Make the most of lucerne

23 September 2016

Lucerne will underpin many livestock finishing systems this summer, but producers often miss out on maximising the benefits of this pasture, recent Tasmanian livestock producers were told.

Agronomist Jason Lynch, a senior consultant with Tasmanian agricultural consultancy Macquarie Franklin, offered practical tips for producers to improve utilisation of lucerne in sheep enterprises at recent MLA More Beef from Pastures  and Making More From Sheep  Maximising Lucerne Productivity workshops in Tasmania.

He described lucerne as rocket fuel – it can drive performance but needs to be carefully managed to protect livestock as well as the crop.

He said September was a good time for producers to prepare their spring/summer grazing strategies.

“Some producers may be gearing up to graze ewes and lambs on lucerne in October/November and others may be waiting for the first cut (for hay or silage) in November and allow pastures to recover before they move lambs onto lucerne in December/January,” he said.

Some ‘rules of thumb’ from Jason to look after livestock as well as lucerne are:

Do not graze immature lucerne: The safest window for grazing is after flower bud through until no more than 30% of the crop is in flower (growth stage three to five). Outside this timeframe, feed quality and digestibility declines and lambs will preferentially selectively graze the richer foliage, which results in poor feed utilisation and can lead to mortality from lucerne red gut. The length of this grazing rotation varies with plant growth rates, which are positively influenced by more available soil moisture and warmer temperatures. For example, it could be 30-40 days on irrigated lucerne, but 40-50 days plus on dryland systems.

Maintain animal health: There are risks for sheep grazing lucerne and producers should be aware of the following (consult an animal health specialist for advice on all animal health treatments):

  • Pulpy kidney: Follow vaccination guidelines to ensure lambs receive appropriate protection. • Red gut: Avoid grazing immature lucerne, provide hay in the paddock to buffer a rich lucerne diet to reduce the risk.
  • Bloat: Do not let hungry sheep on to lucerne, and, if considered appropriate, provide a suitable feed additive or treat with a bloat oil.
  • Sodium deficiency: Lucerne is a ‘natrophobic’ plant meaning it has low sodium levels present in the foliage and sheep grazing on pure lucerne may experience deficiency, therefore consider offering salt licks.

Set appropriate stocking rates: Producers sometimes tend to take a conservative approach to stocking lucerne, however higher stocking rates promote more efficient feed utilisation. Depending on the size of the lambs, 60-80 head/ha can deliver weight gains of 100-200+g/head/day. Use rotational grazing, rather than set stocking, to improve lucerne utilisation and promote persistence. Aim to graze off the lucerne allocation in a maximum of seven days, and target a minimum post-grazing residual target of 1,000kg dry matter/ha.

Fertiliser: Lucerne fixes nitrogen naturally, but will require applications of phosphorus, potassium, molybdenum, sulphur, boron and, potentially, zinc. When developing fertiliser budgets, account for nutrient losses through:

  1. Environmental factors: Nutrients can be locked up in soil or leech out. The amount lost will depend on soil type, for example red clay loam tends to lock up phosphorus, while potassium leaches from sandy soils. Take regular soil tests to assess the fertility levels and determine the phosphorus buffering index.
  2. Fodder production: Every one tonne of dry matter cut as fodder can remove 3kg of phosphorus and 22kg of potassium. (Note: If selling hay/silage off farm, account for nutrient removal, however fodder retained on-farm will see a transference of nutrients within the system.)
  3. Grazing: For every 1,000kg in liveweight, 7kg of phosphorus and 2.3-2.5kg of potassium are removed.

Weed management: Herbicides should be applied during peak dormancy to avoid inhibiting lucerne growth. For semi-dormant lucerne, June/July is the best time, but can be later for highly winter active species (July to mid-August).

More information: Jason Lynch E: jlynch@macfrank.com.au

Resources:

The ‘pasture growth’ and ‘pasture utilisation’ modules in More Beef from Pastures 

 The ‘grow more pasture’ module in Making More From Sheep

MLA pasture tools and calculators 

Phosphorus tool 

Evergraze tools  

NSW Department of Primary Industries pasture AgFacts

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