Transitioning stock onto lush pastures

Lush pastures and forage crops offer high-quality feed and carrying capacity, but careful transition and management are essential to avoid livestock disorders and maintain rumen health

Introducing stock to winter forage crops

There are a range of potential livestock disorders which can result from grazing winter crops. 

Careful attention to your livestock management, with a steady transition onto new feeds (to allow time for the rumen bugs to adjust to a new diet), is important. 

Most winter forage crops provide good quality, highly palatable feed, with:

• energy (ME) ranging from 8 -14 (MJME/kg DM)
• crude protein (CP) 14-32%
• dry matter (DM) ranging from 15 – 32%. 

From May-June, you may be starting or planning to put stock onto winter forage crops. Before you do, there are a few things to consider to get the most out of your forages.

Advice includes:

• never put hungry stock straight onto a crop.  Fill them up with hay and put them in later in the day not first thing in the morning
• make sure your 5 in 1 vaccination is up to date (last 3 months as a minimum)
• provide a mineral supplement
• avoid grazing stock that are susceptible to grass tetany.

Introducing stock to winter pasture

Ruminants tend to graze at a ratio of 70:30, 70% in the morning vs 30% in the afternoon. Therefore, it is best to fill livestock up with hay during the morning graze and then introduce them to the new crop in the afternoon. This will decrease the risk of digestive upset in an unadjusted rumen.

Remember:

1. you are feeding the microbes not the animal, so introduce livestock slowly so that the rumen microflora have a chance to adjust to the high-quality diet
2. it will normally take up to 7 to 10 days to become accustomed to the new feed. Restricting grazing to 1-2 hrs per day, slowly increasing to unrestricted access over 7-10 days will allow stock to become more accustomed to their feed.

If it is not possible for you to slowly introduce the livestock, ensure you have a roughage source available in the paddock, such as medium to good quality hay. The hay’s quality is important. If poor in quality animals will not eat it, so it becomes ineffective in providing roughage to the animals.

Roughage

Roughage is important when introducing livestock onto a new high-quality pasture or crop. Roughage reduces the rate of gut flow, contains enzymes that breakdown fat and starch and helps stabilise rumen fermentation.

Fibre is also important at other times. This includes:

• at late pregnant and early lactation to help rumen function and improve milk fat production
• when scouring is caused by excess protein
• when moisture content is above 83%
• when grazing brassica species, such as canola, as brassicas are highly digestible and have low fibre content, so access to hay may provide a more balanced diet and improve weight gains.

Local Land Services can help with pre-planning and advice on the best winter feed options to suit local conditions.

Stocking densities

Stocking densities on cereals will depend on your animal production targets and what you want to achieve. 

Continuous grazing

Continuous grazing of winter forage cereals gives better animal performance as the best feed on offer will always be selected. This can only be achieved if stocking rates are balanced with crop growth rates and the feed on offer is not being significantly depleted and therefore reducing the animals ability to select better quality feed.

Rotational grazing

High stocking densities are used under rotational grazing but lower animal performance can be expected than from continuous grazing. 

Rotational grazing can, however, be used to maximise the grazing value of a crop, by reducing wastage from trampling and/or frost damage or by the restriction of intake per head. Techniques such as strip grazing or limiting access times to the crop can also be used for rationing feed.

Risks to animal health

Grazing lush feed can come with health risks for stock. There are a few basic animal health considerations to take into account.

Mineral supplementation

Cereals and brassicas can provide high quality forage, as they are high in digestibility, crude protein and metabolisable energy, however grazing crops can have mineral imbalances.

The main deficiencies are magnesium (Mg) and calcium (Ca), also known as grass tetany and milk fever, respectively.

These deficiencies usually occur when livestock are grazing winter or spring pastures or young vegetative dual-purpose cereal crops. This is due to these crops being low in sodium (Na), Mg and Ca, as well as being high in potassium (K), which inhibits the absorption of Ca and Mg.

Therefore, mineral supplementation is needed to get the best out of your livestock on these forages. Mineral supplementation can be either in a form of a loose lick or other commercial products, as long as they contain magnesium, sodium and calcium.

For example, there are three types of loose lick minerals mixes you can used for supplementation:

• 1:1 mix of Causmag® and salt, for growing livestock
• 2:2:1 mix limestone, salt and Causmag®, recommended for pregnant and lactating livestock
• 1:1 mix of lime and salt, recommended for all stock if they find the Causmag® unpalatable.

Vaccination

A change in feed, particularly of high quality such as cereal crops are a common factor in animals developing pulpy kidney (enterotoxaemia). Pulpy kidney most commonly occurs in rapidly growing unweaned or weaned lambs, on lush pasture or grain. This disease affects both sheep and cattle, in which they can be found dead with no previous sign of ill health.

All livestock should be bought up to date with their clostridial vaccinations, i.e. 3-in-1, 5-in-1, 6-in-1 and 7-in-1, prior to being introduced to the crop. It is recommended that if it is a booster vaccination they can be released immediately onto the crop, but if not, leave around 7 to 10 days before introduction.

Nitrates

Nitrate/nitrite poisoning is common during drought or after subsequent rain. Symptoms appear within a day of stock grazing affected plants, though sudden death is also possible, so gradual transition onto these feeds is required.

If you have recently applied nitrogen fertiliser, the risk of nitrate poisoning is higher. The nitrogen in the fertiliser needs rainfall to become available so it is not advised to introduce stock into a paddock that has had nitrogen applied until 2 weeks after the first effective rainfall event following application.

Photosensitisation

Photosensitisation is an ailment in which the skin becomes sensitive to bright sunlight, especially in areas of non-pigmented skin with little hair or wool cover, i.e. in sheep; the face, muzzle and ears. It usually occurs when livestock have eaten certain toxic plants.

Although most issues with photosensitisation occurs due to the consumption of plants that are toxic to livestock, such as Paterson’s curse and St John’s wort, it can also occur in livestock when grazing canola, kale, oats, medic and lucerne. However, the precise cause is not clear. Prompt removal of stock from the source of the toxin, keeping them out of direct sunlight and providing water and cereal hay or lower quality pasture hay with no green colour should help in recovery.