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Livestock productivity depends not only on the quality and quantity of forage available at any give time of the year — strategic selection of pasture species and varieties combined with tactical grazing management are essential in order to optimise animal health outcomes.

During the coming months the Pasture Improvement Initiative will collate the most up-to-date information on pasture management in relation to animal health and providing links to useful resources on this page.

In the meantime, check out the following resources and websites to ensure you are employing the most suitable strategies to maximise the health and productivity of your livestock.

Common pasture-related health challenges

Annual ryegrass toxicity (ARGT)

Annual ryegrass toxicity can occur in stock grazing annual ryegrass infected by the bacterium Rathayibacter toxicus (formerly known as Clavibacter toxic) and is most commonly seen from mid October through December.

The bacterium is carried into the ryegrass by a nematode, Anguina funesta, and produces toxins within seed galls from the end of flowering, through seedset, to seed maturity.

Once infected the grass remains toxic, even when it has dried off, so hay made from toxic ryegrass will be toxic. All grazing animals are susceptible to this disease, including horses.

Signs of ARGT may appear as soon as four days or as late as several weeks after animals are introduced to toxic feed (pasture, hay, grain).

More information can be found on the following websites:

Bloat

Lucerne pasture

Bloat is a seasonal problem in both dairy and beef cattle usually when grazing lush legume pasture species (especially clover and lucerne) during spring. Irrigated pastures during summer or rapid pasture growth during autumn can also lead to bloat.

Bloat is caused by an increase in the gas pressure within the rumen as pasture is fermented. The gas cannot be belched up normally and death results from the pressure causing heart and lung failure. The gas is often trapped in the form of a stable foam.

More information can be found on the following websites:

Grass tetany

Grass tetany is a highly fatal disease associated with low levels of magnesium in the blood.
Grass tetany can affect all classes of cattle but older cows with calves at foot during winter and spring are most at risk. Very thin and overly fat animals are also more susceptible, as are Angus cattle and their crosses.

Nitrate poisoning

Nitrate poisoning is cause by high nitrate levels in pasture and usually becomes a problem during late autumn and winter, often with a flush of growth following a dry summer.

Cattle are most susceptible, with sheep less so.  Cases are most commonly seen on short-term ryegrass, oats, brassica crops and new pastures with high growth rates.

The onset of symptoms is rapid.  Stock appear weak, stagger and gasp for breath.  Deterioration often leads to death.

More information con be found on the following websites:

Perennial ryegrass toxicity (PRGT)

Perennial ryegrass toxicity (PRGT) can be a serious and widespread problem in livestock grazing perennial ryegrass-dominant pastures during summer and autumn. It is caused by a group of toxins that accumulates in the leaf sheaths of perennial ryegrass. The toxins are produced by an endophyte (naturally-occurring fungi) that grows within the leaves, stems and seeds of perennial ryegrass.

The most commonly-recognised sign of perennial ryegrass toxicity is staggers, which usually develops 7 – 14 days after stock graze infected pastures (or hay or silage). Mildly-affected stock develop tremors, which are exaggerated by external stimuli. As the condition worsens, animals lose coordination, develop a stiff gait and lose control of their direction of movement. They may collapse, have convulsions, and be unable to rise, leaving them susceptible to dehydration, starvation and attack by predators.

Endophytes factsheetMore information can be found on the following websites:

The PII factsheet Endophytes and pasture — a complex relationship provides a simple explanation of the relationship between ryegrass and endophytes and contains valuable information on selecting low-risk ryegrass varieties.

General animal health articles