certain decisions will be ‘triggered’.

Trigger points can be identified by considering long-term simulated pasture growth records that indicate whether the next three months are highest or lowest and the variability in growth from year to year. Trigger points can both complement and enhance the use of Southern Oscillation Index (SOI) based seasonal risk assessment for seasonal livestock management decision making.

An example of some trigger points and the ensuing decisions are:

• A spring trigger point that indicates that the seasonal conditions are above average and the next three months are likely to be average or wetter than normal may result in a decision to purchase additional trading stock. This will allow some of additional feed to be utilised and stock to be purchased before higher than normal grazier demand results in a price ‘bubble’ developing for available stock.
• An autumn trigger point that indicates that seasonal conditions are below average and the next three months are likely to be average or drier than normal may result in a decision to bring stock sales forward by selling an age group or undertaking a higher cull of replacement stock earlier than normal. This will assist to reduce grazing pressure relative to feed on offer and potentially result in better stock sale prices that might result in a depressed market later in the season. This strategy is also assisted by maintaining a proportion of the flock that are considered to be trading stock.

This system still needs to be linked to assessments of land condition or vegetation health, but generally provides an early indicator for management decisions.