Procedure 3

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Aim to graze at a pasture mass between 1,500 and 2,500kg DM/ha

Guidelines for determining the start of grazing

Accurately timing the start of grazing is critical to the efficiency of converting green pasture into product and the overall productivity of a beef herd. Assess the grazing start date by adopting a plant growth-based approach to grazing management. Using this approach, the best time to start grazing a unit (paddock) is just before senescence (dying-off of the first leaf) occurs in the most desirable pasture species. This is just before the pasture energy content peaks and growth starts to decline.

  • See Tool 3.6 for the lower and upper pasture mass limits (kg green DM/ha) or the leaf growth stage to determine when to start grazing exotic (introduced) grass-based pastures. In legume-based pastures, the criterion measured is either the leaf area index (a percentage relating to the plant’s ability to capture the energy from sunlight) or the condition (senescence) of the lower leaf. For further information on grazing management of grass and clover-based pastures, visit www.mla.com.au for Tips & Tools factsheets on pastures, weeds, and grazing management (see Tool 3.4 for a list of relevant titles).
  • Use the MLA Pasture Ruler (see Tool 3.1) to measure pasture height and convert it to herbage mass. As a guide, the preferred pasture mass for grazing is between 1,500 and 2,500kg DM/ha. At this level, pasture has the highest nutritional quality (ME > 11.5MJ/kg DM) and provides the best opportunity for pasture regrowth after each grazing event.
  • Aim to graze paddocks to maintain pasture in green leafy vegetative condition with a maximum pasture mass of 3,000kg green DM/ha.

Correct timing for the start of grazing is critical to both efficiency of pasture utilisation and stock performance. When grazing begins too early:

  • the pasture regrowth period is reduced, and plant health and survival may be affected through a lowering of soluble carbohydrate reserves (grasses) and reduced leaf area (legumes)
  • animal growth is reduced through less energy accumulation and reduced animal intake on short pastures.

These issues can be corrected by removing cattle after a short period of grazing (where animal performance is the target) or stopping grazing before pasture reaches the minimum post-graze pasture mass limit (see Tool 3.2). To ensure plants rebuild carbohydrate reserves, an alternative approach is to extend the regrowth period by delaying the start of the next grazing. Tool 3.3 provides a guide to the estimates of daily pasture growth rates. The MLA Feed Demand Calculator provides a more complete set of estimates for different pasture types.

Animal intake and productivity decline when pasture mass exceeds 3,000kg green DM/ha

When pastures exceed 3,000kg green DM/ha:

  • it is possible to increase stocking density to use the extra feed, if pasture is growing rapidly
  • pasture quality (energy content) starts to decline as older leaves begin to die (senesce), reducing animal performance per kilogram of pasture consumed
  • pasture growth (rate of energy accumulation) slows as shading of green tissue, senescence (dying-off of the first leaf) and seed head formation occur
  • output of animals to meet target specifications is lower through reduced energy intake and efficiency of utilisation.

What to measure and when

  • Plant growth stage: the number of live leaves (for grasses), or leaf cover or condition of the lowest leaf (for legumes except lucerne). Lucerne grazing should stop prior to the emergence of the new bud on the crown. The emergence rate is temperature driven (see EverGraze Action factsheet, Growing and using lucerne in southern Australia on the EverGraze website).
  • Pasture mass:  where seasonal indicators are not yet identified or not appropriate.

The recommended frequency of measurement is fortnightly, and then daily once the predicted time to start grazing is less than seven days away.

Further information