This is perhaps the most challenging section of GrazFeed which requires information on pasture quantity (availability) and quality. The potential productivity of the pasture being grazed can be measured in a number of ways such as cutting and drying, pasture meters or visual assessment. The local department of agriculture or primary industry will have programs (eg. Prograze) and advice on how to assess pasture. Pasture weight estimates.
Tip: In highly variable pastures it is likely some plant types are not being grazed. Only include in an assessment for GrazFeed the pasture understood to be grazed by the animals.
Examples: Cattle grazing pasture characterised by large clumps of highly digestible material scattered on ‘bowling green’ type pasture, the latter is ignored. This situation will change if the clumps are grazed down.
Under drought conditions, paddocks with green pasture, often associated with a water course or conservation banks, stock will tend to concentrate grazing in these areas. Hence the pasture description should reflect more the green areas than the whole paddock.
Tip: GrazFeed provides a snapshot of specific animals on specific pasture. As soon as animal condition or pasture begins to change the simulation should be re-run.
Conditions change over time depending on pasture growth rate, stocking rate and grazing management. The nutritional requirement of livestock will also change with growth and breeding stage.
Tip: The assessed digestibility of a particular pasture has a substantial effect on predictions of animal production. The greatest change in digestibility is due to a pasture maturing.
Technique: GrazFeed assumes the dead herbage has recently dried off. If material has been dead for some time, crude protein values may need to be lowered.
Technique: GrazFeed assumes the pasture specified covers the ground uniformly. If the pasture is patchy with bare ground, pasture height may need manual adjustment.
Tip: Weather is only included where extremes in temperature, wind speed and rainfall are experienced. For example newly shorn sheep, young animals and severely underfed animals are likely to be affected by chilling. Feed intake may be depressed by very high temperatures maintained day and night.
Tip: GrazFeed uses mature weight of a female animal in average condition (non pregnant) for simulations. This is not the weight of the animal being tested.