Managing livestock during a green drought

Green paddocks do not always mean adequate feed is available. Short, green feed is usually high in water content and low in key nutritional components, such as metabolisable energy and protein.

A 'green drought' can present a range of animal health concerns as stock burn more energy than they harvest as they wander in search of green pick.

What is a green drought?

A green drought occurs when rain triggers new pasture growth after a dry period, but there is still insufficient feed available to meet livestock needs.

The first flush of green pick is typically:

• very short and sparse
• up to 90% water
• low in dry matter
• unable to provide enough energy or nutrients for livestock.

Although paddocks may look productive from a distance, animals can struggle to consume enough feed to maintain condition.

A green drought can be caused by a combination of limited rainfall, low soil moisture reserves, cold temperatures and slow pasture growth.

A single rain event may be enough to germinate plants and create a green appearance across paddocks, but the soil profile remains dry and unable to sustain ongoing pasture production. During winter, low soil temperatures, frosts, cloudy conditions and reduced sunlight can further restrict pasture growth, meaning feed accumulates slowly despite paddocks looking green.

Farm management practices can also contribute to green drought conditions. Stocking rates that may suit during periods of higher pasture growth can place excessive pressure on limited feed resources during recovery. 

The risk of livestock chasing green pick

When stock are allowed access to short green feed, they often spend considerable time searching for and grazing small amounts of pasture.  

This can create a situation where livestock:

• use more energy grazing than they obtain from the feed
• fail to meet their nutritional requirements
• lose condition despite the paddock appearing green
• cause damage to recovering pastures through excessive grazing pressure.

Sheep and particularly cattle can find it difficult to consume enough green pick to satisfy their daily nutritional needs.

Continue supplementary feeding

One of the most common management mistakes following rainfall is stopping supplementary feeding too early.

If livestock have been receiving hay, silage, grain, mixed rations or other supplementary feeds, these feeding programs will generally need to continue until pastures have developed enough bulk and dry matter to sustain livestock.

Providing supplementary feed in smaller paddocks or designated feeding areas can also help reduce grazing pressure on emerging pasture.

When is pasture ready to graze?

Allowing plants time to establish after rainfall is important for long-term pasture recovery.

As a general guide, consider delaying grazing until pasture has reached:

• approximately 10 cm in height or greater
• around 1,200 kg green dry matter per hectare

It can take up to 8 weeks before pastures offer a useful quantity of feed, with growth depending on the species of pasture and the height and density of these pastures before the rain event.

Assess pasture by bulk, ground cover, plant density and root strength, not colour alone.

Read more about pasture quality. 

Promoting pasture recovery

The period immediately following rain is critical for rebuilding pasture groundcover. Grazing too early can remove valuable leaf area, slow recovery and reduce future feed production. 

Recovering plants are highly vulnerable to repeated grazing and can be quickly grazed out if stock pressure is not managed.

Allowing pastures additional recovery time can

• improve root development
• increase future feed production
• reduce erosion risk
• improve resilience to future dry conditions.

Read more about grazing management. 

Avoid sudden feed changes

Any significant change in diet can increase the risk of digestive disorders and clostridial diseases.

Producers should be particularly cautious when:

• introducing grain
• altering supplementary feeding programs
• moving stock onto fresh green feed
• turning stock directly from hand-feeding onto pasture.

Gradual changes allow livestock and rumen function to adapt safely.

For cattle that have been confined and fed during drier times, consider gradually increasing grazing access over several days rather than allowing immediate unrestricted grazing.

Read more about transitioning stock onto lush pastures. 

Animal health risks during a green drought

Talk to your district vet if livestock body condition is declining or animal health concerns arise.

Pulpy kidney

Pulpy kidney can occur following sudden feed changes or when animals are moved onto lush green feed. Ensuring stock are up-to-date with clostridial disease vaccination prior to a change of feed, and avoiding sudden dietary changes can help reduce the risk of pulpy kidney.

Hypomagnesaemia (grass tetany)

Short, lush green pasture can increase the risk of hypomagnesaemia, particularly in cattle. This risk is greater during cold conditions when green pick forms a significant proportion of the diet. During a green drought, new growth can be very high in potassium, which competes with other minerals like
calcium and magnesium for absorption in the gut. 

To reduce the risk of grass tetany, cattle on short green pick should be supplemented with hay. To provide magnesium supplementation, Causmag at about 60 g/cow per day can be mixed into a slurry and poured over the hay. If possible, cattle should be confined and hand fed until pasture is adequate to sustain them.

Pregnancy toxaemia

Green pick presents increased risks for twin bearing ewes. Twins take up a lot of room in the abdomen, leaving only a small space for the rumen and limiting energy intake. Failure to supply an energy-dense diet to these ewes can put them at risk of pregnancy toxaemia.

Bloat

Bloat occurs when ruminants (particularly cattle) consume lush, immature and rapidly growing legumes, such as clover, medics, and lucerne, or grasses that are high in soluble carbohydrates and protein, and low in fibre.

Symptoms can develop in less than an hour after introduction to a high-risk paddock, but bloat usually develops after a day on immature pasture. 

Plant poisoning

After a drought, weeds often recover faster than desirable species. Hungry stock will look for any green pick and may consume plants, including shrubs and trees, that they would normally avoid. Poisonings are common when stock are sent on agistment and consume plants they are not familiar with.

Short regrowth of some commonly grazed plants, such as sorghum, oats and brassicas, may contain elevated nitrate or cyanide levels that can poison livestock. Nitrate poisoning risk can increase after drought-breaking rain, cloudy weather, frost, herbicide stress or nitrogen fertiliser application. 

Monitor paddocks carefully after rain and seek advice if potentially poisonous plants are present.